Caution Gyrocopter – Handle With Care


ARTICLE DATE: March 1970

IGOR BENSEN, OF GYROCOPTER fame, has lately been ordained a minister, and the comment was not slow in coming that he had doubtless done so in order to be able to supply Last Rites along with his machines.

There are more gyrocopters and gyrogliders than all other sorts of homebuilt aircraft put together, and so it is not surprising that gyro accident reports should look more horrendous than those for other types.

Not surprising, at least, unless you reflect that the gyrocopter is touted as safe, easy to fly, and so thoroughly idiot-proof that no dual instruction is necessary to fly one. The FAA, though it issues gyroplane ratings for passenger-carrying gyroplanes, turns its back on the single-seat gyrocopter, which may be flown with a student permit.

A student permit is today simply a valid third-class medical, issued by an aviation medical examiner; upon demonstration of three takeoffs and landings in a towed gyroglider, it may be endorsed by any CFI, whether or not he has ever flown a gyrocopter himself—or, for that matter, even seen one.

Since gyrocopters generally use the two-stroke McCulloch drone engine, which is equipped with single ignition only, they all fall in the experimental category, and the FAA dismisses them with a sign-off by an engineering inspector who, again, need never have seen a gyrocopter before in his life.

gyrocopters from 1970

Considering that the FAA’s supply of fingers is sufficiently monstrous to provide one or two for every aeronautical pie, it is remarkable that gyrocoptering has remained practically uninvaded by Federal groping and probing.

gyro glider training

Some months ago, Sport Aviation, the EAA’s monthly magazine, published a list of 46 gyrocopter accidents that had taken place in 1967 and 1968 and in January of 1969. Of these, 28 involved serious injury or death to the pilot or, in one case, to a bystander on the ground. Four involved gyrogliders, and at least 34 involved Bensen or modified Bensen equipment.

Of all the accidents, 25 were attributed to “improper operation,” nine to structural failure, six to engine failure, and the rest to miscellaneous or uncertain causes. The characteristic “improper operation” is a push-over-the-top after a steep zoom climb, followed by loss of the rotor.

There are other types of improper operation, however, usually less catastrophic in their effects; taxiing at high speed or in a high wind with improper regard for the limited stability of the landing gear leads to a number of roll-overs, in which the pilot may be injured either by the flailing rotor blades, the shattering propeller or the ground.

A rapid descent can be set up from which it is possible to recover easily at a reasonable altitude; if recovery is delayed for too long, however, a flare may be impossible and the gyrocopter may simply settle to the ground like a parachute, with possible impact damage to the airframe, rotor and pilot (the danger to the pilot in this situation is slight).


Tip-overs, like uncontrolled descents, are generally survivable accidents, and in many cases do not involve any injury at all. Only the soul, however, survives loss of the rotor at altitude.

It may seem to even inexperienced pilots that the proper operation of flight controls to maintain at least a steady path is nearly instinctive—witness the reports we get every few months of a couple of kids who had never before been in a plane getting into one and taking off, and then inadvertently making a successful ILS approach at the local jetport and greasing it on.

Curiously enough, however, the sanguine man in the street with no flying experience whatever may well discover that even a machine as easy to fly as the Bensen gyrocopter is beyond him—especially when he finds himself at 600 feet between a snarling engine and a sinking airspeed indicator.

The gyrocopter rotor accumulates drag prodigiously as its angle of attack is increased, and a steep climb can change quickly from an exultant swoop to an unsteady sag.

The sensible reaction for an airplane pilot is to push the nose down; if this is done too abruptly on a gyrocopter, however, the blades flap downward, strike the rudder or propeller, and fail. Once a blade has been damaged and its balance destroyed, it is likely soon to separate itself from the rotor mast and go off on its own.

Six of the 46 accidents in the EAA list are clear-cut cases of “stall and rotor separation” (though “stall” is a misnomer); all were fatal. Three of the pilots had previous fixed-wing experience, and the rest had eight hours or less in gyrocopters. Only one—a 43-hour pilot—had no gyrocopter experience whatever.

Several other cases are given of “stalls” followed by a dive into the ground. A number of these accidents occurred after the aircraft had been engaged in a porpoising flight, suggesting longitudinal control difficulties and possibly vertigo induced by the large amount of ground and small amount of gyrocopter visible to the pilot.

Like helicopters, gyrocopters lag slightly in responding to control inputs, and this lag may cause an inexperienced pilot to overcontrol in his impatience to get results.

Overcontrol followed by overcompensation may lead to an oscillating path of flight that “gets ahead of” the pilot. The accidents attributed to “uncontrolled descent,” of which four are listed—three serious or fatal—may also involve difficulties of this type.

The accidents attributed to structural failure almost always involve failure of the rotor or of some part of the rotor gimbal—usually the square torque tube on which the flapping hinge and main rotor bearing are mounted.

Builders unacquainted with the rigor of aeronautical design and construction practice sometimes substitute improper materials or parts for the ones called out on the plans. For instance, a number of builders substituted edge-welded tubing for the extruded tubing called for by Bensen; in several cases, the edge-welded tubing proved fatally deficient.

Sometimes this sort of substitution is not even the fault of the builder; it may be due to the ignorance or the unscrupulousness of the dealer from whom he buys his materials.

FAA inspectors can hardly be called upon to detect this sort of deviation from plans; their main responsibility is to discover flagrant cases of poor workmanship and disregard for good engineering practice.

Some gyrocopter builders have attempted to make their own rotor blades by folding an aluminum skin over a piece of bar stock and riveting or otherwise closing the trailing edge.

Such blades may work if great care is taken to assure that they are properly balanced about their quarter-chord line and about the rotor axis, and their pitching moments are properly reacted either by section shape or by torsional stiffness.

The design and fabrication of slender, light-weight rotor blades designed to spin at up to 400 rpm with tip speeds of over 300 mph is not a trivial task, and some builders who have tried it have had a rude—and sometimes brief—shock.

It is ominous that gyrocopter accidents allow themselves to be classified preponderantly into those arising from a certain type of piloting error and those arising from carelessness or ignorance in construction, when ease of piloting and simplicity of construction are precisely the attractions that make the gyrocopter the most popular of sporting aircraft.

The promise of simplicity and ease evidently seduces a certain number of people into forgetting the caution that is associated with other facets of aviation.

The reputation for ease and cheapness on which the gyrocopter built its success threatens to become a reputation for un-reliability and ultimate costliness, which could knock that success right out of the sky.

After all, what other pilot report ever elicited from my friends the request that I call them when I got back from El Mirage to let them know I was all right?

El Mirage Dry Lake is a six-mile-long bed of cracked mud about 60 miles northeast of Los Angeles. Ken Brock, Bensen distributor for Southern California, is here early in the morning with a two-seat gyroglider, a car with which to tow it, and a friend to drive the car.

The gyroglider turns out to be simplicity itself. It consists of a bolted cruciform frame of square aluminum tubing, with a rudder and a small tailwheel at the back and a nosewheel and airspeed indicator at the front.

There is a centrally located stick in front of a lightweight woven-plastic chair that came from beside somebody’s swimming pool. This seat leans against the rotor mast, at the top of which, about eye level, is the “offset gimbal head.” The gimbal head is offset in order to place the axis of the rotor close to the center of gravity of the machine.

The rotor itself is set in a flapping hinge that is in turn mounted on a thrust bearing, and this thrust bearing is fastened to the square torque tube. The torque tube, which is set in a two-axis gimbal, extends several inches aft of the thrust bearing, and to its rear extremity is fastened a cross-piece about a foot long.

The control rods are attached to the ends of this cross-piece, and descend to a mixer, linked to the stick, at the bottom of the mast. The gyrocopter is maneuvered by tilting the rotor in the direction you want to go.

Though it appears that this is done simply by muscling the rotor over with the stick, what is really happening is a pitch change followed by a 90-degree precession, in true helicopter style. Moving the stick to the right side, for in-stance, does not immediately affect the tip-path plane; however, it changes the pitch of the rotor blades when they are in the fore-aft position.

Since the rotor turns counterclockwise as seen from beneath, right stick reduces the angle of attack of the blade behind the pilot, and increases that of the blade in front of him.

Ninety degrees later, because of the gyroscopic precession of the rotor system, the aft blade has dipped to its lowest point and the fore blade has risen to its highest; since the aft blade is now on the right side and the fore blade is on the left, the effect of the pitch change has been to tilt the rotor to the right side.

The thrust vector is now inclined to the right, and the aircraft responds by flying to the right. The stick control of the gyrocopter corresponds to the cyclic on a helicopter; there is no collective pitch control.

(More sophisticated gyroplanes are equipped with a rotor spin-up system and a collective control to permit jump takeoffs; most Bensens and similar designs, however, forego this refinement.)

The autogyro is always in autorotative flight; it maintains altitude by overcoming rotor drag with its engine, just as an autorotating helicopter balances drag with the energy release of its rapid descent.

Since the rotor blades are moving through the air at high speed by virtue of their rotation alone, they are not susceptible to a stall in the normal sense of the term.

Only if the gyrocopter could be accelerated to a very high speed could the retreating blade be stalled, and then only if the flapping hinge permitted a sufficiently large increase of angle of attack on the retreating blade.

I doubt that autorotation would permit a sufficiently high airspeed to induce a retreating-blade stall; and so I believe it can be safely said that the gyrocopter rotor cannot be stalled.

Towed flight in the gyroglider is sim-pie. You get the rotor turning by hand, and then the tow car accelerates you slowly while you hold the stick back and the rotor picks up speed for purely aerodynamic reasons.

When autorotative rpm is reached—360 rpm or so—the machine rotates back onto its tailwheel; you balance it between nosewheel and tailwheel with the stick, and at 40 or 45 mph it lifts off in a nearly level attitude.

Within the limitations of the tow rope, you can now climb high above the tow car, swoop from side to side behind it and make dust-choked landings in its wake.

It is possible to get into trouble doing this, to judge from the fact that there have been several serious gyroglider accidents; but as long as one refrains from trying any excessively fanciful maneuvers, one is perfectly safe. What immediately strikes the fixed-wing or helicopter pilot is the ease with which the gyroglider is controlled.

Stick forces are light, and once the control lag is understood, swooping weaves from one side to the other—the gyroglider equivalent of lazy eights—are easily performed with only fingertip pressures. When I flew my first half hour on the gyroglider, of which 10 or 15 minutes was solo, there was no powered gyrocopter available in which to continue.

A couple of weeks later, therefore, I was back on the lake again with Ken Brock; this time, the rotor (he uses one rotor for several copters) was on N9678Z, his veteran 1,000-plus-hour gyrocopter.

Seven Eight Zulu is similar to a gyroglider in construction, except in having a larger vertical stabilizer, a single seat —which also serves as an eight-gallon fuel tank—and a 90-hp McCulloch engine mounted behind the rotor mast.

gyroglider dry desert lake flying

The gimbal offset is smaller than in a gyroglider because the CG, with the engine, is farther aft, and there is a long panel of inoperative instruments on the front boom. The only necessary instrument, really, is a primitive airspeed indicator consisting of a red pellet in a tube with air inlets at the bottom.

When ram air enters the inlets, the pellet rises in the tube, which is calibrated up to about 80 or 90 mph. The pellet was sticking at 50 mph the day I flew, and it didn’t seem to make much difference.

A small flag at the tip of the front boom serves as a skid/slip indicator. It also is unnecessary. Gyrocopter flying is seat-of-the-pants flying, and your face is as good an airspeed indicator as any other.

I had expected some refresher dual in the gyroglider, but we went directly to the powered machine. Ken gave me a five-minute briefing. You begin the take-off roll slowly, shifting your feet from the very quick direct nosewheel steering to the rudder pedals as soon as you have about a quarter throttle.

You keep the speed of the gyrocopter just under the rotor speed (this is a difficult concept to communicate, and one that can be learned only through experience; in my dozen or so takeoffs in the gyrocopter, I never had the faintest idea whether the airspeed was “over” or “under” the rotor speed).

When the nosewheel comes off, you hold the ‘copter balanced between nosewheel and tailwheel until you fly off. Keep the nose down, maintain 45. Make a flat landing approach, and don’t begin the flare till you’re one or two feet above the ground; it takes a while to get used to the rapidity with which speed pays off in the flare.

No rudder necessary in flight. Throttle is necessary. No turns below 100 feet till you get the hang of it. Don’t lift the nose in turns—lower it a little, in fact.

Keep the nosewheel off the ground after landing. If the rotor starts to shake as you are rolling before takeoff, you are getting ahead of the rotor; push the stick forward a little and reduce speed slightly. Have fun. Got that?


Just to make sure I had it, Ken flew the gyrocopter down the lake as I drove alongside, watching him. He repeated the lesson in dumb show, pointing to each thing he did, calling my attention to the effectiveness of the controls and the correct attitudes for takeoff and landing.

At the end of the lake he turned around and signaled me to get aboard. This I did, and a minute later I was rolling down the lake, swerving uncontrollably from side to side.

My problem was that the pedal application required by the nosewheel is the opposite of that required by the rudder pedals; since the steering bar is fixed rigidly to the wheel, you push the right side of the bar forward to turn left. This is enough to drive you crazy. Luckily, the air rudder is effective even at low speeds.

I had better luck with it, and soon I was racing along the lake bed balanced between nosewheel and tailwheel. After a takeoff run only nine times longer than necessary, by Brock’s estimate, I became airborne. Everything came swiftly and naturally.

The gyrocopter was enormously powerful, with a power loading of less than five pounds per horsepower, and it proved capable of climbing at considerably more than 1,000 fpm. It was highly responsive to the controls, but perfectly stable hands off. I noted a tendency to roll to the left, which is correctable by means of a ground-adjustable roll trim.

I believe this left-rolling tendency is caused by asymmetrical lift not completely damped by flapping. I made a number of rapid climbs and descents to 1,500 feet above the lake (which is at 2,800 feet), and found no difficulty with longitudinal control.

El Mirage gyrocopter flying

The rudder is able to swing the ‘copter through at least 60 degrees of heading while maintaining straight cruising flight; at very low airspeeds, the ‘copter may be mad e to revolve beneath the rotor.

Climbing to 1,000 feet, I gingerly tried to stall the machine; as advertised, it showed no sign of stalling, but simply stopped and settled downward at about the rate of a parachute. After falling several hundred feet in this manner, I lowered the nose and was back at 45 mph in less than five seconds. Spot landings presented no difficulty whatever.

Though “getting behind the power curve” is an ever-present possibility at low speeds, the machine can fly out of any situation without loss of altitude because of its tremendous engine power.

The “stalls” reported in the EAA article were certainly not stalls at all, but abrupt bunts by startled pilots who found themselves in a nose-high attitude with their airspeed disappearing.

They would have done better to hold the stick back and let the gyrocopter settle into a level descent, or apply full power and ease the nose down into cruise. Negative G is the one thing that must be avoided without fail; and negative G is not, after all, very hard to avoid.

The gyrocopter is the most enjoyable aircraft I have ever flown—a title hither-to in dispute between the Fournier RF4D and the Bell 47D, which is the only other rotorcraft I have tried.

The sensation of swooping along close to the ground unencumbered by wings and a fuselage is angelic. The only disagreeable thing about it is the vibration from the high-revving drone engine, which make s you feel as if you were trapped in a full-body vibromassager.

The vibration in my legs was particularly unpleasant; combined with the flapping of my pants in the wind and t he overall chill at speed, it gave met he rubber-legged sensation I used to have when climbing to altitude in a parachute-jump plane. Otherwise, it was the easiest, simplest, most exhilarating thing I had ever flown.

Only Ken Brock waving a big red flag, warning me that fuel was low, brought me down. He obviously had the flag ready; doubtless others before me had succumbed to the addiction of gyrocopter flight.

There you have the gyrocopter puzzle. On one hand, it is exactly what the sellers claim: incredibly easy and delightful to fly, and laughably cheap and simple to build. On the other hand, it has taken a lot of lives.

What can be don e to save the delight and scotch the risk? For one thing, the FAA might take a more active interest in gyrocoptering, and write up a simple set of protective regulations covering gyrocopter licensing.

Three takeoffs and landings in a towed gyroglider are not enough, when three bounces fill the requirement, and being towed in a straight line bears no resemblance to flying in three dimensions.

By requiring a certain number of hours in a gyroglider for candidates with no previous flight experience, or even two or three hours of fixed-wing time to familiarize them with the operation of basic flight controls, the FAA could at least eliminate most cases of extreme recklessness and incompetence.

The gyroglider test flight should involve turns, climbs and descents, and landings to one side and the other of the tow car. Preferably, a two-seat gyroglider should be used for instruction and for the check ride, though this should not be made a requirement until more two-seat gliders are available.

An inspection schedule should be provided by Bensen for FAA inspectors called upon to inspect gyrocopters. Since there are only a dozen or so critical parts, a detailed specification could be made for each one, and the FAA inspector thus equipped to make a meaningful judgment of the airworthiness of a machine.

The McCulloch engine has a reputation for very short TBO. This is due – according to Ken Brock—to the majority of engines in use on gyrocopters being military surplus ones that have been crashed into the ground on drones a number of times.

Brock’s own engines, which are carefully maintained, last almost indefinitely, he says, with very few parts in the engines. Engines to be used on homebuilt gyrocopters should be inspected by a mechanic able to assure their general condition and smoothness of operation before they are let loose in the air.

Landing at a standstill, turning on a dime, flying safely at zero to 90 mph, climbing like a rocket and sinking like a parachute, the gyrocopter is an airplane with t he airplane’s encumbrance and inconveniences removed.

For less than $2,000, it can bet he only way a non-pilot will ever discover the delight of flying; and it may be the only way a seasoned pilot will ever find his way back to it.

Aviation Aircraft Gyrocopter Autogyro Gyroplane

All that is lacking is a realistically cautious policy from the FAA, a little less enthusiasm on the part of the advocates of the gyrocopter, and some – body to restrain people who think they can sail off into the wild blue yonder without a word of advice from anybody.

A few of them doubtless can—flying a gyrocopter really is so simple that you can teach yourself to do it—just as a few people might teach themselves to drive without any supervision whatever; but the risks are high, and odious as Federal intervention in such areas is, a little dose of it might be to the eventual benefit of the sport.

Gyrocoptering is starting to develop a sad reputation which—like most of the gyrocopter deaths—is needless and avoidable if only a few sensible steps are taken now, before it is too late to expect anybody to step sensibly at all.

single seat gyrocopter popularity

Caution Gyrocopter - Handle With Care
Article Name
Caution Gyrocopter - Handle With Care
Gyrocopter popularity in the 1970's was huge and expanding fast. Looking back you could be mistaken for thinking it was the wild west, but there were many taking the lead in professional flying and training.

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