The Douglas A3D Skywarrior had its origin in a 1947 request from the Bureau of Aeronautics for a carrier-based strategic bomber that would serve aboard a new class of supercarriers that was then being planned. The requirements were that the aircraft be able to carry a 10,000-pound nuclear weapon over a distance of up to 2000 nautical miles and then return to its carrier. The gross weight of the aircraft could not exceed 100,000 pounds. Since the nuclear weapon had to be armed in flight, the bomb bay had to be accessible from the cockpit.
Douglas, Curtiss, and North American submitted proposals in response to the request. The Douglas design team was led by project Engineer Harry Nichols and supervised by Ed Heinemann and Leo Devlin. The team came up with a large aircraft with a high-mounted wing that was swept backwards at an angle of 36 degrees. Two turbojet engines were mounted in individual pods extending ahead of and below the wing. Since the wing was shoulder mounted, the a narrow-track undercarriage had to be used, with the main units attached to the fuselage and retracting rearward into wells in the fuselage. The nosewheel was located immediately beneath the cockpit and retracted forward into a well in the nose. The crew of three (pilot, navigator/bombardier, defensive gunner) were to be seated in a single cockpit located immediately behind and above the nose radome.
At that time, the Navy and the new Air Force were locked in a bitter interservice rivalry as to which service would have the responsibility for strategic nuclear deterrence. The Air Force was pushing for a fleet of B-36 intercontinental bombers, whereas the Navy was pressing for a new class of supercarriers that could launch carrier-based strategic bombers against Soviet targets. The first of these supercarriers, the USS United States, had been ordered on August 10, 1948.
Fearing that the Navy would probably lose the contest and that the class of Navy supercarriers would never be built, Ed Heinemann decided that it was absolutely necessary that the weight be kept below 70,000 pounds so that the aircraft would be capable of operating from Midway-class carriers. In mid 1948, Douglas submitted a proposal for a 68,000 pound aircraft. The Curtiss design weighed nearly 100,000 pounds. North American dropped out of the competition, because they did not believe that it was possible to build an aircraft weighing less than 100,000 pounds that met the requirements.
Although the Navy was skeptical that Douglas really could build a 68,000-pound aircraft that met the requirements, both Douglas and Curtiss were given a preliminary 3-month contract so that they could refine their proposals. On March 31, 1949, Douglas was declared the winner of the contest and was awarded a contract for two XA3D-1s and a single static test airframe.
It turned out that Ed Heinemann was right about the bleak future for the Navy supercarriers--the USS United States was officially cancelled on April 23, 1949.
There were three crew members in the cockpit--pilot, bombardier/navigator, and gunner. The pilot and bombardier/navigator sat side-by-side, and the gunner sat to the rear of the pilot on a rearward-facing seat. The crew entered the cockpit via a hatch just aft of the nosewheel. Very early on, the Douglas team decided to dispense with ejector seats for the three crew members in order to save weight. Instead, the crew would have to abandon their aircraft via an escape chute fitted to the rear of the cockpit. Since the A3D was going to serve as a high-altitude strategic bomber, it was anticipated that most emergencies requiring aircraft abandonment would probably occur at high altitudes, giving the crew members enough time to individually get out of their seats, move to the rear of the aircraft, and jump out of the chute. However, if an emergency happened to occur at a lower altitude such as during a carrier landing or takeoff, the crew would probably be out of luck--leading some cynically to say that the designation A3D really stood for "All 3 Dead". The lack of ejector seats later lead to a lawsuit by the widow of a EKA-3B crewman who was unable to abandon his crippled aircraft during a mission over Vietnam on January 21, 1973.
A Navy requirement at the time was that all carrier-based aircraft had to have a canopy or an emergency hatch that could be opened for takeoff and landing. To meet this requirement, an aft-sliding hatch was installed in the roof of the cockpit. The crew could open this hatch manually, or in the case of an emergency a compressed air bottle could be fired from either inside or outside the cockpit to open the hatch. A crewman would typically open the hatch upon entry into the cockpit, and one of the crew would stand up and visually check to make sure that all the control surfaces were working properly and that there was adequate wing clearance, no cross traffic present, and nothing else that might be a hazard to the plane. It remained open during all takeoffs and landings. It was not meant for ordinary entrance or escape, but it was used on at least one occasion for emergency escape while airborne after the lower door escape system failed.
The A3D was equipped with a single swept vertical tail, which was sufficiently tall that it had to be provided with a joint so that it could be folded down for stowage aboard aircraft carriers. The wings themselves folded at hinge points located outboard of the engine pods. The leading edges of the wings outboard of the pods were provided with extensible slats. The inner trailing edge of the wings were provided with a set of flaps which extended all the way from the fuselage sides to the midwing folding point. The outer trailing edge of the wing outboard of the folding point were provided with ailerons.
The rear fuselage had a large speed brake on each side. In addition, there was a retractable tail bumper that was designed to protect against the rear fuselage striking the carrier deck during a too-steep approach.
The Navy had specified that the XA3D-1 should be powered by the Westinghouse J40 turbojet, which had also been selected for several other Navy aircraft of the period such as the McDonnell F3H Demon and the Convair XF2Y Sea Dart. Accordingly, the XA3D-1 prototypes were powered by a pair of Westinghhouse J40-WE-12 turbojets rated at 7000 lb.s.t. each, and plans were made to use the 7500 lb.s.t J40-WE-12 on the production A3D-1.
The A3D was designed to carry a defensive armament of two 20-mm cannon, both housed in a remotely-controlled turret in the extreme tail. These guns were to be aimed and directed by a radome mounted immediately above the turret and were operated by the defensive weapons operator in the cockpit.
The first XA3D-1 (BuNo 125412) was carried by truck out to Edwards AFB. Initially, the the twin 20-mm cannon were not actually installed in the tail turret. BuNo 125412 made its maiden flight there on October 28, 1952. Some problems were encountered with flutter, but the most serious problems were with the J40 turbojet. At that time, the J40 engine was encountering severe reliability problems on many of the other aircraft that had been designed for its use. These problems ultimately proved to be insoluble, leading to the cancellation of the entire J40 program. Since the A3D would have proved to be seriously underpowered with the J40 in any case, Douglas proposed that the J40 be replaced by the Pratt & Whitney J57 turbojet. This proposal was accepted by the Navy, and the two prototypes were later fitted with J57-P-1 turbojets.
125412/125413 Douglas XA3D-1 Skywarrior c/n 7588/7589