Dream Aircraft

by Schiff, Barry

  A double engine failure has more ominous consequences. The blimp suddenly becomes little more than a balloon. Although ballast usually must be dumped to maintain altitude, a pilot’s attention ultimately must be focused on landing. Descending is easy enough; just release some helium. But unless a ground crew is available to hold down the blimp and prevent it from blowing away, the airship pilot must pull a rip cord to tear open a 20-foot-long panel that allows the entire load of helium to escape. And the pilot had better be prepared to jump out and run like crazy to avoid being smothered by the collapsing envelope.

  A conventional landing with power is far less dramatic. It is executed precisely into the wind because there is no way to land one of the world’s largest weather vanes against a crosswind. To help a pilot line up directly into the wind, one of the ground crewmen (there are more than a dozen) stands in the landing area and holds up a portable wind sock that is mounted atop a pole. Although shifting winds are difficult to handle, airship pilots claim that light, variable, and calm conditions are worse. This is because the controls lose effectiveness below 7 knots, yet the airship must be brought to a halt before ground crewmen can grab the lines hanging from the nose and prevent the blimp from drifting away. Ideal landing conditions include a steady, l0-knot wind. The touchdown itself is simply a matter of driving the blimp onto its single-wheel landing gear and using reverse power (when necessary) to slow the craft. (Goodyear blimps do not have brakes.)

  Before the blimp crew deplanes (deblimps?), ground crewmen must add ballast to the car. Otherwise, the reduced payload would allow the blimp to simply float away (along with those hanging on to the lines) and become a pilotless hazard to navigation.

  A normal takeoff requires less effort. Most departures are made at fairly light static weights (between 100 and 200 pounds). Several ground crewmen grab a railing that encircles the car and heave the blimp into the air like a medicine ball. When the blimp is a few feet above the ground, full power and nose-up elevator are applied. That is all there is to it. But do not be shocked by the initial climb attitude of up to 30 degrees. Other categories of aircraft might be in danger of stalling, but not blimps. (They cannot stall and have no minimum airspeed.)

  When a GZ-20 is loaded heavily (up to 800 pounds of static weight) for special-purpose missions or long cross-country flights, a conventional, rolling takeoff is required. This is amusing to watch because the bending and flexing of the envelope is apparent every time the tire hits a rut or a bump. Acceleration is painfully slow and the takeoff roll of 700 feet (at maximum heaviness) seems to take forever. Pilots must be cautious during liftoff not to raise the nose excessively. A 7-degree rotation results in a tail strike.

  When a GZ-20 has completed its daily and nightly chores, the tip of its nose is nuzzled into a locking cup at the top of a 32-foot-tall mooring mast. A blimp is not tied down conventionally because such a broad surface cannot be restrained in a crosswind. Instead, the blimp becomes a ponderous wind sock and pivots restlessly about the mooring mast in response to even the slightest zephyr. So even when not flying, a blimp is still quite unlike an airplane; it is never really at rest.

  Author’s Note: The America, the Enterprise, and the Columbia have been replaced with newer aircraft, the Spirit of Goodyear (based in Akron, Ohio), the Stars and Stripes (Pompano Beach, Florida), and the Spirit of America (based near Los Angeles). Goodyear no longer maintains an airship (blimp) in Europe.

  Looking like a bumblebee with tail fins, the McCulloch J-2 Gyrocopter has an unpowered rotor and is part helicopter and part airplane with some virtues of each.

  It looks like a recontoured Volkswagen “Beetle” with a conning tower and rotor blades, or perhaps like a helicopter with tricycle landing gear but no tail rotor, or perhaps like an airplane with the twin-boom empennage of the Cessna Skymaster and the stubby wings of a bumblebee.

  It is initially tempting to compare the J-2 with either a helicopter or an airplane, but it is neither. It is a hybrid with traits of both and other traits that cannot be duplicated by either a helicopter or an airplane.

  I was introduced to the McCulloch J-2 many years ago when invited to its debut in Lake Havasu City, Arizona. There I attended the manufacturer’s gyroplane school and obtained became rated in the machine. At the time, there were only 50 to 75 pilots in the country with gyroplane ratings, and most of them had not seen one since before World War II.

  According to the FAA, the J-2 is technically a gyroplane although these machines also are informally known as autogyros and gyrocopters. The McCulloch is a 2-place, enclosed-cabin, rotary-wing aircraft that uses a free-wheeling rotor lift (as compared to a helicopter whose rotor is powered). Thrust is obtained from a rear-mounted engine with a pusher propeller.

  Lift is created by the rotor using the principle of autorotation, which requires movement of the gyroplane through the air (see the sidebar on pages 74–75). Unlike a helicopter, the J-2 cannot hover. Because the rotor is not powered, it generates no torque as do powered rotors. Hence, there is neither a tail rotor nor are there any of the yaw-control problems associated with a helicopter.

  Attitude is controlled conventionally with stick and rudder, but instead of moving ailerons and elevator, which the J-2 does not have, the stick controls the tilt of the rotor disk (like the cyclic control of a helicopter). The rudder pedals are conventional and operate the rudders, one on each tail boom. A right turn, for example, is entered by moving the stick to the right and simultaneously applying right rudder pressure. This tilts the rotor disk to the right, which causes the gyroplane to turn in that direction. It turns for the same reason that airplanes do; lift is directed in the desired direction.

  The rudder performs the same function as in an airplane; it corrects for undesirable yaw.

  An advantage of the J-2 over an airplane is that its “wings” (meaning its rotor blades) have airspeed before the takeoff roll begins. After the pilot starts the engine, he accelerates the rotor by coupling it momentarily to the engine via a clutch and transmission (like that of an automobile with stick shift), a procedure discussed later. A 180-hp Lycoming 0-360-A2D powers the J-2 and is controlled with either of 2 throttles. One is a standard push-pull type on the instrument panel; the other is a motorcycle-type of grip-and-twist throttle on the spin-up lever (discussed later).

  The walk-around is straightforward except for checking the rotors and the rotor dampers.

  The stubby wings offer the fixed-wing pilot more psychological lift than aerodynamic. Each contains a 12.1-gallon fuel tank, 10 gallons of which are useable.

  Empty weight (including unusable fuel and a navcom) is 1,049 pounds. This provides a useful load of 451 pounds. With full tanks, this allows only a 331-pound payload. (Maximum baggage of 95 pounds is stored under the bench-type seat.)

  Because of balance considerations, the J-2 may not be flown unless gross weight is at least 1,250 pounds. A lightweight pilot flying with partial fuel must carry ballast.

  The J-2 has 2 large entry doors, one on each side, so getting in and out is gentile. Headroom is generous but shoulder room leaves a bit to be desired. Except for the rotor spin-up controls, the cockpit resembles a typical, uncomplicated airplane. Its small instrument panel is centered between 2 glove compartments and has only the necessary gauges. There is room for more instruments, but the J-2 is not certified for night or instrument flight. One unusual instrument is the dual-reading tachometer that shows both rotor and engine rpm.

  Taxiing is done with engine thrust and the rudder pedals, which control the steerable nosewheel. Because the center of gravity is relatively high, sharp turns must be avoided at fast taxi speeds. When taxiing across rough terrain, the rotor should be spun to at least 100 rpm to prevent the otherwise motionless blades from flapping and damaging the rotor assembly.

  After a conventional runup, the J-2 is taxied into takeoff position and held there with toe brakes—it does not
have a parking brake—for the rotor spin-up procedure. Here is where things get unconventional.

  With the throttle retarded, the transmission engagement lever on the cabin’s rear bulkhead is raised, gearing the rotor shaft to the transmission. Next, the spin-up lever (left of the pilot’s seat) is slowly and firmly depressed, a chore that requires a strong left arm and applying 60 pounds of force. Engaging the spin-up lever connects the engine to the transmission through a drive-belt system and simultaneously changes the pitch of the rotor blades from 5 to 0 degrees to reduce drag during spin-up.

  After the rotor accelerates to between 100 and 150 rpm, the motorcycle-type grip throttle is twisted slowly until rotor speed increases to 450 rpm. The spin-up lever is then raised, mechanically releasing the clutch and disengaging the rotor shaft from the transmission. A red light on the instrument panel extinguishes to confirm that the rotor is freewheeling. The disengagement simultaneously returns the rotor blades to a 5-degree pitch angle.

  The rotor is now up to speed and freewheeling. The blades are “biting” the air at the proper angle and are creating about 1,300 pounds of lift before the J-2 has even begun to move.

  As the rotor takes on the load, the fuselage suddenly rises on its landing gear and catches the new J-2 pilot off guard, leaving him with the feeling of sitting on a kneeling camel that stands up unexpectedly.

  Takeoff power is applied before rotor rpm has a chance to decay. Directional control is a bit tricky because the J-2 is so light on its wheels. Also, the aircraft tends to ride more on the nosewheel than on the mains (like a wheelbarrow). Because all but about 100 pounds of its weight is off the ground during the takeoff roll, the J-2 is well suited for taking off on rough terrain.

  Some rotor rpm is lost during the takeoff roll but is quickly recaptured at 40 mph when the nose is raised to the liftoff attitude and the rotor disk’s angle of attack increases. If the nose is raised too much or prematurely, considerable drag is created by the tilted rotor disk, decreasing aircraft acceleration and prolonging takeoff. At liftoff, the J-2 wants to yaw and roll to the right. When you learn to anticipate this, it is easily avoided with timely stick and rudder inputs.

  This yaw-roll tendency on liftoff is caused by a combination of asymmetrical propeller thrust and engine torque. Although present in fixed-wing airplanes, it is not as noticeable because of the lateral damping effect of the wings. This yaw/roll combination acts to the right and not the left because the pusher propeller turns opposite to a tractor propeller.

  This lengthy description of the takeoff belies its brevity. Although rotor spin-up takes 20 seconds, the takeoff roll itself can be as short as 3.2 seconds. Everything happens so quickly that a new J-2 pilot feels as though he is being launched by catapult. The rapid acceleration is due to so little rolling friction and an exceptionally low power loading (8.3 pounds per horsepower), less than that of most popular lightplanes.

  Taking off at maximum gross weight and during standard, sea-level conditions requires only 540 feet.

  Those who remember the Umbaugh autogyro may recall that it could make a jump takeoff without any ground roll. What followed, however, was a losing race with time to see if it could accelerate fast enough to remain airborne. Including ground roll, the J-2 can take off and climb over a 50-foot obstacle in 600 ft, less than the Umbaugh needed after its jump takeoff.

  One drawback of the J-2 is that it is not certified to take off above 4000 feet msl, which eliminates much of the West for J-2 operations. Another problem with the J-2 is that it compares unfavorably with a Piper Super Cub, for example. The venerable PA-18 not only gets off the ground in less distance but carries a heavier load faster, higher, and farther. The Cub also cost much less to buy and operate.

  A Super Cub flown at minimum speed, however, has sluggish control response. Its wing is on the verge of stalling. Any mishandling could result in control loss, a characteristic of most airplanes.

  The J-2 does not have such low-speed problems. Its “wing” is at cruising speed (rotor rpm) irrespective of indicated airspeed thus providing positive control response at all times.

  Although the J-2 cannot stall, reducing airspeed to below 30 mph results in a gradual descent. Further airspeed reduction increases sink rate. At 0 mph, the J-2 is in level-flight attitude and descends at 1,400 fpm. The effect is fascinating and delightful. You feel as though you are strapped under an open parachute. There is no sensation of falling, but you are aware that the aircraft has no forward speed. Pull back a bit more on the stick, and the J-2 goes backwards.

  During this parachute-like descent, full right or left rudder makes the J-2 revolve slowly about its vertical axis to provide a truly panoramic view.

  During a vertical descent, the stick is held neutral. Moving it in any direction confirms that the control response of a gyroplane does not depend on indicated airspeed.

  Recovery from this intriguing maneuver should begin at least 500 feet agl and results in an additional 200-foot altitude loss. Simply lower the nose 30 degrees and apply full power. Without power, recovery requires about 300 feet.

  The J-2s climb performance is unimpressive, sensitive to small increases in weight and temperature. Climb rate at maximum gross weight seldom exceeds 500 fpm. Fully loaded at 5,000 feet, the J-2 climbs at barely 200 fpm. Best angle and best rate-of-climb speeds are 62 and 70 mph, respectively.

  Because weight has a profound effect on gyroplane performance and allowable payload, McCulloch took great pain to save every ounce and explains the choice of a wooden propeller instead of a metal one.

  The J-2 cruises at 105 mph and rides more smoothly than a helicopter because freewheeling blades create less vibration than powered rotors.

  It takes an hour of flying the J-2 to get used to the differences between its flight characteristics and those of an airplane. Most pilots initially tend to overcontrol laterally because there are no wings to dampen roll. Also, the J-2 has neutral pitch stability, meaning that it does not pitch down automatically to recapture lost airspeed the way the airplanes do. Changing speed requires positive stick forces, thus the fixed-wing pilot initially undercontrols in pitch.

  Turning the J-2 is conventional, but bank angle should not exceed 60 degrees. There is insufficient reserve power available to maintain altitude during steeper turns. This maximum angle of bank decreases to about 45 degrees at 4,000 feet. If maintaining altitude is not important, bank angles up to 90 degees can be made as long as G-loads are kept positive.

  Helicopter pilots are cautioned not to revert to habit and depress the J-2’s spin-up lever in flight as though it were a collective pitch control. Depressing that lever would change the pitch of the rotor blades from 5 to 0 degrees and provide the unexpected thrill that accompanies a sudden loss of all lift.

  During flight there is no reason to be concerned about maintaining a given rotor rpm such as when flying a helicopter. Aerodynamic forces automatically maintain rotor rpm within its 300-to-480 rpm limit at all times.

  Landing the J-2 is childishly simple. Airspeed during the approach is controlled by pitch (as with an airplane) at 60 mph. Rate of descent is controlled with power. At a height of 5 or 10 feet, begin a normal flare to reduce sink rate. Airspeed then decreases rapidly because of the increased rotor drag. Touchdown occurs at 25 mph followed by less than 100 feet of roll. It is that easy.

  With a 10-knot headwind, landing roll is less than 50 feet. Landing over a 50-foot obstacle requires a 500 feet.

  The J-2 is virtually impervious to a crosswind because of its high disk loading (2.8 pounds per square foot of rotor disc area). A minor problem arises however, from the poor rudder response at landing speeds. Considerable downwind rudder is essential after the main gear touches, to prevent weathervaning into the wind. Unless the pedals are neutralized before the nosewheel touches, a quick downwind turn will occur because of the direction in which the nosewheel is cocked.


  The J-2 is an exceptionally safe aircraft, but acceptance was handicapped by the poor safety record of its predecessors, the Umbaugh and numerous homebuilt autogyros.

  The Umbaugh suffered from lateral instability, a characteristic that made side slipping dangerous. When you try to raise the low “wing” of an Umbaugh with top rudder, the condition becomes aggravated. The aircraft rolls farther into the slip, increasing the possibility of lateral upset and inverted flight. The Umbaugh should have been sent back to the drawing board, but instead was equipped with a horn that sounds when a slip exceeds limits. Recovery has to be executed gingerly with stick only.

  The J-2 is laterally stable and can be slipped in either direction without adverse results. When top rudder is applied, the J-2 responds obediently and rolls to a wings-level attitude.

  A maximum effort pullout from a dive at VNE (109 mph) results in only 4.5 Gs, the maximum attainable under any condition. The blades cone slightly and accelerate to maximum-allowable rpm, but that is all. The J-2 decelerates to zero airspeed and begins a vertical descent.

  There are two ways to get into trouble in a J-2. One is to develop a high sink rate at low airspeed near the ground. The other is to fly inverted, at which time the blades slow down and wrap themselves around the fuselage.

  An engine failure obviously results in a forced landing. This is when a helicopter has the edge because it can land in an area barely larger than its rotor diameter and without forward speed. The J-2 would be safer than an airplane because it can land in less distance and at a snail’s pace. Crashworthiness is better, too, because the fuselage frame is stressed to 20 Gs.

  The McCulloch J-2 failed to become a marketing success because it is such a hybrid, a cross between a helicopter and an airplane that is incapable of matching the performance of either. But it sure is fun to fly.