Much has been written in the US naval aviation literature about the Douglas AD/A-1 Skyraider piston-powered attack aircraft (nicknamed "Spad" by many airmen) and the prolific A4D/A-4 Skyhawk (better known as "Heinemann's Hot Rod"), both of which were designed by Ed Heinemann (1908-1991), chief designer at the El Segundo Division of Douglas, However, lost in talk regarding the design of naval warplanes by Heinemann in the early years of the Cold War is the fact, Heinemann himself undertook the first Douglas design for the US Navy with gas turbine power, the A2D Skyshark. Recently, I have seen desktop models of the Skyshark at a number of aviation museums in southern California, the Western Museum of Flight in Torrance and the Planes of Fame Museum in Chino. Unfortunately, for all of its good intentions in being a first step in bringing US naval attack aviation into the gas turbine age, the Skyshark turned out to be a disaster for Ed Heinemann due to technical problems with its engine. Therefore, I will discuss in detail Heinemann's failed effort at a turboprop-powered successor to the Skyshark.
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| Top: Douglas AD/A-1 Skyraider (BuNo 126997, photographed by me at the Planes of Fame Museum in Chino in April 2019), the aircraft that the A2D Skyshark would have replaced Bottom: Three-view drawing of the Douglas D-557C design with one Westinghouse X25D2 turboprop |
On June 25, 1945, the US Navy's Bureau of Aeronautics asked Douglas to design a turboprop-powered attack aircraft as a long-term successor to the new BT2D (later AD/A-1) Skyraider. A few months earlier, on January 25, Douglas had proposed the D-557 turboprop-powered attack aircraft, which was powered by two General Electric TG-100/T31 turboprops mounted side-by-side in the bottom of the fuselage below the pilot, both driving counter-rotating propellers. Armament would consisted of two 20 mm cannons and a 2,000 lb (907 kg) bomb or torpedo under the fuselage rack, plus 1,200 lb (544 kg) rockets or twelve 5 in (12.70 cm) rocket projectiles in wing racks. This proposal was unofficially called BT3D-1 by Douglas in anticipation of gas turbine propulsion rendering the Skyraider obsolete, and BT3D thus never became an official designation. By the second half of 1945, three subsequent designs for the D-557 were worked out. The D-557A was a tricycle design powered by two T31s in wing nacelles, with two 20 mm cannons and wing racks for carrying bombs, unguided rockets, or a torpedo, while the D-557B had two side-by-side T31s below the fuselage driving counter-rotating propellers and provisions for two 20 mm cannons, two 2,000 lb (907 kg) bombs mounted below the wing roots, and two 1,000 lb (454 kg) bombs mounted on mid-wing racks. The D-557C was similar to the D-557B in appearance but had one Westinghouse X25D2 turboprop driving counter-rotating propellers. By April 1946, mockups of all three proposals had been inspected by the Navy and were deemed satisfactory, but none of these projects progressed beyond the drawing board due to developmental problems with the T31 and X25D2.
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| Model of the Douglas A2D Skyshark (photographed by me at the Planes of Fame Museum in July 2021) |
Although the initial D-557 proposals remained paper projects only, Douglas received a Letter of Intent from the US Navy on June 11, 1947, for a turboprop-powered attack plane capable of operaring from the Casablanca-class escort carriers with a combat radius of 690 miles (1,110 km) and a reduced bomb load. Heinemann himself went back to the drawing board to propose a derivative of his earlier D-557 designs powered by one Allison T40 turboprop driving counter-rotating propellers. The new design, measuring 50 feet (15.24 meters) long with a wingspan of 41 feet 2 in (12.55 meters), a height of 17 feet 1 in (5.21 meters), and a wing area of 400 square feet (37 square meters), had a slightly lower wing root thickness compared to the Skyraider and taller and larger vertical stabilizer with greater area, and armament comprised four 20 mm cannons and 5,500 lb (2,500 kg) of bombs, unguided rockets, or a torpedo mounted under 13 hardpoints. A mock-up was inspected in early September, and on September 25 a contract was signed for two prototypes designated XA2D-1 (BuNos 122988/122989). Because the T40 faced technical problems during development and test runs, the first A2D prototype did not make its first flight until March 26, 1950, with test pilot George Jansen at the controls. Although flight tests were marred by vibration problems with the T40, the outbreak of the Korean War prompted the Navy to place an order for 10 production A2D-1s (BuNos 125479/125488) on June 30, followed by another production order on August 18 for 81 more Skysharks (BuNos 127962/128042). Additional orders for 258 more production A2D-1s (BuNos 132793/133042, 134438/134445) were placed on February 10, 1951.
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| Left: First Douglas XA2D-1 Skyshark prototype (BuNo 122988) Right: One of the ten completed production Douglas A2D-1s (BuNo 125480) in flight |
Despite the Navy anticipating the success of the Skyshark, the A2D flight test program suffered a major setback on December 19, 1950, when the first XA2D-1 prototype crashed on its 15th flight during a landing attempt because of a failure of the gearbox of the Allison T40 turboprop, killing Navy test pilot Hugh Woods. Consequently, the second XA2D-1 prototype was fitted additional instrumentation and an automatic decoupler for the T40, making its first flight on April 3, 1952. Even so, the T40 continued to be bedeviled by gearbox problems, and the Navy was having doubts about the Skyshark overcoming all problems with the T40 turboprop, not to mention that carrier-based jet aircraft were starting to become commonplace. By mid-1952, the Navy project office in charge of the Skyshark recommended that the A2D program be cancelled, and later that year, all production orders for the A2D except for the first ten production aircraft under construction were cancelled. The second production A2D-1 (BuNo 125480) became the first production aircraft to fly, making its first flight on June 10, 1953 with George Jansen at the controls. Five more A2D-1s (BuNos 125479, 125481/125484) were completed and delivered to the Navy later in 1953, and the remaining production A2D-1s (BuNos 125485/125488) were built but not flown. During one A2D test flight in 1953, test C.G. "Doc" Livingston was pulling out of a dive when the T40 gearbox failed, caused oil from the engine to cover the airplane's windscreen and the propellers to fall off the A2D, but Livingston safely landed the plane. The second A2D-1 was lost in an accident near Lake Los Angeles on August 5, 1954 after suffering a gearbox failure, and the pilot bailed out of the plane. By this time, the new Douglas A4D Skyhawk had just begun flight tests, and the escort carriers that the Skyshark had been designed to operate from were phased out of service.
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| The only extant Skyshark (BuNo 125485) on display at the Gillespie Field Annex of the San Diego Air & Space Museum in San Diego |
Following cancellation of the A2D program, the second Skyshark prototype was loaned to Allison for help in solving problems with the T40 turboprop in April 1953, and two production aircraft (BuNos 125481 and 125484) were intended to be flight ready and delivered to Allison; BuNo 125484 had originally been slated to be delivered to a naval storage facility in Litchfield Park, Arizona, but was instead flown to Edwards Air Force Base for use by Allison. After the completion of engine tests, the second XA2D-1 as well as the third and sixth production A2Ds were transferred to Navy facilities in Maryland and Rhode Island for various tests, including armament and barrier tests. The fate of these aircraft is unknown, but they may have been broken up for scrap. Meanwhile, the remaining A2D-1s at the Douglas factory in El Segundo were scrapped except for BuNo 125485, which was eventually used for ground radar calibration tests (minus its engine) at Los Angeles International Airport before being donated to the Ontario Air Museum in Ontario, California in the 1960s. It eventually languished in storage at Chino Airport near the Planes of Fame Museum in Chino, until 1993, when it was trucked to Idaho Falls Airport in Idaho Falls, Idaho, and restored to display status by Pacific Fighters. In the early 2010s, the aircraft was moved to the Gillespie Field Annex of the San Diego Air and Space Museum for static display, where it resides today.
Despite offering better performance over the Skyraider, the A2D Skyraider turned out be an engineering disaster because the Allison T40 turboprop failed to live up to expectations in performance, much to the frustration of not only the US Navy but also Douglas and other US companies that had designed several naval aircraft around the T40. In any case, Ed Heinemann learned from the failures of the A2D program and designed a lightweight jet-powered attack plane as an alternative, which became the A4D Skyhawk and eventually supplanted the Skyraider along with the later Grumman A2F/A-6 Intruder all-weather attack aircraft. Although no longer in service with its country of origin, the Skyhawk still serves with the militaries of Argentina and Brazil.
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