Mix one gonzo engine (the Pratt & Whitney XR-4360-10 Wasp with 3,000 righteous HP) and a requirement to carry a large bomb load off a carrier deck for long range strikes against Japan and you have this week’s Flightdeck Friday subject – the Boeing XF8B-1.

In 1943 the Navy contracted with Boeing to produce a long-range fighter capable of carrying, get this, a 3,000 lb bomb load internally along with a main gun complement of 6 x .50 cal which was later changed to 6 x 20mm cannon. Provisions were to be made for a similar external load for a total of over 6,000 lbs. By comparison, the Avenger carried 2,000 lb internally, the Helldiver 2,000 lb and the XBTD-2, which would form the basis of the AD/A-1, with 3,200 lbs, internal only. Range (with internally loaded weapons only) would be over 1300 nm.

Why such extraordinary requirements? Recall that in 1943 the expectation was that long-range raids against the Japanese homelands would have to be undertaken by carrier-based aircraft (and land-based bombers, led by the B-29, then under development). None of the then existent or planned fighter/bombers came close to meeting these requirements, hence the developmental contract for three prototypes from Boeing was let.

Unfortunately, pressing work on the B-29 delayed and slowed the development of the fighter (issues like an unfortunate tendency for the B-29’s engines to burst into fire), but by November 1944, the first prototype was ready for flight. Right off the bat, the XF8B-1 demonstrated outstanding performance. With the dual, counter-rotating props giving bite the air, the XF8B-1 demonstrated a maximum speed of 432 mph at an altitude of 26,900 ft. Still, this was one big aircraft — with a wingspan of 54 ft, length just over 43 ft and a gross weight of 20,508 lbs.

The second and third prototypes saw minor changes (e.g., raised cockpit for better visibility in the CV-landing pattern) and drew some interest from the AAF which examined the final prototype.

Time, however, was no friend to the XF8B-1 and it was clear by early 1945 that carrier operations were going to be conducted much closer to the Japanese homeland than originally expected. On the technology front, the jet engine was already showing promise in terms of significantly increased performance and two other prototypes, one from Martin (the AM-1) and the other Douglas (AD-1) looked to be the next generation attack aircraft for the Navy, ostensibly serving as a bridge from the prop-age to the jet age.

Therefore, despite performance that met or exceeded the Navy’s expectations (unlike other prototypes which fell far short of their paper expectations) the Navy opted to terminate the program in 1945. Owing to Boeing’s commitments with building the B-29, it is quite likely the XF8B-1 would have taken a back seat in production efforts as well. In the end, it will occupy a footnote as the heaviest and largest single engine piston fighter developed in the US.

Specifications (Boeing XF8B-1)

General characteristics

  • Crew: one, pilot
  • Length: 43 ft 3 in (13.1 m)
  • Wingspan: 54 ft (16.5 m)
  • Height: 16 ft 3 in (5.0)
  • Wing area: 489 ft² (45.4 m²)
  • Empty: 13,519 lb (6,132 kg)
  • Loaded: 20,508 lb (9,302 kg)
  • Maximum takeoff: 21,691 lb (9,839 kg)
  • Powerplant: Pratt & Whitney XR-4360-10 28-cylinder radial, 3,000 hp (2,240 kW)

Performance

  • Maximum speed: 340 mph (550 km/h)
  • Range: miles ( km)
  • Service ceiling: 37,500 ft (11,400 m)
  • Rate of climb: 2,800 ft/min (850 m/min) initial
  • Wing loading: kg/m² ( lb/ft²)
  • Power/mass: 0.15 hp/lb (0.24 kW/kg)

Armament

  • 6× 0.50 in (12.7 mm) or 6× 20 mm wing mounted guns
  • 6,400 lb (2900 kg) bomb load or 2× 2,000 lb (900 kg) torpedoes

References

  • Green, William (1961). War Planes of the Second World War – Fighters (Vol 4). London: Macdonald.

  • Jones, Lloyd S. (1977). U.S. Naval Fighters – Navy/Marine Corps 1922 to 1980′s. Fallbrook, CA: Aero Publishers, Inc.

Next week… we go burn some sagebrush…

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