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Earthstar’s Thunder Gull Is Soaring Capable and Was a Pioneer in Electric Propulsion

By Dan Johnson || November 20, 2023 Leave a Comment

Continuing our tour of the Top 50 videos from Videoman Dave's popular YouTube channel, we come to Earthstar Aircraft's Thundergull. My interview with Mark about his electric project garnered 236,000 views and ranks at #11 among the Top 50 of Dave's more than 1,500 videos.

This remarkable small aircraft, a single seater until their Odyssey model came out, was ahead of its time. Over a successful run dating back into the 1990s, Thunder Gull evolved into several variations and developer Mark Beierle experimented with various propulsion systems. A gifted designer, Mark pursued development more than production so the total number of 'Gulls has never become large.

If you are looking to buy, getting a current owner to part with their pride and joy could be challenging. The Earthstar website is functional but does not appear to have been updated in some time. Thunder Gull owners or pilots may be purists insisting nothing compares to their Gull, yet some interested buyers are aware Titan Aircraft makes a very similar aircraft. The Ohio company remains active, attending airshows and displaying their Tornado line.

Gull 2000

The earliest designs from Mark's inventive mind were called Thunder Gull. I recall seeing these at airshows in the '90s being flown as an experienced driver might operate a sports car. Wing span is a mere 20 feet. When you sat in the fully-enclosed cockpit it visually looked like you could open the door and reach out to touch the wingtip. Thunder Gull's diminutive size made it as sporty and agile on the ground as it is in the air, a rare capability for most airplanes.

Later came Odyssey, a side-by-side, staggered-seating two seater. It only had a 26 foot wingspan. Most light aircraft in the space use 30-36 foot wingspans on aircraft that did not carry any more payload. Consequently, I viewed Thunder Gull's wing design to be "hard working." Later still came Soaring Gull with what looked to be a long wing, 28 feet, still shorter than most other comparable aircraft. This gave Soaring Gull a solid 16:1 glide according to Earthstar, meaning any experienced soaring pilot could easily keep Soaring Gull aloft for a long time with the engine shut down. This fact later lead to electric power, which I'll touch on below.

More than airplanes, Mark Beierle also designed a clean sheet radial engine that he called "Rad-Cam," which he is testing in this image.

As you examine this design, you view Mark’s design philosophy. He sought to make the most efficient aircraft he could. One definition of that was a flying machine that uses the least fuel. Mark defined himself as “a minimalist,” and this sentiment is carried throughout his highly-optimized aircraft. For the then-new millennia, when we successfully avoided the predicted terror of Y2K (remember that?), Mark came out with Gull 2000. You can read my full pilot report from 2003 for lots of detail about the aircraft.

On Soaring Gull's lean fuselage, these wings look long though they are only 28 feet in span.

As Gull 2000 arrived Mark had gotten married and his strict minimalism lead to improvements in creature comforts. Notably, the Gull 2000 is wider than previous Thunder Gull aircraft. Here's how Mark promoted his new creation… "Prototypes were flown over 5,400 hours. Considerable care has been taken in the design and testing process," Mark wrote.

Mark often flew long cross country flights to airshows, taking everything he needed to display at the event. Here he's seen before loading the aircraft.

"The result is a stall and spin resistant aircraft with superior handling qualities both on the ground and in the air. The responsive ailerons provide roll control throughout a stall attempt. The beginning flyer will find an easy to fly, stable, and forgiving aircraft. "The Thunder Gull 2000 and Odyssey models maintain the responsive and nimble control necessary for the demanding pilot. All of the Earthstar Aircraft models are fun cross-country machines and have been flown from coast-to-coast many times. "Flight tested to a “G” loading of +5.9 and -3 and are designed to +6 and -4 yield. The ultralight model has been certified to meet the FAA’s FAR-103 requirements. VNE for all models is 120 miles per hour."

Electric eGull

Mark made an efficient aircraft and one measure of success was to use less fuel. As the new millennia arrived, interest in electric propulsion was growing. Given his goals, Mark quickly adopted the idea and his electric experimentation began. This is the subject of the video highlighted in this article.

While giants like Boeing and Airbus spend billions on electric propulsion concepts, electric airplane development of affordable aircraft is often done on tiny budgets by entrepreneurs like Mark. This is also a fast-changing field, perhaps explaining why finding an electric-powered Earthstar Gull will be especially difficult. Nonetheless, the efficiency of Mark Beierle's Gull design combined the high torque of an electric motor with a low airframe weight to make a highly-workable electric propulsion design.

Gene Chase worked with Mark to create this Soaring Gull. With a 28-foot span, the design achieved a 16:1 glide ratio, plenty to do some genuine soaring.

Learn more directly from the designer in the videos below. Combine Gull 2000's more user-friendly interior with the design's great flying qualities and power it with a potent electric motor …you really have something fun!

All specifications and data provided by Earthstar Aircraft, from their website.

ARTICLE LINKS:

Earthstar Aircraft, producer of the 'Gull line, all content on this website
Full pilot report from 2002 on Gull 2000, introduced as the new millennia arrived
Titan Aircraft, manufacturer of a very similar aircraft to the Gull line

Here is the video interview with Mark Beierle about his electric propulsion investigations. It has been viewed 236,000 times. The second video below looks like a duplicate but is a different production. https://youtu.be/ogx48kBEgQU?si=MtIVC2aRj9UrgT7_ Just a year ago, Dave updated his coverage of Earthstar and Thundergull. Flying scenes are featured and fans of Videoman Dave Loveman may enjoy hearing his familiar voice asking questions of Mark. Although this image looks the same as the one above, this is a different video. https://youtu.be/ogx48kBEgQU?si=MtIVC2aRj9UrgT7_

Continuing our tour of the Top 50 videos from Videoman Dave’s popular YouTube channel, we come to Earthstar Aircraft’s Thundergull. My interview with Mark about his electric project garnered 236,000 views and ranks at #11 among the Top 50 of Dave’s more than 1,500 videos. This remarkable small aircraft, a single seater until their Odyssey model came out, was ahead of its time. Over a successful run dating back into the 1990s, Thunder Gull evolved into several variations and developer Mark Beierle experimented with various propulsion systems. A gifted designer, Mark pursued development more than production so the total number of ‘Gulls has never become large. If you are looking to buy, getting a current owner to part with their pride and joy could be challenging. The Earthstar website is functional but does not appear to have been updated in some time. Thunder Gull owners or pilots may be purists insisting nothing compares to their Gull, yet some interested buyers are aware Titan Aircraft makes a very similar aircraft.

Earthstar — eGull (electric power)

By Dan Johnson || August 19, 2016 2 Comments

Mark Bierle is one of the most talented designers I have ever met. The modest, soft-spoken Californian makes a line of the best-flying and genuinely light aircraft in the USA. He's also worked in powerplant design and has now turned his agile mind toward electric power. We talk with him at some length about the advantages of electric-powered light aircraft and what Mark expects for the future.

Mark Bierle is one of the most talented designers I have ever met. The modest, soft-spoken Californian makes a line of the best-flying and genuinely light aircraft in the USA. He’s also worked in powerplant design and has now turned his agile mind toward electric power. We talk with him at some length about the advantages of electric-powered light aircraft and what Mark expects for the future.

Green Power — Earthstar’s All-Electric eGull

By Dan Johnson || March 2, 2009 2 Comments

The hum of interest in electric-powered aircraft continues, a parallel to development of electric automobiles. Despite their woes all over the news, the auto industry is spending millions on electric power. In sharp contrast, electric airplane developments are being done on tiny budgets by entrepreneurs. Yet enough development is happening that the German Aero show will have a show-within-a-show, the e-flight-expo. Says German publisher and co-organizer of the event with Aero management, Willi Tacke, "At this moment we have a dozen trend setting exhibitors to participate at the first e-flight-expo April, 2-5, 2009." I've written about electric projects: Electra Flyer/others and Sonex. The newest entry involves one of my all-time favorite airplanes, the Earthstar Aircraft Gull 2000. This ultra-light single seater flies efficiently on a very small wing, so when I spoke to Mark Beierle recently I got excited when he told me he's working on the eGull. Mark is a remarkably talented and creative designer; his airframe could be a great platform for such a powerplant. While eGull is a single seater, two seaters will follow early development. Meanwhile, I look forward to a flight in an electric powered Gull 2000. Bring it on, Mark!

The hum of interest in electric-powered aircraft continues, a parallel to development of electric automobiles. Despite their woes all over the news, the auto industry is spending millions on electric power. In sharp contrast, electric airplane developments are being done on tiny budgets by entrepreneurs. Yet enough development is happening that the German Aero show will have a show-within-a-show, the e-flight-expo. Says German publisher and co-organizer of the event with Aero management, Willi Tacke, “At this moment we have a dozen trend setting exhibitors to participate at the first e-flight-expo April, 2-5, 2009.” I’ve written about electric projects: Electra Flyer/others and Sonex. The newest entry involves one of my all-time favorite airplanes, the Earthstar Aircraft Gull 2000. This ultra-light single seater flies efficiently on a very small wing, so when I spoke to Mark Beierle recently I got excited when he told me he’s working on the eGull.

Single-Seat Gull 2000

By Dan Johnson || January 1, 2003 4 Comments

ALWAYS FLOWN - Mark Beierle doesn't trailer his ultralights; he flies them. This color-identified map shows the route from the California manufacturing site to the Gull 2000's home in Canada (with one diversion up to Washington state for an airshow).

CLEAN LINES - The Thunder Gull has very pleasing lines, and is easily differentiated from the Tornado through the smaller tail section and rounder lines.

CLEVER ADAPTATION - A parachute believer, Beierle installed a BRS parachute in the nose to help secure the Gull 2000 on all its main wheels. BRS engineers blessed the installation; the main airframe bridle routes up one windscreen cowl post.

DESIGN PERFECTIONIST - This view tries to show the turbulator strips Beierle installed to smooth airflow around this door. He says successive Gull 2000s will have a tighter-fitting door.

S-O-O-O SMOOTH - Mark Beirele's design work is among the best in ultralight aviation in my opinion. He's optimized the Gull's hull shape to be the most efficient it can be, he says.

BIG TAIL - For its size, this tail brings great stability to the Gull series. All metal or painted fabric like the wing, it'll hold up well to the sun's radiation.

In a flying world that seems to think a 2-seater is mandatory, Mark Beierle has released another single-place ultralight. And what a sweet ultralight it is. I love the Thunder Gull series of ultralights. When people ask me what I personally like of the hundreds of ultralights evaluated, the Thunder Gull always springs to mind (among a few other designs). My interests may not be your interests, but I'll bet most pilots would love to fly the Gull 2000. Offered for sale here in the new millennium, the Gull 2000 is an appropriate name that seemed well aimed at lots of American ultralight enthusiasts. Welcome to Gull 2000 For the new century, the Gull 2000 adds to, rather than replaces the older models from Earthstar Aircraft. The company will still sell their Thunder Gull J single-seater and their little-publicized Soaring Gull, which uses a very small engine and long wings to create something of a motorglider. For those desiring two seats, the choices are not mirror images with different engines. The older Thunder Gull JT2 is a tandem seated enlarged version of the J model. Contrasting significantly is the Odyssey, released in 1995. This ultralight features side-by-side seating in a staggered fashion that keeps the 2-seater from becoming too wide, and gives each occupant a little more shoulder room; the right seat is several inches behind the left. The Gull 2000 shows its heritage to the older designs by offering a roomier cabin (somewhat like the Odyssey), yet with the lean lines of the single-seaters. It also employs the agile handling of the single-seaters. One irony of these Earthstar models is that the newest is also the least expensive (though only by a small margin). The Gull 2000 sells for $10,965 without an engine and Earthstar offers a range of engines, including the 40-hp Rotax 447, 46- or 50-hp Rotax 503, 60-hp HKS 700E 4-stroke, and the Zanzottera single- or twin-cylinder models. Certainly I find the Gull 2000 Beierle's best work yet. Sleek Yet Spacious In the past, some larger pilots have complained that the Thunder Gull line is too tight inside. Indeed, in a country of beefy pilots an ultralight designed by a slim and trim Mark Beierle may not have fit the mainstream as well. That changed with the Gull 2000. As proof, CGS Aviation's Chuck Slusarczyk accepted Beirele's invitation to hop inside and - surprise! - he fit with room to spare. Chuck is one of those large pilots, yet he did not look shoehorned into the Gull 2000. We had trouble getting him out, but that was because he appeared to enjoy the experience. The Gull 2000 uses an all-fiberglass body to fair the cockpit; older Earthstar designs used some dope-and-fabric covering. Combined with numerous options, the test Gull 2000 is a little too heavy to qualify for Part 103's weight limits, tipping the scales at 274 pounds. Beierle says that by using a Zanzottera engine, he can keep the Gull 2000 under 254 pounds (before parachute, which, by definition, doesn't add to the total). He referred to the 26-hp single-cylinder Zanzottera, which he'd install in conjunction with a different prop to stay within the 63 mph speed limit of Part 103. Mark admits that the Zanzottera engine will produce a greater amount of vibration owing to its single-cylinder construction, but he believes he can dampen this with softer motor mounts. In an earlier trial with the littlest Zanzottera and by building lightly, Beierle created a Part 103 ultralight, which he says weighs only 241 pounds. Our test Gull 2000 was equipped with the popular Rotax 503, which gave the plane superb performance. Anyone with an FAA ticket may prefer this combination or even the 4-stroke HKS. You can also downsize to the Rotax 447 engine, but as this cuts weight by only 5 pounds, I'll wager few will give up the oomph and reliability of the 503 engine. The inner structure of the Gull 2000 is the same welded steel construction that has always braced the Earthstar ultralights. Most surfaces are metal, but you can choose between all-metal wings or dope-and-fabric coverings. Both will last a long time; I know of no other ultralights that give you such a choice. Flaps don't come standard on Earthstar single-seaters and, indeed, you could easily do without them, I believe. But given the extension of the speed range, many pilots will want them for $700 more. They, too, are all metal. While a few onlookers marveled at the small distance between the main gear, knowledgeable designers noted that the classic ratio of 4:1 is maintained (this ratio relates the width of the landing gear relative to the aircraft span). One of the endearing parts of the Gull 2000 - like the other Earthstar models - is the small wing. At only 20 feet of span and 95 square feet, I have judged this to be one of the hardest-working wings in the ultralight industry. It's hard-working because it doesn't seem small in flight. But you can also select a 24-foot or 28-foot span, for example, if your typical occupant load is high or perhaps if you fly in high density altitude locations like Colorado. As with the wing covering, I'm not aware of other brands that give you such broad choices on a single model. Beierle noted that the Gull 2000 sits very low and this reduces its need for a wider span of the gear. One of my memories is of a single-place Thunder Gull being turned very sharply at speed without noting any tendency to tip. The short span clearly helps keep the Gulls on the gear, thus the narrow gear stance is perfectly reasonable. Beierle's design philosophy is to make the most efficient aircraft he can, one which will use the least amount of fuel. He calls himself a minimalist and this sentiment is carried through the aircraft. While efficiency may be the hallmark of this design, it is my observation that creature comforts have been substantially improved with the Gull 2000. The environment inside the aircraft was more comfortable and wider, good news for large American pilots. One ultralight designer examining the Gull 2000 observed that it does not use the extended dorsal fin that one sees on Titan aircraft. Indeed, though these machines share the design heritage of the early Thunder Gulls, they aren't identical. Levers and Knobs The Gull 2000's trim control has changed from the older models. Beierle moved the control knob from under the seat (on older models) to alongside the seat where you can actually look at what you're doing. Both old and new knobs face backwards. If you think of the inward facing half of the knob and turn it downward, the nose lowers; turn it upward and the nose rises. Though this sounds awkward, it is more intuitive than the older version. Not much twisting of the knob was needed to notice the change in trim. The flap handle is located to the left of your head and offers two notches other than neutral. This is very easy to use and to reach. Mark recommends one notch for takeoff and in most cases two notches will significantly slow the aircraft on approach to landing. In two low passes I made over a field, one with no flaps and one with full flaps, there was a speed difference of about 20 mph at a throttle setting to sustain altitude. Creature comfort improvements include the lone entry door, which now reaches higher and extends lower to make entry and exit easier. The lower door facilitates entry by allowing you to turn around, sit down, and draw your legs in afterward, the preferred method. On this first production Gull 2000, the door did not fit as precisely as it will. So Mark had installed some turbulator air strips to smooth airflow around the aft end of the fuselage. He seems a perfectionist in aerodynamic efficiency; many designers would have been satisfied. The Gull 2000's cabin is approximately 2 inches wider at your hips; the old model was 27 inches wide. What a difference 2 inches can make. Visibility was very good in the Gull 2000, however, it was slightly better to the right because the doorframe obscures some visibility to left. And though the flap handle is a slender steel rod, it also modestly blocks vision if you have flaps deployed. As I did my Dutch roll exercises I noticed a little fuel smell in the cockpit since the tank is in the cabin with you. Fortunately, Mark had installed window scoops on either side, which provided plenty of fresh air. The Gull 2000 was a little bit on the noisy side, no doubt a function of the cockpit acting like the inside of a speaker cabinet. You'll want to use a helmet or headsets. The heel brakes tended to squeak a little bit but did prove necessary as I taxied somewhat down slope with an engine that was idling fast. Mark indicated that the reason for the increased idle speed relates to his use of a product called Energy Release, which uses a chemical process to fill small voids in the cylinder wall. This is claimed to result in a more efficient operation of the engine. The use of this special product, Mark says, caused the idle speed to increase. He'd turn it down but it would creep back up. Ahh, the Flying The Gull 2000 takeoff climbout was done at 55 mph and even 60 mph was useful in the gusty conditions. I approached for landing at 50 mph, but this proved to be a little slow. I ended up touching the small tailwheel in the effort to make a proper flare, though both the Gull 2000's Canadian owner and designer Mark Beierle told me my landing was a good one. As I practiced Dutch roll coordination exercises, I had to add more left rudder during the left turning initiation than I did to the right. This shows coordination of the controls is not perfect on this first production Gull 2000, and Mark felt that this may have something to do with the less-than-perfect door fit. This proved to be quite a very minor defect and my later Dutch rolls were excellent to a steep angle. The whole problem no doubt will disappear when the door is done to final production quality. In general practice I found the rudder to be a very powerful surface. In some dire circumstances where aileron control may be lost, the rudder would suffice to help you line up on a runway. Beierle suggested I climb at 50 mph, however, when I did this away from airport traffic it produced such a steep angle of climb that the lower surface of the wing appeared to have a 45° angle. Climb is exhilarating at nearly 1,500 fpm. Of course, in a Part 103 version of Gull 2000, the climb will clearly not be as strong. Beierle discussed the efficiency gains he's found with the Gull 2000 and, by relating this to gallons used per hour at various speeds, he thinks he is seeing a 25- to 30% efficiency increase in the new model. I feel this is a significant accomplishment because the Gull 2000 has a wider body yet smoother airflow around it. The perfectionist succeeds! I commonly flew at 5,000 rpm, confirming Beierle's feeling about efficiency. However, in sharp contrast to my experience in recent months with the HKS engine, the Rotax lost considerable rpm when the nose was high and gained it when I lowered the nose, an obvious difference between 2-stroke and 4-stroke operations. Fortunately, Beierle is an HKS booster and lists it as an option in his regular literature. However, since Mark designed for and achieved good aerodynamic efficiency, it struck me as odd that the Gull 2000 did not employ wheel pants. This decision may have been a choice of the Canadian buyer. My power-off stalls showed 28 or 29 mph on the airspeed indicator. This is not quite what company literature lists (26 mph) but it's very close if the installed ASI can be trusted. Normal power-on stalls never did break over and more aggressive power-off stalls never dropped toward either wing, a benign occurrence on any aircraft but one which speaks well of Beierle's copious design talents. When I checked for adverse yaw, I did find a liberal amount but the hesitation in the wrong direction did not last too long and didn't go very far. Adverse yaw is common on most ultralights but the quick correction suggests the design is well-harmonized. After trimming for level flight, when I reduced power the nose would rise ever so slowly and when I increased power the nose would slowly begin to drop. The motion was so modest that it isn't worth any worry. Again trimming for level flight, I deflected the stick forward and aft in a longitudinal stability check and found that the effects were positive but that the response was very slow in the desired direction. Some ultralights are faster to correct the stick movement (ideally back to level flight), but those may not enjoy the overall performance package offered in the Gull 2000. Fly Like a Gull Earthstar is not a large producer, and this probably affects pricing. The Gull 2000 isn't the least expensive ultralight you can buy but fortunately it more than compensates by its fine combination of great performance and superb handling. Base price of the Gull 2000 kit is $10,965 (as of summer 2000). To arrive at our test aircraft, you add $4,700 for the Rotax 503 engine and an engine installation kit. Subtotal so far is $15,665. For his Canadian customer, Beierle added other desirable features like powder coated steel structure ($295), custom-fitted carpeting ($425), wide aluminum Hegar main wheels ($240), a BRS ballistic parachute (not quoted, but around $2,200), full fuselage painting plus accent striping ($950), and instrument package including the EIS unit (total $1,215), the right-side side glass and left-side door (standard on the Odyssey but a $415 option on the single-place models), a 3-blade prop ($470) and flaps (again standard on the 2-seat models but a $700 option on Earthstar's single-seaters) . All the above goodies sum to $6,910, making a new subtotal of $22,575. Earthstar can build the plane for its Canadian customer which would add $7,940, or you can order it with completed wings, ailerons, flaps, and wing tips for $3,450. (A fully built Gull 2000 is available to U.S. customers if the ultralight fits Part 103.) Is it worth it all? In my opinion, yes. This is one of the best single-seat ultralight aircraft in the world and a fine aircraft compared to any other you can buy whether general aviation or homebuilt. I'd stretch to gather these funds for two reasons: First, the Gull 2000 is simply a wonderful flying machine. Secondly, it will last a very long time and I feel sure its resale value will hold up well, possibly much better than more common variety ultralights. However, if you feel this is too much for your wallet, then I encourage you to think about the Gull 2000 set up to stay within Part 103. With a smaller (probably Zanzottera) engine, fewer options - for example, flaps you won't really need on a lighter, slower machine - and basic instrumentation, you should be able to hold the cost to about $15,000 or so. At this price, I consider the Gull 2000 a bargain worthy of consideration by anyone who loves ultralight flying. Earthstar is not a large company with dozens of employees, therefore its cost of production is not held down by economies of scale. However, all the better stuff in this world costs a little more and the Gull 2000 is no different. Like a Ferrari automobile, you may wait a little longer to get one and you may pay a little more, but you'll be the envy of anyone who knows just how delightful it is to fly a machine like the Gull 2000. For wired pilots who like surfing the Internet, the company does not maintain their own Website (as of late November 2000). However, you can point your browser to Thundergull.com and you'll see basic information on all models except the Gull 2000. While the Website won't help you compare details of the new machine, it does include a nice bit of history on Mark Beierle. Since this machine is wholly based on his aerodynamic savvy, the background should be of interest to anyone inclined toward Earthstar Aircraft's offerings.

Published in Light Sport and Ultralight Flying

Seating	1
Empty weight	274 lbs (as flown)¹
Gross weight	550 lbs
Wingspan	20 ft. ²
Wing area	95 sq. ft.
Wing loading	5.8 lbs/sq. ft²
Length	17.75 feet
Height	6.5 ft
Fuel Capacity	5 gal. (standard)
Kit type	Assembly kit
Build time	150 hours
Notes:	¹Fitted with the Zanzoterra engine, Beierle feels the Gull 2000 can make Part 103 ultralight weight.. ²Effective span, due to the wing tips, is 22 feet, says Earthstar; a span of 24 or 28 feet is available with 133 square feet of area.
Standard engine	Rotax 503 (as flown)¹
Power	52hp at 6,500 rpm
Power loading	10.6 lbs/hp
Cruise speed	60-105 mph³
Stall Speed	26 mph
Never exceed speed	120 mph
Rate of climb at gross	1,500 fpm
Takeoff distance at gross	125 ft.
Landing distance at gross	75 ft.
Notes:	³Cruise can be held to Part 103's 55 knots with a smaller engine and the right prop, says Earthstar.
Standard Features	Cantilevered wing, Rotax 503, independent main wheel brakes, in-flight trim, counter-balanced ailerons and stabilator, 5-gallon fuel tank, Lexan® windscreen, 4130 chromoly cage, shoulder belt seat restraint, fiberglass seat, fiberglass body, metal wings with drooped tips.
Options	Other engine choices, including the Zanzottera, 60-hp HKS and Rotax 447, longer wings (see specifications), instruments, door and side panels, electric starter, 2- or 3-blade composite prop, aluminum or fabric wing covering, and ballistic parachute.
Construction	4130 steel airframe, fiberglass fairing, aluminum or fabric wings, metal tail coverings.

Design

Cosmetic appearance, structural integrity, achievement of design goals, effectiveness of aerodynamics, ergonomics.

Pros - Few ultralights inspire me more than the Thunder Gull line and the Gull 2000 is the "best of breed" in my opinion. Single-seater but with more room for big pilots and more refinements than ever. Long-lasting materials used in construction. Proven design over many years; even copied. Wider speed range than most aircraft (not just ultralights). Sits on all three gear.

Cons - It may be one of ultralight aviation's best planes, and you'll pay for it. Gull 2000 kit sells for $10,965 and the Rotax 503 engine as tested will add more than $4,000. Cannot qualify for Part 103 with 503 engine and one that will make weight may not satisfy all buyers. Most are fully enclosed, a negative for those who love out-in-the-breeze flying (though you can order it without sides).

Systems

Subsystems available to pilot such as: Flaps; Fuel sources; Electric start; In-air restart; Brakes; Engine controls; Navigations; Radio; (items covered may be optional).

Pros - Well-equipped ultralight with in-flight trim, flaps, and differential brakes all standard; all these systems worked excellently. Electric start is available since the 503 Gull 2000 won't make Part 103 weight. (The test plane was headed to Canada where the weight values are different.) Easy engine access. Flap handle is close yet nonintrusive.

Cons - Trim knob is better than older models, but is still counterintuitive to use. No trim position indicator. Fueling is done inside the Gull 2000 - unless you remove the tank, itself a hassle - and some fumes were noticeable. Panel space is minimal if you must add more instruments or radios. Heel brakes aren't every pilot's favorite.

Cockpit/Cabin

Instrumentation; Ergonomics of controls; Creature comforts; (items covered may be optional).

Pros - Easier entry than older single-seat Gull models, thanks to a door that extends both lower and higher. Beautifully appointed interior; a carpet kit is available. Excellent use of interior space makes it seem larger; big pilots will fit quite easily. Superb visibility out either side and forward. Good seat belt restraint. Comfortable seating for longer flights.

Cons - Rearward visibility no better than many other enclosed ultralights. Baggage area is quite limited (though Beierle flies across America in the Gull 2000, he's a minimalist). Left side door only. No quick seat adjustment.

Ground Handling

Taxi visibility; Steering; Turn radius; Shock absorption; Stance/Stability; Braking.

Pros - Low stance, good weight distribution, and trailing link nosewheel make for easy ground handling. Nosewheel has some suspension, thanks to fiberglass rods. Wide aluminum Hegar tires ($240 option) gave excellent grip. Excellent nosewheel response; extra weight up front surely helps. Turns very tightly. Taxi visibility is very good.

Cons - Clearance could be an issue if you land out in an especially rough field. Main gear is not suspended except via air in the tire and gear leg flex. Heel brakes can be "dragged" without realizing your error. It gets warm inside this (optional) full enclosure, at least until air inlets start working.

Takeoff/Landing

Qualities; Efficiency; Ease; Comparative values.

Pros - Jumps off the ground with the best of them; factory says only 125 feet is needed (with Rotax 503). Gull 2000 slows beautifully for landings in smaller areas; factory reports 75 feet with brake use. Crosswinds are only a problem if your skills are new or rusty. Slips work well, as do the large flaps. Good energy retention means smoother touchdowns.

Cons - Smoother runways are much preferred as ground clearance is less than some ultralights. Except for a warm cabin in hot weather, I found no other negatives in this category.

Control

Quality and quantity for: Coordination; Authority; Pressures; Response; and Coupling.

Pros - Controls are exquisite on the Gull 2000; all Earthstar ultralights are good, this one is the best I've flown. Harmony was very good. Control range and authority are excellent. Very predictable characteristics. Control reach and feel were natural and pleasant. I'd say more but it begins to sound like an advertisement.

Cons - None. If you don't like the way Gull 2000 handles, you may be too picky.

Performance

Climb; Glide; Sink; Cruise/stall/max speeds; Endurance; Range; Maneuverability.

Pros - The widest speed range I can recall in any aircraft; Beierle claims a stall of 26 mph - I could not accurately verify - and a Vne of 120 mph for an astounding 4.6:1 ratio (most designers would be delighted to hit 4:1). Climb rate is a breathtaking 1,500 fpm with the Rotax 503. Design also flies nicely at slow speeds. Can carry more than it weighs.

Cons - Honest, I tried, and I couldn't come up with any performance shortcomings. Performance will be more modest if you stay within Part 103 (which is possible), as you must use a much less powerful engine.

Stability

Stall recovery and characteristics; Dampening; Spiral stability; Adverse yaw qualities.

Pros - Beierle calls his machines "stall- and spin-resistant" and I'd basically agree (though very aggressive use of controls could compromise this statement). Factory reports stall at 26 mph though I could not verify this fact; my stall experience was at 28-29 mph though this is still very slow. A beginner can certainly handle the Gull 2000 if he or she pays attention.

Cons - The Gull 2000 looks like it flies hotter than it does and this may mislead some buyers (though I doubt they'd be disappointed). Adverse yaw is present though it didn't last long. Power changes cause minor adverse reaction. Longitudinal stability was slightly negative as is common on most ultralights with the engine mounted high on the airframe.

Overall

Addresses the questions: "Will a buyer get what he/she expects to buy, and did the designer/builder achieve the chosen goal?"

Pros - Is the Gull 2000 worth $15,000 to $16,000 plus options? You bet! This remains one of the best machines I've flown after sampling more than 250 models and I don't say that lightly. It will also last well with its metal or painted fabric exterior covering. Wonderful flight characteristics for all experienced pilots and most beginners. Build time isn't bad at 150 hours and factory offers help in a couple ways.

Cons - No wheel pants seemed strange on such a clean machine (but you can add them). Does not make Part 103 with the popular Rotax 503. Having it fully built costs $8,000 without finish paint (ultraviolet protectant is included). Payment must be in cash or money order; no checks accepted.

Gull flying in a new millenium

By Dan Johnson || February 21, 2002 Leave a Comment

The Gull 2000, sitting very airplane-like on the ultralight/light plane runway. One of Mark Beierle's goals in designing the Gull 2000 was to get the aircraft to sit on its nosewheel rather than recline on its tailwheel as his previous designs have done. With some ingenuity, he was able to redistribute weight to achieve that goal.

A very happy couple-Mark and Leslie Beierle. Mark has always had a nice smile, but it seems broader now that Leslie's entered his life.

Here's a great view of the mostly metal 20-foot wing span that's standard on the Gull line of aircraft, although an extended version does increase the span to 28 feet. Control surfaces are fabric covered for lighter handling, and wingtips are fiberglass, but the primary wing structure is all metal.

A trademark of Mark Beierle's aircraft is the map he always places on the side of his aircraft to keep track of where he's flown it. Here's where this Gull 2000 has been so far! Mark says airplanes are for flying; he doesn't believe in trailering an aircraft to an air show.

A very wide and high door opening makes entry and exit from the aircraft very easy and comfortable. A very simple cockpit, but it has everything you need, including a rearview mirror! Adding a ballistic parachute in the nose of the aircraft was one of the ways Mark was able to get the aircraft to sit on its nose gear.

This particular Gull 2000 is the first customer aircraft in this model series to be delivered. Its owner, a Canadian gentleman, took delivery here at Oshkosh. Because Canada's microlight regulations allow more weight, he was able to power the aircraft with a Rotax 503 engine.

Folks interested in building the Gull 2000 as a legal ultralight in the United States might choose to power the machine with a Zanzottera engine. Beierle flew the Gull 2000 powered with a Zanzottera engine to the Northwest EAA Regional Fly-In in Arlington, Washington, earlier this year where we captured these photos of the twin-cylinder version-the MZ202. If you'd like more information about the Zanzottera engines, check out their website: www.mzengines.com.

It is Mark's design philosophy to make the most efficient aircraft he can, one that will use the least fuel. He defines himself as "a minimalist," and this sentiment is carried throughout this beautifully optimized aircraft. To me, Mark appears to have grown increasingly comfortable in his role within ultralight aviation. Relaxed and confident, he knows he has created a superior flying machine. He also smiles a lot more these days in my opinion, thanks to a wonderful woman named Leslie who accompanied him to AirVenture 2000 in Oshkosh, Wisconsin. Married a year and a half ago, the two complement each other and make a good team. No more tight squeezes Perhaps it was this new personal relationship that motivated Mark to pay more attention to creature comforts. Notably, the Gull 2000 is wider than the previous single-seat or tandem two-seat Thunder Gull aircraft. Considering Mark is a lean and healthy vegetarian, his concern for broader pilots is no doubt appreciated. A few enthusiasts joined my postflight discussion with Mark and Leslie while standing around the Gull 2000 on AirVenture's ultralight strip. Among them was Chuck Slusarczyk, designer and manufacturer of the Hawk line of ultralights. Now for those of you who don't know him, Chuck is a big boy. He once jokingly bragged that he might be the biggest ultralight manufacturer in America. The reference wasn't necessarily to his aircraft sales numbers but more akin to his belt size. On an invitation from Mark, Chuck hopped inside the Gull 2000 and fit with room to spare. Previous Thunder Gull models were a bit tighter. A single door on the aircraft's left side now extends up higher and down lower to make entry and exit easier. The lower door threshold facilitates entry by allowing you to turn around, sit down, and draw your legs in after you, a preferred method of entry. Many snug aircraft require you to insert one leg first to pass around the joystick, for example. For some less able pilots such a maneuver can be tricky. The aircraft I flew is the first being delivered to a customer. As production continues, refinements always follow. Later models tend to become more polished and smooth. This first Gull has a door fit that would satisfy most manufacturers, but not Mark Beierle. He insisted on installing a short row of turbulator strips to create an improved airflow around that side of the cabin, where the door had perhaps a quarter-inch opening even when fully closed. Mark expects that later production versions will be smooth enough to eliminate the turbulator strips. Another design goal was to allow the Gull 2000 to sit on its nosewheel while at rest. Mark says it has always bothered him that his aircraft reclined on their tailwheel, so changing that was important to him. However, even distributing the weight differently/better came with a creature comfort benefit as this nose-down posture further eases entry. Models not so loaded need to be lowered onto their nosewheel with effort. And as Mark will tell you, the airplane just looks more airplane-like sitting level. Like most of what he says, Mark's airplanes simply make sense. From his earliest designing days, he wanted a machine that would do everything well. The Gull 2000 is one of the closest achievements of that lofty goal in all of light aviation. Let's climb inside Inside the roomier cabin I found the customarily light, yet comfortable seats that are Earthstar's standard. In the Gull 2000 the seat can be adjusted over eight inches to accommodate a wide range of pilot heights. Another change from earlier models has you reaching next to your left hip to twirl the trim knob that faces aft. In the older Gull models you had to reach somewhat awkwardly underneath the seat for a knob that also faced the rear. While this new system is better than the old method, you still must remember which way to turn the new control. I didn't find it intuitive. Mark advises you to visualize just the inward-facing half of the knob. When that vertical half moves downward, the nose lowers; when it moves up, the nose rises. You get used to this convention faster than the old one. The former knob couldn't be viewed while in flight, so you just had to memorize the Earthstar mantra of "knuckles down to make the nose go down; knuckles up to raise the nose." I got it then, but I had to concentrate a bit, and that may not be desirable on landing approaches. The new Gull 2000 system is better, though it is not as obvious as a wheel that moves in the direction you want the nose to go (such as used by RANS in many of their designs). Yet another variation on the creature comforts shown by the Gull 2000 is the clever installation of a BRS ballistic parachute into the nose of the aircraft. Not only does this work to hold the nosewheel down at rest (along with the starter battery), it also provides the pilot an extra layer of security nestled reassuringly right in front of your toes. BRS engineers examined the installation and proclaimed it quite workable. The airframe bridle from the parachute routes almost invisibly up the right windscreen support where it finally connects to spar hard points. Even when I respect a designer as much as I do Mark Beierle, I sure enjoy having a backup system when I evaluate yet another new plane. As passionate as he is about aerodynamic efficiency, I'm pleased Mark also strives for safety. The real pleasure is flying Few would argue that a comfortable airplane is more enjoyable to fly. But for any true-blue aviator, the real joy is in the stick wiggling and the benefits of doing so. In this regard, the Gull 2000 has few peers in light aviation. Oftentimes up-and-coming designers and businesses are compared to Van's Aircraft, producer of the very popular RV series. If you're doing well, you may get compared to Van's designer, Dick Van Grunsven. I think Randy Schlitter and his S-16 Shekari can make it to that league and so could Mark Beierle and his Gull 2000. True enough, an RV-6 is not the same as the Gull 2000, but each achieves its design goals elegantly. I'd be proud to own either. As a sign of its wide versatility, the Gull 2000 can cruise close to its Vne at 120 mph or be restricted to qualify under ultralight rules at 63 mph. Beierle accomplishes this through variations of engine and propeller. Most recently he has been working with the Italian Zanzottera engine. It has generated some favorable comments in other applications where it's been used. It produces 26 horsepower from a single cylinder. Using it in combination with the right prop, Mark has succeeded in staying under the 63 mph speed limit of Part 103. He admits that a single-cylinder engine will have greater vibration, but he believes he can dampen this using softer motor mounts. Having flown four of Earthstar's models, I tend to believe what Mark says he will create. That he has been able to show performance capability at fast or slow cruise speeds is a good achievement in and of itself. But he has also been able to show good qualities of the Gull series throughout the speed range, and it's a wide speed range! Earthstar lists clean stall for the Gull 2000 (without flaps) at 26 mph. My experience wasn't quite so precise, yet the installed ASI (air speed indicator) showed somewhere under 30 mph. Instrument error at such slow speeds and high attack angles can be significant, as proved by the ASI dropping close to zero after I held the stall for a few seconds. But the break clearly came at a very slow speed. If it is indeed 26 mph, and if the Gull 2000 can cruise at 120 mph (another fact I was unable to verify as the 503 engine/prop combo had not been fully optimized), then the speed range of the aircraft substantially exceeds the magical 4-to-1 ratio that is the holy grail of many designers. In fact, it approaches 5-to-1, which helps reveal the superb job of designing that Mark has done. No one I have ever asked has been critical of Mark's design talents. In years past, the sole complaint I heard was long delivery delays. Earthstar is no RANS with dozens of employees, so the factory doesn't turn out aircraft quickly, though that's a relative term. However, those unsolicited comments have dropped away in recent years. While hardly a scientific survey, I feel this shows the delivery issue has been remedied or buyers are merely willing to wait for a Gull. No one can miss the close resemblance of the Titan Tornado line to the Earthstar Gull models. Yet one designer observed to me that Earthstar has never resorted to adding vertical area to the tail, which may suggest that Mark has a more accurate sense of the aerodynamics of his planes. This should come as no surprise, given his origination of this ultralight shape and his many years of refining the design. Fast to slow In my first experience with the Thunder Gull back in 1992, I expected a speedy machine-and I got one. It can zoom, no doubt about it. But it can also slow down, as the stall speed shows. Nonetheless it's easy to see why people may doubt the low-speed capability of this design series. Consider its tiny little wings with only 20 feet of span. To many observers this makes the Gull series look fast, and in this case, looks don't deceive. When you lower those barn door-sized flaps on the trailing edge of a broad-chord wing, things become significantly quieter in the Gull 2000. They work much like the flaps I'm used to on production general aviation aircraft. But those heavier beasts of the air don't retain good handling at such approach speeds. Thunder Gulls do. As one comes in to a tight, crowded, highly controlled site such as the ultralight strip at AirVenture, you immediately realize the benefits of slow speeds and slow-speed handling. True, expert factory pilots make even faster-flying light aircraft look easy on these short runways; they're talented and very accustomed to their airplanes.For someone like me, who flies one aircraft and then another with different characteristics, a cooperative machine brings a sigh of relief. Several turns are needed as you approach AirVenture's ultralight strip. And you can't be going too fast as someone ahead of you may be flying slowly. So, down go the flaps via the handy lever just to the left of your head. Mark only created three flap positions, one of which is neutral. Notch number one produces a little bit of flaps, a good starting point to slow your speed. Notch number two dumps a lot of flaps. I didn't measure the angles, but the first one is effective on downwind to start the process. When you add the rest, the Gull 2000 feels like you pushed the brakes on your car. You can literally feel the deceleration. Fine, so the flaps work well. That hard-working wing also responds well to its equally large ailerons. And in my experience, they retain a high percentage of their authority from the highest to lowest speeds. Even the muscular effort required changes surprisingly little. Exactly how Mark achieves this, I'm not completely sure, but fluid control linkages are part of the secret. When you cruise, the control effort is not overly sensitive, and yet at the slowest approach speeds, forces remain quite light and the resultant action comes quickly, not sluggishly as in a Cessna 182 on slow approach. Touchdown was also very good. Actually, I thought it was not my best performance in smoothness, but both Mark and the new owner complimented my landing. I always aim for full-stall landings. In ultralights this can produce a very high nose angle that may touch the tail of some aircraft on the ground. This is what I thought happened in the Gull 2000. Nonetheless, I tried to accept their kind words graciously. The Gull 2000 sells for $11,000 without engine, propeller, or instruments. Add about $4,000 for the dual carb Rotax 503 and another $1,500 to $3,000 for prop and instruments (your choices can vary widely), and you'll start flying at $17,000 to $18,000. With finishing items, you might even push it toward $20,000. For this outlay, you'll have a mostly metal aircraft-only the control surfaces are dope and fabric to avoid extra weight-and it should last for many years. Treat it as you would a general aviation aircraft with its FAA-required maintenance, and you could possibly fly your Gull for decades. Given this longevity, a Gull 2000 is a good investment. However, the dollar analysis misses the point. Yes, value is important, but what makes the Gull 2000 a joy to own is the way it flies. I recommend the new Earthstar model enthusiastically. Since this latest model from Mark Beierle also offers a large improvement in cockpit comfort, his new aircraft deserves your careful purchase consideration.

Seating	1
Empty weight	274 lbs (as flown)¹
Gross weight	550 lbs
Wingspan	20 ft. ²
Wing area	95 sq. ft.
Wing loading	5.8 lbs/sq. ft²
Length	17.75 feet
Height	6.5 ft
Fuel Capacity	5 gal. (standard)
Kit type	Assembly kit
Build time	150 hours
Notes:	¹Fitted with the Zanzoterra engine, Beierle feels the Gull 2000 can make Part 103 ultralight weight.. ²Effective span, due to the wing tips, is 22 feet, says Earthstar; a span of 24 or 28 feet is available with 133 square feet of area.
Standard engine	Rotax 503 (as flown)¹
Power	52hp at 6,500 rpm
Power loading	10.6 lbs/hp
Cruise speed	60-105 mph³
Stall Speed	26 mph
Never exceed speed	120 mph
Rate of climb at gross	1,500 fpm
Takeoff distance at gross	125 ft.
Landing distance at gross	75 ft.
Notes:	³Cruise can be held to Part 103's 55 knots with a smaller engine and the right prop, says Earthstar.
Standard Features	Cantilevered wing, Rotax 503, independent main wheel brakes, in-flight trim, counter-balanced ailerons and stabilator, 5-gallon fuel tank, Lexan® windscreen, 4130 chromoly cage, shoulder belt seat restraint, fiberglass seat, fiberglass body, metal wings with drooped tips.
Options	Other engine choices, including the Zanzottera, 60-hp HKS and Rotax 447, longer wings (see specifications), instruments, door and side panels, electric starter, 2- or 3-blade composite prop, aluminum or fabric wing covering, and ballistic parachute.
Construction	4130 steel airframe, fiberglass fairing, aluminum or fabric wings, metal tail coverings.

Design

Cosmetic appearance, structural integrity, achievement of design goals, effectiveness of aerodynamics, ergonomics.

Systems

Subsystems available to pilot such as: Flaps; Fuel sources; Electric start; In-air restart; Brakes; Engine controls; Navigations; Radio; (items covered may be optional).

Cockpit/Cabin

Instrumentation; Ergonomics of controls; Creature comforts; (items covered may be optional).

Ground Handling

Taxi visibility; Steering; Turn radius; Shock absorption; Stance/Stability; Braking.

Takeoff/Landing

Qualities; Efficiency; Ease; Comparative values.

Cons - Smoother runways are much preferred as ground clearance is less than some ultralights. Except for a warm cabin in hot weather, I found no other negatives in this category.

Control

Quality and quantity for: Coordination; Authority; Pressures; Response; and Coupling.

Cons - None. If you don't like the way Gull 2000 handles, you may be too picky.

Performance

Climb; Glide; Sink; Cruise/stall/max speeds; Endurance; Range; Maneuverability.

Stability

Stall recovery and characteristics; Dampening; Spiral stability; Adverse yaw qualities.

Overall

Addresses the questions: "Will a buyer get what he/she expects to buy, and did the designer/builder achieve the chosen goal?"

It is Mark’s design philosophy to make the most efficient aircraft he can, one that will use the least fuel. He defines himself as “a minimalist,” and this sentiment is carried throughout this beautifully optimized aircraft. To me, Mark appears to have grown increasingly comfortable in his role within ultralight aviation. Relaxed and confident, he knows he has created a superior flying machine. He also smiles a lot more these days in my opinion, thanks to a wonderful woman named Leslie who accompanied him to AirVenture 2000 in Oshkosh, Wisconsin. Married a year and a half ago, the two complement each other and make a good team. No more tight squeezes Perhaps it was this new personal relationship that motivated Mark to pay more attention to creature comforts. Notably, the Gull 2000 is wider than the previous single-seat or tandem two-seat Thunder Gull aircraft. Considering Mark is a lean and healthy vegetarian, his concern for broader pilots is no doubt appreciated.