The Douglas A2D "Skyshark" grew out of a post-World War 2 United States Navy (USN) need for a prop-driven carrier-based strike aircraft offering good operational range with comparable performance to early-generation turbojet-powered navy types. The A2D was essentially an offshoot of Douglas' classic AD "Skyraider" of Vietnam War (1955-1975) fame which was already enjoying success in service since its introduction in 1946. Despite this the A2D was nearly an all-new, largely separate development due to the changes required to meet the new USN need. Despite its promising design, the A2D was limited to just twelve aircraft as issues with the intended Allison engine fit were never fully resolved while progress on turbojet technology was made.
Douglas was charged with a similar project back in 1945 when the USN came calling for a turbine-powered carrier-based aircraft. While three design submissions were put forth - including one with counter-rotating propeller units - none were selected for development but, in June of 1947, Douglas once again was charged by the USN for development of a carrier-based attacker, this time relying on a turboprop engine propulsion scheme. The aircraft was intended to operate from the compact Casablanca-class escort carriers then in service as some fifty of the type were completed during the wartime output of World War 2 (1939-1945).
The inherent limitations of turbojet technology of the period forced prop-driven aircraft to stay relevant heading into the Cold War years (1947-1991). Early turbojets offered good straight line performance but suffered in reaching maximum thrust output, general operational reliability, and - most importantly - fuel consumption. Often times a single aircraft design was forced to carry two or more turbojets to provide the needed thrust and increase survivability of pilot and aircraft alike. The turboprop engine offered a turbine solution to propulsion in which most of the engine's generated power was used to directly drive the spinning, variable-pitch propeller blades by way of reduction gear - giving the aircraft almost instant thrust power and good overall performance with inherent, proven reliability.
Allison was selected to produce the new engine to drive a contra-rotating propeller arrangement. Each propeller unit, seated at the nose, held three blades and spun in opposite directions to achieve the desired inline propulsion result. The combined rotation offered the new aircraft the needed pull power to take-off from a short carrier deck and give the attacker good cruising performance once in flight. Additionally, the operational range requirement could be met by having the aircraft cruise on only one engaged propeller set - the second unit brought into play when increased thrust was needed. The engine's formal designation became "XT40" - "X" detailing its experimental status.
The Douglas aircraft was arranged in a conventional way - the engine was fitted to the nose with the cockpit directly aft. The fuselage took on a deep shape and tapered towards the tail unit. The propeller fit at the front was capped by an aerodynamic spinner. The pilot's view to the rear of the aircraft was obstructed some by the raised fuselage spine immediately aft of his position. The wing mainplanes were set ahead of midships and were made straight in their general design with clipped tips. Exhaust ports were featured along the fuselage aft sides for the engine. Multiple hardpoints were added for carrying a variety of ordnance loads including rockets and bombs. The tail unit held a single vertical tail fin and fuselage-mounted horizontal tailplanes. A "tail dragger" undercarriage (with arrestor hook for carrier operations) rounded out the physical features of the aircraft. Folding wings were also standard for carrier-based service.
In addition to its stated war load (a maximum of 5,500lb across eleven hardpoints), the aircraft was slated to carry 4 x 20mm T31 series cannons.
Two prototypes were ordered in 1947 under the "XA2D-1" designation. Production models would become A2D "Skyshark" in service.
A first-flight in prototype form was held on March 26th, 1950 over Edwards AFB. Progress was stalled considerably when this prototype crashed on December 19th of that year, killing its pilot. The cause centered on the complex, and wholly new, Allison engine which failed, causing a fast descent and subsequent high-impact runway crash. This inevitably forced changes to the second prototype which was readied for April 1952.
Delays with a finalized version of the touted Allison engine, coupled with advancements made in the area of turbojet-powered flight, all rolled into the USN committed to a new war in Korea (1950-1953), worked against the ballooning Skyshark program. Nonetheless serial production was ordered and this gave life to a preproduction form. The finalized Allison engine was made available in 1953 but a test flight with this fit on a preproduction example ended with the propellers breaking off. Somehow the test pilot was able to land the plane safely. This event further grounded the program into 1954 which, by this time, the Casablanca carriers were all but removed from service and negated the need for a new turboprop-powered attacker.
Of the twelve completed Skyshark aircraft, only eight were ever actually flown with two of these being the original prototypes. The first prototype managed just 20 hours in the air before crashing. Engine issues, as well as changing times, all served to doom the Skyshark initiative.
As completed, the XA2D-1 prototype held a length of 12.6 meters, a wingspan of 15.2 meters and a height of 3.7 meters. Its empty weight was 12,900lb against a Maximum Take-Off Weight (MTOW) of 22,960lb. Power from the Allison XT40-A-2 turboprop engine totaled 5,100 horsepower output. This gave the aircraft a maximum speed of 501 miles per hour, a range out to 2,200 miles, and a service ceiling up to 48,100 feet. Rate-of-climb was 7,290 feet per minute.