In the summer of '58, nothing was faster to 50,000 feet.
- By Carl Posey
- Air & Space magazine, July 2006
(Page 2 of 4)
First flight, and the harbinger of what the Chinese would call interesting times, came on the morning of January 21, 1951. Douglas test pilot Larry Peyton, whose experience was mainly in transports, was chosen for this run. The airplane was to be flown on manual controls to determine some of the nuances of takeoff trim. Then, after some light maneuvering, back it would come to the lake bed. Piece of cake.
Peyton lifted off at 140 mph for what he intended to be a gradual climb to 10,000 feet. The Skyray had other ideas. As speed increased, so did nose-up pitch, even with the stick pressed against the instrument panel. When Peyton hit the trimmers, the nose pitched sharply down, and pulling the stick all the way back had no effect. Another try with the trimmers and the Skyray flared and mushed back to earth.
With the vast Edwards lake bed largely ahead of him, Peyton stayed with it, lifting off again. He brought the Ford into a steady climb at 160 mph—with the stick full forward. After a few test maneuvers, he turned for home and fluttered to the ground, fighting the weird pitch behavior. He never flew the Skyray again.
Another Douglas test pilot, Russell Thaw, took up the preliminary work of fixing the trim problems on takeoff. Then the Skyray passed to Robert Rahn, a top hand among the experimental test pilots. He had flown Spitfires with the Army Air Forces during World War II, and had since tested a host of aircraft types for Douglas.
Having seen Thaw’s flights, Rahn was not sure he wanted to fly the XF4D, but in October 1951, he tried it on. “I flew on manual flight control and quickly learned why Larry wanted no part of the Skyray,” he wrote in his memoir, Tempting Fate. “The stick forces were exorbitant for the small control-surface deflection achieved. The plane was tough to handle unless below 200 knots and in smooth air—not a good sign for a fighter which may have to make an approach onto the pitching deck of an aircraft carrier at night.”
Still, the Skyray’s potentially breathtaking performance, maneuverability at altitude, and the forgiving qualities of that huge wing found a spot in Rahn’s affections. “This aircraft,” he wrote, “was just what I had been looking for in a fighter since my flying days in the Spitfire. The F4D was a fighter pilot’s dream.” As Rahn would soon learn, it could also be a fighter pilot’s nightmare.
“The Skyray,” says Mal Abzug, “was the first Douglas airplane to have the phenomenon known as inertial coupling, in which the airplane goes out of control at high roll rates. It’s caused by the way the weight is distributed. Ever since airplanes were made with the swept wings, they’ve all had that property. First airplane was the F-100. We had a problem about the same time, around 1950. The Skyray was one of the pioneering airplanes in this area.”
Fighter aircraft are required to be able to enter and recover from spins, defined as uncontrolled rotations around any axis of a fully stalled airplane. Conventional recovery is a simple matter of applying opposite rudder to stop the rotation and moving the stick forward to get the nose down and restore airflow over the wing. The Skyray evidently thought this was too easy.
After preliminary spin tests with conventional recoveries, Bob Rahn took his prototype, now equipped with a non-afterburning but more powerful J40 engine, into the California skies to see how it performed with the center of gravity slightly aft, a change resulting from the installation of the new engine.
“I was down on the desert floor in the communications shack,” Abzug recalls. “At 35,000 feet he kicked it over in a spin. There was a long silence. Then he finally said, ‘Jesus Christ!’ ”
When he entered the spin at 35,000 feet, Rahn had intended a couple of turns to the left, then recovery. Instead, he later wrote: “Spun one and a half turns then reversed direction, even as I held full pro-spin controls (full left rudder and full aft stick).” With the aircraft now in a slow, flat spin to the right, Rahn tried something else: He added left rudder against the spin and neutralized the stick. “The XF4D rolled abruptly upside down and started spinning inverted,” Rahn reported. “I experienced severe oscillations in pitch as much as 120 degrees in a half turn and fell through the sky upside down. At this extreme attitude in pitch, I had the impression I was in a 60-degree, nose-down, upright spin.”
Rahn deployed the spin recovery chute at 10,000 feet above sea level, just half a mile above the high desert floor, and the Skyray, having done its thing, resumed normal behavior. But he had been seriously spooked about spin testing the Ford.