Sometimes I’m amazed that we’ve now got ultralight pilots buying engines that cost more than $10,000. Twenty years ago, Eipper Formance (Quicksilver) sold complete ultralights that cost $3,499. Even in the ’90s, many complete ultralights – engine and all – cost less than the price of a Rotax 912 4-stroke engine on its own. One that meets that description is Kolb Aircraft’s Mark III with a 50-hp Rotax 503 dual carb 2-cycle engine.
Nonetheless, the 81-hp Rotax 912 has invaded the realm of what is loosely called “ultralight” flying. Of course, a Rotax 912-powered aircraft simply cannot be used on a single-place Part 103 ultralight. And any 2-place plane with a 912 is less likely to qualify as an ultralight trainer under the training exemption to FAR Part 103; the big engine may push the plane too fast and could make it heavier than 496 pounds (the ultralight trainer empty weight limit).
With the larger engine, the weight will be close but within the definition if you don’t add too many optional extras, believes Brian Blackwood, the owner of the Mark III 912 we were to fly. He’s also one of the new owners of The New Kolb Aircraft Company (yes, The New Kolb Aircraft Company is the new company name, though we’ll abbreviate it to New Kolb for convenience).
Therefore, the Mark III 912 is a candidate for an ultralight trainer even with the big 4-cylinder 4-stroke engine. Certainly someone who operates a flight school may see the value in employing the bigger engine: lower fuel consumption and lower noise.
The New Kolb
Blackwood and partner Bruce Chesnut now own one of the most venerable companies in ultralight aviation. Started some 20 years ago by Homer Kolb, Kolb Company was sold to key man Dennis Souder and partners when Homer decided to retire, and was renamed Kolb Aircraft.
Acquiring its third owner, the company should benefit from the success of the two businessmen who own The New Kolb Aircraft Company. Before the acquisition, the two were avid Kolb enthusiasts.
Blackwood owns a metal products company specializing in custom-made metal windows and doors. The company enjoys a leading position in its industry and operates plants in Kentucky and Florida.
Chesnut owns a food distribution business based in Kentucky. Business is good enough that they plan in the near future to trade in a couple general aviation aircraft on a Cessna Citation jet. Of course, New Kolb isn’t the business entity that will buy the biz jet, but it will surely benefit from this kind of financial depth.
The two partners report they are building a new plant in Kentucky for Kolb aircraft production. They plan to move the enterprise soon to Chesnut Knolls Aviation Foundation Airpark, a Chesnut development with the goal of promoting ultralight aviation.
Besides a large plant built for ultralight manufacturing, New Kolb will have an adjacent 2,100-foot strip the two owners say is “dedicated to Kolb ultralight flight, testing and sales.” The site will give the company a base of operations as secure as the Kolb family farm in Pennsylvania that has housed Kolb since its inception.
In fact, the airpark itself sounds interesting. Established as a foundation, Chesnut Knolls Airpark is open to the public. Some fishing ponds and an abundance of wildlife in the area make it even more appealing for those who want to come and become exposed to ultralight aviation.
Blackwood also invited enthusiasts to build a cabin on the grounds, something he’s nearly done for himself. “It’s a real beautiful place,” he says, and this seems a welcome development for ultralight aviation.
Blackwood and Chesnut also have plans to improve the production facility. “State-of-the-art computer and direct Internet parts management will provide immediate response to owners’ requests anywhere in the world,” they announced in mid-April this year.
The two directors will also assure continuity to the Kolb aircraft production effort by retaining John Yates to head New Kolb as chief operations officer. Yates is credited as manager of many aspects of Kolb for the past 3 years. “John is a talented manufacturing engineer who brings a wide range of skills and abilities to New Kolb,” says the company. To further smooth the transition of ownership, former Kolb Aircraft president Dennis Souder will work with the new company in a consulting capacity.
As The New Kolb Aircraft Company presented itself publicly for the first time in ’99, both Souder and Homer Kolb were present to make introductions of Blackwood and Chesnut to many fellow ultralight industry leaders who were present at Sun ‘n Fun in Lakeland, Florida. While change is in the winds for Kolb designs, it appears the popular planes will be well-cared-for under the new ownership.
Since we haven’t reviewed the Mark III since ‘91,1 long before the popular emergence of the Rotax 912, it is timely to focus on the machine once again.
Four-Stroke Mark III
The Mark III has been the Kolb 2-seater for several years, despite the recent return of the Laser. Over time, customers have been adding increasingly larger powerplants. With the Rotax 912, you’d think we would have found the limit, but given pilots’ interest in more and more power, who knows?
In any event, the factory gave their blessing to the installation of the large engine, and I was finally able to evaluate the plane.
Our test plane was Brian Blackwood’s personal Mark III, so you may not be surprised to hear that his is more liberally equipped than earlier Kolb factory aircraft. Blackwood gave his seats a more deluxe covering, installed dual joysticks, and added the big powerplant plus hydraulic brakes. Brian is a big guy, so the larger engine makes sense.
A flight school operator may want to keep the aircraft lighter and simpler. Blackwood agrees this might be desirable, and believes a Mark III with a Rotax 912 engine can make FAR Part 103’s ultralight training exemption maximum of 496 pounds empty weight (although, since that had not been his goal, he could not be absolutely sure). In addition, such a simple thing as excessive paint can sometimes push an airplane over the allowable weight.
Although we flew without doors in steamy Florida, Blackwood has fitted the tube-and-Lexan® doors. I did not care for the Mark III 912 without doors. As I regularly caution readers, my opinions are simply that – my opinions. You may feel differently. In fact, I’d be surprised if we felt alike on all aspects of a plane.
Flying at near gross weight, I found the Mark III with no doors to be a very windy cockpit that also allowed a lot of air to hit me partly in the face. Since the Mark III tapers toward the nose beginning at your hip, one side of you in the side-by-side 2-seater is going to feel the breeze very noticeably. For me, given the speed of the Mark III 912, the windblast was distracting.
Neither did the cockpit please me as much as some other brands. That same taper toward the nose means that both your legs must angle in toward the rudder pedals. They aren’t located directly in front of you. I found I had to work my feet slightly differently to press the pedals equally.
You can reply that this is merely something you get used to, and I agree. However, if you have enough things to “get used to,” you can become overwhelmed. If a designer can make the controls more intuitive, more standardized, the pilot is less likely to make a mistake.
These design features combine with the throttle position to make the Mark III less than optimal for me. The lone throttle lever was located just to the left side of a center “console,” requiring a reach across for a right-seat pilot. From the right seat, you’ll use your left hand. However, unless you have an empty left seat or a very slender occupant in it, the throttle will rub against the leg of the left-seat occupant.
Normally this throttle location wouldn’t matter so much, but when we fly for cover photos for Ultralight Flying! magazine, we operate in fairly tight formation. To stay close in moving air, you must constantly work the throttle, sometimes to its full range. Doing so while pawing the leg of the guy next to me was somewhat awkward and uncomfortable. A longer throttle handle might help.
No airplane is perfect (thank goodness, or I’d have nothing to nit-pick about). Blackwood’s Mark III did, however, have plenty of virtuous qualities.
The dual joysticks were positioned very comfortably, and a big improvement over the shared center stick of an earlier Mark III. When I last flew the model solo from the left seat (this time I flew on the right), I found the joystick positioned high and forward, plus I had to reach across with my left hand to move the throttle. This crossed-arm posture was less than optimal.
On this flight, I was unable to use trim at all, as the trim lever is located on the left side of the cockpit. If past experience was any indication, it would be of medium effectiveness, but hardly necessary. Every Kolb I’ve flown has such light and responsive controls that trim is hardly needed, except possibly on long level-flight segments of a cross-country flight.
Stalls in the heavily loaded Mark III 912 went very well, showing very mild characteristics, a continued credit to Homer Kolb’s design work. Stall break power-off came in the high 30s to low 40s. Throughout all stall examinations, I found the controls would get a little sloppy, but the plane stayed highly controllable.
The last Kolb I’d flown for a “Pilot’s Report” in Ultralight Flying! magazine was the SlingShot,2 a potent blend of other Kolb models that sits up high on its long gear. Conversely, as it always has, the Mark III sits lower on stubbier gear legs and therefore has a rather flat deck angle. Between the two, the Mark III will be an easier transition for pilots without taildragger experience.
In addition to reliable Rotax 912 4-stroke power, the newest Kolb maintains the company’s best features. Snappy handling is part of the Mark III, just like all other Kolbs. In fact, it’s a trademark quality for the brand.
The cable-linked controls are smooth thanks to careful routing and fluid joints. Homer Kolb’s original sense of design was simple and clean, and this tradition has been faithfully upheld throughout the years. The result is a smooth, easily moving control system honed to a fine point of harmony. Pedal pressures unite with aileron and elevator forces to allow a graceful flight through the air.
Brian Blackwood’s 912-equipped Mark III maintained the tradition, as well. I felt comfortable at very slow speeds while flying in close to our photo plane. I don’t do that in every ultralight I evaluate, and I usually don’t have a second occupant in the plane.
The Mark III’s panel has adequate room for instruments compared to single-seat Kolb aircraft. The FireStar I and FireFly have limited panel space due to a narrower cockpit.
I enjoyed great visibility thanks to an overhead skylight. With the forward openness, the pilot is given a very wide panorama. Your eye sights right down the leading edge so, with a small nod forward, you can see upward. Kolb is one of the top four or five ultralights for sheer visibility. Of course, the single-seaters are best, but the Mark III’s visibility remains very good.
Engine noise is reduced by using the Rotax 912 4-stroke. By comparison, I recall the SlingShot with a 65-hp Rotax 582 engine seemed loud. Certainly for an ultralight instructor or someone who flies a great deal, lower noise can provide a significant reduction in pilot fatigue.
While taxiing for takeoff, I noted the comfortable sure-footed feeling of steering a Kolb. Combined with a full swiveling tailwheel, maneuvering around crowded airport ramps is quite easy. (Ramps would’ve been nice; Florida’s sandy bone-dry soil this year was a literal drag on the best of tailwheels.)
Takeoff distance was understandably short given the 81 horses pushing their hardest. However, we didn’t jump off the ground like a Kolb single-seater because of the added mass. I should’ve remembered this when the time for landing arrived.
After a fine approach, I didn’t handle touchdown as well as I might. I added a safety margin of speed, but I slowed once near the ground. The Kolb sits low and I misjudged the round-out. I had reduced power fully and lacked any forward push.
My last landing in Blackwood’s Mark III was also my first. You see, for the first time in all the pilot reports I’ve done for Ultralight Flying! magazine (well over 100 in the last 12 years), I managed to bend the landing gear. The responses to this event were different.
Blackwood said, “I thought you were a damn good pilot until then,” though he appeared to enjoy giving me a friendly hard time about it. Of course, neither he nor I were the ones to replace the gear leg. It bent only a couple inches and looked like a quick remove-and-replace job, but apparently it takes 2 to 3 hours. My thanks to Kolb’s Bill Martin for handling this.
Another frequent comment was, “Well, join the crowd.” Apparently this happens with some frequency, and for that reason, “we brought a box of replacement gear legs with us,” Blackwood noted.
Finally, more than a couple others said, “Ah, it’s good to see you’re human, Dan.” Indeed, I have bent a couple airplane parts in 33 years of flying. However, this was a first on the job for Ultralight Flying!. I hate to admit it, but my perfect 12-year record of doing these reports without damaging the ultralight is now broken. I guess it’s a little like that first parking lot scratch on your brand-new car. You hate it, but at least you aren’t as nervous about it afterward.
A case of pilot error, I got too slow in the Mark III and ran out of float. If I’d kept speed up better and flared lower, the gear and my perfect record would still be intact. Using a touch of power also would have helped, and we did have a 4,000-foot runway (but I wanted to use only a few hundred feet). It happens to all of us at one time or another, I guess.
Power = Performance
Having enough power goes both ways. A stereo salesman might tell you that having enough power lets you turn the music down lower with more quality. Airplane power is like that on more efficient designs.
However, Kolb designs are optimized for the slower speed flight of ultralight aircraft. Within that range, the Rotax 912 engine is helpful. However, if you want to win a race, go for a Tornado or something. To me, this is one of the charms of a Kolb: the Mark III flies so well at the lower speeds where our form of flying is unique.
The big engine does well carrying a larger load in high-power demand situations like faster cross-country flight, repeated climbs to pattern height during training, or low terrain flying where reliable ample power gives a feeling of assurance and an ability to climb quickly.
Despite the big 4-stroke’s appeal, a Mark III with the modest 50-hp Rotax 503 dual carb engine flies very well, if you can build lightly. You may need to consider this, as the Rotax 912 engine by itself is about $11,000, says Blackwood. That will boost a Mark III 912 to $20,000 or more. A Mark III with a Rotax 503 engine is only about $11,000, and that’s for the airframe kit and the engine.
One place to spend extra money – at least for those who’d rather fly than build – is for Kolb’s quick-build package. It sells for about $2,500, but is said to decrease build time by one-third to one-half. The quick-build package could cut 225 hours. Many Kolbs normally take 450 to 550 hours to build, I’m told.
Any of the Kolb models gets good marks from me, though my personal preference is clearly for the lighter versions. However, desirable qualities – brilliant handling, superb performance, respected company and a good track record – come together in this aircraft for those in the market for a 2-seater.
Whether you are attracted to the reliability of the Rotax 912 4-stroke engine or prefer the more docile and proven Rotax 503 2-stroke, the Mark III offers a solid choice in the ultralight field.
Welcome to The New Kolb Aircraft Company.
1 See “Pilot’s Report: Flying Kolb’s Mark III,” July ’91 Ultralight Flying! magazine
2 See “Pilot’s Report: SlingShot Gets Up and G-O-E-S,” September ’96 Ultralight Flying! magazine
|Seating||2-seat, side by side|
|Empty weight||500 pounds|
|Gross weight||1,000 pounds|
|Wing area||160 square feet|
|Wing loading||6.3 pounds per sq ft|
|Length||22 feet 6 inches|
|Height||6 feet 4 inches|
|Fuel Capacity||10 gallons|
|Build time||450-550 hours|
|Standard engine||Rotax 912 4-stroke|
|Power loading||12.3 pounds per hp|
|Cruise speed||75 mph|
|Never exceed speed||100 mph|
|Rate of climb at gross||1,000 fpm|
|Takeoff distance at gross||200 feet|
|Standard Features||Dual controls (shared center throttle, shared center joystick), factory-welded chromoly steel fuselage, in-flight elevator trim (left seat only), folding wing and tail, 3-position flaps, half-span ailerons, steerable tailwheel, adjustable rudder pedals.|
|Options||Rotax 503, 582 or 618 2-cycle engine, dual joysticks, hydraulic disc brakes with heel pedals or drum brake with hand lever, full enclosure, skylight, upholstery, 2- or 3-blade composite prop, ballistic emergency parachute, strobe light, instruments, finished wing ribs, quick-build kit (225-275 hours), partial kits.|
|Construction||Welded 4130 chromoly steel, aluminum, spring steel landing gear, fabric covering.|
Cosmetic appearance, structural integrity, achievement of design goals, effectiveness of aerodynamics, ergonomics.
Pros – Kolb’s Mark III design hasn’t changed materially since our last report in ’91, but that’s because the design works well. Successful new business owners appear highly likely to assure the Kolb name lasts a long time. Former Kolb Aircraft (in Pennsylvania) employee John Yates will transfer to Kentucky, assuring continuity for all former customers.
Cons – The Rotax 912 adds considerably to the price tag of the otherwise fairly reasonable Mark III. Traditional Kolb handling suffers noticeably with the addition of the larger powerplant. Lack of changes – except to add more and more system complexity – means the Mark III is becoming somewhat dated.
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 – Flaps are quite effective, go down deeply in two deployment settings. Flaps are easily deflected even at some speed. Loaded Mark III with 912 power can have additional systems like hydraulic brakes and electric start (though added weight robs some control responsiveness). Trim is handy for left-seat pilot only.
Cons – Flaps control above and behind you means you need to turn and look at setting until you’re familiar. Trim cannot be reached at all from right seat (where I flew). Throttle between seats rubs against left-seat occupant’s leg making fluid movements tougher (though this is not a problem while cross-country flying).
Instrumentation; Ergonomics of controls; Creature comforts; (items covered may be optional).
Pros – Deluxe seats offered more padding than the standard Mark III sling-style seats. Full enclosures and doors are possible; they were removed for my warm Florida flying. Shoulder belts were installed. Side-by-side seating is optimal for instruction. Entry was very straightforward, especially with doors removed. Dual joysticks were an improvement over standard shared center stick of a standard Mark III.
Cons – Windscreen was only marginally effective with doors removed; very windy cockpit (especially considering strong push of the 912). Tapering nose placed rudder pedals inward, requiring an angled leg posture that was not comfortable. Panel is quite a reach from the steeply raked seats, especially with tight seat belts.
Taxi visibility; Steering; Turn radius; Shock absorption; Stance/Stability; Braking.
Pros – Good ground clearance allows rougher field operations. Excellent visibility for ground operations, especially with doors removed. Full swiveling tailwheel makes for easy ground handling, either taxiing or manually pushing; taxiing further aided by powerful hydraulic brakes. Light rudder pedal forces.
Cons – Typical Kolb cable “slap” (tail control cables routed inside the boom tube) while taxiing is distracting at first. No other negatives.
Qualities; Efficiency; Ease; Comparative values.
Pros – Robust takeoff performance with 81-hp Rotax 912, even while heavily loaded. All Kolb models climb very fast, but the big Rotax really adds energy. Takeoff run is short. Approach visibility is huge. Crosswind capabilities are as excellent as they always are on Kolb designs.
Cons – The Mark III is not a particularly speedy design. Heavily loaded with the big Rotax, a well-equipped aircraft and big occupants, I felt the Mark III lost energy quickly during round-out, though I must confess my experience was limited to a single unworthy landing. I’d advise landing with some power at first, or building and flying lighter. (See article for more on landings.)
Quality and quantity for: Coordination; Authority; Pressures; Response; and Coupling.
Pros – Handling has been legendary on Kolbs since the company started; light responsive controls are one of the plane’s main attractions. Well-coordinated system with good harmony. At near gross weight, we were still able to maintain a fairly tight formation with the photo plane. Crosswind operations are limited only by pilot skill; controls are responsive at all speeds. Adverse yaw is less than the full-span aileron SlingShot.
Cons – If you prefer handling with “feedback,” a Kolb may not be for you, as it handles quickly and with a very light touch. I believe you can easily get used to it, but the point is you must. Taildraggers present challenges to many pilots; handling during touchdown and round-out may be too “sensitive” for some.
Climb; Glide; Sink; Cruise/stall/max speeds; Endurance; Range; Maneuverability.
Pros – The Rotax 912 guarantees lots of power to lift you and a loaded Mark III aloft, yet with a smoothness 2-strokes cannot deliver. Climb in most Kolbs is awesome, and the Mark III 912 is no different, despite its added weight. Fuel economy is reportedly better than a Rotax 582. Sink rate is very reasonable. Slow-flight qualities are very good.
Cons – Even with 81 horsepower, a Kolb won’t be a speed demon. However, the big 4-stroke engine practically assures no one will be outclimbing you. Added power by larger engines means weight increases with some resultant loss of responsiveness. Design can rapidly lose energy in ground effect; try carrying some power at first.
Stall recovery and characteristics; Dampening; Spiral stability; Adverse yaw qualities.
Pros – Stalls were benign and slow thanks to Kolb’s hard-working wing design (picture how steeply they can climb). Power-on stall simply turns to mushy burbling flight that is easily recognized. Controls remain quite effective down to stall; very reassuring when doing low-speed approaches. Emergency parachute is always appreciated, as are 3-point (my minimum requirement) seat belts.
Cons – High thrust line pushes the nose over on power addition, the reverse of most certified airplanes (though rather common among ultralights). Stalls in the Mark III 912 got very steep with a nose wallowing at break.
Addresses the questions: “Will a buyer get what he/she expects to buy, and did the designer/builder achieve the chosen goal?”
Pros – The story is the new company ownership; however, they appear to bring adequate funding and capable business skills to the task. Some Kolb employees will make the move to Kentucky, adding continuity. The brand is one of the most successful in the ultralight industry, and the safety record is good. According to founder Homer Kolb and former president Dennis Souder, the new owners are dedicated to maintaining Kolb’s excellent reputation. The Mark III is part of a broad family of similar designs.
Cons – Most Kolb designs, including the Mark III, are said to be “build intensive,” though a quick-build option can cut the task by close to 50% depending on your level of customization. You’ll invest some real money to have a plane like the one test-flown; a Mark III can cost considerably less with a smaller engine. Taildragger designs aren’t for everybody; Kolb has no tri-gear options. Side-by-side seating too cozy for some (though usually valued for instruction).
max adams says
What happen to the Kolb SS model?
I would like to know if a Mark III or Firefly would be best for me. Like the owner I am a big guy I am six foot but weigh 300 pounds. I am not round just big. Rather than a 912 I would use an EA82 Subaru or VW TDI, both engines are under 200 pounds. My intention is not to over throttle either one but fly within their comfort zone low and slow where the fun is.
Naturally I do not need or want a two place so how can I combine things to get a single place with the lift I need?
Dan Johnson says
Hi Doc: I feel sure some solution awaits you in the Kolb Aircraft product line. I urge you to make contact directly with the factory and pose your questions of them. See their banner in the right column of this website for all contact information.