The best fighter never – Part I

Occasionally, a military service will have a requirement for a new aircraft and find that not one, but two aircraft meet, even exceed, the parameters established.

This embarrassment of riches happened to the U.S. Navy when, in 1955, it began to search for an all-weather interceptor/fighter as a replacement for its outstanding F8U-1/2 Crusader, a fighter that would earn the nickname “MiG Master” in the skies over Vietnam in the late 1960s.

The Vought Aviation Company offered the Navy a high performance, single seat, fighter derived from the F8U, the XF8U-3 Crusader III.

Though it was a development of the F-8U-1/2, the Crusader III was almost an entirely new aircraft, much larger and powered by a Pratt & Whitney J75 turbojet, with 60 percent greater thrust than the earlier Crusader engines.

It was spectacular looking – the lower lip of the chin-mounted variable air intake was raked forward, making it look very much like an open mouthed shark, a resemblance that was heightened by the larger vertical stabilizer and a pair of large, retractable ventral fins that were extended vertically downward when the aircraft was in flight.

The swept wing was not optimal for the slow speed required for carrier landings, so the XF8U-3 retained the original, and very successful, F8U variable wing incidence. At low speed, the leading edge of the wing was actually lifted above the fuselage so it provided the proper angle of attack for slow carrier landings without forcing the nose up and limiting the pilot’s visibility.

To change the F8U from a day fighter to an all-weather interceptor, the Crusader III carried an AN/AWG-7 fire control computer and AN/APG-74 radar controlled and guided three radar guided AIM-7 Sparrow missiles, capable of hitting an enemy aircraft at long range day or night.

This fire control system could simultaneously track six and fire at two targets and, since the XF8U-3 was single seat, the controls for the radar and fire control system were optimized for one person operation.

The XF8U-3 first flew June 2, 1958, and quickly showed spectacular performance.
Initial tests showed it was the fastest accelerating fighter in the world from subsonic to supersonic speeds – from a speed of Mach .98 at 35,000 feet, it took only three minutes and 54 seconds to reach Mach 2.2, compared to a time of nine minutes for the F8U-1/2 and USAF fighters. Few of which could even reach Mach 2.2!

During subsequent flights, the XF8U-3 hit a top speed of Mach 2.39, approximately 1,600 mph, and was still accelerating at 0.1 Mach every 17 seconds when the test pilot pulled back on the throttle. The F8U-3 eventually reached Mach 2.6 during flight tests. The only reason it did not fly faster was because of heat limitations on the Plexiglas windshield.

A design for a laminated glass windshield was under way, which would have allowed the aircraft to achieve a maximum speed of Mach 2.9, a speed that could not be maintained for extended periods because of the effect of high temperature on the aircraft structure, but would have made the F8U-3 easily the fastest jet fighter in the world.

The maximum altitude capability was also remarkable. The Crusader III could maintain a sustained flight at 65,000 feet and could zoom to an altitude of 90,000 feet.

But the XF8U-3 had a two seat competitor for the Navy contract, and while the Navy wanted to build, both funds were too limited and in 1958 there was a congressionally-directed competition between the F8U-3 and its competitor.

The fly offs showed the Crusader III had a definite advantage in speed and maneuverability, but also indicated that the single pilot in the F8U-3 was overloaded when he had to use the radar to locate and lock on to a target, then provide the constant radar illumination the rather primitive beam riding Sparrows required to hit the target.

On Dec. 17, 1958, the Navy announced its decision to proceed with the two-engine, two-place competitor and canceled the better-performing single engine, single-place Crusader III.

Three XF8U-3s were flown during the seven months flight test period and they logged more than 250 hours.

After the cancellation of the program, the three F8U-3s flew with NASA on various test programs.

But in retrospect, it is difficult to fault the Navy for its choice – the aircraft that beat out the XF8U-3 was the McDonnell F-4, the “Phabulous Phantom.”

For questions or comments, contact Dr. Michel at marshall.michel@ramstein.af.mil.