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.
Wind tunnel work indicated that Skyray pilots would have to unlearn what they thought they knew about spin recovery. In an upright spin, the pilot had to apply full opposite rudder, but also full aileron with the direction of spin. “I was the guy who briefed Rahn,” says Abzug. “Ailerons with the spin: They were the predominant spin control. I had a hard time convincing him to do it.” In the end, Rahn followed the new guidance and solved the problem, more or less. But the Ford never lost its reputation for unrecoverable spins.
When things worked well, however, they worked very well indeed. A year and a half into the Ford’s testing—in mid-1952—a team of Navy and Marine pilots came to Edwards to evaluate the product. They noted its quirks but liked what they found at altitude, where the Skyray’s big wing and inherent instability let it out-turn anything then flying. Rahn wrote approvingly, “All of the Air Force chase airplanes fell out of the sky during these maneuvers.”
Perhaps the highest praise came from Marine Major Marion Carl, one of the evaluating pilots, who said: “If we had this airplane now in Korea, I could just pop off the MiGs—one, two, three.”
A month later Rahn put the cherry on top. The nominally supersonic Skyray had gone through 18 months of testing without reaching Mach 1, a milestone delayed by severe buffeting and the nose-down “tuck under” peculiar to swept-wing aircraft in the transonic region. (As aircraft approach Mach 1, shock waves begin to form in the airflow over the wings and the center of lift, the point at which the force acts on the wing, shifts aft. This shift causes the aircraft to pitch down. The Skyray was equipped with trimmers, in part to counter this effect.) After considerable tweaking, Rahn put his Ford into a shallow dive and at 30,000 feet pushed past the speed of sound—the first supersonic moment for a delta-wing airplane.
With this achievement, the Skyray was a natural to try for the world closed-course speed records, which had recently passed from the Air Force’s F-86D to the Royal Air Force’s Hawker Hunter. After fitting an afterburner to the J40, the team ran enough trials to see how the Ford would handle with the added power. Lieutenant Commander James Verdin, a veteran Navy combat pilot, was set to try for the three-kilometer speed record, undaunted by the fact that it had just been broken again by a British Vickers Supermarine Swift in Libya going 737.3 mph.
On Saturday, October 3, after several failed attempts, Verdin’s Skyray was streamlined, polished, stuffed with fuel pre-cooled for increased capacity, and ready for its final try. Verdin flew four passes 100 feet above the ground at an average speed of 752.9 mph—more than enough to strip the title from the British. Only eight minutes elapsed between the beginning of the first pass and the end of the fourth one, with the afterburner guzzling 3,450 pounds of fuel.
Two weeks later, Bob Rahn took on the 100-kilometer record at the Edwards course, a circle defined by 16 smoke pots and painted pylons. Flying 100 feet off the ground, Rahn flew straight lines to each pylon, rounding them with a brutally sharp, 70-degree bank. His average speed on the final, official run: 728.11 mph, a new world mark.
The Skyray—and Heinemann’s design shop—entered a brief golden age. While Rahn and his colleagues had been wringing out one prototype at Edwards, Navy and Marine pilots had been growing the second prototype’s sea legs at Naval Air Station Patuxent River in Maryland. The Skyray was headed for the fleet.