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Flight Review: The Sleek Sting S4

By Dave Unwin || 2 Comments

“Look at that groundspeed!” I exclaimed, pointing at the Garmin EFIS. “Our TAS is nearly 125 knots, which means we’ve got a 60 knot headwind straight on the spinner!” “Can you imagine being up here in a traditional microlight?” asked the Sting’s owner, John Palmer. “No, because not only would I be scared out of my mind at the prospect of having to land, but right now we’d practically be going backwards!” I said.

I’ve written before about just how capable and potent the new breed of light sport microlights is, and several of the aircraft I’ve tested recently are not only comparable to traditional GA types, but are demonstrably superior. An excellent representative of this new breed of speedy sport planes is the Sting S4, from Czech airframer TL Ultralights.

As I wait at Saltby for John to arrive in the Sting, I’m aware that it’s extremely windy, and that if I’d told someone that I was planning on flying a microlight in such conditions, they’d probably think I was mad—or suicidal.  That’s because the traditional image of a microlight as little more than a hang glider powered by a lawnmower engine is still uppermost in many laypeople’s eyes, but as the Sting lands, it looks nothing like a microlight. It’s very much a light aircraft. Usually, I’d have a good look around the aircraft and then spend some time acquainting myself with the cockpit, but today we’re on a tight schedule, and I have flown a Sting before. About 10 years ago, admittedly, but I think I can hack the program. However, pride often comes before a fall (or on this occasion a call). More on this later.

So Let’s Fly

Having hurriedly strapped myself down with the excellent four-point harness (the seats are fixed, although the rudder pedals adjust) we start up, line up and go. With around 13 gallons of fuel and no baggage, our mass is quite close to the 1320-pound max takeoff weight. But we use less than 10% of the 3600-foot runway before I rotate at 50 knots and the Sting springs off the runway. It settles into a 65-knot climb with the VSI indicating just over 1000 fpm.

The flaps retract quickly with no discernible change in pitch, and I point the shapely spinner towards Fenland. It’s a Jekyll and Hyde day. Below the clouds it’s gray and bumpy, but above them it’s smooth and sunny, while the strong tailwind is giving us a very impressive groundspeed.

Fenland quickly appears, we can see the Cessna 172 photo ship climbing away right on schedule. I’m soon slotting the Sting neatly into echelon port. Photographer Keith Wilson opens his window, and we’re off.

Initially all goes well, but remember what I said earlier about pride coming before a call? The stick top is liberally studded with six switches and buttons, and while replying to C172 pilot Steve Brown, I accidentally changed frequencies! That minor SNAFU aside, this is a fun shoot. It’s nice and smooth above the clouds, with great visibility and beautiful light. Steve flies a smooth lead, and the fantastic field of view provided by the big bubble canopy, crisp handling and constant-speed prop ensure the shoot is completed quickly—which is just as well, as the wind has blown us almost to Norfolk.

As is often the case, the formation work has already told me what I need to know about the control response and harmony. They really are excellent, with authoritative ailerons, an effective elevator and influential rudder. The ailerons and elevator are actuated by pushrods—and you can tell. It’s very crisp in pitch and roll but not twitchy. It has the ideal blend of control and stability.

It’s maneuverable when you want it to be, and stable when you don’t, although I note an interesting anomaly. When turning tight to port, there’s a subtle but definite rumble through the stick.

Breakout forces are low, and the roll rate rapid, with a 45-45° reversal taking less than two seconds. There is negligible adverse yaw. The stick-free stability is exactly as I remember it, being a little weak directionally (in yaw), positive longitudinally and neutral laterally. The soft directional stability is typical of many light aircraft fitted with large nosewheel spats, as there’s often not a lot of side-area aft of the center of pressure.

Slowing down for some stalls reinforces that the Sting is as slippery as it looks, as it decelerates quite slowly even with the throttle at idle and the prop set fairly fine. All the stalls are very benign. With flaps up or down, throttle closed or wide open—there are no alarming attributes or unpleasant peculiarities, and to recover, just lower the nose and the wing begins flying again almost instantly, with minimal height loss. With the flaps down the deck angle is just preposterously precipitous. You’d have to be asleep to inadvertently stall it.

At such high angles of attack, position error makes the ASI unreliable, but the book speed of 43 knots IAS seems perfectly plausible. However—and again this is a trait it shares with many similar types, the flap-extension speed is quite low at only 65 knots. On a day with any real wind, 60 knots is a sensible speed on final, and if you decide to go around, you need to pitch up and reconfigure quickly to avoid busting the Vfe.

(Keith Wilson photo)

In cruise, the speed tape soon settles on an IAS of 123 knots at 4000 feet, for a TAS of 131 knots and a fuel flow of around 5 gph. Cruising back to Saltby, I briefly examine the cockpit environment. The heater works well—but bafflingly the only vent is on the copilot’s side. It really should have at least two vents and it would be even better if you could get some hot air onto the windscreen as well. Ambient noise levels are low, and would be perfectly acceptable without an ANR headset.

It’s almost agreeable sitting up there in the sunshine, but even with our impressive TAS, we’re barely making 60 knots over the ground, which means the wind at our altitude is 65 knots. It occurs to me that the landing promises to be interesting, and although the wind’s velocity has clearly increased, I sincerely hope its direction has remained the same. Rather reluctantly, I lower the nose and we descend. Beneath the clouds it’s a much drabber world, and rather turbulent, so I decelerate out of the yellow arc to the top of the green at 108 knots.

At 1000 feet, the wind has dropped by 30 knots, giving us a 15-knot net gain, and Saltby slowly comes into view. My first landing is safe but untidy, so for the second I only use the first stage of flaps and make a much steeper approach at 70 knots with the throttle at idle. This works much better, and I must reiterate that it really is very windy—not traditional microlight weather by a long shot!

(Keith Wilson photo)

It’s been a great test of the airframe, engine and prop, but John wants me to fully experience and appreciate the advanced avionics, switch-studded stick, touchscreen EFIS and integrated autopilot, and very generously schedules a second flight with Neil Grantham. Neil used to be a training captain for a major airline—and although the TADS describe the Sting as a microlight, that’s only because it weighs 1320 pounds and has a slow stall speed. In many respects this aircraft is way more sophisticated than most traditional GA types, and Neil proves to be the ideal instructor for such advanced systems.

As this is a much less hurried affair, I can take some time to also study the airframe, as well as its systems. The engine is—no surprises—a Rotax 912S, which turns a three-blade constant-speed PowerMax propeller made by TL. The Rotax is fed by a 20-gallon tank mounted in the fuselage, which is in turn fed by two wing tanks with a combined capacity of 11.6 gallons. Each tank has its own filler cap, with the fuselage tank filler in the starboard wing root.

Engine access is excellent, with the top and bottom halves of the cowling secured by Dzus fasteners. The airframe is beautifully made, and drag reduction was obviously at the forefront of the designer’s mind. For example, the aileron Rose joints and pushrods are covered by streamlined fairings. Build quality is very high with the finish comparable to that of a high-performance sailplane.

The spar and all other load bearing structures are constructed from carbon-fiber-reinforced fiberglass (the primary structure is an impressive 85% carbon fiber), while the shell structure of the wing is of foam sandwich construction covered with carbon fiber skins. Unsurprisingly the wing uses a laminar-flow airfoil, but surprisingly there aren’t stall strips. The wing’s trailing edge is slightly swept forward and features ailerons with a relatively short span but a very broad chord and large-span electrically operated split flaps. Aft of the cockpit the rear windscreen incorporates a round frangible panel for the Galaxy ballistic recovery system to fire through, then the fuselage tapers before flaring up into the sweptback fin.

(Keith Wilson photo)

Interestingly, although the Sting seems somewhat dissimilar to its Sirius stablemate, it actually shares considerable component commonality with its high-wing cousin.  For example, the undercarriage is basically the same, and the steerable nosewheel strut features a sliding steel tube with an internal spring for shock absorption, while the main wheels are carried by a composite bow.

Continuing the pre-flight inspection, another size-related anomaly is the disproportionally large pitot under the starboard wing, which wouldn’t look out-of-place on a small airliner. I also wondered why it was so far out on the wing.  This type of aircraft does a lot of farm strip flying, and in the summer many strips have crops either side of the mown runway, so at times (such as when doing a 180 having backtracked) one of the wings may be over the crop. I’d prefer it if the pitot was just outboard of the port wheel, as that would keep it out of the crop and the propwash.

The cockpit is nicely outfitted, and surprisingly spacious. The instrument panel features a 10in Garmin G3XTouch, an iPad for SkyDemon and a Garmin G5 standby EFIS. The transceiver is also Garmin, a GTR225A, while the GTX335R ADS-B Out transponder is integrated in the G3X, as is the GMC507 Autopilot. ADS-B In is courtesy of a PowerFlarm Eagle.

Apart from the key-type rotary magneto/starter switch, most of the electrical services are operated by push buttons; an excellent design choice in an aircraft where people tend to step down into the cockpit.  A centrally located sub-panel links the center consul to the main instrument panel, and it contains a curiosity—two small toggle switches. The red left switch has two positions:  up is “auto” and down is “manual.” Basically, with auto set the propeller is in constant-speed mode and controlled with the blue lever. With manual selected, the prop now functions as a variable-pitch prop, controlled by the right switch, up for fine and down for coarse.

(Keith Wilson photo)

I don’t get it, especially as apart from the rpm changing the only indicator is a green light that comes on when it is fully fine. I bet everyone just leaves it in auto, so what’s the point?

This panel also carries the autopilot control panel, flap selector, fuel gauge and plungers for the choke and cabin heat control. If you’re wondering why—despite the fuel system consisting of three tanks (one in each wing and one in the fuselage) there’s only one gauge, it’s because the wing tanks drain into the fuselage tank, so the gauge always reads full until both wing tanks are empty.

A neat quadrant carries the throttle and prop levers, with the fuel valve between the seats. Similarly, the fuel selector is simply an on/off valve that shuts off the fuel between the fuselage tank and engine. It’s almost a masterclass in cockpit ergonomics, and I was almost relieved to note that the plungers for the choke and cabin heat are practically identical, as it gave me something to complain about. I think the choke should be a different shape and red (same as the fuel valve). This is actually a safety issue—as if you want cabin heat and pull the choke on, the engine could stop. There’s no carb heat, as the carbs are heated by hot coolant.

However, my real beef is with the location of the T-handle for the ballistic parachute release. It’s not only poor, it’s actually dangerous. Take a look at the picture of the cockpit, and you’ll see what I mean. At the very least it should be relocated to the side of the throttle quadrant by the P1’s right thigh.

Back to Flying

(Keith Wilson photo)

Taxiing is delightfully simple, with a fine view over the nose. The nosewheel steers through the rudder pedals, and if a very tight turn is required differential braking can be applied via the toe-operated hydraulic disc brakes.  Many microlight manufacturers install hand brakes as they’re lightweight, easy to make and simple to install, but I like toe brakes—possibly because I have a lot of tailwheel time. Taildraggers are easier if you have good differential braking.

Neil shows me how to load a flight plan into the Flight Management System, and we’re soon launching into a rather gray sky. The object of this flight is to test the avionics, so at 500 feet I engage the autopilot. The autopilot control panel is intuitive, with the lateral (heading and track) functions on the left side and vertical (VNAV) on the right. Of course, there’s no autothrottle, so Neil recommends that I climb using a sensible cruise/climb IAS, but descend using vertical speed mode. The reason is that if you tell it to climb at say 750 fpm, but the engine subtly loses power, it will try and maintain the vertical speed until the wing stalls.

Of course, descending using VS also has a trap—and this is definitely one of those occasions when the throttle needs to be your intention and not your reaction. If you’re zipping along straight-and-level and then select 600 fpm down without adjusting the throttle, you’ll be at Vne before you know it.

Flying with Neil is great. He’s a very patient instructor, and I rapidly begin to appreciate just how sophisticated the systems are, and how they relieve workload. As with all things digital, you must sit down with the book to get the best out of it, but Garmin’s G3X Touch suite is quite intuitive. It’s also extraordinarily powerful, and on more than one occasion I turn to Neil, grin and say: “You sure this thing’s a microlight?”

    • Length: 19.5 ft
    • Height: 6.6 ft
    • Wingspan: 29.9 ft
    • Wing Area: 11.7 sq/yrds
    • Climb Rate (Max TOW): 1250 fpm
    • Horz Tail Area: 2.12 sq/yrds
    • Cruising Speed: 124-155 mph
    • Never Exceed Speed: 189.5 mph
    • Minimum Speed: 49 mph
    • Climb Rate (Max Tow): 1200 fpm
    • Empty Weight (By Type): 654.8 lbs
    • Max Take-Off Weight: 1042 lbs
    • Fuel Consumption (75% Max Continuous Power): 4.8 gph
    • Fuel Tank Capacity: 20 gal (with +11.6 w/ aux tanks)

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“Look at that groundspeed!” I exclaimed, pointing at the Garmin EFIS. “Our TAS is nearly 125 knots, which means we’ve got a 60 knot headwind straight on the spinner!” “Can you imagine being up here in a traditional microlight?” asked the Sting’s owner, John Palmer. “No, because not only would I be scared out of my mind at the prospect of having to land, but right now we’d practically be going backwards!” I said. I’ve written before about just how capable and potent the new breed of light sport microlights is, and several of the aircraft I’ve tested recently are not only comparable to traditional GA types, but are demonstrably superior. An excellent representative of this new breed of speedy sport planes is the Sting S4, from Czech airframer TL Ultralights. As I wait at Saltby for John to arrive in the Sting, I’m aware that it’s extremely windy, and that if I’d told someone that I was planning on flying a microlight in such conditions, they’d probably think I was mad—or suicidal. 

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Look Out — A Hybrid Merlin is Coming!

By Steve Ashby || 17 Comments

First introduced in Europe in 2013, the all aluminum single seat enclosed cabin Merlin LSA has sported a variety of engines, including a Rotax 582, a specially built four stroke V-twin and even an electric motor. In fact, the Merlin airframe has served as a test bed for all kinds of propulsion and aerodynamic innovations. At AirVenture 2023, Aeromarine chief designer Chip Erwin even showcased a Merlin model with twin propellors imbedded in the wings. Erwin promises an even bigger surprise at Oshkosh later this month: a common-sense hybrid propulsion system for the Merlin.

Erwin, who has done work for the Air Force Research Lab in Dayton, Ohio, has developed a parallel hybrid drive system for light sport aircraft that utilizes an electric motor to add to thrust generated by a

The electric motor is built into the belt reduction drive!

piston engine during takeoff and climb, but shuts down during cruise. He points out that a major limitation of all electric aircraft is the need to lug around a heavy battery capable of providing thrust for a limited period of time. The advantage of a piston engine is that it can provide the reduced thrust necessary for cruise flight in a lightweight package, utilizing a relatively small amount of fuel.

A typical flight plan for the hybrid system would entail using the piston engine, supplemented by the parallel electric motor, to provide the combined thrust necessary for takeoff and climb. Once a cruise altitude is reached, the electric motor would be shut down and cruise would be accomplished on the piston engine alone. Erwin points out that the electric motor would be free wheeling during cruise flight (through the use of a sprag clutch) resulting in insignificant drag to the thrust produced by the piston engine.

This parallel thrust setup allows the use of a smaller, lighter and more fuel efficient piston engine, supplemented by a light weight electric motor. Since the electric motor is only used for takeoff and climb, it utilizes a fairly small battery, which is recharged by the gas motor during cruise. Formula One race cars have been utilizing this concept for the past several years, using a small but powerful electric motor to provide added torque for critical phases of each race such as the standing start and powering out of corners. The Formula One batteries for these cars are the size of a laptop battery, discharging their energy for relatively short bursts and being recharged on the straights.

The electric motor components of the drive.

The parallel hybrid system is designed to provide greater efficiencies for light sport aircraft, resulting in lighter weight and increased range.  We should be able to see it all in person at Airventure, where Erwin promises an impressive display.

 

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First introduced in Europe in 2013, the all aluminum single seat enclosed cabin Merlin LSA has sported a variety of engines, including a Rotax 582, a specially built four stroke V-twin and even an electric motor. In fact, the Merlin airframe has served as a test bed for all kinds of propulsion and aerodynamic innovations. At AirVenture 2023, Aeromarine chief designer Chip Erwin even showcased a Merlin model with twin propellors imbedded in the wings. Erwin promises an even bigger surprise at Oshkosh later this month: a common-sense hybrid propulsion system for the Merlin. Erwin, who has done work for the Air Force Research Lab in Dayton, Ohio, has developed a parallel hybrid drive system for light sport aircraft that utilizes an electric motor to add to thrust generated by a piston engine during takeoff and climb, but shuts down during cruise. He points out that a major limitation of all electric aircraft is the need to lug around a heavy battery capable of providing thrust for a limited period of time.

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If It Flies Like a Duck and Floats Like a Duck, Maybe It IS a Duck

By Dan Johnson || 4 Comments

Article Updated July 17, 2024 — After this article was posted, Miguel Rosario reported, “Duck is still in tests. Now we will install a 912 ULS 80-horsepower engine, as requested by future customers.” He continued, “Molds are under construction for production, which we hope to start in three months” (approximately October 1, 2024). He finished, “I will keep you updated on all developments regarding Duck.” —DJ

You probably know Seamax. This longtime, performance-oriented LSA seaplane was one of the first to make a splash in the U.S. light aircraft market way back in December, 2007.

Today, regretfully, the Seamax company is going through some very difficult circumstances as noted in this State of the Seaplane Sector report. We don’t know the end of those stories yet.

Miguel Rosario is an enthusiastic and talented designer.

Nonetheless, Seamax M-22 designer Miguel Rosario remains active. You can’t keep a good man down but apparently you can keep him on the water.

Welcome Duck!

Seamax and Duck share a love of water but otherwise they could hardly be more different.

Seamax (several articles here) was an early entry in the LSA sweepstakes. Despite earning its FAA acceptance only three years after the SP/LSA regulation was released, Seamax clocked in as #63 to receive its Special Airworthiness Certificate. New Light-Sport models arrived regularly in those beginning years, sometimes four or more new entries in a single month.

Many of those models — 158 show on our SLSA List — have gone quiet, perhaps never finding sufficient market to continue in the crowded and highly competitive U.S. market. Some off-shore designs have steady markets at home but found America challenging.

Welcome Duck!

Since Seamax gained acceptance as a Special LSA, lots has happened. Only a year after its approval, we experienced the global financial crises of 2008 and more recently Covid and regional conflicts. During this turbulent period, currencies around the world continued to lose purchasing power such that a modern new LSA today is reaching toward $200,000 while some of the best-equipped, highest-performing models have shot past $300,000.

In these gusty conditions, affordable airplane builders have been hit hard by rising input costs and seaplanes even more so. Two top seaplanes — Searey and Seamax — are presently off the market. Icon just survived an expensive bankruptcy. Vickers Wave and Finland’s ATOL continue to progress (article) but are not actively being sold yet. We’re still waiting on other promising designs covered on this website.

Fabricating the hull for Duck mated to a V5 Fox Neo.

Aero Adventure stands out as one strong survivor with fairly low costs, though even those are rising as the dollar sinks and the company has established a Brazilian factory, as was recently reported.

Duck Entry

Fortunately, challenges in the LSA seaplane sector need not affect all affordable aircraft.

While Seamax design Miguel Rosario admits the business part of aircraft building is not his forte, this prolific designer is one of those types who can’t sit still while the bean counters sort out Seamax, Inc.

“I am still working in airplane design (and race cars),” Miguel recently wrote via email. “I just developed a new amphibian that should have a low cost.”

“I want to share with you the Duck, a design specially made for a Brazilian company called Fly Fox, located in Goiania, Brazil.” Miguel cautioned, “So far, the info I am sharing with you… is for your personal information.” He promised to supply more details; when I hear more I’ll pass it along.

Fly Fox is the manufacturer of the Fox ultralight family consisting of V4, V5, and V6 (nearby images). Miguel noted that for the last 20 years, Fly Fox has been successfully manufacturing kit-built ultralights. “In manufacturing quality and flight characteristics, these are very good aircraft,” Miguel expressed.

He continued, “What I made is a ‘reassembled’ Fox V5, using same wings and tail, repositioning
the boom on top, installing the engine in tractor position, and adding a small composite boat hull.”

“The flight test program is finished,” Miguel declared, “and Fly Fox is now preparing for production.”

Main Technical Data
supplied by Miguel Rosario

  • Empty Weight — 540 pounds (245 kilograms)
  • Useful Load — 485 pounds (220 kilograms)
  • Wing Span — 31.7 feet (9,66 meters)
  • Stall Speed — 32 mph / 28 knots
  • Cruise Speed — 78 mph / 68 knots
  • Engine — Rotax 582, 65 horsepower
  • Propeller — Warp Drive 3-blade 68 inch

About Fly Fox

“Since the end of 2018, Fly Ultraleves (English website) created the company Fly Fox to manufacture kits for assembling Fox V-5 and Fox V-6 aircraft under license.” wrote the Brazilian company.

“[In the last] year, we developed manufacturing templates, where all parts, without exception, are drilled in the same pattern. We made improvements to the aircraft, such as tanks on the wings, laminar landing gear, Celeron pulleys, lighter fairings due to improved resin quality and several other improvements. During this time, parts were manufactured for the kits, today designed in Solid Works, finished with CNC and water cutting. All tubes are made of 6061-T6 aluminum, manufactured under strict quality control.”

“Fox V5 Super Neo is an ultralight built side by side for the pilot who wants the “open cockpit feel.” [With] the strength and safety of the Fox line, and with its docile controls, low stall speed and configuration of an aircraft with unsurpassed flight quality, V5 Super Neo will certainly be the choice for the adventurous aviator.”

A 3D rendering of the project as it began.

“The Fox V5 Tandem Neo is an ultralight with tandem (fore and aft) seats, incorporating the latest technological solutions. The landing gear has a laminar spring system for softer landings. The simplicity of the aircraft makes it a fun machine. It has the strength and safety of the Fox line, and with its docile controls, low stall speed and configuration of an aircraft with unsurpassed flight quality, it will certainly be the choice for the aviator who likes the wind in their face.”

Fly Fox of Australia featured this earlier floatplane version of Tandem Neo.

Fly Fox’s V5 series use sewn dacron wings and offer “internal comfort, and a highly reinforced structure.” Various Rotax engines are recommended though builders may install the engine of their choice, said Fly Fox.

How Low Cost?

My title slide suggested Duck will be relatively inexpensive but it’s still too early to know details. As a kit based on ultralight construction, it’s reasonable to project a modest selling price. Fly Fox is not presently represented in the USA. Nonetheless, given rising LSA prices and even more costly Mosaic LSA to come in a year or so, economical choices like Duck may be worth investigating. You won’t likely get one for summer 2024 but you can dream ahead.

Interested? Contact Fly Fox directly…

This video was composed from clips sent by Miguel Rosario in June 2024. The finished Duck may look different than seen in this proof-of-concept aircraft. It is seen here making its maiden flight.

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Article Updated July 17, 2024 — After this article was posted, Miguel Rosario reported, “Duck is still in tests. Now we will install a 912 ULS 80-horsepower engine, as requested by future customers.” He continued, “Molds are under construction for production, which we hope to start in three months” (approximately October 1, 2024). He finished, “I will keep you updated on all developments regarding Duck.” —DJ You probably know Seamax. This longtime, performance-oriented LSA seaplane was one of the first to make a splash in the U.S. light aircraft market way back in December, 2007. Today, regretfully, the Seamax company is going through some very difficult circumstances as noted in this State of the Seaplane Sector report. We don’t know the end of those stories yet. Nonetheless, Seamax M-22 designer Miguel Rosario remains active. You can’t keep a good man down but apparently you can keep him on the water.

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Paths to Affordability

By Don Yarbrough || 4 Comments

It’s become almost folklore. The quest for affordability in the world of general aviation has been like trying to see the aurora on a cloudy night, or recalling a dog set loose on a squirrel in the forest, or even encountering Bigfoot. From the crash of the post-WW-II airplane buying frenzy, to the mid-1980s liability-fueled dissolution of the general aviation manufacturing industry, to the relative lack of affordability following what the introduction of LSA promised to be, we’re still here, waiting for a real solution.

Parallel paths toward increased affordability exist. One is hopeful and one is tangible.

On the hopeful side we have MOSAIC, which promises to increase capability and affordability within the LSA category by expanding Sport Pilot privileges and making a range of aircraft available to pilots limited to those privileges. Moreover, the MOSAIC-style LSAs could get a lot heavier and faster and more capable—including potential use at night and in instrument conditions. Finally, “simplified flight controls” provisions may pave the way for personal aircraft with amazing performance characteristics operated via something like an iPad—rapid implementation of such significant automation with the reliability required to move people is likely an expensive endeavor, but production cost decreases due to economies of scale are possible in the long-term.

But here’s the rub:  MOSAIC isn’t real yet and won’t likely be until 2025, perhaps even late in the year. Isn’t there something you could do now, rather than wait? Absolutely—let’s apply some elbow grease, tenacity, and sticktoitiveness:

  • Consider buying a reasonably priced used LSA and attending a Repairman course to begin learning the relevant maintenance practices.
  • Become a Sport Pilot Instructor with 100 less hours than a traditional CFI, realizing the opportunity to begin flying for an income at 150 hours, lowering the cost to enter the profession and motivating more flight schools to purchase LSAs, reducing training and acquisition costs across the fleet.
  • Develop great relationships with mechanics and wield the privileges afforded to you by Part 43, Appendix A, leading to a much more financially fulfilling love affair with Part 23 certified aircraft.
  • Support organizations like EAA, that advocate for big wins like VARMA, which reduces parts replacement costs, and, if proven effective on older types, may lead to utilization in later models.
  • Show up to have coffee with the old guard at your local airport and connect with someone that has an airplane but doesn’t fly it for various reasons—maybe they’re interested in cost sharing.
  • Involve yourself with the local flying club, whether they have a sleek, sexy, nicely equipped LSA, or a ratty (but mechanically sound) Skyhawk.
  • Advocate through your preferred organizations for careful and thoughtful revisions to strengthen the liability protections afforded to manufacturers and maintainers.

These paths to affordability actually do converge. Countless intersections join the expansive future potential bound-up in MOSAIC, and the real, tangible, existing world of general aviation. Some important intersections are the result of:

  • Individual development efforts associated with growing your ability to contribute to operational and maintenance cost management, notwithstanding your preferred aircraft certification category.
  • Volunteerism and financial contributions to general aviation advocacy organizations and an informed awareness of the work being done on your behalf by those entities.
  • Meaningful revisions to the liability protections afforded to manufacturers and maintainers who make aviation possible when the NTSB rules something along the lines of “the pilot’s failure to …” in order to maintain an environment of business agility in both the LSA and Part 23 aircraft arenas.

It seems like a tired trope to say “put in some effort,” but that, in conjunction with what MOSAIC hopes to accomplish, inspires in me loads of optimism about future affordability within general aviation.

My concern with leaning too far in the direction of a regulatory cure is our history of reliance on failed regulatory cures, so we must contribute to the outcome, not simply sit waiting for an external solution—all while believing that those folks working so hard to support us with regulation are gonna knock it outta the park.

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It’s become almost folklore. The quest for affordability in the world of general aviation has been like trying to see the aurora on a cloudy night, or recalling a dog set loose on a squirrel in the forest, or even encountering Bigfoot. From the crash of the post-WW-II airplane buying frenzy, to the mid-1980s liability-fueled dissolution of the general aviation manufacturing industry, to the relative lack of affordability following what the introduction of LSA promised to be, we’re still here, waiting for a real solution. Parallel paths toward increased affordability exist. One is hopeful and one is tangible. On the hopeful side we have MOSAIC, which promises to increase capability and affordability within the LSA category by expanding Sport Pilot privileges and making a range of aircraft available to pilots limited to those privileges. Moreover, the MOSAIC-style LSAs could get a lot heavier and faster and more capable—including potential use at night and in instrument conditions.

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Longest-Running Midwest Event Celebrates 16 Years — GO! FLY! MORE!

By Dan Johnson || Leave a Comment

Let me be clear — I think the Midwest Aviation Expo is the premiere event I’ve ever attended for pilots to take demonstration flights in several aircraft as they consider a purchase. That’s a major benefit.

Sure, Sun ‘n Fun, Aero Friedrichshafen, and AirVenture Oshkosh are far larger… and that’s the problem. Size does matter but not always the way you think.

At these wonderfully huge events, you have so much to see and so many people to talk to that you cannot get to everyone. When you do end up in the front of a waiting line to talk to a vendor, you may have be quick as many others are waiting and the vendor wants to serve all the customers he or she can. The sheer size of these events also means literally miles of walking on some days. I don’t even want to mention the lines of plastic portapottys baking in the sun. Whew!

Instead, come relax in Mt. Vernon (KMVN), now the longest-running light aviation-focused event in the country. Yep, this is their 16th year, making it the grandaddy of such events.

Comfortably after Oshkosh, on September 5-6-7, 2024, Midwest Aviation Expo is a calm and thoroughly enjoyable gathering. They’ve selected this date carefully and weather has usually been excellent. The area around the airport is wide open, very accommodating of demo flights.

“Several Sponsorships and Partnerships are in place and some 9-10 new Exhibitors are registered,” said lead organizer Jana Filip. Vendors commonly return year after year; see articles below. “Chris Collins will be going to Oshkosh to promote the event.”

Articles on Midwest Expo:

Midwest Brain Trust — Chris Collins (R) talks with aides including Jana Filip at Midwest 2023.

Put on for 16 years by the airport run by longtime manager Chris Collins, this event has every single year gotten rave reviews for how well everyone is treated when they attend Midwest. Vendors love it and pilots love it. Um, so do we media types. It’s great for us, too, as we work to gather information and images.

Midwest always hosts a series of forums that have proven increasingly popular. One reason: they take place inside, where it’s quiet and cool. You also have access to an excellent airport restaurant plus other services. Not least: regular bathrooms. Tell me you don’t wish for that while occupying a plastic portapotty at one of the big shows on a scorching hot day. A fellow aviation journalist once sighed and said, “Yeah, nothing like porcelain.” I won’t go into further detail.

See. Fly! Perhaps Buy?

I made a long career out of helping pilots choose the right aircraft to buy. I’ve tried to provide good, reliable, unbiased information to aid your selection. I’m pleased to have created thousands of articles and videos but the absolute best way to know if an airplane is right for you is to try it on for size and take it aloft.

Rebadged for 2024, Midwest Aviation Expo — formerly the Midwest Light-Sport Aircraft Expo — may be the best place I’ve ever been to get time in aircraft. I urge you to make arrangements with vendors ahead of time as their flight schedules can get filled but you could fly 5 or more different aircraft if you set your mind to it.

That is the #1 best way I know to select your dream plane. Follow the opportunity and go to Mt. Vernon in early September. It’s about an hour’s drive east of St. Louis, Missouri.

But, first…!

Going to Oshkosh?
Got News We Can Report?

If you are a vendor, or a builder who finished a handsome kit, or someone with a great aviation story to tell, we want to hear about it.

I know, I know… if you are a vendor, you’re so busy about now that stopping work to tell your story is often not a priority. I get it.

Yet in a mere five minutes of downtime, you could inform us generally of what you are preparing so we can try to check out your project at the big Wisconsin show.

Send news to: Editor

You’re going to a lot trouble making your aircraft look its best and planning how to best display it. You’ll spend plenty of money to make it happen — and I hope it’ll be totally worth it.

Take five minutes to tell us your story. You inform us. We’ll tell pilots. Attendees can plan what they need to see when they arrive at the big show. Everyone smiles.

Airplane noise — here we come!  😎

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Let me be clear — I think the Midwest Aviation Expo is the premiere event I’ve ever attended for pilots to take demonstration flights in several aircraft as they consider a purchase. That’s a major benefit. Sure, Sun ‘n Fun, Aero Friedrichshafen, and AirVenture Oshkosh are far larger… and that’s the problem. Size does matter but not always the way you think. At these wonderfully huge events, you have so much to see and so many people to talk to that you cannot get to everyone. When you do end up in the front of a waiting line to talk to a vendor, you may have be quick as many others are waiting and the vendor wants to serve all the customers he or she can. The sheer size of these events also means literally miles of walking on some days. I don’t even want to mention the lines of plastic portapottys baking in the sun.

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Gas Pains — The Latest Mayhem Surrounding a High-Octane Avgas Replacement

By Marc Cook || 4 Comments

The ongoing issue of finding a replacement for leaded avgas took an ugly turn recently after Cirrus advised owners that use of anything other than an “approved” fuel would likely invalidate the engine warranty. “Per Continental and Lycoming, only approved fuels may be used for an engine to be covered by warranty. As the GAMI G100UL fuel is a non-approved fuel per Continental and Lycoming, engines known to have run this fuel may not be covered by the OEM engine warranty. For specific details, please refer to the respective Continental and Lycoming engine warranty documents,” Cirrus said in a statement. “While some aspects of the initial Cirrus testing of the GAMI G100UL fuel are encouraging, other areas, including materials compatibility, remain inconclusive.”

At issue is that the GAMI fuel has not been submitted to the ASTM for “approval” but has received FAA approval in the form of a Supplemental Type Certificate that applies to virtually every spark-ignition aviation engine made. Cirrus’ stance is that this is, therefore, not an approved fuel by way of ASTM.

Soon after, GAMI responded by noting that an SR22 has been flying on GAMI fuel since 2010. In its statement, GAMI said: “G100UL Avgas is fully approved for use in all Cirrus Aircraft and in all Continental and Lycoming engines!” In the case cited by Cirrus regarding fuels compatibility, GAMI says that “Cirrus failed to inspect the condition of the fuel tank before use of 100UL Avgas in the wing of their model year 2014, company owned, ‘R & D’ aircraft, an SR22T, N72DF. Therefore, Cirrus does not know that the fuel tank sealant had not already ‘failed,’ i.e., partially de-bonded, before Cirrus first began to use 100UL avgas in one wing of N72DF.” Moreover, GAMI says that “in 2013, Cirrus engineers fully tested G100UL Avgas at Cirrus in their fiberglass/epoxy wing fuel tanks and wrote a favorable report which was formally approved by the FAA. A few weeks after Cirrus first observed the condition of the PTE sealant in the wing of N72DF, Cirrus told GAMI that Cirrus had reverted back to the exclusive use of the industry standard polysulfide (PSD) sealant in the Cirrus tanks on their production line.” The company concludes by saying, “The FAA has fully investigated this matter, for nearly a year. To date, the FAA has found no ‘safety of flight’ issue associated with the single adverse report from Cirrus.”

Hot on the heels of the GAMI rebuttal, Lycoming chimed in with this statement: “Lycoming Engines provides a Limited Warranty against defects in material or workmanship. Lycoming’s Limited Warranty does not cover damage caused by operation outside of Lycoming’s published specifications or the use of non-approved fuels or lubricants. Lycoming publishes specifications for approved fuels in Service Instruction 1070. G100UL is not listed as an approved fuel in Service Instruction 1070. Lycoming evaluates warranty claims on a case-by-case [basis] in accordance with the terms of its Limited Warranty. However, customers should be aware that use of fuels not approved in Service Instruction 1070 would constitute operation outside of Lycoming’s published specifications.” The FAA followed by saying that warranty issues were between the manufacturer and the customer; it’s not in that chain at all.

And then came word that the key player in the EAGLE program for an unleaded avgas alternative had pulled its ASTM application. “Lyondell had balloted its ASTM Test Spec and had received some negative comments, so have pulled it and are addressing the feedback and plan to re-ballot in the near term,” Castagna quoted an FAA official as telling him, as reported on AVweb. Which now leaves Swift to complete its work on a 100-octane unleaded fuel and the already FAA-approved GAMI G100UL on the table, though it’s broadly considered that Lyondell/VP Racing will go back to work on remedying the unstated issues found in early testing. It’s unclear what those were, though it’s reasonable to assume they related to either the fuel’s ability to suppress harmful engine detonation or materials compatibility, or both.

In the days since that reporting, Lyondell clarified the status of its unleaded avgas, per reporting in AVweb. “LyondellBasell has not paused or suspended our efforts to obtain an ASTM test fuel specification. We continue to pursue ASTM certification for our UL100E unleaded fuel through the normal balloting process. We balloted a test fuel specification and research report on UL100E in May for the first time and the ballot closed on June 9, a week before the ASTM meeting. The ballot received 65 affirmative votes, 5 negative votes and 228 abstentions for a 93% affirmative rate. Since our first ballot received a negative comment on our proposed color method that we found persuasive and others we are still reviewing, we withdrew the ballot to make the correction and reach out to the other commenters. This is the standard procedure for making even minor changes to specifications. We will ballot a revised test fuel specification and research report for additional review and comment from the ASTM community as soon as we review the other comments and reach out to their authors. Since an ASTM specification is a required element of PAFI fleet authorization, we are committed to obtaining both as expeditiously as possible.” Parsing this, the “others we are still reviewing” is, again, unclear: Are the complaints of a similarly minor nature as the color of the fuel or is there more?

LSAs running the 900-series Rotax engines might be in a far better place than many should there be more trouble finding a true 100-octane unleaded replacement for avgas.

Since you’re reading this on ByDanJohnson, you’re probably wondering how this applies to you. Since most of the LSA market is powered by Rotax engines, it’s good to consider their guidance, which is relatively straightforward. In the current set of Service Instructions, Rotax defines the leaded option as our conventional avgas that conforms to ASTM D910, but also lists a number of other global standards including unleaded fuels that comply with ASTM D4814 as well as the UL94 conforming to ASTM D7547. According to Rotax, “In addition to AVGAS, various automotive fuel types with different quality are available. Due to various environmental, economic and political reasons a number of fuel types with different amounts of ethanol blend are available.”

Rotax then allows use of auto fuel with as much as 10% ethanol, though it notes that “it is the responsibility of the aircraft manufacturer to test their fuel system components and supply any further information on techniques, procedures and limitations of using ethanol blended fuel.” Some airframe manufacturers fall back on Rotax’s fuel recommendations rather than make their own, though the ASTM process theoretically puts that definition on the airframe manufacturer. At this point, Rotax doesn’t explicitly say the GAMI fuel can or cannot be used. For now it’s an academic point because while GAMI says that it has had fuel produced—making it “commercially viable”—it is not yet widely available. What’s more, the STC held by GAMI does not include Rotax engines, though, technically, if G100UL works on old-technology highly turbocharged powerplants there’s no reason to believe it won’t also work with Rotaxes. And remember back at the beginning that Cirrus’ prime argument wasn’t that the engine wouldn’t run well on G100UL but that there may be materials issues with the airframe and systems.

For now, if you’re flying behind (or in front of) a Rotax, you’re relatively well protected. Commonly available auto fuel is, in fact, the preferred fuel for most applications. Should there be continued issues with a candidate avgas replacement—say, one that doesn’t quite get to 100 octane, as required by the big engines—there’s also a viable path to using 94UL exists. Overall, then, for most airplanes in the LSA sector, fuel will continue to be an issue—something we all watch like a slow-motion train wreck—but primarily an economic one.

Compress Post ...

The ongoing issue of finding a replacement for leaded avgas took an ugly turn recently after Cirrus advised owners that use of anything other than an “approved” fuel would likely invalidate the engine warranty. “Per Continental and Lycoming, only approved fuels may be used for an engine to be covered by warranty. As the GAMI G100UL fuel is a non-approved fuel per Continental and Lycoming, engines known to have run this fuel may not be covered by the OEM engine warranty. For specific details, please refer to the respective Continental and Lycoming engine warranty documents,” Cirrus said in a statement. “While some aspects of the initial Cirrus testing of the GAMI G100UL fuel are encouraging, other areas, including materials compatibility, remain inconclusive.” At issue is that the GAMI fuel has not been submitted to the ASTM for “approval” but has received FAA approval in the form of a Supplemental Type Certificate that applies to virtually every spark-ignition aviation engine made.

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Building the Affordaplane, Part 3

By Jon Croke || Leave a Comment

Empennage components rigged on the fuselage.

In the previous installment, I described construction details for the fuselage section of the Affordaplane ultralight project. Now let’s look at construction of the empennage and wing assemblies. Remember, this is a plans-only type of build using off-the-shelf materials and tools intended for a novice builder. Keep this objective in mind when reviewing the construction and design details. A complete free video series on YouTube shows each step of this construction.

The components of the empennage (rudder, elevator, vertical and horizontal stabilizers) are all formed from 1-inch 6061-T6 aluminum tubing. These tubes must be bent into their respective shapes, matching template patterns drawn on your workbench. (Use some craft paper for this!) What is the easiest way to form these simple bends? I found that using an electrician’s conduit bender did the job nicely. With a little practice, each tube was formed to the proper shape and then fitted with a gusset to join its ends.

A typical hinge assembly used throughout

Hinges are needed between the rudder and vertical stabilizer as well as the elevator and horizontal stabilizer. The plans call for a simple, strong design using stainless steel L brackets attached with stainless steel rivets. As can be seen in the photo, the L brackets are positioned so they align for joining with conventional AN clevis pins and cotter pins. My job in demonstrating this construction was to show how to locate these hinges for perfect alignment before drilling in place. While this technique for creating hinges is not unique, it was a good fit for this project where we want easy installation using robust components. The hardware needed to attach the tail feathers to the fuselage is also shown in a photo and illustrates how only off-the-shelf hardware is used to reduce the need for complex components.

An electrician’s conduit bender can form the aluminum tubing for the tail feathers

In a similar fashion, the wings for the Affordaplane were easy to fabricate from 6061-T6 tubing of various diameters. The spars, ribs and bracing structures are all made from this tubing fastened with AN hardware. Using standard lumber, I made a full-size jig for the wing utilizing the workbench as the platform. The Affordaplane wing design has a leading and trailing edge spar made from this aluminum tubing, and the lip of the workbench edge holds each of these spars in their exact position during the build. This results in wings that can be built precisely without requiring advanced skills or tools.

Wing ribs were shaped from half-inch tubing that was formed around a simple wood jig. This could be done by hand and the wood jig provided consistent bends. The ribs were attached to the front and rear spars with gussets and rivets. To obtain a strong connection to the front spar, the forward ends of the ribs were shaped by trimming with a large-diameter hole saw so that they would match the curve of the spar at the attachment point.

The workbench is used as a jig for an accurate wing build.

After weighing the wings for future reference, the tail feathers and wings were joined to the fuselage and rigged. The elevator-to-stick connection is implemented with a push-pull tube. The rudder is controlled by cables. The ailerons are managed by a combination of pulleys and cables using all AN hardware components. After rigging was complete, everything was taken apart for covering and painting.

Fabric and Paint

Covering the Affordaplane wing using lightweight fabric.

Is it fair to expect a first-time builder to be able to fabric cover their aircraft? Yes! My videos show the step-by-step process for covering this ultralight with the extra-lightweight Poly-Fiber fabric using water-based glue from Stewart Systems. While I am not a fabric covering expert, there is no specific task that is difficult in this process. The water-based glue system means there are no bad fumes or dangerous solvents. Scissors, an electric iron and a paintbrush will get your wings and tail covered and ready for flight. I am not exaggerating that this final step of aircraft building (which often scares first-time builders) is quite easy when you can watch videos showing each step of how to cover specific Affordaplane components.

Colorful latex house paint saved weight and money.

You can’t leave the fabric uncoated—and I was not going to fall into the trap of using expensive aircraft paint—as the Affordaplane would quickly become not so affordable. I experimented with premium, exterior, high-gloss latex house paint. Just a couple coats and it worked great. I was very happy with the result and the ease of applying it with a foam roller. You can spend as much or as little time as you want with colors and designs, and the paint is available at your local hardware store.

In our final installment next issue, we will entertain the need for an engine and engine mount. Can you guess how a first-time aircraft builder is going to fabricate an engine mount? And remember, no welding! The Affordaplane plans do not require a specific engine for this airframe, so builders are on their own to choose one that fits their needs. Remember, our need is that the aircraft makes the 254-pound ultralight weight limit, so this will guide our decision. Plane and Simple.

Compress Post ...

In the previous installment, I described construction details for the fuselage section of the Affordaplane ultralight project. Now let’s look at construction of the empennage and wing assemblies. Remember, this is a plans-only type of build using off-the-shelf materials and tools intended for a novice builder. Keep this objective in mind when reviewing the construction and design details. A complete free video series on YouTube shows each step of this construction. The components of the empennage (rudder, elevator, vertical and horizontal stabilizers) are all formed from 1-inch 6061-T6 aluminum tubing. These tubes must be bent into their respective shapes, matching template patterns drawn on your workbench. (Use some craft paper for this!) What is the easiest way to form these simple bends? I found that using an electrician’s conduit bender did the job nicely. With a little practice, each tube was formed to the proper shape and then fitted with a gusset to join its ends.

Expand Post ...

Inside the Transatlantic Crossing of the Risen

By Marc Cook || 14 Comments

We recently reported that the newest version of the sleek, retractable-gear Risen had made a successful transatlantic crossing. From what we could piece together from outside accounts and posts on social media, it went well. But here’s a more first-person look at the crossing, from the perspective of the right seat.

Andrea Venturini accompanied designer Alberto Porto on the epic journey across the pond. Here’s his account.

Ready to depart Voghera in Italy.

It all started last December, with a phone call I received from Alberto Porto. At the time, I was in Australia doing a report at the Gliding World Championship for theItalianTeam. Onthephone Alberto, designer and builder of the fastest ultralight in the world (430 kph/232 knots), with the simplicity that always distinguishes him, says: ”Andrea, keep yourself free for next June, I’ll detail everything when you return to Italy.” 

You can imagine my curiosity in the meantime. A few weeks later, the mystery was revealed: the Risen Superveloce with the brand new Rotax 916 iS must be brought to Oshkosh, to AirVenture, the largest and the most important aviation fair ‘of the Universe.’ I knew well what Oshkosh meant. A strange word in Italian; it’s the headquarters of the EAA, basically an immense display of aircrafts with thousands of people camped under their wings for about a week. The show comprises hundreds of aeronautical displays that take place from 6am until deep into the night. I still remember the flames from a show with a squadron of A10s that made a low-pass. The napalm explosions made my face hot from hundreds of meters away, a huge fireball raised in the night sky. As I have always said, every pilot, at least once in his life, must visit Oshkosh.

The planned routing.

So, if I understand correctly, Alberto wants me to accompany him on the Risen to Wisconsin. Mmm,  but which way do we actually go? I know well that the year before he delivered a Risen Superveloce to the States but he then passed through the “classic” North Atlantic route Scotland, Iceland, Greenland, Canada.

This time, however, the plans are way more ambitious: The idea is to fly the new Risen Superveloce, with a Rotax 916i without stopping to refuel, leaving from Stornoway, Scotland. Basically doing something that only the Risen Superfast can do—fly at speed beyond 300 km/h, with 20 knots of headwind consuming only an average of 18 liters (4.5 gallons) per hour.

Andrea, foreground, dons the survival suit before crossing the Atlantic.

First comments I heard were: “It is not possible.” Instead I thought: Well, let’s see if it’s really impossible. The plane is here, the two “crazy” pilots are here, for me the mission it’s already done….

We still have to do the math properly and analyze the flight data in detail, but the approximate summary is this: we left from Voghera [near Genoa, Italy] with only one straight route, landed at the Outer Hebridean islands, Scotland, to the only refuel before the second important leg.

The ocean route, directly from the Hebrides to Canada, was approximately 3300 km flown in 11 hours. As I said before, at the moment we are still gathering the data, but the average speed estimated in the various sectors for each leg, was between 165 knots (305 kph) and 200 knots (370 kph), covering a total of 4050 nautical miles (7500 km), all of this using just over 100 gallons!

The first sign of civilization after 10 hours over nothing but water.

The ocean crossing, against the wind toward the west, with an aircraft that is truly an ultralight and without stops either in Greenland or Iceland for refueling—it’s now a reality. An incredible flight has just been completed with a recreational aircraft, all this thanks to extremely efficient parameters of the plane. The secret of the Risen relies precisely on this: efficient and clean aerodynamics, like no other aircraft, which allow you to make the best use of the engine. All of this is available to pilots whether you want to break a speed record or just cruise along at 2.1 gallon an hour at speed.

The two-seat all-composite Risen has proven itself a speedster with the normally aspirated 912 and even more so with the turbocharged 915 previously fitted. With the new, more powerful Rotax 916 iS available, this is the first of the Risen to use it. This airplane will be on display at AirVenture next month.

An escort into Canada.

From the customs office in Appleton… success!

Compress Post ...

We recently reported that the newest version of the sleek, retractable-gear Risen had made a successful transatlantic crossing. From what we could piece together from outside accounts and posts on social media, it went well. But here’s a more first-person look at the crossing, from the perspective of the right seat. Andrea Venturini accompanied designer Alberto Porto on the epic journey across the pond. Here’s his account. It all started last December, with a phone call I received from Alberto Porto. At the time, I was in Australia doing a report at the Gliding World Championship for theItalianTeam. Onthephone Alberto, designer and builder of the fastest ultralight in the world (430 kph/232 knots), with the simplicity that always distinguishes him, says: ”Andrea, keep yourself free for next June, I’ll detail everything when you return to Italy.”  You can imagine my curiosity in the meantime. A few weeks later, the mystery was revealed: the Risen Superveloce with the brand new Rotax 916 iS must be brought to Oshkosh, to AirVenture, the largest and the most important aviation fair ‘of the Universe.’ I knew well what Oshkosh meant.

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Advanced Degree in Rotax-erie

By Steve Kessinger || 4 Comments

Trying not to melt in the Florida heat, students take notes. Dean Vogel (right, facing students) combines a wicked sense of humor and encyclopedic knowledge of the engine. He’s passionate about the Rotax and wants us to succeed.

Editor’s Note: This story originally appeared in KITPLANES magazine but since so much of the LSA world depends on Rotax engines, we thought this was worth a read here.

Thirteen years into my two-year SeaRey build, OspRey finally had its engine mounted. But when I signed on the dotted line for my new Rotax 914, and with little more knowledge than how to change the oil in my car, I was nervous about my abilities to maintain this expensive engine. Because of this, back in 2014, I attended a weeklong service and maintenance class at Canadian Rotax distributor Rotech Motor, Ltd. Thanks to an excellent hands-on instructor, who acted like he had all the time in the world and a bagful of instructor tricks to teach us, by the second afternoon I had dropped my skepticism and distrust of the price/power ratio of the Rotax engine and was (almost) ready to go out and get a Rotax tattoo.

But a mind is a terrible thing to waste. It was nine years later when I finally purchased, unpacked and mounted my Rotax 914, and I found myself struggling to remember the lessons from the class. Rotech was a 5-hour drive from my house but there were no classes being offered until the fall. Luckily, the Rotax Flying and Safety Club (RFSC) is an authorized Rotax training organization, and their website (www.rotaxirmt.com) maintains a list of upcoming classes and locations around the world. Ultimately, I chose Lockwood Aviation in Sebring, Florida, from whom I had purchased my engine.

The demo 912 S is all put back together and read for the next class to tear down. This must be one of the circles of hell for an engine.

Three classes are offered. Service is designed for the basics you’d want as an owner/operator to change the oil, balance the carbs (more on that later) and perform scheduled maintenance. Maintenance is where you get to tear an engine down all the way short of pulling the flywheel or splitting the case in half. The third class, a single day, is dedicated to the fuel-injected engines.

The Prep Work

A week before the class the instructor, Dean Vogel, emailed all of us links to a bunch of documentation, suggesting we familiarize ourselves with it. While I have a 914, the class documentation was all for the Rotax 912, but from the 2014 class I knew the engines were similar enough that about 95% of the material would be the same or similar. Plus when I called and registered for the class, Dean told me to prepare to stay late both days for some extra one-on-one instruction particular to my engine. The material Dean had us download was about what you’d expect: installation and parts manuals, light and heavy maintenance manuals, all stuff Dean said we’d need to take the test to pass the class. Wait, there’s a test? No one said anything about a test.

The classes are primarily designed for mechanics to get or renew their iRMT (independent Rotax Maintenance Training) certification, so recurrent training and testing is required biannually by Rotax to be listed as a certified Rotax mechanic and for access to current documentation. But the class is open to all, homebuilders and owners included. Dean recommends builders attend at least the service course, and I strongly agree with him. There’s nothing like getting excellent, in-person, hands-on instruction from a factory- trained expert to make you feel much better about what you can or can’t do with your engine.

Once On Site

You might be tempted to make the Sebring trip a working vacation by bringing the family down, but I’d advise against it because Sebring isn’t very close to Disney. However, there are several nice hotels in the area ranging up and down the luxury scale, and since it was the off-season I took advantage of an arrangement Lockwood has with the Seven Sebring Raceway Hotel, located on the seventh turn of the Sebring Raceway. It’s a short 5-minute drive or shuttle ride from Lockwood and I got a nice balcony room overlooking the racecourse at a surprisingly good rate because of this.

I had swapped emails before the class with Dean, who is a former F-15 pilot and was a key employee at Cirrus Aircraft before coming to Lockwood in 2006. In person, he appeared to be a grayed version of the Robert Patrick T-1000 in the Terminator 2 movie. A bit intimidating at first, he still has the cold, steely eyes of a fighter pilot, but I was relieved to find he had a wicked sense of humor and often punctuated classes with jokes and stories of terrible things people had done to engines in the past.

In the class, we had a wide mixture of male and female, professional and general aviation pilots, FBO mechanic/owners and mechanics sent by their schools, as well as another homebuilder like me. I felt a bit self-conscious taking the classes for the second time but Dean quickly reassured me that it was not uncommon and was a smart thing to do, reminding me that certified Rotax mechanics are required to take it every other year to stay current. He encourages builders to take the class both before and after acquiring their engines because (as I can attest) learning it on the school’s engine and then going back home and applying the knowledge to your own is a huge gulp moment.

When you consider that the price of a mistake could easily be hundreds or even thousands of dollars and at worst loss of life, the cost to come to a class is trivial. In my case, tech support is now a bit easier when I call in for help since Dean and I have now gotten to know each other and, to be honest, I’ll probably take the class again or see if I can arrange a one-on-one visit before I run it for the first time. It’s cheaper than a ruined engine.

About the Engines

Rotax engines have more in common with motorcycle technology than legacy aircraft engines. This is not better or worse, just different, which of course, pilots hate. Rotax engines are higher revving and geared (like a Continental GTSIO-520 on a Cessna 421), liquid cooled (like a P-51 Mustang’s Merlin engine) and engineered for a higher power/weight ratio. They use a hybrid cooling system, with air-cooled cylinder barrels and liquid-cooled heads. Since the heads are liquid cooled there is no need for huge cooling fins on the cylinder heads, allowing the cylinders to be closer together and the engine to have a smaller frontal section. The liquid cooling of the cylinder heads also results in a more stable thermal environment for the heads.

Gearbox inspection and maintenance is a big part of the course.

One huge advantage is that the engine is designed to run on unleaded autogas. The Rotax will tolerate some use of 100LL, or you can use a fuel additive such as Decalin RunUp to help counter the lead in avgas, but this requires more frequent engine maintenance, not an ideal situation. Rotax owners are in a better place than those with high-compression legacy engines when it comes to an alternative to 100LL fuel. In fact, for the last eight years Lockwood has been running their engines exclusively on Swift’s 94-octane unleaded fuel—and the engines reportedly love it.

Course Work

There is no way I can cover how much I learned in those four days, but I’ll try to give you some highlights. This is not a “death by PowerPoint’’ class. You’re going to get your hands on hardware from day one. Dean started off with classroom work describing the history of the engine and company. The service class is primarily a general overview of the engine and basic maintenance, things like oil changes and general troubleshooting a mechanic would see often at a flight school or as an owner, and the depth of the course is just right. While you get certified as an independent Rotax maintenance technician, the class is not designed to make you an instant expert on the engine, but instead to give you a broad familiarity with it and show you the resources to get help.

The oil system was first, and this system was one Dean emphasized heavily and often came back to all four days. While you could suffer a complete failure of the cooling system for the cylinder heads and still fly a long time without having the engine seize, the high-revving engine and gearbox literally are bathed in and live or die by a healthy oil system. The dry-sump oil system allows a lower frontal area for the engine and a more compact installation resulting in less drag. The oil system is also one of the primary areas where the engine will be affected by running on 100LL. If used on avgas more than 30% of the time, Rotax reduces the oil-change interval from 100 hours to 50. You can see from some of the photos what lead buildup does to the engine.

As the class went on we quickly got into the guts of the engine. No, you don’t need to bring safety glasses or rubber gloves to keep your hands clean, and Dean was generous with passing around parts to examine and using them to illustrate the system he was talking about, telling the story behind a broken connecting rod or dented piston and how to avoid it happening. Training is also done on a “penguin,” a flightless aircraft that had been damaged in a mishap. The engine mounted to it was also non-flyable, making it a perfect training tool for mechanics to practice on an engine that can run, but will not put lives at risk if someone makes a mistake.

One thing that made me nervous about the Rotax is “balancing” the dual carbs. The Rotax engine has sometimes been called two engines connected by a common crankshaft, and that’s one way to look at it. Each side of the engine has its own Bing carburetor. They must be “synced” or “balanced” so they run at the same rpm and manifold pressure at a given throttle setting. Making this happen was probably one of the biggest horror stories I’d been told about the engine, and Dean made sure that we knew he was going to go over the procedure backward and forward until we had it down.

The need to balance carbs is different than what we’re used to in legacy aircraft engines, but it’s one of the many differences that make the engine more efficient. The Bing carburetor has no separate mixture control; instead, in an elegantly simple design it automatically balances the fuel/air mixture as the airplane climbs or descends. Once the operation of the Bing carburetor is understood, you just shake your head at it and go neat!

The carb sync procedure alone was worth the cost of the course, and as Dean promised we went over it until we all felt comfortable with the procedure. The technique he teaches is proprietary so I won’t be able to explain it here, but I can tell you it took a lot of the anxiety away from me about the procedure. Lockwood also sells the tools to do this procedure, and mine came a few days after I got home. Lockwood also rents tools for 30 days, under the caveat “If you break it, you buy it,” reducing the outlay for mechanics to buy new tools.

Making Sparks

Engines are repaired and rebuilt in-house at Lockwood. Here a damaged engine is being torn down for diagnosis and possible repair.

Another thing different about the engine is that there are no magnetos. Instead, the engine has a large flywheel that is a combination permanent-magnet generator and charging coil, and the timing is permanently set via the position of the trigger coils located just outside of the flywheel. Spark is triggered by a capacitive discharge system, and the plugs fire on what’s called a “wasted spark” system, which means they spark on every stroke, be it a compression or exhaust/intake. This may seem counterintuitive for efficiency, but it eliminates the complexity of timing of having the plug fire every other stroke. (This is also how common electronic ignitions for legacy engines work.)

The third day, as part of the maintenance course, we started off with Dean unrolling a tarp and asking us to try not to get oil on his carpeted floor. Laying out a bunch of tools, he pointed to an engine at the front of the classroom and said, “OK, you’re going to take this apart. Who’s first?” The day was spent dissecting the engine, laying the parts out on the table and giving us an intimate look at everything we had talked and read about during the first two days of the service course, with breaks as we examined the beauty of a finely designed and machined oil pump, for instance, and discussing the strengths and weakness of a particular system.

Can you guess what we did on Day Four? Yup, we put it all back together. Because of the rather large hole in the crankcase (another engine that had been abused by an owner), we could not take the engine out and run it, but as a training tool it served its purpose. We got to examine in detail how the engine worked and while I doubt any of us were going to run right out and replace a gearbox or pull a cylinder head, it gave us a considerable insight about how the whole thing tied together.

Is the maintenance course necessary for the builder/operator? Nope. You can do just fine not knowing how to pull a gearbox or a cylinder head; in reality most builders would most likely not attempt to do this repair. However, knowing what’s going on inside the mass of gray metal gives you a solid reason why you should (or shouldn’t) do something flying your plane, and it gives us an appreciation for the precise engineering that goes into it. Every procedure is laid out in the manuals, step-by-step with torque values, specific Loctite application and even pictures.

I had debated buying the fuel-injected 912 iS for OspRey but decided not to be the test airplane for the SeaRey community and stay with the proven track of the 914 in SeaReys. So while curious about them, I didn’t stay for the class on the fuel-injected engine. The introduction of the fuel-injected 912 iS, 915 iS and now the 916 iS has many wondering how long carbureted engines will still be produced. There is still a very strong demand for the carb’d 912 and 914, and Rotax has made not a hint or whisper about discontinuing them. With over 50,000 carbureted 912/914s in use around the world they have earned their keep.

Dean Vogel. “You see this? Don’t do this!” Given his knowledge of Rotax engines, his advice should always be heeded.

One of the big questions now is how the Rotax engines are holding up. I flew a 912-equipped Katana as a CFI back in the early 1990s, so the engines have almost 30 years of being abused by students and CFIs alike, and there has been continual improvement over the years as the engines have accumulated hours, with the last major one in 2006 when the crankcase had a few design changes.  Surprisingly, few flight schools are taking their engines to TBO; instead the trend is for them to sell mid-time engines to homebuilders who are eager to snap up an inexpensive mid-life modern engine—the flight schools just buy new engines. I asked Dean how many engines overall make it to TBO, and he answered “How do you tell? The Experimental guys pay no attention to TBO, they just keep going. So we never see them unless something goes wrong. The Experimental guys who buy new engines might fly 50 hours a year. It’ll take them 40 years to get to operating TBO. I know of 1993 engines that are still going strong. It’s not like I recommend people operate that way, but I know people are doing it.”

The motors are a combination of engineering art, science, and I’m convinced maybe a schmecken of black magic; it doesn’t seem that the tight tolerances in the engines are possible in a mass-produced product but it’s true. I cut my teeth turning wrenches on warbirds and am used to slathering gasket material on, but the one time during the rebuild we did apply gasket material it was put on sparingly, just tapped on with a fingertip so you could see the aluminum through the goo—and even then some of that was squeezed out when the parts were fitted. Incredible machining.

One example of the precision in the engineering is that the piston to cylinder clearance has a tolerance of 0 to 8 ten-thousandths of an inch. That’s less than a human hair. The cylinders have a ceramic coating on the inside—that way the cylinder and the piston can be made from the same material and have the same thermal properties, making this kind of precision possible. You’d think that would make the engine high-strung and fragile, but at the end of the Rotech class when we were running the 914 demo engine, the instructor called me over and had me rapidly run the throttle full travel up and down several times, while I cringed thinking about the rapid heating/cooling effect on the cylinders and turbo. But the instructor chuckled and told us that the liquid cooling protected the head from the temperature cycle, and the engine could do this all day long with no damage.

The class is standardized around the world, so you can rest assured that you won’t miss anything by taking a class at another location closer than Lockwood. I found that taking classes from two separate schools complemented my knowledge, with each instructor and location having their own separate style and training aids. In my case, having bought the engine from Lockwood added to the reasons to take a trip to Florida.

Of course, having bought my engine from Lockwood and being a cheap pilot, I did ask if there was a discount. It’s easy to multiply X number of students by the tuition of the class and think Lockwood is making money hand over fist for a seemingly few days of Dean talking. But remember: You’re not paying for the class; you’re paying for the decades of experience Dean and the Lockwood crew have accumulated and are passing on to you. More than once Dean called me out with SeaRey-specific maintenance or installation instructions, and by the end of the course I lost track of how many potential hours of frustration and thousands of dollars in mistakes Dean saved me.

Note that this is not a “gentlemen’s course” where Dean will stomp his foot for something that will be on the open-book, take-home exam. However, he was also willing to help with the more obscure topics, telling us to wait to answer some questions if we can’t find the answer, and we’d probably hear it from his lecture before the exam. The class is not airline ground school intense, but it did remind me of what a friend of mine says about formation flying: It’s not work, but it is very, very hard play.

There’s an old saying that you get what you pay for. Airplanes are an investment of time and money, and the knowledge you get from this class will save you both in the long run. At a minimum, I think any Rotax builder/operator needs to take the service class and, if possible, hang out and do the maintenance one as well.

Oh, how did I do on the test? Well, let’s just say I passed, but I won’t be hanging out a shingle to do work on Rotaxes. What I have, though, is a license to learn.

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Editor’s Note: This story originally appeared in KITPLANES magazine but since so much of the LSA world depends on Rotax engines, we thought this was worth a read here. Thirteen years into my two-year SeaRey build, OspRey finally had its engine mounted. But when I signed on the dotted line for my new Rotax 914, and with little more knowledge than how to change the oil in my car, I was nervous about my abilities to maintain this expensive engine. Because of this, back in 2014, I attended a weeklong service and maintenance class at Canadian Rotax distributor Rotech Motor, Ltd. Thanks to an excellent hands-on instructor, who acted like he had all the time in the world and a bagful of instructor tricks to teach us, by the second afternoon I had dropped my skepticism and distrust of the price/power ratio of the Rotax engine and was (almost) ready to go out and get a Rotax tattoo.

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Buying Used: Flight Design CTs

By Mark Timney || 1 Comment

If you’ve ever shopped for a used sport plane you’ve probably noticed there are almost always a number of Flight Design CT series LSAs up for sale. This shouldn’t be surprising since Flight Design was an early player in our segment of aviation, and in the past two-plus decades the company has sold more than 400 CTs in the U.S. alone.

The planes have proven popular, in part, due to their speed (for an LSA), having a cabin wider than a Cessna 172 and their generous payloads. This article is an introduction to the various CT models, their flight characteristics, and advice for a pre-buy inspection and ownership.

Development

The first CT was produced in Germany by a company that began with hang gliders and paragliders in the 1980s and ultralights in the early 1990s. Now part of LIFT Air Gmbh, Flight Design has faced financial woes over the years, having gone into receivership, and then challenges caused by the war in Ukraine where the aircraft were being built. Money is less of an issue now and production is being done in the Czech Republic. There is a completely different company making the CTLS in China for that country’s market only, according to Tom Gutman, Jr., who imports CTs into the U.S..

There have been a number of CT models/variants over the years. The original CT flew in 1996 and was superseded by the CT2K in 2000. But as Dan Johnson has reported, it was the CTSW ”short wing” developed just after that helped Flight Design become an LSA market leader. While the CTSW proved popular, it had its critics. Flight Design responded by introducing the CTLS in 2008 to make the plane a little more forgiving and to introduce other improvements.

Around the same time, the company produced a slightly heavier and slower all-metal version for flight training, the CTMC (metal concept), and the CTLS-Lite, a lighter and reduced feature/budget model CT. Quick to follow were the CTLE, a version for law enforcement featuring a wing mounted camera, the fuel injected Rotax 912iS powered CTLSi, the CT Supralight for the European ultralight market, and the CTLS GT with a Rotax 914.

If you’re thinking that it’s going to be difficult to decide which model to buy, stop. The odds are good your choice will be limited to either a CTSW or CTLS since these models were made in the greatest numbers. This article will focus on them exclusively.

Features & Flight Characteristics

Specifications for these two CTs and the other models vary. (You can easily find them online.) You can generally expect an empty weight between 700 & 800 pounds, a stall speed between 35 and 40 knots, cruise speeds between 115 and 130 knots and a fuel capacity of 34 gallons. The CTSW is lighter and faster than the IS, but has a higher stall speed. Many models come with a ballistic parachute system. Avionics vary, with older planes sporting round gauges and later models featuring glass. Almost all of the used CTs available will have a Rotax 912ULS.

“I would look for a 2009-2010 CTLS because of the simplicity of its carbureted engine and overall build quality,” recommends Tom Peghiny, EAA Hall of Famer and the man behind the importation of CTs into the U.S. until his retirement in 2022. He says many of the planes from this period came with autopilots and glass avionics, and it’s common to find many have been upgraded over the years.

All CTs feature composite bodies, a blessing or a curse depending upon your viewpoint. (More on this later.) Flight Design uses a carbon fiber-foam-carbon fiber and Kevlar laminate over Rohacell foam for the wings and tail, and over Airex foam for the fuselage core. The LS model introduced composite landing gear.

CTs have a reputation for being challenging to land, according to several CFIs contacted for this article. Some pilots have found them difficult to slow down because of the sleek fuselage, and others have trouble with pitch control at slower speeds. These factors, combined with the springy, aluminum landing gear on earlier models, sometimes meant CTs were bounced down runways.

One advantage of the LS model is its composite landing gear, which helps soak up less than perfect landings. Another possible advantage of the LS over the SW is its slightly longer length and greater wingspan, which reportedly offer better longitudinal stability. “The LS is less squirrely than the SW at lower speeds next to the ground,” contends CFI Helen Woods, owner of Chesapeake Sport Pilot, a Maryland flight school and maintenance center that has considerable experience with Flight Design’s planes.

Review owner comments on the internet and you’ll find that all CTs require solid stick and rudder skills. The planes demand attention to maintain coordinated flight, especially the shorter winged SW. Some critics say the SW is a little too difficult to fly, but others are up for the challenge in return for increased speed and payload.

“It’s possible to teach someone to fly the SW safely,” says Woods, “but it does take specific training and pilots need to fly frequently to remain proficient.” (Those who buy new planes from Flight Design in the U.S. are required to take transition training, according to Gutman.)

Pre-purchase Inspection

Anyone buying a used aircraft should have a pre-buy inspection done by an A&P who’s familiar with Flight Design’s planes, according to Mike Ripley and Hannah Lagno, who oversee aircraft maintenance at Chesapeake Sport Pilot, LLC. They’ve both worked on numerous CTs and know what to look for during a pre-buy inspection.

“We’ve seen a lot of bent landing gear and bent rudder pedals,” said Ripley when asked about CTs and rough landings. “And the composite bodies need to be inspected for delamination, especially if the plane’s been kept outside.”

“Always check the tail area for water,” warns Lagno. “It can collect inside there and cause corrosion which can freeze the controls or, in the winter, split the composite.”

The engines on CTs should also be gone over by someone familiar with Rotaxes. As an early player in Light Sport, CTs were among the first LSAs many A&Ps ever worked on. Woods says some weren’t as knowledgeable about Rotaxes as they should have been.  “Look for specific Rotax maintenance things in the logbook—like rubber replacement and carb floats,” she suggests. “And see if all of the service bulletins have been followed.” (There have been relatively few SBs considering nearly 30 years of production.)

Maintenance & Ownership

Owners seem to be very happy with the reliability of their planes, noting easy access to parts and excellent support from Flight Design in the U.S. Some CTs have logged more than 5000 hours, according to the company.

Ripley and Lagno say concerns about the planes’ composite bodies shouldn’t automatically steer you away from them or other composite planes. They believe this type of manufacturing has come a long way in the past couple of decades, and that it is possible to make successful repairs to composite body aircraft without too much difficulty. They say keeping a CT hangered is the best way to ensure the longest lifespan of the aircraft.

The sleekness of the design made possible by composite construction, however, can occasionally make CTs a little more difficult to work on. The engine’s in a tight space, and getting to the starter, for example, isn’t as straightforward as on conventionally constructed aircraft, notes Ripley.

Peghiny says “once mastered, they are fast and really a hoot to fly.” Guttmann, who owns a CTSW, says their cabins and payload capabilities put them way ahead of other Light Sport planes. “Both my father and I are 300 pounds and 6-foot-5. There’s nothing else we can both get into and fly as comfortably,” he said.

Woods highly recommends flying any CT you’re thinking of buying before writing the check. “Be sure you’re happy with what you’re getting into,” she advises.

 

 

Compress Post ...

If you’ve ever shopped for a used sport plane you’ve probably noticed there are almost always a number of Flight Design CT series LSAs up for sale. This shouldn’t be surprising since Flight Design was an early player in our segment of aviation, and in the past two-plus decades the company has sold more than 400 CTs in the U.S. alone. The planes have proven popular, in part, due to their speed (for an LSA), having a cabin wider than a Cessna 172 and their generous payloads. This article is an introduction to the various CT models, their flight characteristics, and advice for a pre-buy inspection and ownership. Development The first CT was produced in Germany by a company that began with hang gliders and paragliders in the 1980s and ultralights in the early 1990s. Now part of LIFT Air Gmbh, Flight Design has faced financial woes over the years, having gone into receivership, and then challenges caused by the war in Ukraine where the aircraft were being built.

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MOSAIC – A Different Perspective

By Phil Solomon || 12 Comments

A lot has been written about the contents of the MOSAIC NPRM and many people and organizations have been able to comment on it to the FAA. Much of the commentary has been around the extension, or in some cases, curtailing of existing privileges for Sport Pilots, aircraft that can fit into the Light Sport definition and Light Sport Repairman certifications. I don’t plan to re-hash any of that here. This article will focus on what some of these changes could mean, in practical terms, to the market for Light Sport Aircraft and its customers. As you will see, it has the potential to be highly disruptive which not everyone will be happy about but will do so in a way that also opens up opportunities to a wider audience.

Before delving any deeper, let’s dispel the myth held by some in general aviation that Light Sport has been a “failure”. Yes, like pretty much any revolution, its first manifestations probably did not meet the hype, but it has indelibly changed the aviation landscape in positive ways for all aviators. I will briefly hit a few of these:

  • BasicMed would still be a twinkle in the eye of AOPA and others if the hard proof from Sport Pilots not dying en-masse and crashing into houses the moment their medicals expired had not provided the empirical evidence supporting the proposed relaxations.
  • Angle of attack indicators, glass panels, digital autopilots and other aids to safe flight and situational awareness came from the experimental market into the Light Sport market and proved very quickly that compulsory FAA approvals only served to delay and make less affordable, potentially lifesaving technologies.
    Major changes to Part 23 certification for small aircraft to allow them to conform with ASTM consensus standards came directly from the (largely) positive experiences from Light Sport aircraft that were being made to a consensus standard.
  • The number of pilots exercising Sport Pilot privileges far exceeds the number of Sport Pilot licenses issued because every expired medical creates a Light Sport eligible pilot. A very large percentage of pilots exercising Sport Pilot privileges fall into this category. Accident statistics clearly support the notion that expanding the range of potentially eligible planes would likely maintain Light Sport and Sport Pilot safety on the desired continuum of safety—between Experimental and fully certified.
  • As soon as BasicMed came along and had proven to be a success, the medical justification for keeping Light Sport aircraft within a somewhat arbitrary weight, equipment and performance envelope were no longer justifiable or sustainable, but it took the FAA a while to reach that same conclusion.

Having set the scene, this article is going to examine how some of these changes could play out from a fixed wing aircraft and pilot perspective.

Fate of Existing Light Sport-Eligible Aircraft

Many, but not all, of the current Light Sport specific aircraft (S-LSAs) could accommodate higher gross weights and have modifications that would give them adjustable propellers and higher speeds but there is some uncertainty as to whether this would be allowed under the final regulations and whether the current manufacturers would want/be able to make these changes. From a consumer perspective, the desirability of these options is very clear. However, some manufacturers might not have the capability to make these changes while others may see upgrades of existing planes as a detriment to future sales of new aircraft that do meet the new standards. The downside to manufacturers not giving an answer prior to the final regulations coming into effect could be a freezing of sales of current new and used aircraft. Some manufacturers have committed to providing an upgrade path for existing owners. As time moves on, we could see a divide in the market between those manufacturers who have committed and those who have either kept silent or specifically declined to offer upgrades.

Where things could become controversial, is what owners of E-LSAs (Experimental Light Sport) will, or won’t be able to do to modify their aircraft to take advantage of the expected expanded definition of a Light Sport aircraft. E-LSAs fall into two main types—those built from kits based on a model that has been shown to be S-LSA conforming and those that started life as an S-LSA but whose owners chose to re-register them as E-LSAs.

Lets say that an S-LSA manufacturer opts to provide an upgrade path to a higher useful load for its existing models, could E-LSAs that either started life as the same make and model or those built from a kit follow suit? Well, the current E-LSA regulations might suggest not, as E-LSAs must be operated in accordance with the operating limitations issued to the aircraft at the time it receives its airworthiness certification. So, you could have the strange situation where Experimental aircraft are being held to a tighter standard than the one that is being applied to a higher level of aircraft. Basically, a reversal of the FAA concept of a continuum of safety.

The NPRM does little to clarify any of this, but it would not be the first time that there has been this effective reversal of safety logic. Here’s another example.  At the present time, a fully certified aircraft under Part 23 can run over engine TBO when operating under Part 91 but an S-LSA might not be able to, depending on the whim of the aircraft manufacturer. Many of the proposed changes are considered to be beneficial to safety, such as increased weight and controllable propellers, so why would it be in the general interest of safety to create a two-tier market?

About Legacy Aircraft

Something else to consider: How might the expansion of Light Sport definitions affect existing legacy aircraft that will now fall within the Light Sport Eligible category?

Let’s start with a little history lesson. For liability reasons Cessna stopped producing light aircraft in 1986 and re-started production of the Cessna 172 in 1996 following the passage of the General Aviation Revitalization Act, making its first shipments in 1997 at a “typically equipped” price of around $136,000. Fast forward 28 years, and the US Bureau of Labor Statistics, tells us that the Consumer Price Index has increased by a factor of 1.97 times. So, if all things were equal, which they never are, the same plane would be selling at $267,920 today. It is not easy to find an exact current list price, but full retail is in the region of $650,000 or 4.8 times the 1997 price. Yes, the 2024 plane would come with an incredible suite of avionics in the form of the Garmin G1000 that would command a premium price but it has basically the same engine and airframe as before.

Here is where things get interesting. Part 23 certification can act as a two-way barrier by protecting legacy aircraft manufacturers that have amortized their investments many times over due to the ultra slow/no pace of technological advances in legacy engines while limiting new entrants to the four-seat certified market because of the costs of entry.

The Cessna 172 has effectively set the price expectation for training aircraft which has then increased the profitability and attractiveness for other companies as well such as Piper, Cirrus, Diamond and Tecnam who are able to price at similarly elevated levels due to shortage of capacity and high flight school demand. Product pricing can certainly come from a formula that starts with costs and adds a margin, but in the case of a protected market (which is what certification does) pricing can be whatever the market will bear.

MOSAIC potentially lowers both the barriers and the cost of entry for new four-seat aircraft as they can be manufactured to an agreed standard and use components that have not, themselves, had to go through very expensive certifications. With many traditional legal design burdens lifted, we can reasonably expect to see new aircraft that are lighter but potentially stronger than their legacy colleagues, full of avionics that are a fraction of the cost of the fully certified versions and with engines that are more efficient, use less expensive fuels and weigh less.

It is certainly possible that new entrants will simply follow existing pricing trends, but given volume opportunities and the need to break into a very restricted, brand-conscious market, they are more likely to seek market share through price and features. Most flight schools cannot afford brand new aircraft from any of the current market leaders because a new plane offers no discernible operating cost advantages over the same model that is 20 or more years old, and any ability to price at a premium for new versus old is negligible.

UND’s training fleet is underwritten by school tuition, something that smaller flight schools can’t bring to bear.

The new aircraft market for training aircraft is currently limited to a very few, very large flight schools who are often part of a college program so can cross subsidize through tuition fees for academic courses. New, four seat Light Sport aircraft built to the new ASTM Light Sport standards could easily be sold profitably for half of the price of a legacy aircraft while offering engines that could decimate operating costs and avionics that are at least comparable, if not better, in functionality and ease of use.

Taking the Cessna 172 as an example, this plane would now be Light Sport eligible but still constrained by certification limitations and a price that could be double that of new competition. Is that a sustainable position? Only time will tell but the legacy models could potentially be re-tooled and equipped in line with ASTM standards and relaunched as a Light Sport. This would bring certain costs down but require new investment in manufacturing practices which may leave the net costs of production unchanged but pricing at a potentially much lower level in line with new generation Light Sports.

How Will MOSAIC Influence Flight Training?

The answer is probably in multiple parts. The first, and immediate, answer is that it will boost the attraction of holding a Sport Pilot license or exercising Sport Pilot privileges. The vast majority of flight schools and rental fleets do not offer any Light Sport aircraft for rent and do not see the benefits of having multiple training options just to cater for this audience. With existing aircraft in the fleet becoming Light Sport eligible, schools could well see a fast expansion in Sport Pilot training and rentals. Existing Sport Pilots who downgraded from full private and above certifications will get rapid check outs in legacy aircraft and owners who had previously needed to sell aircraft because they did not feel comfortable with full medical renewals or BasicMed, will likely keep them. The possible downside of this could be a further restriction on the supply of affordable used aircraft as owners choose to retain them plus more people looking to rent.

Secondly, for others, the Sport Pilot license would become a more affordable and accessible option to get into flying as more airports would now have planes they could fly once they achieved their Sport Pilot Certification. However, there is a certain stigma still attached to both Light Sport Aircraft and Sport Pilots probably due to lack of understanding and some of the myths discussed above.

Thirdly, and potentially most importantly, this would be an opportunity to expand the pilot population and increase the proportion of successful completions from the 20-30% (for a Private Pilot License) highlighted in AOPA’s 2010 study to something significantly higher. With a Sport Pilot license theoretically achievable in 20 hours compared to 40 for a Private Pilot License it could and perhaps should be the starting point for all aspiring pilots. However, there are barriers to this including the current lack of Light Sport aircraft in flight schools and the need to take another written test and check ride to move up from Sport to Private. The former will change almost overnight with the publication of the final regulations following the NPRM but the latter is not impacted by MOSAIC. However, this would open up one of MOSAICS many opportunities for productive change.

At the present time the content of a Sport Pilot check ride and Private Pilot check ride is effectively the same with no difference in expected performance or maneuvers. The oral exam would have some differences concerning limitations and privileges that come with the certification. Currently a Sport Pilot could, through experience and with an instructor, gradually add-on the capabilities and training that would be required for Private Pilot privileges—3 hours of instrument training, 3 hours of night, airspace clearance, towered landings and additional solo time. Ironically, none of these “add-ons” are actually specifically tested during a second flight test for Private Pilot beyond what had already taken place under the original Sport Pilot check ride. Consequently, a Sport Pilot moving to Private Pilot is being tested twice for the same skills with the same performance requirements but having to pay for both an extra written test and flight test.

Not surprisingly, this acts as a disincentive for people to start with the more affordable and swifter option of a Sport Pilot license if their ultimate goal is to add ratings later. The obvious solution to this would be to make Sport Pilot the starting point for all aviation certifications with a formal DPE conducted check ride and then gradually move up to Private Pilot through adding endorsements with one CFI and a final endorsement from a different one, as is currently allowed for moves between Light Sport Categories. The endorsements would cover both knowledge and flight skills/experience. This would increase the number of pilots who are able to complete something and give them the incentive to continue to add skills and experience knowing that there is not another massive expense waiting for them to be able to move up. As with many aspects of the Light Sport/Sport Pilot revolution, the success of this low-risk modification could also provide data for whether non DPE instructors can be relied upon to safely transition these pilots.

In conclusion, MOSAIC is going to have a major positive effect on aviation accessibility and affordability but not just because of the obvious changes but also from its direct consequences on related matters that might not, at first sight, even be in play.

Compress Post ...

A lot has been written about the contents of the MOSAIC NPRM and many people and organizations have been able to comment on it to the FAA. Much of the commentary has been around the extension, or in some cases, curtailing of existing privileges for Sport Pilots, aircraft that can fit into the Light Sport definition and Light Sport Repairman certifications. I don’t plan to re-hash any of that here. This article will focus on what some of these changes could mean, in practical terms, to the market for Light Sport Aircraft and its customers. As you will see, it has the potential to be highly disruptive which not everyone will be happy about but will do so in a way that also opens up opportunities to a wider audience. Before delving any deeper, let’s dispel the myth held by some in general aviation that Light Sport has been a “failure”.

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“Icon in Flat Spin,” UK’s Flyer Reported — Here’s the Latest

By Dan Johnson || Leave a Comment

Icon Aircraft, creator of the A5 LSA seaplane, is in the spotlight again as bankruptcy proceedings finally come to a close.

Short story: Icon will continue making aircraft, after the bankruptcy heard from a new buyer — not the buyer mentioned before in this recent article. The court sought a change in ownership and an effort to grapple with a large amount of debt.

From beginning (in April 2024) to an end in mid-June, this proceeding moved very swiftly. Here’s the final settlement.

“Icon In a Flat Spin
as Bankruptcy Looms”

Earlier in the day on June 18th, 2024…

Britain’s Flyer magazine reported online that Icon found a buyer but not the one mentioned in the prior link.

“Buy an aircraft manufacturer with a certified product and also selling in the Light-Sport Aircraft class for, what? …£100 million? Try again and aim low: just over £12m ($15.3 million),” wrote Flyer staff.

The UK magazine reported that was the winning bid for the assets of Icon but continue reading.

“£134m ($170m) worth of debt was written off during the bankruptcy case for Icon Aircraft when it came before Judge Craig Goldblatt in Delaware last week,” wrote Flyer.

Earlier, a Chinese buyer was going to absorb the prior debt while paying slightly less for the company. The supposed Chinese buyer never explained how they would earn such a large amount to cover that debt service.

“The winning bid came from a unit of 160-year-old German textile machinery producer Dürkopp Adler. Hang on… why would a manufacturer of textiles want an amphibious aircraft maker? It’s a complicated story,” continued Flyer. 

Dürkopp Adler Group describes itself as “a global innovation and technology leader in the field of industrial sewing. We develop, produce and sell high-quality sewing machines and equipment.”

ByDanJohnson.com readers will already know the prior Chinese buyer was also a sewing machine producer. Do you find it odd that two sewing machine companies would vie for Icon? Here’s more…

“Icon Aircraft had already selected SG Investment America Inc. as the stalking horse bidder – the back-up in case of no better bids,” wrote Flyer.

“However, SG Investment is a newly formed subsidiary of Dürkopp Adler GmbH, now owned by ShangGong Group based in Shanghai, China, which also makes sewing machines.” So… these two companies are already affiliated.

Flyer reported the opposition, “According to Law360, a legal reports website, a group of Icon investors — including former directors, officers and founders and other equity holders — filed legal claims against the company’s Chinese majority shareholder in the bankruptcy court, urging it to halt the company’s proposed sale. The group said the stalking horse bidder is indirectly controlled by the debtor’s current majority holder.

“The group of equity holders had asked the court to evaluate what they called ‘insider relationships in play,’ said Law360.

“They alleged that the majority shareholder, Shanghai Pudong Science and Technology Investment Co. Ltd., which has been the controlling equity holder of Icon since 2017, seized control of the management, operated the company as its own property, and systematically dismantled it to expropriate Icon’s intellectual property to China.

“In other words,” Flyer summarized, “Icon has been bought for a song from its main shareholder, writing off its debts in the process and ending up with the intellectual property of the aircraft producer. The Delaware court is due to approve – or not – the deal this week.”

It Is Done

Later in the day,  a headline said, “Icon’s Chapter 11 Sale Cleared With Higher Price”

Law360 (paywall) reporter, Vince Sullivan wrote later in the afternoon of June 18, 2024, “Light-Sport Aircraft producer Icon received a Delaware bankruptcy court’s approval Tuesday for a nearly $15.8 million sale of its assets after securing an agreement to increase the price by $250,000, just hours before a hearing on the transaction.”

So settles another chapter in the exiting life and times of Icon Aircraft and their handsome A5 LSA seaplane.

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Icon Aircraft, creator of the A5 LSA seaplane, is in the spotlight again as bankruptcy proceedings finally come to a close. Short story: Icon will continue making aircraft, after the bankruptcy heard from a new buyer — not the buyer mentioned before in this recent article. The court sought a change in ownership and an effort to grapple with a large amount of debt. From beginning (in April 2024) to an end in mid-June, this proceeding moved very swiftly. Here’s the final settlement. “Icon In a Flat Spin as Bankruptcy Looms” Earlier in the day on June 18th, 2024… Britain’s Flyer magazine reported online that Icon found a buyer but not the one mentioned in the prior link. “Buy an aircraft manufacturer with a certified product and also selling in the Light-Sport Aircraft class for, what? …£100 million? Try again and aim low: just over £12m ($15.3 million),” wrote Flyer staff.

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Risen Completes Transatlantic Leg

By Marc Cook || 5 Comments

On June 14, a Porto Aviation’s Risen completed the transatlantic leg of its journey from Milan, Italy, to Oshkosh, Wisconsin. The company posted on social media: “We made it!!! I have been reluctant to post anything here before accomplishing this epic flight , being Italian I guess makes me more superstitious.A page in aviation history has been written by Alberto Porto and Andrea Florence (Venturini). 1900 nautical miles, average speed [of] 165 kts, with just over 43 gallons of fuel!!! We left this morning early in rainy Scotland and landed in the afternoon at Goose Bay the same day without refueling.”

The company announced its cross-the-pond plans this May to bring the newly re-engined Risen to the U.S. While many versions of the retractable-gear Risen use the Rotax 912, the company had been fitting the turbocharged 915 iS. But this example has the newer, more powerful Rotax 916 iS. The turbo Risen normally carries around 32 gallons of gas (120 liters) but this example has longer-range integrated tanks with 50 gallons’ capacity; Porto and Florence did not carry special auxiliary fuel tanks.

The total distance is more than 5100 nm from Milan to AirVenture, but the Risen seen here has only 1200 nm to go, all of it with land beneath the slender, efficient wings.

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On June 14, a Porto Aviation’s Risen completed the transatlantic leg of its journey from Milan, Italy, to Oshkosh, Wisconsin. The company posted on social media: “We made it!!! I have been reluctant to post anything here before accomplishing this epic flight , being Italian I guess makes me more superstitious.A page in aviation history has been written by Alberto Porto and Andrea Florence (Venturini). 1900 nautical miles, average speed [of] 165 kts, with just over 43 gallons of fuel!!! We left this morning early in rainy Scotland and landed in the afternoon at Goose Bay the same day without refueling.” The company announced its cross-the-pond plans this May to bring the newly re-engined Risen to the U.S. While many versions of the retractable-gear Risen use the Rotax 912, the company had been fitting the turbocharged 915 iS. But this example has the newer, more powerful Rotax 916 iS.

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Grassroots Success Story — Dunnellon’s X35 Attracts New, Younger Aviation Businesses

By Dan Johnson || 1 Comment

If I’ve heard one lament repeatedly over a long career, it is that current pilots don’t see enough new pilots coming into aviation. Are you one who worries a little or a lot about that? If not, you are a rare pilot.

Marion County Airport attracts a wide variety of aircraft.

Is it any wonder, though? The price of aircraft is way, way up. This applies to used aircraft and new — just like it does with your groceries or gasoline. The cost of maintenance is high and rising. Insurance is very expensive (for airplanes as well as cars or houses). Hangars are unavailable with years-long waiting lists at many airports.

More than ever it can seem, aviation is an activity for those with fairly thick wallets. The squeeze on modest budgets has rarely been this demanding.

Marion Main Men — X35 airport is managed by Mike Grawe (L), supported by industry experts Troy Townsend and Roy Beisswenger (R).

Yeah, all that, but this website nonetheless discovers the affordable end of aviation. In that pursuit, I was drawn to an airport with an encouraging twist on the affordability squeeze play.

This story is about an airport but it focuses on affordable aviation and the aircraft serving that market.

Dunnellon’s X35
Marion County Airport

Have you ever heard of Ocala, Florida in the central-northwestern portion of the state? If you aren’t into horses, maybe not. If you are, you probably know this area bills itself as the “Horse Capital of the World.” Drive around Ocala, in town, or by handsome country estates and you’ll notice this is quite the affluent area.

Dunnellon is in Marion County, not Ocala but the close proximity helps both. Under airport manager (and pilot) Mike Grawe‘s leadership through the last six years, X35 has become a thriving facility with energetic new businesses sprouting up.

What may be most important is the presence of new, younger businessmen entering affordable aviation. People like me with decades of experience fill a useful role but we’re like disappearing airline captains. We’ll be moving on and entry-level aviation needs fresh blood. X35 put out the welcome mat… and it’s working.

Placid Lassie takes on fuel at X35.

Led by Mike, Marion County Airport, X35 is backed up with some local OG (“Old Guy”) talent. First, I’ll mention that Mike has engineered the construction of 40 new T-hangars. Although he still has a waiting list, those new quarters did two things: they relieved the prior need somewhat, and they provided a drawing card to new enterprises. An airport on the move is an attraction and Mike has the engine running.

Mike and I talked briefly about hangar challenges. I’ve visited more airports than I can remember. Management at every single one said essentially the same thing, “If we could get (insert main need here), we could fill more hangar requests.” Most airports have plenty of square area but permitting and financing on leased land presents major challenges. Constructions costs have risen sharply so hangar owners must charge substantial rent to recover investments.

Troy Townsend shows off his RV-10 project. His Icarus C42 is in the background.

Mike can be rightly proud of his new T-hangars and this impetus has attracted more enterprises who want to be part of something happening. Some of the talent surrounding Mike Grawe has been around longer. Others are new. All are supportive.

Airfield entrepreneur, Troy Townsend, while not old is certainly one of the original OGs at X35. He became well known working for ITEC, the enterprise that created the Maverick flying dune buggy for use in their South American missionary work. Maverick was a rough and tumble ground vehicle that could hoist a large powered parachute wing up high on a long mast allowing it to launch from a surprisingly short field. As a dune buggy, it scooted energetically.

Since his Maverick days, Troy has built his Pilot Examiner business, FliteChek.com, especially catering to the Light-Sport and light kit crowd in America’s southeast employing his deep knowledge of this segment. He flies an Icarus C42 (Germany’s most popular light trainer), which he uses to help Sport Pilots, Privates, and beyond earn their FAA certificate. Oh, and on the side, he’s building an RV-10 kit, an aircraft with which he is also very familiar. I could fill an entire article with his exploits but this gives a taste.

Roy Beisswenger poses by his growing fleet of flight training aircraft housed at X35. He also occupies a corner office in the airport terminal building where he produces video and books.

Roy Beisswenger is another highly accomplished light aviation entrepreneur who gravitated to Dunnellon and X35 as he searched for an ideal place to operate his powered parachute flight training enterprise during fall, winter, and spring — in the summer months Roy operates from the Greenville, Illinois airport. After designing a soup-to-nuts professional training system and having literally written the Bible of powered parachuting, EasyFlight is the country’s leading provider of PPC instruction.

At X35, Roy Beisswenger’s EasyFlight consulted on testing for SkyRunner’s PPC.

That’s what Roy is doing now but what preceded that would take two or three articles to cover. Among them: Ultralight Radio, a very early online news outlet; Powered Sport Flying magazine for the rest of light aviation; his leadership at U.S. Ultralight Association and Light Aircraft Manufacturer’s Association; a growing YouTube channel. I’m getting tired typing all this yet I’m only skimming the surface.

Troy and Roy make a solid backup to Mike Grawe’s management. Yet… now they have more.

Welcome, Newbies
…the Aircraft Producers

As I wrote earlier, Randy Dorsey has brought back to Florida an iconic aircraft sought after around the world for its very particular flight qualities. Randy purchased the rights and tooling to Dragonfly, an affordably priced LSA or kit specially built to tow hang gliders but which is enormously fun to fly around for low-and-slow aerial sightseeing.

Randy has taken over an existing operation, is preserving the originator’s names BaileyMoyesDragonfly and he’s getting the supply line geared up for new production at Marion County Airport. He may start deliveries later this year but parts to existing owners are a present priority, a mission dear to most of the 150 Dragonfly owners/operators.

A little further down the development timeline will come Nick and Charlotte Jones SkyKicker Aviation operation. This is a brand-new business (see recent article) by new entrepreneurs, a husband and wife who bring solid experience to the task. Nick and Charlotte are setting up to build the former Belite Chipper 2, originally created by James Weibe.

Screenshot

James had created strong interest for his Chipper project but a fire took him out of the game. Nick and Charlotte rescued this design after being drawn to it in one of those I-liked-the-product-so-much-I-bought-the-whole-company stories. They are currently improving the builder manuals and working to simplify the kit-building effort as much as possible while they renew relations with James’ former suppliers.

These two new businesses join the veterans at X35 adding to the success Mike Grawe has been building.

Central-northwestern Florida and its fancy equestrian ranches exist alongside a vibrant X35 airport that is attracting new businesses and fresh faces. I think this is worth celebrating and I trust you agree.

Compress Post ...

If I’ve heard one lament repeatedly over a long career, it is that current pilots don’t see enough new pilots coming into aviation. Are you one who worries a little or a lot about that? If not, you are a rare pilot. Is it any wonder, though? The price of aircraft is way, way up. This applies to used aircraft and new — just like it does with your groceries or gasoline. The cost of maintenance is high and rising. Insurance is very expensive (for airplanes as well as cars or houses). Hangars are unavailable with years-long waiting lists at many airports. More than ever it can seem, aviation is an activity for those with fairly thick wallets. The squeeze on modest budgets has rarely been this demanding. Yeah, all that, but this website nonetheless discovers the affordable end of aviation. In that pursuit, I was drawn to an airport with an encouraging twist on the affordability squeeze play.

Expand Post ...

Hot-Rodded Rotaxes? That’s What Edge Performance Is All About

By Eric Stewart || 3 Comments

Editor’s Note: Recent commentary on the future of Rotax engines brought out a few comments that high-spec versions of the 900-series engines already exist, just in the aftermarket. For a deeper dive into the topic, here’s a story that ran in early 2023 in KITPLANES from Eric Stewart, a regular contributor to that magazine. Prices for Edge’s modified engines run from 26,000 Euro for the 108-hp EP912i to 45,000 Euro for the 180-hp EP917Ti.

Edge Performance of Notodden, Norway, has been around for little more than a decade, but their EFI and Rotax upgrades have quickly become popular, setting a high bar with race-quality components. I’ll be putting the EP912sti in the SR-1 race plane—not only does it have exceptional power to weight (important given the 661-pound weight limit for the SR-1’s record category), but racers go best when it’s hot and high—and the EP912STi’s turbo ensures we can still make power in those conditions. Wanting to know more about the engine I was buying, I recently traveled to Notodden (a 90-minute drive west of Oslo) to learn more about the company’s background and processes.

Thomas Hauklien installs a cylinder head on a Rotax 900-series engine.

Edge CEO and founder Thomas Hauklien has a long history with both Experimental aircraft and engine modification. He’s been an engineer for 15 years, having graduated with an electro-mechanical degree. His first plane was a RANS S-5 with a Rotax 503 two-stroke that he flew for about a year and a half. “I got to overhaul that engine. It seized up on me like most two-strokes.” This was followed by a Kitfox Model 4 he restored and flew for a couple of years with a Jabiru 2200 that he’d converted to a turbo. “That was kind of stretching it at the time, no one had ever done anything like that.”

This was followed by a Sonex with an AeroVee that Hauklien bought from the U.S., followed by another Sonex that he built himself. “Coming from a racing background, it bothered me that the engine produced too little power. So the first thing I did was get bigger-bore cylinders, bigger pistons, ported the heads and did regular tuning stuff to get a bit more horsepower.” This was followed by fuel injection and, finally, a turbo.

Appreciating that he’d pushed the Volkswagen-based engine too far—making a claimed 120–140 hp—Hauklien’s next step was to acquire an at-TBO Rotax 912. “Doing a full turbo and fuel injection for that one as well was only natural,” he says. Friends who were struggling with notoriously finicky Rotax carbs started to ask Hauklien to retrofit their engines as well, and from there word spread. In 2010 Edge attended AERO Friedrichshafen (think of it as Europe’s version of Oshkosh), “and that is when it really started to kick off,” says Hauklien.

Hauklien welding the crank for an EP912STi conversion

“We got a lot of exposure [at Friedrichshafen]. At the time neither Rotax nor any of the other major brands were offering fuel-injected engines, so understandably enough there was a lot of skepticism among pilots. My argument was always if you go to the auto dealer today and buy a new car, would you have it fuel injected or would you want carbs that you have to maintain? The answer is simple. The next obvious question is how often does your car break down on the highway because the fuel injection system fails? It’s next to none. A lot of people approached us and said the Rotax has redundant dual ignition, and it has dual redundant fueling because it has two carburetors. Well clearly that isn’t the case. Basically you end up with double the risk of getting a carburetor failure and engine out because you have two carburetors, which both need to function perfectly in order to have an operating engine. If you lose one injector, it will still run on three cylinders. It will vibrate but you will maintain altitude. But if you lose one carburetor you lose one cylinder bank,” or half the engine, he says. Plus, injection eliminates the possibility of carb icing.

A Menu of Mods

Edge has clearly gone beyond just fitting fuel injection to Rotaxes. The table on Page 52 shows Edge’s available kits and upgrades, starting with straightforward big bore/EFI kits up through highly experimental mega-hp conversions of 1000cc motorcycle engines. (Note that although EP’s conversions start with a factory-new Rotax engine, its mods void any Rotax warranty and Rotax no longer considers these engines as Rotax.) The common thread among Edge’s engines is a conversion to its EFI, substitution of the intake/throttle body and for the relevant models, a turbo upgrade. The invisible part of the upgrade though is equally important: tuning.

“We have our own optimized intake and induction system that has been flow optimized, trying different runner diameters and lengths,” says Hauklien. “Inside the plenum the velocity stacks use a trumpet mouth to accelerate the airflow and keep it laminar, all of which has been meticulously tested on the dyno. But it’s always a compromise with tuning, regardless if it’s header or intake tuning. So rather than just focusing on making peak power, which is easy, we’ve always tried to focus on the rpm range where the engine typically operates. This is also really evident in dyno testing: We took a stock 100-hp carbureted 912 and it made 100.2 hp on our dyno. We then bolted on our intake and EFI system and it made almost 109 hp. With carburetors you have the venturi, so you get a pressure drop. But running EFI with a shaftless throttle body, we have no pressure loss whatsoever,” he says.

Here to Stay

Hauklien says that to date EP has sold approximately 300 engines, 2500 fuel injection kits, 300 big bore kits and approximately 30 EPeX Yamaha conversions (with North American dealer Jason Busat of BadAss PowerSports having assembled a handful of Epexes as well). Clearly, the company is expanding (they added their fourth employee in June), but it’s still relatively young and it’s not unreasonable to ask if they’ll be around in another 10 years to support these custom engines.

Hauklien preps the engine for dyno testing in Edge’s SuperFlow test cell.

On the other side of the dyno: The left screen monitors engine parameters while the screen to the right is where Hauklien inputs changes to the programmable ECU map.

So where does Hauklien see the company heading? “If we can make it faster, stronger, lighter, we’ll continue to do so. The big question mark is the electrification of aviation in the future,” he says. “What is that going to do to our existing market? There are 60,000–80,000 Rotax engines flying worldwide, and they’ll continue to do so for decades. It’s not like people are going to throw out mid-time engines and replace them with factory fuel-injected engines, because they are getting so expensive now that it makes more sense to retrofit a fuel injection kit even if it’s a midlife engine. So I think there is a huge aftermarket for decades ahead for us.”

While support is important to customers and a steady business in core modifications is key, that’s not all that Hauklien is about. “What drives me now and motivates me to come to work in the morning is working on the R&D projects. We’ve done one-off helicopter engines, gyrocopter engines and UAV engines. I’m really dedicated to working on R&D and the engineering side of things. Hopefully as we continue to grow with increased staff, I can step back and spend more time on what I enjoy doing, which is development, improvements, testing.”

When asked if Edge was married to the Rotax core, Hauklien pointed out that for him, it’s the only engine that makes sense to be modifying or
servicing. Edge offered turbo kits for the Jabiru four- and six-cylinder engines but discontinued them due to anemic demand (though he still stocks parts to service existing customers). There are only a couple of ULPower engines in Norway, and Hauklien doubts that there’s much he could offer on an engine that is already EFI and has a turbo version as well. Yes there is a decent market in EFI retrofits on conventional, large-displacement aircraft engines, but he sees SDS and FlyEFII (for which Edge is a European reseller) as already doing a good job supporting that market.

One Big Question

So let’s get to the elephant in the living room: How does Rotax feel about Edge modifying their engines? “We get asked that a lot,” laughs Hauklien. “It’s a funny story. Until three or four years ago, we had a quite intense relationship with Rotax. They obviously didn’t fancy what we were doing because they were obviously afraid of us hurting their brand and reputation for reliable engines with our modifications, which is understandable. What was funny, though, was that every time we went to an exhibition the Rotax salespersons would give us the most intense stares. Meanwhile the young engineers from Rotax came by and really appreciated the work we had put into the engine. They would say, ‘Why didn’t we think of this, what clever solutions!’ That was always fun for us to watch. I think Rotax just got fed up with all the local NTSBs approaching them who would say, ‘We have a Rotax engine with this serial number and there was a crash, it had an engine failure, we need you to investigate it, we need a statement from BRP [parent company Bombardier].’ And obviously as soon as Rotax got pictures from the site or the wreckage, they could see that it was a modified engine.”

The solution was straightforward. “Eventually what we agreed with Rotax in order to buy engines and parts unrestrained was that we remove any part from the engine that clearly states Rotax, like the valve covers and the Rotax serial number plate, and we install our own plates,” continues Hauklien. “However, we do maintain the original Rotax serial number so that the owner is able to follow up in terms of service bulletins. That took out the headache from Rotax if ever there were an accident. I’m not sure if they really like what we are doing, but it’s gotten to the point where we’ve gotten so much recognition and proven that we can make stuff reliable.”

Which raises the question: Why doesn’t Rotax just make these improvements themselves? “Well, they kind of have,” says Hauklien, pointing to the 912 iS and 915 iS. “But it probably doesn’t make sense for them financially to make retrofit kits. I think it has a lot to do with cost. It is directly comparable with the automotive industry. Making high-performance racing parts is tedious, time-consuming and expensive. It is exactly what OEM manufacturers want to avoid.”

Interestingly, even though Edge is not an official Rotax dealer, they receive discounts, support and training from the Rotax dealer in northern Europe. Hauklien ventures that they are one of Rotax’s biggest customers. He sees this as beneficial, since it gives Edge the freedom to work on engines as they see best. And he sees an advantage for Rotax as well. “Because we acquire a new engine from Rotax and modify it, it’s not like they are losing out on sales. We are in a way beneficial to them. From Rotax’s perspective, they get a sale but they get to take out liability, because we are carrying the liability now, it’s an Edge Performance engine. So that is an easy-money, trouble-free, no-liability sale [for them].”

Beyond the Mods

The Edge workshop accommodates engine mods and other maintenance.

It should be noted that engine modifications are only half of Edge’s business. They also perform annual inspections, maintenance and repairs for European ultralights (a category akin to Experimental in the U.S.), teardowns and overhauls of Rotax engines, and are resellers for a number of European brands such as Shark.Aero, TL-Ultralight, Eurofox and Zlin. They are also authorized dealers for Garmin avionics, Beringer wheels/brakes, and quite a few propeller brands including Airmaster, Woodcomp, Duc and Noah. “We do everything. It’s not Aircraft Spruce, exactly, but we are the only ones who keep those parts in stock here in Norway,” says Hauklien.

Even with the growing success of his business, Hauklien remains an avid pilot. The Sonex was followed by a 200-knot Shark, a glider license, an instructor’s license for both gliders and ultralights as well as multiple other ratings. Since those humble RANS S-5 beginnings in 2006, Hauklien has racked up 3500 hours of flight time in all manner of aircraft. He was Norway’s aerobatic Sportsman national champ in 2019 and just won the 2022 Intermediate national championship flying the Extra 300; his current ride is an RV-4 with inverted oil. Hauklien is also building an Experimental Norden Cub with the 300-hp EPeX300Ti and also has on order a Shark Turbo to be powered by his EP912STi. Which is all to say that Hauklien is not just an engine builder, he is an avid pilot who flies—and test flies—behind the engines he’s built.

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Editor’s Note: Recent commentary on the future of Rotax engines brought out a few comments that high-spec versions of the 900-series engines already exist, just in the aftermarket. For a deeper dive into the topic, here’s a story that ran in early 2023 in KITPLANES from Eric Stewart, a regular contributor to that magazine. Prices for Edge’s modified engines run from 26,000 Euro for the 108-hp EP912i to 45,000 Euro for the 180-hp EP917Ti. Edge Performance of Notodden, Norway, has been around for little more than a decade, but their EFI and Rotax upgrades have quickly become popular, setting a high bar with race-quality components. I’ll be putting the EP912sti in the SR-1 race plane—not only does it have exceptional power to weight (important given the 661-pound weight limit for the SR-1’s record category), but racers go best when it’s hot and high—and the EP912STi’s turbo ensures we can still make power in those conditions.

Expand Post ...

Checking in With Sonex’s Mark Schaible — Update on the High Wing and Will it Be a MOSAIC Design?

By Marc Cook || Leave a Comment

Light Sport enthusiasts who appreciate light, simple, inexpensive airplanes have been watching Sonex Aircraft develop the High Wing model for a couple of years now. It’ll first come out as an Experimental/Amateur-Built version but the company is very much open to considering an E-LSA and even, with some outside help, an S-LSA version. (Or whatever we’re going to call that once MOSAIC is real.)

Company owner Mark Schaible joins us to talk about the airplane’s gestation and expectations for performance and when it might fly. Hint: You’ll be able to see a cabin mockup at AirVenture this year at the least. In general, Sonex is hoping for performance similar to the low-wing Sonex designs and will be building the first example as a taildragger with a 130-hp ULPower engine. Schaible also discusses changes to the design now that MOSAIC is closer to reality. Expanded Sport Pilot rules could allow Sonex to give the High Wing a gross weight above the current 1320-pound maximum for LSA.

By expanding the max-weight envelope, Schaible hopes that the High Wing will have even better useful load and will be a better option for those owners and builders who inevitably want more stuff in the airplane that ultimately adds weight.

Compress Post ...

Light Sport enthusiasts who appreciate light, simple, inexpensive airplanes have been watching Sonex Aircraft develop the High Wing model for a couple of years now. It’ll first come out as an Experimental/Amateur-Built version but the company is very much open to considering an E-LSA and even, with some outside help, an S-LSA version. (Or whatever we’re going to call that once MOSAIC is real.) Company owner Mark Schaible joins us to talk about the airplane’s gestation and expectations for performance and when it might fly. Hint: You’ll be able to see a cabin mockup at AirVenture this year at the least. In general, Sonex is hoping for performance similar to the low-wing Sonex designs and will be building the first example as a taildragger with a 130-hp ULPower engine. Schaible also discusses changes to the design now that MOSAIC is closer to reality. Expanded Sport Pilot rules could allow Sonex to give the High Wing a gross weight above the current 1320-pound maximum for LSA.

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Building the Affordaplane, Part 2

By Jon Croke || Leave a Comment

The front fuselage with the landing gear mounted.

In a previous post,  introduced our video project for building the Affordaplane. To review, this is the plans-only project I demonstrated on YouTube for building an ultralight from raw materials. (You’ll find this free 50-part series here.)

My objective was to build an “FAA-legal” ultralight using approved aircraft materials and techniques. This month, I will review some of the challenges encountered while building. My approach on making these videos was to show and explain to first-time builders how to take a set of plans and translate them into a series of steps for completing the project.

From a construction standpoint this ultralight design is quite unusual in some ways and very traditional in others. The designer, Dave Edwards, had a goal of making sure the aircraft could be built by an amateur with common shop tools and readily available materials. Most of the aircraft is made from round and square 6061-T6 aluminum tubing. The square tubing is used primarily for the fuselage; the round tubing is used for the wings and other flight surfaces.

Weighing the fuel tank before installation.

The fuselage is unique in appearance as it resembles a ladder turned on its side. Yes, it is a thin, flat fuselage that the pilot straddles while sitting in an attached seat. The fuselage is fashioned from a dozen various lengths of 2-inch square aluminum tubes. These straight, square tubes are joined to one another by ⅛-inch-thick aluminum gussets attached on each side of the ends where they connect to the next tube. A set of AN-4 bolts pass through each “sandwich” of tube and gussets on either side to hold them tightly together. The construction skills needed to build this fuselage consist of cutting the square tubes to proper length, along with using a band saw to shape the gussets to match the full-size templates included in the plans. As holes need to be carefully drilled through the gussets and square tubing for the AN bolts, I show a technique for match drilling these items so that everything lines up when finished. You should get the idea that there are no difficult tasks required—just some easy techniques and careful use of drills and saws.

Due to the two-dimensional ladder-type fuselage design, there can be enormous stress developed at each square tube and gusset junction. These in-flight stresses include tension, shear and twisting (torsion) between the connected tubes. The AN-4 bolts that hold these joints together provide more than enough strength to do the job. A problem that arose was that many builders inquired about substituting the AN bolts with rivets, and others wanted to just weld the gussets to the tube! It is reasonable and encouraging that builders question construction alternatives—maybe for saving weight or cost. However, I felt it was my job as a teacher to address these desires by new builders to divert from the plans so that the aircraft can remain safe and strong, as well as communicating the reasons for these decisions.

The tail end of the fuselage braced with diagonal tubes .

One of the Facebook forums used for information about the Affordaplane seems to entertain modifications to the plans. (I refuse to participate in this forum.) On repeated posts, “professional” welders explain how their welding expertise and industry experience results in an aluminum welded joint that is superior in strength compared to using AN bolts as depicted in the plans. Forum moderators have tried to explain that eliminating the bolts, regardless of how perfect a weld might be, will drastically reduce the joint strength that comes from the side-to-side load transfer that the bolts provide with their clamping strength on each side of the tube.

Simple, wire-braced landing gear with nylon wheels.

The same issue is found with substituting rivets. While most builders can understand this and respect the decision to never weld or rivet, others are vocal about not agreeing and telling the community that they know better. My concern about this forum is that future new builders will read these comments made by “professional” welders and believe that it is OK to skip the bolts. It is certainly OK to experiment with your own butt on the line, but giving life to the idea that this might work well for others is not something I want my project to be associated with! This is the nature of public forums. But when it comes to building airplanes, we should take special effort to guard the facts that ensure safety. Remember—ultralights do not get inspected by the FAA. This places a huge responsibility on the builder.

The desire to eliminate AN bolts is just one example of the many requests to modify the Affordaplane design on this forum. I am genuinely surprised at how often the topics of changing things come up—everything from making the wings longer for better performance to adding reinforcements to make the landing gear “better.” It seems like a full-time job for the moderators to explain that it is best to build the plane properly first before changing things!

Learning to respect the plans while building an aircraft seems to identify which builders will have a future for more complex aircraft projects. Desiring to make changes and questioning a design is a hallmark of Experimental aviation, but only when done responsibly by way of researching known principles first and then testing.

Some components of this design are left to the builder. For example, the pilot seat, wheels and gas tank are to be of the builder’s choosing. It is in selecting these items where too much weight can creep into the final project. Take, for example, the wheels. We know the weight and size can vary widely. I made some choices that I thought would provide a good compromise. You cannot know in advance if your choices will bust the 254-pound final weight limit. I did weigh each of these “optional” components for later reference in case I needed to choose something lighter.

The tailwheel spring is from a small utility trailer.

With the fuselage on its wheels, it was now time to construct the tail section along with the wings. Lots of round tubes of various diameters are used for these assemblies. However, these tubes need to be bent into shape following templates drawn on the table. We will discuss this building process in our next installment. Here, stainless steel rivets will now be our main choice of fastener. Plane and Simple! J

Compress Post ...

In a previous post,  introduced our video project for building the Affordaplane. To review, this is the plans-only project I demonstrated on YouTube for building an ultralight from raw materials. (You’ll find this free 50-part series here.) My objective was to build an “FAA-legal” ultralight using approved aircraft materials and techniques. This month, I will review some of the challenges encountered while building. My approach on making these videos was to show and explain to first-time builders how to take a set of plans and translate them into a series of steps for completing the project. From a construction standpoint this ultralight design is quite unusual in some ways and very traditional in others. The designer, Dave Edwards, had a goal of making sure the aircraft could be built by an amateur with common shop tools and readily available materials.

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A Seaplane You Can Afford; Aero Adventure Begins a New Chapter for the Aventura Line

By Dan Johnson || 2 Comments

Here’s the backdrop of today’s update on the LSA seaplane sector as summer approaches.

According to Law360, an online legal news source, “Light-Sport Aircraft manufacturer Icon Aircraft filed for Chapter 11 protection in Delaware bankruptcy court with more than $170 million in debt and plans for an asset sale and liquidation.” You may have read (here) that Icon got an initial offer of $13.5 million. As an industry contact told me for the earlier report, “That would hardly make a dent in their liabilities.” The person was right, it appears. A proposed new buyer referenced in the earlier article agreed to take on Icon’s debt but the sales must still go through an auction process, I was told.

OK, let’s come back to Earth… or water perhaps …or either. Aero Adventure continues to fly as it has for three decades (though management has changed at least three times over the period). For a tiny fraction of $13.5 million, much less $170 million, Aero Adventure has built a line of aircraft, including kit versions and an SLSA version. They’ve also offered the S-17 with (for that time) extraordinary horsepower.

Looking to the Global South

Recently editor Marc Cook offered news from Aero Adventure. His article spoke to new leadership but couldn’t go into much detail as little was provided. I reached out to  Alex Rolinski to fill in some blanks. He was traveling but we spoke a few days later.

The Big News — Aero Adventure is moving all production of the Aventura line to Brazil. If that sounds like a rather big move somewhat out of the blue, it’s really not.

As part of Aero Affinity — a group including several different enterprises in light aviation — one of the founding partners was Montaer Aircraft USA representing the MC series from Brazil. Aero Adventure, now in the business several decades, has made contact with people in many countries and found fertile ground in Brazil.

Alex Rolinski has been the leader of Aero Adventure for more than a decade; photo taken in 2013.

The country has been deep in aviation for many decades so it has a supply of experienced workers, engineers, and aviation-grade suppliers who work for less dollars than their counterparts in America. The so-called “global south” is rising in most standards but wages and salaries lag behind Europe or the USA. Aero Adventure is merely taking advantage of this asymmetry.

Alex Rolinski (L) partnered with Bristell importer Lou Mancuso when Lou wanted to add a seaplane. Photo taken in spring 2020 right before Covid hit.

Aero Adventure was able to snare several light-aircraft technicians due to the financial woes at Seamax (whose problems are covered in this article). A number of workers freshly employed are no doubt pleased.

They’ll be lead in Brazil by American Wesley Queiroz aided by sales manager Shawn Morgan, Alex informed me. They will manage a facility and personnel aiming for 12 kits a month in 2024, stepping up to 18 kits a year in 2025. These numbers sound very realistic and achievable yet insure a supply of much more affordable LSA seaplanes than anyone else. More on affordability below.

“We will also have a new operations person, however, we will be releasing the name at EAA AirVenture Oshkosh,” Alex finished.

The U.S. operation of Aero Affinity ranges widely through the light aircraft space and has entered somewhat larger aviation, no doubt a good direction to be going as we contemplate Mosaic LSA that require new expertise for equipment like retractable gear, adjustable props, alternate propulsion systems, and more. Last year Alex took factory training by Continental to perform service work on the Alabama company’s diesels as part of an agreement to assist Tecnam Aircraft with service for their broad lineup. The Italian company offers an aircraft with a diesel powerplant.

Meanwhile Aero Affinity also includes partner Doma Andreka of Magnus Aircraft. His Hungarian supplier this week announced a new deal to build aircraft in China though for what market these aircraft will be was not specified.

As to affordability, a regular focus of this website, Alex noted that a new Aventura fully-built SLSA model remains about $150,000,  significantly modest at a time when almost everything else you buy has gone higher. As we can all see at our grocery store or a gas pump, inflation has driven everything considerably higher in the 2020s. Honestly, though may not fit your budget, $150,000 qualifies as a bargain. Seriously, go price any other seaplane anywhere. You probably know an Icon A5 lists for more than $400,000. Then we have Mosaic LSA coming, but that’s another story…

Affordability in this age of inflation is a challenge not only for the consumer but for the producer. Their material costs have gone up. The challenge of finding labor is surprisingly difficult for many American businesses. This predicament is partly why Aero Adventure made the decision they did.

To hold prices from soaring even higher, this move by Aero Adventure makes economic sense. I’d bet they can also add new sales from South America.

Regardless of price questions, Aero Adventure appears to be one of the steadiest producers in the LSA seaplane sector along with Scoda Aeronautica and their Super Petrel XP.

Perhaps we’ll learn even more about this company on the move at AirVenture in just seven weeks!

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Here’s the backdrop of today’s update on the LSA seaplane sector as summer approaches. According to Law360, an online legal news source, “Light-Sport Aircraft manufacturer Icon Aircraft filed for Chapter 11 protection in Delaware bankruptcy court with more than $170 million in debt and plans for an asset sale and liquidation.” You may have read (here) that Icon got an initial offer of $13.5 million. As an industry contact told me for the earlier report, “That would hardly make a dent in their liabilities.” The person was right, it appears. A proposed new buyer referenced in the earlier article agreed to take on Icon’s debt but the sales must still go through an auction process, I was told. OK, let’s come back to Earth… or water perhaps …or either. Aero Adventure continues to fly as it has for three decades (though management has changed at least three times over the period).

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Chip Erwin and the TrueLite Mow the Lawn — And Then Go Flying! (UPDATED AGAIN!)

By Marc Cook || 2 Comments

 

In our original post, we linked to video of the TrueLite performing taxi tests. Now it’s done better: flying! See the new videos below as Chip Erwin documents the first flights of the TrueLite happening now in Florida.

Those of us looking for pure flying in lightweight form can’t help but be intrigued by the TrueLite ultralight, marketed here by Chip Erwin’s Aeromarine company. “The taxi test went fine. I didn’t have any airspeed reading so I’ll have to see what’s going on there,” Erwin says in the video. While the 36 hp Vittorazzi Cosmos 300 ran a bit hot during the taxi tests, he feels it was because it sat idling for 5 minutes before the test, saying that it cooled down once he got moving.

Here’s a sampling of videos related to the TrueLite.

 

 

 

Compress Post ...

  In our original post, we linked to video of the TrueLite performing taxi tests. Now it’s done better: flying! See the new videos below as Chip Erwin documents the first flights of the TrueLite happening now in Florida. Those of us looking for pure flying in lightweight form can’t help but be intrigued by the TrueLite ultralight, marketed here by Chip Erwin’s Aeromarine company. “The taxi test went fine. I didn’t have any airspeed reading so I’ll have to see what’s going on there,” Erwin says in the video. While the 36 hp Vittorazzi Cosmos 300 ran a bit hot during the taxi tests, he feels it was because it sat idling for 5 minutes before the test, saying that it cooled down once he got moving. Here’s a sampling of videos related to the TrueLite.      

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Crystal Balling — What Will Rotax Do Next?

By Marc Cook || 19 Comments

The Rotax 916 on the Carbon Cub UL (Jon Bliss photo).

Untethered prognostication is what you do waiting for the rain showers to blow through and the sun to reemerge on your long cross country. Me? I sorta do it for a living. (Such as that is.) And I get to do it often enough in front of people who work deep in the industry to see if I’ve landed close to the truth. Like playing Battleship with engineers and PR people.

My latest prognostication jag centers on what’s next for Rotax. And it’s driven by a feeling that there’s no time to waste moving up the horsepower ladder. Here’s my argument.

First, the traditional engine manufacturers have still not recovered from what they say are pandemic-related supply-chain issues, which causes huge delays in deliveries and helps drive prices quite high. In the Experimental realm, where I also live, new engines have become exceptionally more expensive, leading some builders to reassess their budgets and stop their projects where they stand.

Second, Rotax has scored a big hit with the 916. Yes, it’s also expensive, but that extra increment from 141 to 160 hp has opened the door to new performance in several designs that were good on the 915 but are significantly better with the newer engine. Some of those airplanes would be even better with more power.

Third, Rotax takes the world view that its products have to work around the globe, which means they can’t depend on 100-octane fuel. In the next slot up, which I’ll call the 200-220 hp range, we basically have traditional aircraft engines that require big octane to make power. You could, of course, run an even bigger Lyconsaurus at a lower compression ratio but the power-to-weight figures get even uglier. So a Rotax product at this power level that could use, say, the equivalent of a high-octane auto gas (as the 916 does) would be a huge win and provide owners with the option of using auto gas, the currently available 94-octane unleaded avgas that’s sparsely available or something else. Point being that any future engine should be not designed to require 100LL.

Some Perspective

It’s worth looking at where the Rotax line currently fits to help see a potential future. Of course, the 900-series engines are small four-stroke, flat-four engines with a gear reduction drive and liquid-cooled heads. The gear drive allows these small engines, which displace just under 83 cubic inches, to rev higher and make more horsepower. Our traditional engines, unburdened by gearboxes are, in effect, burdened by the inability to rev much higher than 2700-2900 rpm with any usefully sized propeller. As anyone who bases at an airport with a Cessna 185 present, as I am, you know that a big Continental spinning 2850 rpm for takeoff with a large propeller is a gloriously noisy thing. But it’s not something you’d aim for with modern sensibilities or worldwide acceptance in mind.

Continental’s IO-520: Big, slow turning.

By gearing the 900-series engines, Rotax allowed them to make more power than their displacement suggests but also to turn their propellers more slowly, which is good for noise and, to some extent, aerodynamics. The downside is weight and complexity, but the relative simplicity of the 900-series engines and their small size more than makes up for it. More advantages to the 900-series designs include modern combustion chambers—especially compared to the ancient chambers found in parallel-valve Continental and Lycoming engines, a good reason these engines need high-octane fuel to make decent power—and liquid cooling. In short, you can run a modern design harder—more compression ratio, more turbo boost—before destructive detonation begins to impact power and the liquid cooling further adds to the detonation margin.

So, What Should Rotax Build?

Let’s get back to the assumption that Rotax needs to build an engine in the 200-220 hp range. (I’ll set aside for now the need for a 300-hp-class engine but not completely ignore it.) I believe the 900 series as we know it has reached its limits. Consider this: The 912 iS makes 100 hp without a turbo on just under 83 cubic inches, which is 1.2 hp per cubic inch—itself more than double the power density of a Lycoming. It needs to make 91 pound-feet of torque at 5800 rpm to do so, and that requires a BMEP (brake mean effective pressure) in the combustion chamber of 165 psi to get there. While the horsepower-per-displacement number seems impressive, that’s actually a modest BMEP, or about what a 180-hp Lycoming runs. Clearly the 912 iS isn’t working all that hard.

Everyone’s fave: The 100-hp Rotax 912 iS.

But the 916 is. With 160 hp on tap for takeoff (limited to 5 minutes, then it’s 137 continuous), it’s working really hard. First of all, power-per-cube is a really impressive 1.93 hp/cubic inch. For that power, the engine has to make 145 foot-pounds of torque at 5800 rpm, a big jump from the 912’s figures, and that requires a BMEP of 263 psi. That is a huge number, one that really stresses the engine’s ability to resist detonation, which it surely only does through strict electronic control. If you’re old enough to remember the Cosworth DFV Formula 1 engine, you may be surprised to know it made its 500-ish-hp on a BMEP of just 230 psi. Oh, how our heroes have fallen. (And, yes, I know the DFV was not turbocharged…)

Where do we go from here if the current 916 is right on the hairy edge of power production from its displacement? Well, you make it bigger. We’ve all seen the April Fool’s photos of the 912 Photoshopped into a six-cylinder but I personally think Rotax will go with a bigger four. Why? Parts count, mainly. Yes, there are good reasons to have six smaller instead of four larger cylinders, mainly for smoothness. But the manufacturing cost difference in cylinder assemblies of different dimensions is virtually zero. So the fact that the six-banger has one-third more of them only adds to weight and cost. (Though it should be said that if you’re thinking of retrofitting aircraft originally designed for Lycoming engines, weight isn’t quite the enemy you think it is.)

The Lockwood 915-powered RV-9A required a long nose for weight and balance.

No, I think it’s going to be a bigger four. And knowing that Rotax is a naturally conservative company, I’m thinking incremental from the 900 series. Back-of-the-napkin thinking has a four-cylinder flat engine with a 4.0-inch bore and 2.85-inch stroke. Why? Because this is close to the bore/stroke ratio Rotax uses in the 912 and because the shorter stroke allows the engine to continue to be geared. And if you take the average piston speed seen in the 900-series and apply that to our hypothetical 143 cubic inch engine, you’d have to limit max rpm to 5200.

I’m already way out on the limb so I might as well continue. This hypothetical engine could make 180 hp naturally aspirated on a bit more BMEP than the 912 iS musters. But turbocharged, 220 hp seems easily achievable and even, if you ran this engine as hard as Rotax does the 916, it could theoretically make 250 hp running the same BMEP of 263 psi.

Of course, not everything scales the same way. There’s more internal friction in a larger engine even if the average piston speed is the same—you have more ring area to drag around. And there are countless other interactions that people who do this for a living know about, can predict with the help of a computer and eventually discover when they actually build and test prototypes.

It’s worth noting that Rotax is not the only player in this space. The ULPower 520T engine is impressive in its own right. It’s a 321 cubic inch six-cylinder engine with, like the Rotax, two pushrod-operated valves per cylinder. (Truly, until you decide you need high revs, a two-valve head is plenty; until then, you’re just adding weight and complexity.) The 520T uses a modest amount of boost, just 38 inches for takeoff, and makes 220 hp at 2700 rpm. To do so, it’s making a phenomenal 428 pound-feet of torque from an almost-square bore/stroke ratio of 1.056:1. Heck, even a Lycoming is more “over square” than that, with a bore/stroke ratio of 1.717:1.

The ULPower’s BMEP is a modest 201 psi, above the naturally aspirated Rotax 912’s but well short of the turbo Rotaxes. I think in part this has to do with the ULPower being air cooled. No matter how nice the fins and effective your air-cooling scheme is, it’s really hard to beat the efficiency of liquid cooling. The offset is the weight and complexity of a cooling system, of course, but you have the opportunity to make much more power from any given displacement.

All this discussion is merely educated guessing. I’m 100% sure Rotax is working on an engine in the next horsepower class up. Maybe two classes up. And for all I know they could design the next engine with a more conventional up/down intake and exhaust system that would allow them to make both four- and six-cylinder versions with the same cylinders. I’m also fairly sure Rotax will take a careful approach. The 900 series has been around for more than three decades, carefully developed and curated in that time to double the power output. I don’t see a 400-hp, fire-breathing, flat-eight breaking cover, but I’d be mighty impressed if they did it.

What are your thoughts? 

 

Compress Post ...

Untethered prognostication is what you do waiting for the rain showers to blow through and the sun to reemerge on your long cross country. Me? I sorta do it for a living. (Such as that is.) And I get to do it often enough in front of people who work deep in the industry to see if I’ve landed close to the truth. Like playing Battleship with engineers and PR people. My latest prognostication jag centers on what’s next for Rotax. And it’s driven by a feeling that there’s no time to waste moving up the horsepower ladder. Here’s my argument. First, the traditional engine manufacturers have still not recovered from what they say are pandemic-related supply-chain issues, which causes huge delays in deliveries and helps drive prices quite high. In the Experimental realm, where I also live, new engines have become exceptionally more expensive, leading some builders to reassess their budgets and stop their projects where they stand.

Expand Post ...

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