Kaiser-Fleetwings XBTK Prototype Dive Bomber / Torpedo Bomber
The single-seat Kaiser-Fleetwings XBTK naval bomber prototype was produced in just five prototypes and never adopted.
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The "escort carrier" was adopted by the United States Navy during World War 2 (1939-1945) to provide an aircraft carrier-type vessel that was comparably smaller in dimension to full-sized carriers but could be produced at a much quicker pace during wartime. This led to the USN need for lighter-minded bomber/strike aircraft to stock this growing light carrier fleet. In turn, this need produced a 1943 requirement which was answered by the Kaiser-Fleetwings concern. Kaiser-Fleetwings was formed by the merger of Kaiser Cargo and Fleetwings and from this pairing emerged a January 1944 proposal for such an aircraft. To date, the Kaiser company made a wartime profit from shipbuilding while Fleetwings contributed to aircraft production for other companies.
The USN responded with a formal go-ahead in February of 1944. The specification would bring about a single-seat, single-engine, carrier-based dive bomber in two prototype forms under the "XBK"designation. Power would come from a Pratt & Whitney R-2800-22W radial piston engine and armament to be cannon-centric (2 x cannon featured in the wings). Of course there would be ordnance carrying capabilities and this set across three hardpoints total hardpoints - one fuselage centerline and two under the wings. Additional underwing space would be reserved for the carrying (and launching) of 8 x aerial rockets. The wings were also designed to fold for improved storage aboard the light carriers.
In March of 1944, the USN returned with an increased order for five aircraft.
By the fall of 1944, Kaiser-Fleetwings - with no experience in designing and developing combat fighter aircraft - produced a mockup for review. The USN now contracted for 17 pre-production units in October though authorities were now more interested in a torpedo-carrying attack aircraft than a dive bomber. As such, Kaiser-Fleetwings revised their original design, which increased the centerline hardpoint tolerance to carry a single USN-standard torpedo, and this begat the "XBT-1" designation of February 1945.
As completed, the XBTK-1 was a very nice looking aircraft with a form akin to the Vietnam War-era Douglas A-1 "Skyraider". The XBTK-1 featured a forward-mounted engine compartment with forward-set cockpit, the later under a teardrop-shaped bubble canopy for excellent vision out-of-the-cockpit. The monoplane wings sat low along the fuselage sides in the usual way and were properly strengthened for the rigors of carrier-based service. The fuselage was well contoured and tapered to the empennage to which a large-area vertical tail fin was affixed. Horizontal tailplanes were mid-mounted along the fin sides. The undercarriage - wholly retractable and featuring the requisite arrestor hook - was of the "trail-dragger" configuration showcasing two main landing gear legs and a diminutive tail wheel. A special exhaust system was installed which attempted to turn cooling drag into additional thrust. As a low-level attack aircraft, the XBTK-1 was also given the requisite self-sealing fuel tanks seen in other aircraft of the period and the cockpit was armored for improved pilot survivability.
Progress on the XBTK-1 was a slow affair while the war evolved at a quickened pace. First flight was not recorded until April 12th, 1945 and subsequent testing eventually saw the original -22W engine replaced with the supercharged Pratt & Whitney R-2800-34W engine of 2,100 horsepower to drive the four-blade propeller assembly. Performance specifications included a maximum speed of 373 miles per hour, a range out to 1,400 miles and a service ceiling of 33,400 feet.
Further testing also forced some changes to the design - special cowls were added around the engine casing to help with overheating issues and the special exhaust feature - promising a performance boost - did not produce as expected - it just added complexity to an already complex design. On the whole, however, Kaiser-Fleetwings submission was quite a solid one and certainly promising in the scope of the USN requirement. The aircraft was eventually delivered to USN hands for additional review.
In September of 1945, World War 2 had come to its official close. This spelled the death for many-a-promising aircraft venture including the Kaiser-Fleetwings torpedo bomber. Some five aircraft were eventually completed with four of these flyable. The massive American defense drawdown in both military products and budget after the war left little room to grow such programs as the XBTK-1 and this signaled the end of the road for the machine.