YOU HAVE TO fly it to believe it
From a distance, Martin Hollmann’s HA-2M Sportster gyroplane doesn’t look too much different from any other whirlybird. It has a cabin area, a pusher propeller to make it go forward and a big twin-bladed rotor swinging around overhead to keep it up.
But once you slide into the seat next to its designer-pilot, you know this is something great: a two-place aircraft that flies with the freedom of a bird in all axes; cruises cross country with companionable comfort; and is inexpensive to build and operate.
Besides that, it’s a machine you can tow home behind your compact car at a legal 55 mph with no sweat. To know the HA-2M Sportster, you must know the guy who designed it, an enthusiastic, likable chap who lives in Cupertino, California, in the San Francisco Bay area.
Born in 1940 in Germany, Martin is the son of a prominent German scientist who escaped East Germany after World War II and came to America as part of Operation Paperclip, a government project to provide talented scientists with refuge in the United States from the Communist takeover.
An avid surfer and backpacker, Hollmann, who stands 6 feet 7 inches barefooted, was turned onto gyroplanes back in 1968, when his instructor at San Jose State University introduced him to the work of Juan de la Cierva.
Hollmann won a student fellowship grant, and with that financial support built and successfully tested a 20-foot diameter fiberglass laminated rotor. In 1974 he followed that with the design, construction and flight testing of the Sportster, a 1050-pound gross weight two-place gyroplane.
Hollmann completed his schooling that year and won his Master’s Degree in mechanical engineering at Florida Tech; he then moved to California where he now works for Lockheed Missiles & Space Company at Sunnyvale as a senior design engineer.
He towed his gyroplane west with him, behind the family Volkswagen Beetle — all the way at 55 mph! When you first talk to Hollmann about building a Sportster, he may try to discourage you, unless he’s sure that’s the kind of flying machine you really want He says: “If you’re looking for a fast, economical, cross-country aircaft with a cruise speed above 90 mph, forget it.”
Go to a fixed-winger — and there are many to choose from — with a high cruise speed, fuel economy, and long range compared with an equivalent rotorcraft. Generally, twice as much horsepower is required for a rotorcraft, either helicopter or gyroplane, to lift a given weight, as that required for a fixed-wing aircraft.
“This means we must use an engine of 65 hp or more for a single-seat rotorcraft, or 125 hp or more for a two-seater. By dual seating, I mean one such as the Sportster, which on a standard day at sea level can carry two people with a combined weight of 450 pounds plus a quarter-tank of fuel.”
“I don’t know of any other homebuilt helicopter or gyroplane capable of this kind of performance. Then there’s the noise level — the combination of rotor and pusher engine/propeller does make more noise than many fixed-wingers. Rotorcraft — especially gyroplanes — are not quiet”
So now you know what’s wrong with gyroplanes, what’s good about them? Hollmann starts off with safety first. “Unlike any other aircraft,” he points out, “the gyroplane can be safely landed power-off from any altitude and on most terrain where enough rotor clearance is available.”
“With fixed-wing aircraft, the major cause of general aviation accidents is loss of engine power and the ensuing forced landing, which may end in complete loss of the aircraft and too often loss of life due to the high speed at the moment of touchdown.”
“Should you experience engine failure in a gyroplane, whether at 10 meters (33 feet) or 2000 meters (6600 feet) ACL, you can still make a safe landing on level but rough terrain, since the rotor is autorotating at all times Your approach slope is steep, about 45 degrees, and your sink rate about 1000 fpm.”
“Your steep approach allows you to drop into a small clearing surrounded by trees, and your touchdown speed is almost nil, since during the landing flare, in which you simply pull the control stick back, the rotor speed builds up and increases the lift so that the landing is short and soft. Zero ground roll can be achieved by proper flaring.”
Hollmann likes to point out that the Sportster gyroplane has complete control response at all flight speeds, unlike stiff-wingers in which the controls become mushy near a stall. And since the rotor is autorotating you can’t stall or spin a gyroplane. If the airspeed drops below 28 mph with power on, it slowly settles under full control.
Safety is further enhanced, he says, by the gyroplane’s excellent visibility and high maneuverability in the horizontal plane, which improves see-and-avoid capability when encountering other aircraft.
Piloting a gyroplane like the Sportster is easier than flying a Cessna 150, Hollmann maintains:
“Coordinated turns are made by simply pushing the control stick to the right or left. The aircraft can be flown hands-off, and no trim is needed for flying one or two people.”
“I have flown the Sportster in clouds under IFR weather conditions without the aid of instruments, and though I do not recommend this, it demonstrates the aircraft’s exceptional stability. Ease of flying is such that rated fixed-wing pilots easily transition to flying the Sportster in one hour”
As standard equipment, the Hollman HA-2M utilizes a rotor prespin drive, allowing the rotor to spin up to about 240 rpm prior to takeoff From a dead stop.
HA-2M can accelerate to 45 mph for takeoff in from 350 to 500 feet, depending on wind, temperature, etc. This capability, with a zero ground roll on landing, permits flight operations from off-airport sites such as dirt roads, where legally permissible.
Hollmann designed the Sportster with road-towing in mind; it has a removable trailer hitch attached by two bolts to the airframe structure, consisting of two-inch square tube 6061-T6 aluminum bolted together with AN bolts.
He’s road-towed the Sportster more than 17,000 miles coast to coast with no problems, carrying the rotor blades in a car-top box. Stressing the simplicity of design and construction.
Hollmann maintains that the Sportster is easier for the home-builder to construct than an equivalent fixed-winger With the exception of control rod ends, only three bearings, costing around $30, are used in the rotor head and aircraft.
The rotor head control system uses a simple push-pull linkage, and all flight control, except for throttle operation and nose-wheel steering, can be achieved with it.
Twin rudders at the rear of the Sportster are used primarily to increase the turn rate up to 360 degrees in 10 seconds. A rear-mounted Lycoming 0-320, 150-hp engine drives a wooden 66/35 Troyer propeller directly attached to the crankshaft, with no transmission or drive trains common to helicopter installations.
The rotor is designed to be built by the amateur constructor as a two-blade aluminum system of NACA 8-H-12 section, solidity ratio 0035, pre-cone angle 2; and blade pitch +2Va degrees.
The blades are pop-riveted and bonded, a technique similar to that used in building a conventional metal aircraft wing. The leading edge extrusion is of 2024-T8511 aluminum, with small ribs and aluminum sheet-covering riveted and bonded to the extrusion to form the trailing edge.
Hollmann used extensive computer programming to calculate blade bending moments and deflections in forward flight, and the entire rotor system was designed to meet FAR Part 27 Airworthiness Standards for Normal Category Rotorcraft. Hollmann supplies rotor ribs for those who don’t want to make them, along with fiberglass fairings.
Other hard-to-make parts are available from distributors listed at the end of this article Building time averages 1500 hours, or roughly two years of spare time and weekends, and the cost runs roughly $6,500 including engine.
The Sportster was designed with a high ground turnover angle making it virtually impossible for it to roll over, groundloop or otherwise get out of control on landing. There are no porpoising tendencies, says Hollmann, nor are the rotor blades readily unloaded in flight.
The HA-2M’s rotor system employs a high-inertia design, making it difficult to slow down and so avoiding an in-flight unloading — the cause of frequent accidents in other gyroplanes. The high interia rotor also provides a low control sensitivity and good flare capability, he says.
Hollmann’s research program, curiously, helped others get started in the gyroplane business well ahead of him, due to his development of a special rotor system capable of providing a low disc loading (18 pounds per sq.ft.).
He started off using an aluminum blade system rather than a laminated fiberglass structure, and a low solidity ratio to keep the weight down He chose a teetering, two-bladed rotor system and was well along with the design when he heard that a San Francisco firm was having difficulty flying their gyroplane, the Boomerang, with smaller Rotordyne blades.
He built them a set of HA-27 blades from his design and they worked very well. Another set of HA-27 blades was built for a British firm’s gyroplane, the Cougar, and it was flown to the 1972 Paris Air Show with them.
In addition to installing a bigger, 150-hp Lycoming 0-320 converted GPU engine to replace an earlier 130-hp Franklin Sport 4B. Hollmann made other changes to improve performance of the HA-2M model.
The cockpit enclosure was modified with better streamlining to decrease drag and improve airflow into the propeller disc. Other improvements included lengthening the hub and rotor diameter from 27 to 28 feet, and increasing the blade pitch one-half degree. The result was a climb rate improvement from 350 to 500 fpm.
My introduction to the Sportster came in a visit to Hollmann’s Cupertino home where the machine was parked in the garage next to his VW Beetle.
In a moment he hitched the gyroplane behind the car and we were off, weaving through heavy Sunday traffic and taking the freeway route around the south end of San Francisco Bay to Fremont Airport, a nice little sport flying field with a 2310-foot paved strip.
In about 10 minutes Hollmann had unhitched the Sportster, attached the rotor blades and taxied out for a demo flight. There was a nice, fresh wind blowing down the runway, and after a prespinup he leaped off in about 200 feet, to show off.
After some low passes for photography he landed and invited me to join him in a ride around the patch. It was truly exhilarating. lifting off and climbing steeply with no fear of stalling, then pirouetting around the sky in a lovely ballet with all the world to look at.
Back at the field, our approach was breathtakingly steep for me, a stiff-wing pilot; at the end Hollmann gracefully flared and set her down on the numbers with virtually no landing roll I stepped out and with no qualms gave my seat to my daughter, Toni, who experienced the same thrill of flying in a twin-seat gyroplane that opens a whole new world of fun.
Hollmann isn’t much on cross-country flying in the Sportster, but has logged some 200 hours flying low and slow along the lovely foothills behind San Francisco Bay, as well as some longer, 120-mile flights from Fremont to Tracy to Patterson to South County Airport and back to Fremont.
To sum it up, HA-2M Sportster is the world’s first two-seater homebuilt gyroplane, a craft that utilizes a collective pitch mechanism with a mechanical prerotator that engages the engine, via a clutch, to prespin the rotor to 240 rpm prior to take off.
This permits a very short takeoff run and opens the way to jump-starts, with some further development. A rotor brake is used to slow the rotor down after landing, and to stop the blades”for taxiing on narrow strips.
Like other rotorcraft, the Hollmann Sportster is not idiot-proof; in 1976 a commercial pilot checking out in an HA-2M at Rockford, Illinois, crashed when he failed to maintain adequate rotor rpm, causing substantial damage, according to a NTSB report. Its safety record, however, is far better than that of similar rotorcarft.
Hollmann has formed an organization called the International Gyropalne Association to spread the good word about this exciting new kind of sport flying that appears headed for a boom in the coming years.
More than a score of Hollmann Sportsters are being built or are flying today in various parts of the world, including the United States, Canada, Sweden, Australia and New Zealand, and there’s even one being built by a pretty girl named Debi Hawrysko, address unknown.
|Hollmann HA-2M Sportster Gyrocopter|
|Gross Weight||1050 lbs|
|Empty Weight||620 lbs|
|Fuel Weight||83 lbs|
|Rotor Diameter||28 ft|
|Disc Loading at Gross Weight||1.7 psf|
|Blade Pitch from Zero Lift||°|
|Maneuvering Load Factor||+ 3.5, -0 5|
|Landing Load Factor||+ 3.0|
|Cruise Speed||75 mph|
|Rate Of Climb||500 fpm|
|Power Off Sink Rate||1000 fpm|
|Takeoff roll||550 ft|
|Landing Roll, minimum||0 ft|