Douglas A-3 Skywarrior
The Douglas A-3 Skywarrior is a jet-powered strategic bomber that was developed and produced by the Douglas Aircraft Company. It was designed by Douglas on behalf of the United States Navy, which sought a carrier-capable strategic bomber. In July 1949, Douglas was awarded the contract to produce its design, having beaten eight other aircraft companies' submissions. Unlike rival designs, which had aimed for a maximum take-off weight, the Skywarrior was developed for a take-off weight, facilitating its use from the navy's existing s. Large portions of the aircraft were produced by the Westinghouse Electric Corporation, including its early Westinghouse J40 turbojet engines, which failed to meet expectations and were replaced by the rival Pratt & Whitney J57 engine by mid-1953. On 28 October 1952, the prototype XA3D-1 performed the type's maiden flight.
On 31 March 1956, the Skywarrior entered squadron service with the US Navy. Initially used in the nuclear-armed strategic bomber role, the emergence of effective ballistic missiles led to this mission being deprioritized by the early 1960s. Throughout the majority of its later service life, the Skywarrior was tasked with various secondary missions which included use as an electronic warfare platform, tactical reconnaissance aircraft, and high-capacity aerial refueling tanker. It was among the longest serving carrier-based aircraft in history, having entered service during the mid-1950s and withdrawn from use in 1991. Throughout its service, the Skywarrior was the heaviest operational aircraft to operate from an aircraft carrier, which contributed to its nickname of "Whale".
The Skywarrior is one of only three U.S. Navy attack aircraft to enter service in the strategic bomber role. The first was its predecessor, the North American AJ Savage, while the third was the supersonic North American A-5 Vigilante, which initially supplanted the A-3 in the strategic bomber role but the A-5 was then converted to the tactical strike reconnaissance role.
A modified derivative of the Skywarrior, the B-66 Destroyer, served in the United States Air Force, where it was operated as a tactical bomber, electronic warfare aircraft, and aerial reconnaissance platform up until its withdrawal during the 1970s.
Development
Background
During World War II, the United States Navy began to explore the concept of operating jet-powered aircraft from its aircraft carriers. Success encouraged further development of the concept; early in the post-war years, officials within the USN began to investigate the use of jet power as a potential means of operating larger carrier-based aircraft that would be capable of performing the strategic bombing mission. The USN had a growing awareness that it could operate in a broader role than had been previously possible, and that the strategic bomber fleet operated by the United States Air Force was unable to reach large parts of the world, a lesser limitation to forward deployed USN aircraft carrier groups and their air wings.In January 1948, the Chief of Naval Operations issued a requirement to develop a long-range, carrier-based attack plane that could deliver either a bomb load or a nuclear weapon. The envisioned aircraft was intended to be operated from the planned United States-class "supercarriers," which were significantly larger than the USN's existing carriers, thus the specification set a target loaded weight of. Additionally, the USN sought for this bomber to possess greater speed and range than its existing North American AJ Savage fleet. A total of eight aircraft manufacturers produced responses to the specification, but all except Douglas Aircraft Company and Curtiss-Wright would drop out, declaring that there was no means that the requirements could be met within the 100,000 lb weight limitation. Uncertainty over the performance and requirements of both engines and bombs were major contributing factors towards this climate of negativity.
Ed Heinemann, Douglas' chief designer, later to win fame for the A-4 Skyhawk, fearing that the United States class was vulnerable to cancellation, proposed a significantly smaller aircraft of loaded weight, capable of operating from the USN's existing carriers. Heinemann had reasoned that as technology developed, the size and weight of nuclear weapons would substantially decrease, which increased the rationale for designing a more compact bomber. However, figures such as USAF general Hoyt Vandenberg ridiculed Heinemann's proposal as "making irresponsible claims". During this period, the USN and USAF were vigorous rivals, each seeking to maintain funding for its projects at the expense of the other in a time marked by drastically declining defense budgets; specifically, USAF officials frequently voiced their open opposition to the construction of the United States-class carriers.
Selection
In late 1948, both Douglas and Curtiss-Wright were awarded preliminary design contracts to further develop and refine their proposals. While Douglas managed to maintain the take-off weight at 68,000 lb, Curtiss were unable to meet the more generous 100,000 lb target during this phase, and thus were eliminated from consideration. During April 1949, the USN's critics succeeded in getting the United States-class carriers cancelled; this outcome validated Heinemann's decision to focus on a design that could operate from the navy's smaller s. During July 1949, the USN, recognizing the suitability of Douglas' design, awarded a contract for the production of two flight-capable prototypes and a single static airframe to the company.Douglas sourced significant portions of the aircraft, including responsibility for the turbojet engines, radar, tail-mounted turret, electrical generators and various other secondary systems, from the Westinghouse Electric Corporation; this heavy reliance on Westinghouse allegedly caused some discomfort to Douglas. In particular, development of the Westinghouse J40 engine proved to be incapable of meeting development schedules or performance promises; Heinemann later commented that "the first thing we learned was that the J40 was not powerful enough". Even prior to the first flight being conducted, Douglas was considering switching to rival manufacturer Pratt & Whitney's J57 engine, which was heavier, but allowed the overall aircraft to be lighter as it used less fuel.
On 28 October 1952, the prototype XA3D-1 performed the type's maiden flight; flown by George Jansen, this initial test flight was carried out with a high degree of secrecy. Early on, the aircraft was found to handle particularly well in flight, in part due to the attention Heinemann and the design team had paid to the hydraulically-boosted control surfaces. On 16 October 1953, the first YA3D-1, powered by the rival J57 engine, made its first flight.
Considerable development problems, largely associated with the original J40 engines, had delayed the introduction of the Skywarrior until 31 March 1956. The A-3 was, by far, the largest and heaviest aircraft ever designed for routine use on an aircraft carrier, though ironically it was the smallest proposal among other proposals that could only be deployed on even larger carriers not yet in service. As had been predicted by Heinemann early on, the Skywarrior had been designed to carry larger and bulkier bombs than it ever would in service due to the rapid improvements made in weapons technology. Despite this, at the Navy's insistence, the aircraft was qualified for an 'overload' payload capacity of, the testing of which would establish a weight-related record for carrier operations. Because of its cumbersome size, and less-than-slender profile, it was nicknamed "Whale".
By the end of the 1950s, it was becoming clear that the nuclear mission of the Skywarrior would be passed onto ballistic missiles; however, its high weight clearance and size meant that the aircraft would be useful in various other capacities. Accordingly, large numbers of Skywarriors were retrofitted as aerial refuelling tankers or as electronic warfare platforms; notably, the EKA-3B model could readily swing between performing strike, refuelling, and electronic warfare duties as required. Numerous other models of the type were developed, leading to the type being used for aerial reconnaissance and as a trainer aircraft as well. Production of the type ceased in 1961.
Design
The Skywarrior had a 36° degree swept wing and two Pratt & Whitney J57 turbojet engines. Early prototypes had used the intended Westinghouse J40, a powerplant that proved to be disastrous and was subsequently canceled. The turbojets could be supplemented by a provision for twelve thrust JATO bottles. The aircraft had a largely conventional semi-monocoque fuselage, with the engines in underwing nacelles. Flight controls were hydraulic, and for storage below deck, the A-3's wings folded outboard of the engines, lying almost flat, and its vertical stabilizer was hinged to starboard. Capacious internal fuel tanks provided long range.The early A-3 variants had a crew of three: pilot, bombardier/navigator and crewman/navigator. An unusual cockpit configuration was incorporated with the three crew sitting under a framed canopy. In the raised compartment, the pilot and bombardier/navigator sat in a side-by-side arrangement with the pilot's station on the port side having full flight controls. On initial variants, a third crew member, who also acted as a gunner for the twin tail-mounted 20mm cannon that briefly equipped the original bomber version of the A3D/A-3A, sat behind the pilot in an aft-facing seat. The third crewman station had the sextant for celestial navigation and the defensive electronic counter measures equipment. Later electronic reconnaissance variants could accommodate a crew of seven with the flight crew consisting of a pilot, co-pilot and navigator plus four electronic systems operators occupying stations in the former bomb bay in the spacious fuselage.
Efforts to reduce weight to make the aircraft suitable for carrier operations had led to the deletion of ejection seats during the design process for the Skywarrior, based on the assumption that most flights would be at high altitude. A similar arrangement with an escape tunnel had been used on the F3D Skyknight. Aircrews began joking morbidly that "A3D" stood for "All Three Dead". In contrast, the US Air Force's B-66 Destroyer, not subject to the weight requirements for carrier operations, was equipped with ejection seats throughout its service life.
The documented history of mechanical failures in the A3D/A-3 showed a rate well above average. Originally, the Skywarrior bombers were assigned to all attack carriers, which included the World War II-era and the immediate-postwar Midway class.
The Skywarrior could carry up to of weaponry in the fuselage bomb bay, which in later versions was used for sensor and camera equipment or additional fuel tanks. An AN/ASB-1A bomb-director system was initially installed, later replaced by a revised AN/ASB-7 with a slightly reshaped nose. Defensive armament was two 20mm cannons in a radar-operated tail turret designed by Westinghouse, soon removed in favor of electronic countermeasure equipment. Although some bombing missions would be carried out early in the Vietnam War, most bombing would be carried out by more manoeuvrable aircraft, and the Skywarrior would serve mostly as a tanker and electronic warfare support aircraft.