In the summer of '58, nothing was faster to 50,000 feet.
- By Carl Posey
- Air & Space magazine, July 2006
Near dawn on a sparkling spring day, a tailless jet fighter shaped like a manta ray taxied into position on Runway 21 at the Naval Air Missile Test Center at Point Mugu, California. Pointing the airplane into the dense, cold air flowing off the Pacific, Marine Corps Major Edward N. LeFaivre applied full power with the brakes on, then, brakes off, lit the afterburner. The aircraft screamed down the runway for the ten seconds it needed to reach 150 mph and lifted off in a 70-degree climb, tracked by missile-range cameras and radar. Two minutes and 36.05 seconds after releasing the brakes, LeFaivre was at 50,000 feet. It was the fastest time to that altitude in history.
The airplane that set that mark was not a daring experiment in delta-wing technology, but a Navy fighter that had been in development for more than a decade, had served with the fleet for two years, and was already entering the twilight of its service life. Yet as of May 23, 1958, Ed LeFaivre’s airplane could still outclimb any other military jet, foreign or domestic.
Douglas designed the aircraft to meet the Navy’s 1947 requirement for a land- or carrier-based jet interceptor quick enough to catch and kill an approaching enemy bomber flying at 500 knots (575 mph) and 40,000 feet within a 100-mile radar range. To do this, the jet would have to reach 40,000 feet in five minutes and be able to fight when it got there.
Named the Skyray for the unique shape of its wing, LeFaivre’s aircraft was known by those who flew and cared for it as the Ford, from its designation, F4D, and fighter pilots’ penchant for understatement. In fact, there was nothing Ford-like about the Skyray. It was exotic and fast, the first of the high-performance designs born during the post-World War II fascination with delta wings, which sprouted on military aircraft around the world like fins on late-1950s automobiles. Many had been inspired by the 1930s experimentation of German aircraft designer Alexander Lippisch. He, in turn, attributed the delta wing to a gift of a zanonia seed, sent him by a colleague during the 1920s. Triangular and airworthy, zanonia seeds can glide a good distance from their parent vine on the weak thermals of the Indonesian rainforest.
The more immediate provenance of the Skyray was a visit to Paris in the week following VE Day, during which Douglas engineers Gene Root and A.M.O. Smith acquired a trove of German wind tunnel data and were able to listen to Lippisch, then in Allied custody, brief his captors on the flying-wing interceptors he believed were aviation’s future. Smith and Root returned to El Segundo and the legendary California design-works run by Edward H. Heinemann, where engineers started playing their own supersonic variation on the Lippisch theme.
“The original layout we had at Douglas was very much like Lippisch’s plan, which had a sweepback of 45 degrees,” recalls Malcolm J. Abzug, a control and stability engineer present at the Skyray’s creation. “As I remember, it was okay, but the airplane couldn’t be balanced. So the sweepback was increased to 52.5 degrees.” Increasing the degree of sweep balanced the aircraft by shifting the wing’s area in relation to its center of gravity, the point around which the aircraft pivots in pitch. “All this was under A.M.O. Smith,” Abzug says. “His first name was Apollo, so he went by initials; we called him Amo Smith.”
The first design was a wing that could easily have flown off the drawing board of Lippisch himself. Then, like a reptile morphing into a bird, the new fighter began to take shape: A rudimentary fuselage appeared, and the wings shrank to a smaller triangle.
One of the youngest members of the design team was Erven Heald, who had come to Douglas in 1940, fresh from the University of Michigan. “Heinemann would just come up with a design and take it to one of the engineers to be turned into an airplane,” he says. “When he showed me the Skyray he asked if we could make one, and I said yes, but the center-of-gravity travel can’t be more than about five percent.” That limited what could be hung on the airplane, and where. “My role was just the flying qualities, how to make it stable and controllable.” With a grin, he adds, “Stable and controllable was a challenge.”
In October 1950, not quite a year after the Navy awarded a contract to build two prototype Skyrays, Douglas rolled out the XF4D. It was neither a flying wing nor a delta-wing airplane, but something in between. To those who would come to love the craft, its planform looked like a valentine. To others it looked like the ace of spades.
Because the Skyray had no horizontal tail, pilots controlled pitch and roll with elevons on the trailing edge of the wing—control surfaces that have combined the functions of ailerons and elevators on all delta-wing airplanes right up through the Concorde. The Skyray’s elevons were boosted hydraulically. Were the hydraulic system to fail, the stick could be extended about a foot to give the pilot enough leverage to move the control surfaces. Pitch trimmers augmented the elevons. Control in yaw was provided by a swept dorsal fin with an unboosted rudder.
Westinghouse had not yet delivered the J40 engine specified by the Navy, but with deadlines looming, Douglas jury-rigged the prototypes with Allison J35-A-17s, which left the airplanes sorely underpowered. In the fall of 1950, the prototypes were trucked to Edwards Air Force Base in California to see if they were more than just a pair of pretty faces.