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  • Boeing XF8B Carrier-Based Long-Range Fighter Prototype

    Boeing tried - unsuccessfully - to fit the long-range XF8B-1 prototype into long-term U.S. Navy plans.

     Updated: 4/25/2016; Authored By Dan Alex; Content ¬©www.MilitaryFactory.com

    The Boeing XF8B "do-everything" carrier-based fighter-bomber prototype of World War 2 (1939-1945) emerged at a time in Boeing's history when it was already heavily focused on producing and evolving their bomber line for the United States Army Air Forces (USAAF). The aircraft began as a self-directed company proposal which eventually caught the eye of the United States Navy (USN) - itself already committed to its healthy stable of Vought F4U "Corsair" and Grumman F6F"Hellcat" carrier-based fighters. Interested in the Boeing navy fighter-bomber concept - a design intended to fulfill roles beyond that of a fighter and include dive bomber, torpedo bomber, escort, and interceptor - the USN ultimately fleshed out its list of specifications for Boeing to begin work on. Such was the project scope for the do-everything fighter-bomber that it earned the nickname of the "Five-in-One" Fighter. It was known in-house as "Model 400".

    The USN specifications called for an aircraft that could serve on its carrier decks so dimensions, storage and structure were a key consideration. Maximum speed was in the vicinity of 342 miles per hour with a service ceiling of 30,000 feet. The subsequent USN contract then commissioned for three flyable prototypes and one static testbed under the "XF8B" designation beginning with prototype "XF8B-1". The contract was formally awarded to Boeing on April 10th, 1943.

    Design work began in short order with a mockup available for review in October of 1943. XF8B-1 was then completed in 1944 and its first flight recorded on November 27th of that year. Boeing engineers developed a dimensionally large airframe with a smoothly-contoured fuselage from nose to tail. Wings were set low on the fuselage sides and ahead of midships. The spacious cockpit was centrally-located with the pilot under a useful teardrop canopy with good vision to the sides of the aircraft, above and behind. The engine was of a slender form but its installation necessitated a rather long nose assembly making ground running difficult. The fuselage tapered nicely into the empennage to which a large, rounded vertical tail fin was fitted (ala the Boeing line of famous World War 2 bombers). Horizontal tailplanes were affixed to the fin's sides in the usual way. The engine, held in its forward-set compartment, drove 2 x three-bladed propeller assemblies in a contra-rotating arrangement. This supplied the necessary thrust from the ultra-powerful engine installation while negating the effects of torque encountered when using just one three-bladed propeller (seen on many aircraft of the period). The undercarriage was of the "tail-dragger" arrangement which used two main landing hear legs. These retracted into the wings after pivoting at 90-dgrees. The tail wheel was also retractable to keep the aircraft as streamlined as possible when in flight.

    Engineers selected the Pratt & Whitney XR-4360-10 28-cylinder, four-row radial piston engine for the airframe - this being the most powerful propeller-driving engine fitted to any fighter design at that time. The powerplant outputted at 3,000 horsepower on full throttle and was the same as used in the other experimental mount - the Republic XP-72 "Super Thunderbolt" detailed elsewhere on this site. The two-stage supercharged engine, coupled with the outstanding profile of the aircraft, allowed for a maximum speed of 432 miles per hour to be attained with a cruise speed near 190 miles per hour. Range measured out to 2,800 miles which would prove handy over the large reaches of sea in the Pacific Theater when battling the forces of the Empire of Japan. Its service ceiling was listed at 37,500 feet - surpassing the USN's initial specifications - while rate-of-climb proved an impressive 2,800 feet-per-minute - a key quality for an interceptor and carrier-launched aircraft. As designed, the engine installation was intended for easy replacement - improving both maintenance turnaround times and perhaps any future powerplant upgrades sought.

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    Boeing XF8B-1 Technical Specifications

    Service Year: 1944
    Type: Carrier-Based Long-Range Fighter Prototype
    National Origin: United States
    Manufacturer(s): Boeing - USA
    Production Total: 3

    Structural (Crew Space, Dimensions and Weights)

    Operating Crew: 1
    Length: 42.65 feet (13 meters)
    Width: 54.13 feet (16.50 meters)
    Height: 16.40 feet (5.00 meters)

    Weight (Empty): 13,525 lb (6,135 kg)
    Weight (MTOW): 21,693 lb (9,840 kg)

    Installed Power and Standard Day Performance

    Engine(s): 1 x Pratt & Whitney XR-4360-10 28-cylinder radial piston engine developing 3,000 horsepower while driving 2 x three-bladed contra-rotating propellers.

    Maximum Speed: 432 mph (695 kph; 375 knots)
    Maximum Range: 2,796 miles (4,500 km)
    Service Ceiling: 37,402 feet (11,400 meters; 7.08 miles)
    Rate-of-Climb: 2,800 feet-per-minute (853 m/min)

    Armament / Mission Payload

    6 x 0.50 caliber heavy machine guns OR 6 x 20mm cannons mounted in the wings.

    Up to 6,400lbs of conventional drop stores OR 2 x 2,000lb torpedoes.

    Global Operators / Customers

    United States

    Model Variants (Including Prototypes)

    XF8B - Base Project Designation

    XF8B-1 - Base Prototype Designation; three examples completed.