Vought XF8U-3 Crusader III
The Vought XF8U-3 Crusader III was a single-seat supersonic carrier fighter built by Chance Vought as a fleet-defense interceptor and successor to the F-8 Crusader. First flown on 2 June 1958, it was faster than McDonnell's rival F4H-1 Phantom II and more maneuverable, but its lone pilot carried the whole intercept workload, and on 17 December 1958 the Navy chose the two-seat, more versatile Phantom. Five aircraft were built and three flew; the flown aircraft passed to NASA, which used them briefly, including sonic-boom measurements at Langley, before all were scrapped. No example survives.
Why It Mattered
In December 1955 the U.S. Navy opened a competition for a fleet-defense interceptor able to exceed Mach 2, fast enough to reach Soviet bombers before they could threaten the fleet. Chance Vought developed the Crusader III as the successor to its successful F-8 Crusader. The company's designer Russell Clark pointed out that the new fighter was 100 knots faster than its rival, McDonnell's Phantom, and used 20 percent less carrier deck space. The Navy chose the Phantom instead, and Navy engineer George Spangenberg's verdict — "the best fighter never produced" — fixed the Crusader III's reputation as the outstanding fighter the service declined to buy.
Design Notes
Despite the shared name, the Crusader III was an almost entirely new design: a NASA caption describes it as an entirely new design compared with the earlier Crusader series, and it shared few parts with the F8U-1 and F8U-2. It kept the earlier Crusader's variable-incidence wing, which improved the pilot's view during deck landings. A single Pratt & Whitney J75-P-5A turbojet produced 29,500 pounds of thrust with afterburning, breathing through a chin-mounted "Ferri scoop" inlet that used three shock waves to slow the air, and the aircraft was designed for brief excursions to Mach 2.7. Two large ventral fins beneath the tail kept it stable beyond Mach 2 and rotated to the horizontal for takeoff and landing. Armament was missiles only — three Sparrow radar-guided missiles and no gun — and Vought provided for a Rocketdyne rocket motor in a variant called the F8U-3F, though the Crusader III never flew with a rocket engine. In practice, heat limited speed more than thrust did: the Plexiglas windscreen and lower wing skin temperatures held normal operation to about Mach 2.32, although the aircraft demonstrated Mach 2.39.
Operational History
The first Crusader III took to the air on 2 June 1958, with Vought test pilot John W. Konrad at the controls, only five days after its archrival, McDonnell's F4H-1, had first flown. On 14 August 1958, during its 38th test flight, it exceeded Mach 2 in level flight, well before the rival F4H-1 did so. Five aircraft were built, of which three flew during the test programme. Testing also exposed real weaknesses: an unacceptable tendency to go into compressor stalls at high Mach numbers, and a takeoff run three times longer without afterburner than with it. In the fly-off, the Vought design demonstrated a definite advantage in maneuverability, and Konrad later said it could easily outmaneuver the Phantom II. But the Crusader III's single pilot had a heavy workload flying the intercept and firing Sparrow missiles, which required constant radar illumination, while the Phantom's radar intercept officer shared that work. The Phantom also carried far more ordnance and could fly strike missions as well as intercepts, where the Crusader III was a single-purpose interceptor. On 17 December 1958 the Navy announced its selection of the F4H-1, and the Crusader III programme was cancelled without entering production.
Afterlife
The three flown aircraft were transferred to the new NASA: two went to its Langley facility in Virginia, and the third to its Ames center in California, at Moffett Field. Langley used the type for some of the earliest flight measurements of sonic booms, in an investigation flown at Wallops Island from June to August 1959. NASA made very few flights with the Crusader IIIs, and the California-based aircraft apparently never flew in NASA markings. For years afterwards, aviators told tales of NASA F8U-3s beating Navy F4H-1s in east-coast mock dogfights; the stories are reported rather than documented, and Defense Media Network notes that it is unclear where the lore originates. By the time the Pentagon's military designation system was overhauled on 1 October 1962, all three NASA aircraft had been scrapped, so the F8U-3 never received a new designation. The two unflown airframes were scrapped as well, and no Crusader III survives.