A Gift of Design
The UltraCruiser was born under rather unusual circumstances. Its designer, Morry Hummel, was not a young engineer with a passion for flying ultralights. On the contrary, Hummel is one of aviation’s pioneers with many years of experience. His story identifies how he found the time to create the UltraCruiser and, in particular, why the ultralight is fully named UltraCruiser, God’s Gift.
Hummel wrote, “I crashed my miniMAX on July 19, 1995. I lost my right leg below the knee, my left leg was badly broken, and my face crushed. My teeth were wired shut for 10 weeks and I was fed through a tube in my stomach.
“While I was in the hospital for 5 months, I had time to think. God had spared my life for a reason. The UltraCruiser is named God’s Gift because I am only 85 years young and flying again.”
I found it an inspiring story. Certainly most pilots reaching the ripe age of 85 years would have hung up their wings and retired to the easy chair. An octogenarian who was still flying after surviving a crash of the severity Hummel describes could be forgiven for parting ways with the delight of flight. But to survive such a grueling crash, go on to design a new aircraft, and then fly again proves Hummel is far more than your ordinary aviator. Clearly, resigning and retiring weren’t how Hummel chose to proceed.
Hummel is also known for use of VW engine conversions. Long before the Rotax 4-stroke became available, the VW engine conversion powered light aircraft. Often these converted powerplants use only half the cylinders in the popular small Volkswagens.
In July ’02, Terry Hallett bought Hummel Aviation from Morry Hummel and his wife who had started the business. Hallett says he got involved to help upgrade the drawings and he ended up purchasing the enterprise. Still, “Morry comes in every day,” says Hallett.
When a Half VW engine powers the UltraCruiser, it can employ 28 to 37 hp. The engine on our test aircraft produced 37 hp. I was told it burns about 2 gallons per hour, which makes it one of the most fuel-efficient engines you can install on an ultralight. Though these engines lack the favorable power-to-weight ratio of 2-strokes, 4-stroke engines hold large appeal among many pilots. Their noise is less whine and of lower decibels than most 2-strokes, fuel economy is substantially better, and ecological concerns favor the 4-stroke over the 2-cycle engine.
These days, Scott Casler produces Hummel’s converted engine in a location different from Hummel Aviation. The VW conversion is a Hummel creation now built by another company. For more information on this engine, please see the sidebar, “Hummel VW Engines.”
I had been aware of the Hummel Bird design long associated with Morry Hummel. Circumstances prevented me from flying one of the intriguing little aircraft in the past, but when factory helper Jon Jacobs brought the UltraCruiser to Florida’s South Lakeland Airpark, I was ready. Jacobs patiently gave me a preflight review of the ultralight and provided an approximation of flight qualities that proved to be right on the mark. Later in this story, I’ll add some of Jacobs’ impressions of the machine.
Spin Her Up
I’d have to work at installing either a pull start or electric start, even if it meant not flying under FAR Part 103. My fingers and arms are too important to me to risk losing them in an improperly executed prop start. I’ve done these starts and they aren’t particularly hard. But, like all pilots, I make my share of mistakes. Why should I jeopardize my precious digits just to start an engine? I try to avoid it now, though I’ll accept such a start from someone who doesn’t mind the threat. Jacobs pulled the prop for my flight.
In order to keep the UltraCruiser within Part 103 with its 4-stroke engine, pull or electric starting simply isn’t feasible. You’ll have to judge for yourself if hand-propping is acceptable to you.
Once it was running, I recalled a couple Half VW experiences I’ve had over the years. It lacks the “big engine” sound of more potent powerplants, but it’s audibly different than any 2-stroke. It’s also different from the Rotax 912 series, which run at nearly twice the revolutions.
I very much liked flying with this engine. At one point in my airborne tape recording, my notes reflect that I removed all ear protection and was surprised at the low-noise results. It simply sounded like a VW Beetle engine running at low revolutions and was a pleasant change from a 2-stroke whine or the higher-rev noise produced by the Rotax 912 series.
Compared to the Rotax 582 and its 65 hp or even the Rotax 503 and its 50 horses, the Half VW with 37 hp – the highest power offered by Hummel’s 2-cylinder powerplants – sounds rather weak. Even the Rotax 277 with its single cylinder produces 28 hp and the lightweight 2si engine yields nearly the same power with many fewer pounds. However, I found the UltraCruiser to be quite sprightly in its performance, and others, whom I’ll quote later in this article, echo my feelings.
Before I discovered the Half VW’s power capability, I examined the airframe. The UltraCruiser is an unusual ultralight built of all metal. Rare as that is in ultralights, aluminum is an excellent way to keep the weight low. Metal also lasts a long time and we know a lot about aluminum so watching it over its life span is fairly straightforward. The downside of the metal finish is the build time and complexity. Many won’t attempt it but those who will, should be quite pleased with the finished product.
I found the UltraCruiser adequately roomy for my average-sized body, but larger folks could look into the UltraCruiser Plus, though it cannot fit inside Part 103 weight limitations. Once inside, you’re surrounded by shiny metal.
Taxi steering is quite precise with the tailwheel and the UltraCruiser’s braking was more than adequate. The brakes are differential to allow tighter maneuvering and are actuated via heel brakes. These aren’t my favorite as I prefer toe brakes (old Cessna habits die hard, I guess), but they worked without challenge. Your feet slide readily on the interior’s metal finish, so heel brakes were easy enough to operate.
Steering is via a foot bar, that is, a solid bar that pivots much like that go-cart you made as a kid. However, some pedal extensions – not unlike what little children have on their first tricycles so they can reach the pedals – made the pivoting bar feel much like actual rudder pedals. The overall control experience was satisfying.
When you open the throttle on the Half VW, the feeling and sound is much different than a 2-stroke. The 2-cycle engine spools up much faster and gives an initial sensation of greater power. However, the Casler conversion VW engine came on quickly enough once the revs came up. I was pleasantly surprised at the acceleration. It can even function well at high elevation fields.The Half VW’s 37 horses display a lot of energy and I estimate the brief launch roll was 100 to 150 feet.
The UltraCruiser’s tailwheel lifts quickly and ground run was short. Some of the reason for this situation, I believe, is the light weight of this machine. Though the tailwheel lifts quickly and easily, I found that the UltraCruiser showed no tendency to overlift the tail.
Landings went very well. I initially approached at 70 mph to allow plenty of room for error and slowed to 60 mph over the threshold. Later I discovered that I could make an approach at considerably slower speeds, in the area of 45 mph, which significantly decreased ground roll.
Once I got down in ground effect, an earlier feeling that the UltraCruiser was sinking rather fast disappeared. The UltraCruiser rounds out very cooperatively and sustains height above the runway very well.
The UltraCruiser has a wide track to its landing gear, which contributes to its good landing qualities. It felt very stable on the ground. Hummel Aviation’s UltraCruiser Plus has a 6.5-foot gear track for improved ground handling.
Despite the smoothly contoured aluminum fuselage, the UltraCruiser showed respectable slips. Since the design does not use flaps (in an effort to keep weight down), slipping is useful. However, a slow approach speed will also help contain the landing roll. Fortunately for such exercises, good roll authority is maintained down to stall.
Roll Without the Rock
The UltraCruiser’s roll response was quite brisk, not in the range of aerobatic aircraft, but faster than your average ultralight by a clear margin. I had been told to expect this. Morry’s older Hummel Bird was noted for its ability to roll 360° in 3 seconds. The UltraCruiser, which flies slower, is not as quick in roll but was certainly responsive. Short span and a small wing area contribute to this quality though the Hummel Bird uses even smaller wings (18-foot span and 57 square feet of area). Though the ‘Bird must be licensed Experimental, and though it has to be N-numbered and flown with an FAA certificate, the older model only weighs 300 pounds empty.
Hummel’s harmonized controls were delightful to use and I adjusted to them quickly, finding the UltraCruiser very desirable to fly.
The UltraCruiser’s rudder was proportionately weaker than the ailerons, but I only found this by slipping hard to a landing where I was able to exhaust the rudder range (at relatively slow speeds).
Hummel Aviation has a Website with a good deal of information that prospective buyers may want to study. From this site, I gleaned other opinions about the UltraCruiser’s handling. I’ve employed these comments as they closely mirrored my own experience with this enjoyable ultralight.
Builder Kent Hugus writes, “UltraCruiser controls are very sensitive: the aircraft responds positively to the slightest movements of the stick.” However, he believes the rudder is too small and its response sluggish. Contrarily, Hugus finds the ground steering very brisk, which suggests a rudder size issue, not a rudder pedal linkage one.
Hugus also reports that another UltraCruiser builder, Jack Roberts, designed a spring-loaded cartridge for the tailwheel steering arm, which damps the tailwheel response. Hugus likes the view over the UltraCruiser’s nose while taxiing. It is so good, he says, “One hardly needs to S-turn.”
Hugus’ home field sits at 5,600 feet MSL. He flies the 37-hp version of the Half VW produced by Casler. About his experience, he writes, “My UltraCruiser climbs very well.” He didn’t provide numbers about the climb rates as he says the panel is too small for a VSI when he prefers “more important instruments.” But he notes the 37-hp UltraCruiser “accelerates to 75 to 80 mph at full throttle and holds that airspeed with about 3,100 rpm.” I consider this a good performance for a small engine at a high starting elevation.
Keep in mind that the prop you install determines if you’ll stay under Part 103’s 55-knot (63 mph) speed limit. My test UltraCruiser went too fast, but the prop can easily contain the machine, assures Hummel Aviation.
Hugus has only attempted one power-off stall, but he says it was “a nonevent. The UltraCruiser warned me with mild aileron buffet and it simply mushed.” He reports that all he did was to release backpressure and the ultralight resumed flying.
On returning to his mile-high airport, Hugus found that the UltraCruiser “is easy to land and wants to [land in a] three-point [attitude].”
My checkout pilot, Jon Jacobs, also posted a few comments. Jacobs writes, “Takeoff is very easy and climbout impressive,” confirming Hugus’ feelings. Jacobs adds, “Cruise speed [is] very good and stall very low.” He likes the quick response and adequate power of the ailerons.
Like Hugus, Jacobs feels “landings are easy,” but he adds, “Proper airspeed is important, as this bird is slippery and loves to float.” I also found these qualities and I tried slower approach speeds to reduce the float.
Jacobs concludes that after flying 43 different ultralights, the UltraCruiser “is one of the nicest” he’s flown.
Finally, pilot Jayson Scantlen adds his thoughts. “The UltraCruiser is a joy to fly. From the time I accidentally got airborne for its first flight, I couldn’t wait to get back up in it.” Sometimes first flights aren’t quite so inspiring as a pilot takes time to master the controls. But Scantlen adds, “It has light plane characteristics, in a low-drag airplane.”
Though I am loath to perform prop starts if I don’t have to, Scantlen almost seems to enjoy the experience. He writes, “Flip the prop over once, and the Half VW comes to life. Line her up at the end of the runway, shove on the power, and in 150 feet you’re off.” He noted that his experience was on a turf runway and that he expects even a shorter takeoff run on pavement.
Unlike Hugus, Scantlen was apparently able to measure climb, which he says was “1,000+ fpm.” Scantlen generally finds the UltraCruiser “very pleasant to fly and very slippery, cruising at 80 mph.”
“Landing is my favorite part,” he says. He likes it so much that he often does a touch-and-go “just so I can go around and do it all over again.” Scantlen recorded touchdown at 25 mph and notes he has “very little rollout at that speed.” He added that folks often comment to him how impressed they are with his UltraCruiser’s performance. Even with the wind blowing 45° to 60° to the runway, the UltraCruiser “was still very manageable,” a significant statement for an aircraft he says weighs 249 pounds empty.
I did not have Scantlen’s experience with crosswinds, but the aileron authority is sufficient that I feel sure he is right about the crosswind capability. However, I cannot verify the very slow touchdown speed he reports and I’m aware most gauges are not accurate at such low speeds.
Faster than a Beetle
Since I fly aircraft for an hour or two (and then, regretfully, have to give them back to their owners), I tend to base my evaluations on the numbers available to me in the cockpit. To put more definition on the performance of the Half VW engines that Hummel uses, I recorded a few power and speed ranges.
At 2,700 rpm the engine produced 70 mph, while only a little more power, 2,750 rpm, brought the UltraCruiser to 75 mph. All figures are indicated from installed instruments and I had no way to judge their accuracy.
Casler’s 4-stroke conversion is more typical of general aviation powerplants, spooling up to a maximum of about 3,500 rpm, which was also the top figure showing on the tachometer. In contrast, an 81-hp Rotax 912 substantially exceeds 5,000 rpm at max power.
The VW-style engine spools up noticeably slower than a 2-stroke engine but a vernier throttle (one that smoothly adjusts by twisting or screwing) allowed precise control of the power setting. However, this same feature – which I like on general aviation aircraft intended to cruise in a straight line – made formation flying for photography somewhat harder. In such tight-quarters flying I make nearly continuous throttle adjustments and the vernier control worked against this, at least when combined with the engine’s slower response (compared to a 2-cycle engine).
In a maximum climbout evaluation I logged 3,350 to 3,400 rpm with the throttle fully opened.
I agree with Hugus on another point. Stalls were quite mild. In my several trials, they always broke through, dropping the nose, but it was nothing too radical. I found no tendency for the UltraCruiser to drop a wing at stall, another desirable characteristic.
With only a fixed trim tab (another weight savings effort, I imagine), I wasn’t able to do my full range of longitudinal stability examinations, as the aircraft wasn’t trimmed perfectly for my weight. But I did find the aircraft behaves conventionally on power changes. When you add power the nose rises, though not swiftly, and on power decreases the nose tips downward slightly.
God’s Gift to You?
The 37-hp UltraCruiser, as tested, possesses the light feel of a genuine ultralight. Hummel Aviation also offers the UltraCruiser Plus for pilots weighing more than 200 pounds and taller than 6 feet. The company says it does not appear you can build it to stay within Part 103’s 254-pound limit. The UltraCruiser Plus still uses the 37-hp Half VW engine but you can carry more fuel in its 8- to 10-gallon tank. Hummel Aviation is positioning the UltraCruiser Plus as a candidate for FAA’s proposed Light-Sport Aircraft category.
The larger UltraCruiser Plus has been totally redrawn and provides much more detail than the earlier model, says Terry Hallett. It offers more cabin space and more foot room at the rudder controls. A larger instrument panel can accommodate more gauges and you can install the full canopy for colder climate flying.
Those keen on remaining within Part 103’s low regulation environment can also consider Hummel Aviation’s CA-2 model. This genuine ultralight resembles a metal form of TEAM’s miniMAX, and it holds weight and speed without trouble, says the company. At least two CA-2 models have been constructed.
The plans for the UltraCruiser are $280 including a video providing details of construction and flying. A good list of parts is available – Hummel’s Internet site offers photos of the prefabricated parts you can buy – but you must obtain much of your own metal and perform a significant amount of basic fabrication.
One builder indicated that he invested $3,750 in a VW engine conversion, close to $3,000 in materials, and a year of his time (and the latter reflects some prior experience at building).
Though most customers will regard the UltraCruiser as “scratch kit” – meaning you must obtain many raw material items and fabricate them to the plans – Hummel Aviation does offer a selection of prefabricated parts. For example, the somewhat larger UltraCruiser Plus for larger pilots lists the following items: formed parts such as laser-cut bulkheads, laser-cut rib sets, control linkage components, laser-cut stabilizer and tail fin ribs; welded parts such as the yoke assembly, landing gear, tailwheel bracket, rudder control, elevator control components; plus other items such as fuel tanks, canopies, hardware package, templates, and 4130 steel parts. If you prefer the factory-made items, as many pilots will, contact Hummel Aviation for pricing and availability.
For those who want to hold their investment as low as possible, Hummel indicates that their “step-by-step manual is very complete with all materials listed as well as addresses for where to buy off-the-shelf items.”
Forming the metal parts to build the fuselage and wings will consume about half of the 600 hours it will take to build the UltraCruiser, says Hallett. “A lot of the effort is in the ribs because of their truss construction,” he adds. If you buy all the parts Hummel Aviation can sell you, you’ll slice 200 hours off the 600 and if you also choose their new quick-build wing, you can reduce the total to 320 to 340 hours.
Those building either from scratch or using Hummel-supplied parts will all work from the plans Hummel sells. The plans have similarities to those from Fisher Flying Products in that many parts are drawn in full size so you can build directly on the plans to ensure greater accuracy. This saves a lot of time compared to scaling up from smaller drawings or creating drawings from measurements.
If you choose from Hummel Aviation’s optional parts you will increase your investment in dollars while decreasing your investment in labor hours. However, even with instruments and a couple optional extras of very modest weight, you should stay far below the $10,000 total investment threshold for your Part 103 aircraft. If you want the full canopy, shock-absorbing gear and other options, you’ll creep over the limits of Part 103 and must then N-number your aircraft.
Still in all, for those looking to remain within a smaller budget, the UltraCruiser is a good choice if you feel your building skills are up to the task. When you’re done with the project, I believe you’ll love the flight characteristics of Hummel’s nifty little ultralight. The UltraCruiser’s flight qualities really put a smile on my face. It just might do the same for you.
|Empty weight||254 pounds 1|
|Gross weight||500 pounds|
|Wing area||94 square feet|
|Wing loading||5.3 pounds per square foot|
|Fuel Capacity||5 gallons|
|Kit type||Construction 2|
|Build time||600 Hours 2|
|Notes:||1249 pounds without shock-absorbing gear.
2Build time is 400 hours with prefabricated ribs; and a ready-to-assemble wing is coming soon, saving another 60 to 80 hours for a total of 320 to 340 hours.
|Standard engine||Hummel Half VW, 37 hp at 3,500 rpm|
|Power loading||13.5 pounds per hp|
|Cruise speed||60-80 mph|
|Stall Speed||28 mph|
|Never exceed speed||95 mph|
|Rate of climb at gross||1,000 fpm 1|
|Takeoff distance at gross||150 feet|
|Landing distance at gross||150 feet|
|Range (powered)||160 miles (2.5 hours)|
|Notes:||1 As tested with 37 hp 1/2 VW; test aircraft may not have met Part 103 as equipped.|
|Standard Features||Hummel Half VW 4-stroke engine, cantilever wing, monocoque construction, mostly enclosed cabin, detachable wings, steerable tailwheel, all-metal coverings.|
|Options||Engine power choices from 28 to 37 hp, shock-absorbing gear, remote choke, mechanical or hydraulic brakes, alternative props, instruments, quick-build wing option coming, tinted canopy and windshield, cabin heat. (Note: Some items are supplied by companies other than Hummel Aviation and the addition of some items will disqualify the UltraCruiser from Part 103 participation.)|
|Construction||All-aluminum airframe, formed aluminum wing ribs, small steel parts. Made in the USA and distributed worldwide by an American company.|
Cosmetic appearance, structural integrity, achievement of design goals, effectiveness of aerodynamics, ergonomics.
Pros – All-American design for those who enjoy single-place flying. Cantilevered wing with no struts. Designed around 4-stroke power, which many pilots prefer. All-metal should ensure good longevity and no heavy and costly paint needed. With optional canopy, the UltraCruiser has a P-51 look.
Cons – Challenge of building this kit will eliminate it from interest by many pilots and already-built ones for sale are scarce. Some ultralight buyers believe riveted structures are more vulnerable than aluminum tube frames and certainly damage repair would be more time-consuming.
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 – Four-stroke power is worth giving up systems to some pilots. Vernier throttle on test aircraft was an interesting feature. Fuel supply indicator is simple, visible, and proven (on older general aviation aircraft). Differential brakes were easy to operate. Test aircraft had a cockpit choke control.
Cons – No flaps or in-flight trim can be accommodated if UltraCruiser is to remain within Part 103. Lack of pull starter or electric starter (to stay within Part 103’s weight limits) is a no-deal to some buyers. Engine access comes only after removing cowl.
Instrumentation; Ergonomics of controls; Creature comforts; (items covered may be optional).
Pros – Panel has enough for the basic instruments you’ll need and it’s within easy reach for adjustments. Cabin is roomy enough for pilots weighing less than 200 pounds and less than six feet tall. Four-point seat restraints were appreciated. Optional full bubble canopy available, even tinted, though the open cabin is a delight in good weather.
Cons – Entry won’t be easy for some less agile owners. Some builders will yearn for more panel space for goodies. Long flights will require extra attention to seat comfort. Very limited cargo area. No seat adjustment provided unless builder adds it.
Taxi visibility; Steering; Turn radius; Shock absorption; Stance/Stability; Braking.
Pros – Very precise and responsive tailwheel response. Superb visibility while checking for incoming traffic. Differential braking on test aircraft aided ramp maneuverability. Wide gear track gives great ground stability.
Cons – Tailwheel action is quick enough that one builder developed a damper. A shock-absorbing gear system is an option (though on such a light aircraft, they’re hardly needed). Elevator sits very close to ground if field is rough; inspect carefully.
Qualities; Efficiency; Ease; Comparative values.
Pros – Half VW engine provides surprising pep on takeoff runs, which are about 150 feet. Landing touchdown is very easy due to potent ground effect. Excellent visibility throughout landing approach. Good crosswind capability. Moderate slips work well. Approaches can be done down to the 40-mph range.
Cons – No flaps to aid steep approaches to short fields or in emergencies (however, slips are reasonably effective). Ground clearance is minimal at tail; keep your tail flying in the event of an out-landing. Long ground float will stymie landings after a too-fast approach.
Quality and quantity for: Coordination; Authority; Pressures; Response; and Coupling.
Pros – Light, brisk response from ailerons. Roll rate is better than the average ultralight, perhaps due to small wing and short span. Precision turns to headings were straightforward. Substantial crosswind capability. Steep turns went well as did Dutch roll coordination exercise.
Cons – Rudder response is weaker than ailerons (suggesting harmony shouldn’t be as good as it feels). Ailerons may be a bit fast for some less experienced pilots. No other negatives.
Climb; Glide; Sink; Cruise/stall/max speeds; Endurance; Range; Maneuverability.
Pros – Little plane that carries its own weight in useful load. Climb is very vigorous at 1,000 fpm. Takeoff roll start is surprisingly energetic for a small 4-stroke engine. As tested – with a prop that won’t work under Part 103 – speeds hit more than 75 mph. Burns only 2 gph; good range even with a 5-gallon fuel tank.
Cons – Four-strokes don’t spool up as rapidly as 2-strokes, something to keep in mind if you need a quick burst of power, say on approach to landing. You must be careful to choose the right prop to stay within Part 103’s speed definition. No flaps to permit low and slow over-the-field flying.
Stall recovery and characteristics; Dampening; Spiral stability; Adverse yaw qualities.
Pros – Many pilots believe safety is enhanced when the engine is in front of the pilot. Secure seat belts were installed on test UltraCruiser. Good power response test; power-up raised the nose and vice versa. Stalls broke only modestly and with good warning.
Cons – Longitudinal stability test didn’t work well as the UltraCruiser has only a fixed trim tab that wasn’t perfect for my weight (though light elevator forces made coping easy). Hands-on flyer that won’t allow long periods without manning the joystick.
Addresses the questions: “Will a buyer get what he/she expects to buy, and did the designer/builder achieve the chosen goal?”
Pros – The UltraCruiser makes Part 103 and so can your 4-stroke-powered ultralight. Based on proven Hummel Bird design, which has a long history. Wings can detach for transport (though not a fast-folding wing). Bargain price by anyone’s standard: can be flying for less than $8,000.
Cons – Build times are lengthy, even the fastest configuration is more than 300 hours. More affordable kits call for lots of “tin bending.” Full kit with every part supplied is not available. No 2-seat models are available or planned. Thin aluminum construction could see hangar rash more easily.