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.
A 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. Contrary to USAF philosophy, which was to employ only
supersonic fighter bombers such as the F-105 Thunderchief and F-100 Super Sabre,
the Navy felt that a subsonic design could carry the most payload the farthest distance.
Theoretically, a "slow fat duck" could fly nearly as fast as a supersonic one, since
carrying dozens of iron bombs also restricted its entry speed, but a fast aircraft
with small wings and an afterburner would burn more fuel.
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 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 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. Turbofans achieve greater efficiency by moving a larger mass
of air at a lower velocity.
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 F-4 Phantom II. It was the first U.S. aircraft to have a modern
head-up display, now a standard instrument, which displayed information such as dive
angle, airspeed, altitude, drift and aiming reticule. 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's integrated weapons computer provided highly accurate bombing with CEP of
60 ft (20 m) regardless of pilot experience. When Vought technical representatives
were available to "tweak" the inertial systems, the CEP was often less than five
meters for experienced fleet aviators. The inertial navigation system required a
mere 2.5 minutes on the ground for partial (coarse) alignment, a big improvement
over 13 minutes required in F-4 Phantom II. For newly manufactured E models, the
A-7 required only 11.5 man hours of maintenance per mission resulting in quick turnaround
and high number of combat-ready aircraft. However, after several years of exposure
to the harsh marine conditions aboard aircraft carriers, the maintenance hours per
sortie were often twice this amount.
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.
Length: 46 ft 1.5 in (14.06 m) Wingspan: 38 ft 9 in (11.81 m) Height: 16 ft 0.75
in (4.90 m) Wing area: 375 ft² (34.8 m²)
Empty weight: 19,490 lb (8,840 kg) Max takeoff weight: 42,000 lb (19,050 kg)
Maximum speed: 600 knots (698 mph, 1,123 km/h) ; at sea level
1x 20 mm (0.787 in) M61 Vulcan gatling gun with 1,030 rounds Hardpoints: 6× under-wing
plus 2× fuselage pylon stations (for mounting AIM-9 Sidewinder AAMs only) holding
up to 15,000 lb (6,800 kg) of payload.