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.