On 25 June 1945, the
Bureau of Aeronautics (BuAer) asked Douglas Aircraft for a turboprop-driven aircraft. Three proposals were put forth in the next year and a half: the D-557A, to use two
General Electric TG-100s (T31s) in wing nacelles; the D-557B, the same engine, with
contra-rotating propellers; and the D-557C, to use the
Westinghouse 25D. These were canceled due to engine development difficulties, but BuAer continued to seek an answer to the high fuel-consumption of
jet aircraft. On 11 June 1947 Douglas received the Navy's letter of intent for a
carrier-based turboprop. The need to operate from
Casablanca-class escort carriers dictated the use of a turboprop instead of jet power. While it resembled the
AD Skyraider, the A2D was different in a number of unseen ways. The 5,100-
equivalent shaft horsepower (3,800 kW)
Allison XT40-A2 engine had more than double the horsepower of the Skyraider's
R-3350. The XT40 installation on the Skyshark used
contra-rotating propellers to harness all the available power. Wing root thickness decreased from 17% to 12%, while both the height of the tail and its area grew. Engine development problems delayed the first flight until 26 May 1950, made at
Edwards Air Force Base by
George Jansen. The investigation found the starboard power section of the coupled Allison XT40A turboprop engine had failed and did not declutch. This meant the surviving engine was powering the failed engine's compressor, using up much of its available power. Additionally, the propellers failed to feather. As the wings' lift disappeared, a fatal sink rate was induced. Allison failed to deliver a "production" engine until 1953, and while testing an XA2D with that engine, test pilot C. G. "Doc" Livingston pulled out of a dive and was surprised by a loud noise and pitch up. His windscreen was covered with oil and the chase pilot told Livingston that the propellers were gone. The gearbox had failed, but Livingston successfully landed the airplane. The
A4D was ready to fly by the summer of 1954, but the escort carriers were being mothballed, so time had run out for the troubled A2D program. Twelve Skysharks were built, two prototypes and ten pre-production aircraft. Most were scrapped or destroyed in accidents, and only one has survived. ==Aircraft on display==