page_title: Douglas A-4 Skyhawk
section_title: Design and development
hierarchical_section_title: Douglas A-4 Skyhawk / Design and development
caption_attribution_description: A Wright J65 engine is rolled into a Douglas A4D-2 Skyhawk by U.S. Marines of Marine Headquarters and Maintenance Squadron 12 (H&amp;MS-12) at Marine Corps Air Station Iwakuni, Japan.
context_page_description: The Douglas A-4 Skyhawk is a single-seat subsonic carrier-capable light attack aircraft developed for the United States Navy and United States Marine Corps in the early 1950s. The delta-winged, single turbojet engined Skyhawk was designed and produced by Douglas Aircraft Company, and later by McDonnell Douglas. It was originally designated A4D under the U.S. Navy's pre-1962 designation system.
  The Skyhawk is a relatively lightweight aircraft, with a maximum takeoff weight of 24,500 pounds, and has a top speed of 670 miles per hour. The aircraft's five hardpoints support a variety of missiles, bombs, and other munitions. It is capable of carrying a bomb load equivalent to that of a World War II–era Boeing B-17 bomber, and can deliver nuclear weapons using a low-altitude bombing system and a "loft" delivery technique. The A-4 was originally powered by the Wright J65 turbojet engine; from the A-4E onwards, the Pratt & Whitney J52 engine was used.
  Skyhawks played key roles in the Vietnam War, the Yom Kippur War, and the Falklands War.
context_section_description: The Skyhawk was designed by Douglas Aircraft's Ed Heinemann in response to a U.S. Navy call for a jet-powered attack aircraft to replace the older Douglas AD Skyraider (later redesignated A-1 Skyraider). Heinemann opted for a design that would minimize its size, weight, and complexity. The result was an aircraft that weighed only half of the Navy's weight specification. It had a wing so compact that it did not need to be folded for carrier stowage. The first 500 production examples cost an average of $860,000 each, less than the Navy's one million dollar maximum. The diminutive Skyhawk soon received the nicknames "Scooter", "Kiddiecar", "Bantam Bomber", "Tinker Toy Bomber", and, on account of its speed and nimble performance, "Heinemann's Hot-Rod". The XA4D-1 prototype set a world speed record of 695.163 mph on 15 October 1955.
  The aircraft is of conventional post-World War II design, with a low-mounted delta wing, tricycle undercarriage, and a single turbojet engine in the rear fuselage, with two air intakes on the fuselage sides. The tail is of cruciform design, with the horizontal stabilizer mounted above the fuselage. Armament consisted of two 20 mm (.79 in caliber) Colt Mk 12 cannons, one in each wing root, with 100 rounds per gun (the A-4M Skyhawk II and types based on the A-4M have 200 rounds per gun), plus a large variety of bombs, rockets, and missiles carried on a hardpoint under the fuselage centerline and hardpoints under each wing (originally one per wing, later two).
  The short-span delta wing did not require the complexity of wingtip folding, saving an estimated 200 pounds (91 kg). Its spars were machined from a single forging that spanned across both wingtips. The leading edge slats were designed to drop automatically at the appropriate speed by gravity and air pressure, saving weight and space by omitting actuation motors and switches. Similarly the main undercarriage did not penetrate the main wing spar, designed so that when retracted only the wheel itself was inside the wing and the undercarriage struts were housed in a fairing below the wing. Thus the wing structure was lighter with the same overall strength. The rudder was constructed of a single panel reinforced with external ribs.
  The turbojet engine was accessed for service or replacement by removing the aft section of the fuselage and sliding out the engine. This obviated the need for access doors with their hinges and latches further reducing weight and complexity. This is the opposite of what can often happen in aircraft design where a small weight increase in one area leads to a compounding increase in weight in other areas to compensate, creating a demand for more powerful, heavier engines, larger wing and empennage area, and so on in a vicious circle.
  The A-4 pioneered the concept of "buddy" air-to-air refueling. This allows the aircraft to supply others of the same type, reducing the need for dedicated tanker aircraft—a particular advantage for small air arms or when operating in remote locations. This allows for greatly improved operational flexibility and reassurance against the loss or malfunction of tanker aircraft, though this procedure reduces the effective combat force on board the carrier. A designated supply A-4 would mount a center-mounted "buddy store", a large external fuel tank with a hose reel in the aft section and an extensible drogue refueling bucket. This aircraft was fueled up without armament and launched first. Attack aircraft would be armed to the maximum and given as much fuel as was allowable by maximum takeoff weight limits, far less than a full tank. Once airborne, they would then proceed to top off their fuel tanks from the tanker using the A-4's fixed refueling probe on the starboard side of the aircraft nose. They could then sortie with both full armament and fuel loads. The A-4 was rarely used for refueling in U.S. service after the KA-3 Skywarrior tanker became available aboard the larger carriers. The versatility of the capability and the retirement of the Skywarrior meant that the Boeing F/A-18E/F Super Horn
caption: An A4D Skyhawk with the rear fuselage removed and an engine being slid into place, Marine Corps Air Station Iwakuni, Japan, 1959
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