In the summer of '58, nothing was faster to 50,000 feet.
- By Carl Posey
- Air & Space magazine, July 2006
(Page 3 of 4)
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.
In mid-December 1953, the airplane’s reputation was burnished further when Heinemann received the Collier Trophy for the Skyray; he shared the honor for the first supersonic fighter with North American’s Dutch Kindelberger, father of the F-100 (and Heinemann’s former boss). And there was more good news: Another Heinemann creation, the D-558-2 Skyrocket, made Scott Crossfield the first human to reach Mach 2 in an airplane and enabled Marion Carl to set an unofficial world altitude mark: 83,235 feet.
By this time no one believed Westinghouse could deliver a reliable afterburning J40. (Indeed, the J40 fiasco would drive the company out of the jet engine business.) But Heinemann had seen the problem coming, and had built the Ford’s fuselage with enough space to accommodate a larger engine: Pratt & Whitney’s afterburning J57-P-2, with 14,500 pounds of thrust. The Skyray would finally have enough power to serve as the interceptor that Douglas and the Navy had envisioned.
Production began in 1954. Once the F4D-1s were ready for flight testing, they were towed across Imperial Boulevard to Mines Field, now better known as Los Angeles International. The airplanes were supposed to include an Aero-13 fire control system, built around the Westinghouse An/APQ-50 radar, a system that could see targets 18 miles away and lock onto them at 12 miles. Like the J40 engine, however, the radars were slow in reaching Douglas, and not all Skyrays flew with that equipment; some spent their careers as day fighters, as their creators had intended.
The Ford’s foibles remained, but were not seen as insurmountable. “It had a lot of complicated restrictions,” says Abzug. “Get the thing rolling at high speed, you had to tell the pilot about restrictions. For example, at 400 knots do not exceed two-thirds aileron or one-third back stick. But there’s no way pilots can remember all that stuff. We resorted to placarding,” putting up the small warning signs that dot even Cessna cockpits with no-no’s for the pilot.
On an afternoon in 1955, Bob Rahn leapt off the Los Angeles International Airport’s runway in a production Skyray, heading out over the Pacific a hundred feet above the waves. The idea was to see whether enough pitch trim was available with the new engine to compensate for the airplane’s tuck-under at transonic speeds. He later wrote, “I had accelerated to Mach .98 (approximately 750 mph) in afterburner. This Mach speed created the maximum tuck-under. Full trimmer deflection was required to maintain trimmed flight. Therefore I concluded that the engineers had done a good job with respect to adequate trim for this low-altitude, high-speed flight environment. For all practical purposes, the test was completed. So I nonchalantly shut off the afterburner.”
The Skyray decelerated so rapidly that the trimmer became super-effective, flipping the nose suddenly skyward. “My Skyray and I were pitched up at a gut-wrenching 9.1 Gs,” Rahn wrote. “The airplane had a design limit of 7.0 Gs. Moreover, I wasn’t wearing a g-suit…. I immediately blacked out.” Rahn lost his vision but was aware of his situation. Reluctant to touch anything for fear of making a bad situation worse, he endured the ride. When his eyes cleared, his windscreen was all blue Pacific. “I was in a vertical dive after completing three-fourths of a loop.” Gingerly recovering at about 3,000 feet, he looked out at the wings. “They were wrinkled from wing tip to wing tip, resembling dried prunes.”
Back on the ground at LAX, Rahn found that the rest of the Skyray’s skin was wrinkled, the wings were incurably bent, and some of the vertical stabilizer’s stringers were protruding, like broken bones. The engine had torn off its mounts and was resting on the engine-compartment access door, pinching a fuel line. Later, Rahn reckoned that the event had been caused by the added thrust and the resulting increase in tuck-under. The corresponding increase in nose-up trim had made the Ford go nuts when it suddenly decelerated. Scratch one Skyray.