Above & Beyond: Jump Ship
- By E. Stuart Gregg
- Air & Space magazine, March 2001
Courtesy E. Stuart Gregg
In 1942 the U.S. Army Air Forces held a competition for development of an autogiro that could take off and land vertically with little or no roll, unlike the typical autogiros of the day, which required a short takeoff roll. The AAF wanted an aircraft that could be operated in close confines. Prototypes of the Kellett XO-60 and the Pitcairn XO-61 “jump giros” were evaluated, and Kellett won a contract for six YO-60s. (The XO-61 had run into cooling and power problems due to its pusher propeller configuration.)
The following year, my outfit, the 445th Test Squadron of the 50th Fighter Group, stationed at the Air Forces School of Applied Tactics at Orlando, Florida, was tasked with determining how these aircraft could best be used in combat operations. Lieutenant Bob Miller and I, both primarily fighter pilots with no prior experience with such strange aircraft, were ordered to pick up two at the factory in Lansdowne, Pennsylvania, and fly them to Orlando.
In the course of some 20 hours of training under Kellett chief test pilot Dave Driskill, we learned that taking off vertically in the YO-60 was a complicated process, and dangerous if mishandled. Driskill had been in a near-fatal accident in the prototype, and he delighted in showing the resulting scars to us novice giro pilots to drive home the importance of proper technique.
An autogiro uses a standard propeller to pull it through the air, and the airflow over the rotor blades turns its freewheeling lifting rotor. A jump giro has an auxiliary drive shaft from the engine to the rotor, which allows the rotor to build up speed in flat pitch while on the ground, storing kinetic energy like a flywheel. The stored energy allows the aircraft to rise vertically when the pilot abruptly increases rotor blade pitch to lift off. A clutch then disengages the drive shaft to prevent rotor torque from spinning the jump giro like a top.
The YO-60 had a conventional throttle for the 300-horsepower Jacobs engine, a constant-speed propeller on the nose, and traditional stick and rudder controls. However, because of excessive feedback from its mechanical connection to the rotor that caused the stick to thrash about at low rpm, the control stick was secured in a lock on the instrument panel unless rotor speed was above 200 rpm. Only then could it be disengaged. During takeoff, the pilot held it firmly forward and right, to counter rotor feedback and engine torque.
Power was taken off a drive shaft from the rear of the engine to the rotor head and was engaged by a T-handle clutch on the left side of the instrument panel. There was also a rotor pitch-angle lever that the pilot pulled back and locked for flat rotor pitch during rotor rev-up. On top of this lever was a red quick-release button that caused a spring-loaded nine degrees of pitch to be suddenly applied to the rotor blades to facilitate a jump takeoff. All these exotic controls were very confusing to the student pilot, and if not used in proper sequence, the results could be disastrous.
Lightly loaded and in cool weather, the YO-60 could make a spectacular vertical takeoff. It could jump five to 15 feet straight up before accelerating forward in a climbout. In hot weather, with a full load of fuel and a passenger, it would merely lurch into the air, where its straining engine and propeller could eventually make it climb rather handily.
Landing gave us fits. It required one to glide down final approach at only 40 mph, flare at an exaggerated angle 10 feet off the ground, and in this absurd nose-high attitude, allow the aircraft to settle on its tail wheel, then pitch forward onto the nose gear.
After 20 hours of dual and solo flight, we two newly certified autogiro pilots flew the YO-60s to Orlando on a circuitous route: The jump giros had fuel for only two hours, cruised rather slowly, and, since the program was classified, could be refueled only at military bases.
From our training, we were accustomed to landing on the ramp in front of operations, rather than on the long runway with the usual traffic, so we asked the air traffic controllers at various airports if we could land on the ramp. Occasionally, if a ramp had open space, our requests would be granted. Most times, though, we were sternly told to land on runway so-and-so. If we repeated our request, we were asked just what sort of aircraft we were flying that could land on a crowded ramp.
On one occasion, with the tower’s permission, we landed right in front of base operations at Richmond Army Air Base in Virginia. The ops officer, who had not heard our conversation with the tower, spied us through the window and came storming out, ready to throw the book at us. But as he took in the sight of the strange wingless aircraft that had landed almost vertically on his crowded ramp, his stride slowed. By the time we shut down and got out of the aircraft, he was cordial, full of questions and begging for a ride.
Less than two weeks after we got the YO-60s to Orlando, Miller was killed while flying a Bell P-63 Kingcobra. In an evasive maneuver during a mock dogfight with a P-51, he flew into a thunderhead and spun out the bottom. At the time, I was flying one of the YO-60s, and, hearing a report of the crash, spotted the wreckage. I checked in with the tower, then flew slowly ahead of the ambulance and crash wagon, leading them down back roads and across fields to the scene. It was a terrible loss.
Because of the YO-60’s classified and unconventional nature, we had been ordered not to check anyone else out on the aircraft. Now the tactical test program was mine alone.
I flew at Camp Rucker in Alabama for the Infantry Board, at Camp Bragg in North Carolina for the Artillery Board, then finally with a division training in Florida for overseas duty. There I faced some unusual hazards. I delighted in landing in tight spots near “enemy” lines, but often these tree-lined sites were much too tight to attempt a takeoff. I did a lot of taxiing along roads in the woods and between trees, dodging branches that could hit the delicate rotors, while searching for sufficient open space for a safe takeoff.
We learned a lot from these operations in the field. For one thing, the YO-60 was very sensitive to rotor trim. Metal trim tabs near the ends of each of the three rotor blades sometimes had to be adjusted on the ground and by hand. Bang a rotor tip on a branch, or subject the fabric-covered blades to prolonged moisture, and when you revved the rotor, the YO-60 would oscillate and dance alarmingly on its spidery landing gear. Several times I had to rectify bent trim tabs and rotor imbalance with a pair of pliers—real shade-tree maintenance.
Ultimately, these field tests showed that in some respects the YO-60 could outperform the L-3 Aeronca, L-4 Piper, and L-5 Stinson liaison aircraft, but it was more expensive and complicated to fly and to maintain in the field.
The sight of this bizarre aircraft flying at low altitudes around northeast Florida occasionally prompted unusual requests. One day, Orlando sent down word to fly the YO-60 to the football stadium in Jacksonville, and report back if I thought I could land on and take off from the football field inside the stadium. After a casual flyby, I reported that it looked doable, so I was told to fly out of the stadium as a stunt for a war bond rally.
At twilight on the evening of the rally, with my crew chief in the back seat, I landed in the middle of the field. No problem. In the waning daylight, the prospect of a takeoff from this limited space seemed easy enough. But as darkness descended and the rally droned on, the tiers of stadium seats seemed to increase in height alarmingly.
As things finally began to wrap up, I was asked to tell the crowd about this unusual aircraft. Dry-mouthed, I mumbled a few sentences into the microphone, then climbed into the YO-60 and went through rev-up. As insurance, and out of desperation, I exceeded the rotor rpm redline and popped the quick-release pitch button, only to have the YO-60 stagger a few feet upward in the hot, still air, then fall back almost to the ground. The engine was snarling and the propeller did its best to pull us up and out of that big hole. I counted the entire alphabet of seat rows as we clawed our way upward. After I barely cleared the row of flagpoles and the stadium lights, everything immediately went black. The only instrument-flying aids the YO-60 had were rudimentary gauges, and I had never flown it at night. I resolved never to try a fool thing like that again.
Late in 1943, before the YO-60 test program was complete, I was ordered to the Sikorsky factory in Bridgeport, Connecticut, to evaluate the YR-4B helicopter. After just a few hours of flying, it was clear that the primitive but functional machine could perform vertical takeoffs and landings with far greater ease and dexterity than a jump giro—an observation I included in the final test report of the YO-60, virtually killing further military procurement of autogiros.
When I was sent overseas for combat duty in 1944, the YO-60s were still sitting on the ramp at Orlando, with no one there authorized to fly them. I later heard that a few jump giros were sent to Texas to join the conventional autogiros the border patrol used, and that every YO-60 crashed. Having been fortunate enough to have flown 150 hours without an accident in this imperfect, somewhat dangerous, but strangely enjoyable aircraft, I wasn’t surprised.
Nearly 60 years after the fact, I can now confess that in spite of regulations and common sense, I often used a YO-60 to fly home for lunch, landing in my front yard. I also flew it to the local golf course, where I landed on the ninth fairway, parked behind the caddy shack, and put in a quick nine holes of therapeutic golf.
—E. Stuart Gregg