Vought's A-7 is one of the world's most cost/effective and capable attack aircraft ever flown. Although derived from Vought's legendary F-8 Crusader, the A-7 is a completely different aircraft. Limiting speed to below Mach 1 and eliminating other features of the F-8 dramatically reduced structural weight and cost, allowing the A-7 to carry three times the Crusader's weapon load and deliver it extremely efficiently and with unprecedented accuracy. The A-7 has seen service in numerous conflicts and performed very well in the attack role - in US service in Vietnam it achieved one of the lowest aircraft loss rates.

History
The A-7 went through a very quick development programme before entering production and service. The conception of the A-7 began in 1962 when the United States Navy (USN) began looking for a new single seat close support aircraft that could carry a very heavy weapon load over a long range. On 17 May 1963 the Navy announced the VA(L) competition (standing for Navy Attack Bomber, Light, or Light Attack Aircraft) for an aircraft to replace the Douglas A-4 Skyhawk. Its mission was to carry as much as 6 800 kg (15 000 lb) of conventional weaponry at long ranges and be very cost-effective. This was to be achieved by modifying an existing airframe and limiting performance to subsonic speeds. The aircraft would also have to be in service by no later than 1967.

Towards the end of June 1963, a Request For Proposals (RFP) was sent out to the aviation industry with just four competitors responding. These were Douglas with its proposed TF-30 turbofan-powered and enlarged A-4D-6 Skyhawk, Grumman with its single-seat A-6 Intruder (Model 128G-12), North American Aviation with a TF-30-powered version of the AF-1E Fury and Ling-Temco-Vought (LTV, into which Vought had merged in 1961) with the Model V-463, a modified version of the Crusader.

On 11 February 1964 the USN named LTV the winner of the competition as the A-7 would be available soonest and would be the cheapest since it used a tried and tested airframe and engine. LTV was contracted to develop and build one prototype, six flight test machines and 35 production aircraft under the designation A-7A. Another 140 aircraft were ordered on 10 November 1965.

Wary from previous experiences with contractors incurring huge cost escalations and delays in aircraft development, the Navy imposed strict penalties on any conditions that could not be met. As a result, the contract was the only true fixed-price contract ever issued for a major weapon system. Each A-7A cost a little over one million dollars, which was an impressive bargain even in the 1960s.

Some of the penalties that might be paid to the Navy if the targets were not met were $50 000 per day per aircraft for each day inspection trials were delayed, $750 000 if the weight target was missed and another $750 000 if the maintenance requirements were not met. The only requirement LTV missed was the weight limit, by 270 kg (600 lb). LTV had to pay the fine, but the design team, headed by Sol Love, decided that the extra weight was essential in order to strengthen the wing, allowing the A-7 to carry more weaponry. This turned out to be cheaper in the long run as later modifications to the wing were not needed.

Progress with the project was very rapid, with the first YA-7A prototype being rolled out of the factory on 13 August 1965. It made its maiden flight on 27 September 1965, flown by LTV test pilot John Konrad. It was christened Corsair II on 10 November 1965 in honour of Vought's famous World War II piston engine fighter. By mid-1966 the other six aircraft were flying.


The Aircraft
As it did not need to fly at supersonic speeds, the A-7 had a different wing to the F-8 and was powered by a more efficient turbofan without afterburner, making the airframe shorter. The area-ruling of the F-8 was eliminated and the fuselage was made larger and fatter. By decreasing structural strength for subsonic flight, much weight was saved. The F-8's variable wing incidence mechanism was eliminated, saving even more weight weight. Of all-metal semi-monocoque construction, the A-7's airframe was a multi-spar structure with integrally stiffened aluminium alloy upper and lower skins.

The high-mounted wing, with an anhedral of five degrees, had an outer leading edge dogtooth extension, (similar to the F-8's) but less swept back, with a sweep of only 35 degrees at quarter chord. The outer wing section folded upward for carrier stowage, the hinge being located at the edge of the dogtooth. Flying controls consisted of full-span leading edge flaps, large single-slotted trailing edge flaps on the inner wing trailing edge, conventional aluminium ailerons on the outer wing trailing edge and spoilers above each wing forward of the trailing edge flap hinges. The vertical tail, with integral rudder, was very large and was swept back 44.3 degrees at quarter-chord. Both tailplanes were one-piece all-moving units and were swept back 45 degrees and had a dihedral angle of five degrees.

There were eight external stores stations on the A-7, capable of carrying an impressive load of more than 6 805 kg (15 000 lb), but the A-7 had also proved able to carry 9 070 kg (20 000 lb) of ordnance. There were two stations on the fuselage sides just ahead of the wing leading edge, each capable of carrying 227 kg (500 lb), including AIM-9 Sidewinder air-to-air missiles (AAM). There were six stations on the wings; two outboard pylons on each wing that could each carry 1 587 kg (3 500 lb) and the inboard pylon on each wing could carry 1 134 kg (2 500 lb). Virtually every single type of weapon in the Navy's armoury could be carried by the A-7A. Weapons included air-to-air and air-to-ground missiles, (including anti-tank and anti-radar missiles), electro-optical and laser guided weapons, general purpose ('iron') bombs, bomblet dispensers, rockets, gun pods and fuel tanks. The A-7A also had fixed weaponry - a pair of 20 mm Colt Mk 12 cannon with 600 rounds per gun. One gun was mounted on each side of the chin-mounted air intake.

In order to improve efficiency and range, a new engine was needed in place of the F-8's afterburning turbojet. The chosen engine for the A-7A was the non-afterburning Pratt & Whitney (P&W) TF30-P-6 turbofan delivering 5 148 kg (11 350 lb) of thrust. As the new engine required a larger mass flow of air, the intake was enlarged and made blunt. Fuel was carried in the wings and fuselage, giving a maximum internal capacity of 5 678 litres (1 249 gallons), with a weight of around 4 620 kg (10 200 lb). In addition, 4 542 litres (999 gallons) of fuel could be carried externally, and the A-7A could be refuelled in midair by a retractable in flight refuelling probe mounted on the starboard side of the fuselage adjacent to the cockpit.

Landing gear was a hydraulically retractable tricycle type with a single wheel on each main unit and two wheels on the nose unit. The mainwheels retracted forward into the fuselage while the nose unit retracted rearwards. An anti-skid braking system was fitted to the landing gear. A nose gear launch bar was fitted for carrier catapault launching and a sting-type arrestor hook under the rear fuselage was used for carrier landings, emergency landings or aborted takeoffs. A large door-type speed brake was mounted under the centre of the fuselage, with the hinge attached towards the front of the fuselage. It could be extended downward to a maximum of 60°.

The A-7A was equipped with an AN/APN-153 Doppler radar, AN/APQ-116 attitude reference set, an AN/APN-141 radar altimeter and AN/ASN-41 air navigation computer.

Deliveries of the A-7A proceeded rapidly, with the first aircraft being delivered only 12 months after the Corsair II's first flight and well before the 1967 deadline. Two fleet readiness squadrons (VA-174 and VA-122) received their first A-7As in September and October 1996 respectively. Initial carrier qualifications had been performed by 15 November 1966 aboard the USS America and the first operational A-7A squadron, VA-147, was commissioned on the first of February 1967. Although beating the deadline by several months, the A-7 was not yet cleared for combat. After satisfactorily completing testing on the first of June 1967, the first combat-ready A-7As were delivered to VA-147 in the last quarter of 1967.

In service the A-7A performed very well. Compared to the A-4 Skyhawk, it was much more likely to survive combat damage as it had duplicated hydraulics systems and the pilot's McDonnell Douglas Escapac rocket-powered ejection seat was protected with boron carbide cockpit armour. Compared to the A-4 the A-7 was also much easier to maintain. Maintenance man-hours per flight hour (MMH/FH) were an impressive nine to 11 hours when the norm was around 40 to 50 man-hours per flight hour. The A-7 also had a considerably longer range than the A-4, allowing it to fly missions the smaller A-4 could not. However, there were problems with steam ingestion into the air intake during catapult launching which caused a loss of thrust, and the CP-781 weapons release system was not very reliable. The steam problem was solved by modifying the 12th engine compressor stage, but the CP-781 problem was more difficult to solve.


Variants
A total of 199 A-7As were built before production switched to the A-7B model with a variety of minor improvements. The aircraft was fitted with an upgraded TF30-P-8 engine rated at 5 530 kg (12 200 lb) of thrust, giving an 8% improvement in performance over the A-7A. A-7Bs also had improved flaps, were 593 kg (1 308 lb) heavier than the A-7A and had upgraded TACAN systems and radar altimeters. The A-7B first flew on 6 February 1968 with test pilot Joe Engle at the controls. A total of 196 A-7Bs were manufactured in just one batch in FY (Fiscal Year or Financial Year) 1967. The fist operational A-7Bs went to VA-146 and VA-125 in late 1968. They deployed on the USS Enterprise on 6 January 1969, bound for Vietnam.

The A-7C designation was originally reserved for a proposed two-seat training version of the A-7B, but it never materialized - the TA-4J Skyhawk was ordered instead. But the A-7C designation was applied. The Corsair II performed so well that in 1966 the United States Air Force (USAF) ordered the A-7D powered by an Allison TF41-A-1 turbofan. The Navy also liked the idea of the upgraded Air Force variant and decided to buy it as well, under the designation A-7E. However, delays in producing the new engine for the A-7E resulted in the first 67 A-7Es ordered being delivered with TF30-P-8 engines and getting the designation A-7C after delivery. These aircraft also had the improvements of the A-7E, including a head-up display, new avionics and an M61 rotary cannon. However, they also had A-7B features such as dual instead of triple hydraulic systems and Escapac IG ejection seats.

On 25 November 1968 the first A-7C made its maiden flight, piloted by Robert Rostine. Deliveries began in July 1969 to the training squadron VA-122 at NAS Lemoore, California. Only two operational squadrons received the A-7C and these were VA-82 and VA-86. All A-7Cs were later converted to A-7E standard, but retained the A-7C designation.

A-7D
Although the US Army was not allowed to operate fixed-wing combat aircraft, it required close air support for its troops on the battlefield, especially with the United States' increasing involvement in Vietnam. The Army wanted a single-purpose, specialized and effective subsonic attack aircraft that would be many times more cost-effective than the high-performance fighter-bombers equipped to drop bombs which the USAF preferred. They wanted a replacement for the ageing North American F-100 Super Sabre with a much better payload. A quick and inexpensive way to achieve this was to buy the A-7, and so on 5 November 1965 the USAF announced a decision to order the Corsair II for the Tactical Air Command (TAC) arm of the Air Force with Congress approving the funds in 1966. Two YA-7D prototypes were built, with TF30-P-6 engines, the first making its maiden flight on 6 April 1968. Both aircraft were later retrofitted with TF41-A-1 engines.

As the Air Force began issuing requirements for their version of the Corsair II, it became obvious that a new designation was needed to reflect the 20-plus changes made to the airframe. The designation A-7D was thus assigned. Most significant among the new changes was the fitting of a new, more powerful engine. More thrust was wanted for the A-7D, but the TF-30 couldn't deliver. As an afterburning variant of the TF-30 would take too long to develop, the Air Force selected the British Rolls-Royce RB162-256 Spey turbofan instead. It was licence-built in the US by Allison as the TF41-A-1 and developed 6 460 kg (14 250 lb) of thrust, which was 1 300 kg (2 900 lb) more than the TF30. A-7Ds also had a revised avionics suite and their two Mk 12 cannons deleted. These were replaced by a M61A-1 Vulcan 20 mm six-barrel cannon firing at a selectable rate of 4 000 or 6 000 rounds per minute with a maximum rate of fire of 6 600 rounds per minute. It was mounted in the port side of the fuselage and provided with 1 000 rounds of ammunition. A KB-18A strike camera in the lower forward fuselage engine compartment was used for strike damage assessment.

Avionics were radically upgraded, the main changes going into the sophisticated new navigation and weapon delivery system that allowed all-weather operation. The AN/ASN-91 navigation/weapon delivery computer was the primary element of the system and continuously computed weapons delivery and navigation data for greatly increased weapons delivery accuracy. An AN/ASN-90 inertial measurement set provided basic three-axis navigation and an AN/APN-190 Doppler radar measured speed and drift angle. The new AN/APG-126 forward-looking radar provided nine modes of operation for air-to-ground ranging, terrain-following, terrain-avoidance, ground mapping, and other functions. An AN/AVQ-7 head-up display received and displayed computed attack, navigation and landing data from the tactical computer, and a projected map display showed navigation data.

The pilot's accommodation was modified, with the McDonnell Douglas Escapac IC ejection seat adapted to utilise the USAF survival kit and restraint system and low-pressure oxygen system. A few other changes were made, including higher energy-rated wheels, tyres and brakes, and the fitting of a boom receptacle in place of the probe. This receptacle, mounted on the top of the fuselage behind the cockpit and offset to port, was only introduced from the 17th production aircraft onwards.

The first five A-7Ds built were delivered to the USAF for testing purposes and given the temporary designation YA-7D. Unusually, these retained the in-flight refuelling probe. The first production aircraft was delivered on 23 December 1968 and the first delivery to the Tactical Air Command was in August 1969.

A total of 459 A-7Ds were built between FY1967 and FY1975, each with a unit cost of $2 860 000. The first aircraft entered service in 1970 with the 57th Fighter Weapons Wing at Luke Air Force Base (AFB) and 354th Tactical Fighter Wing at Myrtle Beach AFB in South Carolina.

In 1973 the USAF began sending A-7Ds to the Air National Guard (ANG), and by 1987 they were being flown by ANG units in ten states in the US as well as in Puerto Rico, eventually equipping a total of 14 ANG squadrons. Many of these ANG machines were new from the factory. They were later upgraded with Pave Penny laser target seeker pods, which were mounted just below the engine air intake. Another upgrade was the addition of manoeuvring flaps in 1976 to increase agility at low level and low speeds.

In 1988 40 A-7Ds and eight A-7Ks were upgraded with the Low Altitude Night Attack (LANA) system which allowed automatic low-altitude flight at night. These aircraft received a forward-looking infrared system, wide-angle head-up display, CP-1117/A mission computer, night vision cockpit lighting, an improved autopilot and a programmable NavWeap Computer.

During the early 1980s most A-7Ds were replaced by A-10s in USAF front-line service, but remained in ANG service for a while longer before being retired in the late 1980s and early 1990s. By 1993 all had been retired.

A-7E
The US Navy observed the Air Force's progress with the A-7D and was impressed by the new aircraft, especially by the increased power offered by the Spey engine. The Navy then decided to use this engine for its own variant of the Corsair II, which would succeed the A-7A in production. It was designated A-7E and had virtually all the modifications of the A-7D, except a more powerful engine and retractable in-flight refuelling probe. The upgraded engine was the TF41-A-2 developing 6 800 kg (15 000 lb) of thrust. However, because of delays in delivering this uprated engine, the first 67 were delivered with the TF30-P-5 engine and designated A-7C (see details above).

The first Spey-powered A-7E made its maiden flight on 9 March 1969 and between FY1968 and FY1979 a total of 529 A-7Es (not including A-7Cs) were built. A total of 22 Navy squadrons were equipped with the type. To ensure continued effectiveness, a number of A-7Es were upgraded with improved avionics. 222 aircraft were equipped to carry the Texas Instruments AN/AAR-45 forward-looking infrared (FLIR) pod on the inboard starboard stores pylon for night and bad-weather operations. The pod was also linked to a new Marconi raster-type head-up display for improved night attack capability. On 15 September 1978 the first FLIR-modified aircraft took off on its maiden flight and in July 1979 VA-81 became the first squadron to receive the upgraded aircraft.

The A-7E began to be replaced by McDonnell Douglas (now Boeing) F/A-18 Hornets in 1987 with the last two squadrons transitioning to the Hornet in FY1992. By replacing the A-7s with Hornets allowed the same aircraft to carry out both attack and fighter missions and also allowed a smaller number of aircraft (85) to equip a carrier air wing instead of the 94 required for an A-7E wing.