The Ling-Temco-Vought A-7 Corsair II is a carrier-capable subsonic light attack aircraft introduced to replace the Douglas A-4 Skyhawk. The A-7 airframe design was based on the successful supersonic Vought F-8 Crusader. It was one of the first combat aircraft to feature a head-up display (HUD), an inertial navigation system (INS), and a turbofan engine.
The Corsair II initially entered service with the United States Navy during the Vietnam War. It was later adopted by the United States Air Force, including the Air National Guard, to replace the Douglas A-1 Skyraider, North American F-100 Super Sabre and Republic F-105 Thunderchief. The aircraft was also exported to Greece in the 1970s, and Portugal in the late 1980s.
Design and development
In 1962, the United States Navy began preliminary work on VAX (Heavier-than-air, Attack, Experimental), a replacement for the A-4 Skyhawk with greater range and payload. Particular emphasis was placed on accurate delivery of weapons to reduce the cost per target. The requirements were finalized in 1963, announcing the VAL (Heavier-than-air, Attack, Light) competition.
The first A-7 mock-up in 1964
To minimize costs, all proposals had to be based on existing designs. Vought, Douglas Aircraft, Grumman and North American Aviation responded. The Vought proposal was based on the successful Vought F-8 Crusader fighter, having a similar configuration, but shorter and more stubby, with a rounded nose. It was selected as the winner on 11 February 1964, and on 19 March the company received a contract for the initial batch of aircraft, designated A-7. In 1965, the aircraft received the popular name Corsair II, after Vought's highly successful Vought F4U Corsair of World War II. (There was also a Vought O2U Corsair biplane scout and observation aircraft in 1920s.)
Compared to the F-8 fighter, the A-7 had a shorter, broader fuselage. The wing had a longer span, and the unique variable incidence wing of the F-8 was omitted. To achieve the required range, the A-7 was powered by a Pratt & Whitney TF30-P-6 turbofan producing 11,345 lbf (50.5 kN) of thrust, the same innovative combat turbofan produced for the F-111 and early F-14 Tomcats, but without the afterburner needed for supersonic speeds.
was the first operational U.S. Navy A-7 squadron, in 1967.
The aircraft was fitted with an AN/APQ-116 radar, later followed by the AN/APQ-126, which was integrated into the ILAAS digital navigation system. The radar also fed a digital weapons computer which made possible accurate delivery of bombs from a greater stand-off distance, greatly improving survivability compared with faster platforms such as the McDonnell Douglas F-4 Phantom II. It was the first U.S. aircraft to have a modern head-up display, (made by Marconi-Elliott), now a standard instrument.which displayed information such as dive angle, airspeed, altitude, drift and aiming reticle. The integrated navigation system allowed for another innovation – the projected map display system (PMDS) which accurately showed aircraft position on two different map scales.
The A-7 had a fast and smooth development. The YA-7A made its first flight on 27 September 1965, and began to enter Navy squadron service late in 1966. The first Navy A-7 squadrons reached operational status on 1 February 1967, and began combat operations over Vietnam in December of that year.
The A-7 offered a plethora of leading-edge avionics compared to contemporary aircraft. This included data link capabilities that, among other features, provided fully "hands-off" carrier landing capability when used in conjunction with its approach power compensator (APC) or auto throttle. Other notable and highly advanced equipment was a projected map display located just below the radar scope. The map display was slaved to the inertial navigation system and provided a high-resolution map image of the aircraft's position superimposed over TPC/JNC charts. Moreover, when slaved to the all-axis auto pilot, the inertial navigation system could fly the aircraft "hands off" to up to nine individual way points. Typical inertial drift was minimal for newly manufactured models and the inertial measurement system accepted fly over, radar, and TACAN updates.