Corsair with more: A-7 Plus

Take a successful, proven aircraft that is popular with its pilots, improve it even more, and you will have an outstanding winner by anybody's stan-dards. LTV, based at Dallas, Texas, is about to do just that, turning the A-7 Corsair II into what is now called (after several name changes) the A-7 Plus.

The original 1960s US Navy require-ment for a single-seat, carrier-based light attack aircraft (VA-L), stipulated that it should be developed from an existing aircraft to speed delivery and keep costs down. LTV's study was based on the F-8 Crusader, and two design teams were set up; the Blue Team to revamp the F-8 and a parallel Red Team to conduct its own studies, criticise Blue's design, and gener-ally play devil's advocate. It worked, and in March 1964 the Navy chose LTV to build the VA-L, later dubbed A-7 Corsair II, which made its first flight on September 27, 1965, 25 days ahead of schedule.

The A-7 Corsair is being re-engined and updated to fulfil the US Air Force's close air support, battlefield air inter-diction role. Mike Gaines reports from Dallas on

Vought's thoughts.

The Navy's A-7A, B, and C-models were powered by Pratt & Whitney TF-30s which produced 13,4001b thrust and, initially, were dogged by problems of steam ingestion from catapults. When the A-7 was adopted by the US Air Force the engine was changed to the Allison TF-41

Above The A-7 Plus will be capable of day/night bad weather operation

(a licence-built version of the Rolls-Royce Spey) which produced 14,2501b thrust (15,0001b thrust for the Navy A-7E).

In Vietnam the Navy and Air Force A-7s handled the "low and dirty" jobs of very close air support, strafing, Sam and AAA suppression, interdiction of roads, rail-links and bridges, as well as high- and medium-level bombing. They even conducted low-level minelaying in Haiphong harbour. The Corsair was called the Little Hummer initially. Other soubriquets were Sluf (short little ugly f---er) and Supersluf. , Ling-Temco-Vought built 1,545 A-7s in all, and they have flown around 100,000 corribat sorties with the US Navy and US Air Forcemainly in Vietnam, but also in Grenada, Lebanon, and Libya. In the US Navy the "Sluf' is now being replaced by the F-18 Hornet, and the US Air Force's regular A-7 units are now dwindling, but the type is still flown by the Air National

FLIGHT INTERNATIONAL, 22 August 1987 21

It is likely that the A-7 Plus will be in service until 2010

Fin cap

Augmented flaps

Lift dump spoilers

Forward stretch

Cockpit changes

HUD

Modified aft section Radome modification

Airspeed system

Above The modifications needed to make an A-7 Plus, the "Lana" mods, are in blue. Below The A-7 Plus looks more like an F-8 Crusader than a Sluf. Opposite How Vought will run its A-7 Plus production line at Dallas

Guard to great effect. The A-7s in USAF service were largely

replaced by the Fairchild A-10 Thunder-bolt in the close-air-support role. But in 1984 it became apparent that the A-10 would need replacing in the mid-to-late 1990s, and would need supplementing, until it was replaced, by another faster aircraft. So the requirement was born for a close air support/battlefield air inter-diction (CAS/BAI) aircraft, and in early 1985 the USAF put out an official CAS/BAI Request for Information (RFI) for a low-cost aircraft (based on an in-service type) with high speed, heavy warload, and the ability to deliver accurate weaponry around the clock in bad weather. Four proposals came back from industryNorthrop's F-20 Tigershark, the General Dynamics F-16 Fighting Falcon, the McDonnell Douglas/British Aerospace AV-8 Harrier, and the A-7 Corsair from LTV.

The USAF chose the Corsair as the CAS/BAI winner, and the plan is to convert 337 Air National Guard A-7D and A-7K (two-seaters) to A-7 Plus config-uration. The Guard shares the CAS/BAI role with the USAF and assigns three A-7 units to the Rapid Deployment Force. It also has to reinforce Europe, so anything that cuts down the requirement for airlift capacity, improves field performance, and enhances bad-weather capability can only be good news to detachment planners, and the A-7 Plus design bears these criteria in mind. Jim Gilbert, the A-7 Plus programme manager, says "It's a no-yellow-gear aircraft. The number of C-141 Starlifters needed to deploy an A-7 Plus squadron is cut by 53 per cent over the number currently needed for an A-7 unit."

To provide the higher speed, heavier warload and better combat. radius called for by the CAS/BAI role it was necessary to change the Allison TF-41 for a more modern afterburning turbofan. The A-7 Plus will be able to accept either the General Electric F110 or the Pratt & Whitney F100, but they are heavier, and their adoption will cause a change in e.g. This is put back within limits by instal-ling a 29-5in-long section forward and

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an 18in aft plug to lengthen the fuselage. The extra space is used to accommodate more fuel and extra avionics.

But the longer fuselage adversely affected the aircraft's longitudinal control and stability. So a taller, more elegant fin, like that of the A-7's ancestor, the F-8 Crusader, is fitted and wing leading-edge strakes are added. This cures the tendency for the nose to slice and depart on the stall, and the tailplane is given 5 25' anhedral (on the A-7D the tailplane has 525' dihedral). The longer body and tailplane anhedral cut down the ground clearance, so this is restored by canting the aft fuselage upwards by 4..The nose radome will be enlarged to take a bigger antenna, and become more pointed to improve flow.

The short-field requirements (part of the overall problem of adopting the austere basing concept) call for the A-7 Plus to be airborne in 3,000ft at its planned maximum take-off weight of 46,0001b (the A-7D's MTOW is 42,0001b), and to be able to land and stop in 2,500ft. These specifications drove the wing modifications, with lift spoilers and augmented flaps. The new flaps consist of automatic manoeuvring flaps to which a 5in-chord trailing-edge augmentor flap is added for use on landing.

The A-7 Plus will land fairly hard in short-field operations, but this is no prob-lem because the carrier-qualified landing gear can accept a teeth-rattling 26ft/sec sink-rate naval arrival, whereas the

A-7 Plus Performance Combat radius, high-low-high (n.m.) Combat radius, tow-low-low (n.m.) Maximum take-off weight (lb| Maximum speed, clean/full load* (M) Approach speed, clean, at 24,0001b (kt) Stall speed (kt) Steady-state roll rate (deg/sec) Positive/negative structure limits (g)

F100 6 7 0 290

46,000 1 1 / 0 - 9 8

122 106 190 7/6

* Pull load assumed two Mk84 bombs, Lana pod, ECM pod and two AIM-9 Sidewinders plus two AIM-9 Sidewinders and 50 per cent fuel.

F110 685 290

46,000 1-4/1-02

125 109 190 7/6

50 per cent fuel. Clean assumes

requirement is only for a more gentle-manly lOft/sec Air Force landing. However, the landing gear will be modified to improve maintainability. The A-7's gear bays are cluttered and difficult to work on.

The new engine, whichever is picked, will have a higher fuel flow because of the afterburner (which the TF-41 lacks), so the fuel system needs modifying both for higher supply rate and to feed the auxil-iary power unit (APU), also new on the A-7 Plus. Likewise, the electrical genera-tion capacity needs to be higher, at 80k VA, rather than the Corsair's 20kVA. An aircraft-mounted accessory drive (Amad) replaces the engine-mounted vari-ant, thus cutting down on engine-change times and improving its reliability by being left in situ during the change. An on-board oxygen generator system (Obogs) is to be fitted, again cutting down on support equipment (and thus airlift

requirements) and enabling longer endur-ance to be achieved on air-refuelled ferry flights.

Either of the USAF's Alternate Fighter Engines (AFE) could be fitted to the A-7 Plus. Allison also made an unsolicited proposal to the USAF to upgrade the TF-41's performance to the AFE range by fitting an afterburner, but the service turned down this idea. Besides extra performance, the AFEs provide inter-fleet commonality which reduces both logistics and cost.

The TF-41 in the A-7D produces a maximum thrust of 15,0001b. The General Electric F110-GE-100 produces 15,5001b at military power and 27,8501b in full afterburner. Like the F110, the Pratt & Whitney F100-220 is a two-spool turbofan, and it produces 14,3751b in military power. Put the loud lever in the left-hand corner and the F100 goes up to 23,8301b thrust. Both engines are

Control surfaces augmented flaps R/H shown, L/Hopp

Join and connect systems

A-7 Plus flow plan

FLIGHT INTERNATIONAL, 22 August 1987 23

extremely reliable, each having demon-strated 4,000 tactical air cycles between overhaul on bench tests. The new engine will submit the old airframe to higher stress and thus reduce its life, but Jim Gilbert is confident that the A-7 still has enough hours left. "The A-7 is lifed at 10,600hr, so if we are conservative and halve it to 5,000hr and assume 170hr to 200hr a year of flying for the Guard, then the aircraft will still last till 2010." The Guard is to receive 337 A-7 Plus and, says Gilbert, LTV is planning on a four-aircraft-a-month conversion rate. "We could do eight a month, but that's up to the customer and the dollars he has avail-able."

The 337 aircraft is the worst case, but it could go to 462, if the ex-Navy A-7s were to come off the back burner. "Most Guard squadrons have 24 aircraft. They will probably take them down to say 28 or 20 each to give us a pool to get the programme under way. I don't think they'll upgrade squadron by squadron." Avionics There are two levels of avionics systems currently on offer for the A-7 Plus. One is a cheaper variant called Fast Lana. The "Fast" comes from the A-7 Plus engine and airframe modifications for higher penetration speed; the "Lana" from the Low Altitude Night Attack pod system, currently being fitted to 48 Guard A-7Ds and six A-7Ks. Carried on the starboard inboard pylon, the Lana pod is a Texas Instruments AAR-49 forward looking infrared kit, with a Singer Kearfott navi-gation and weapon delivery computer feeding a GEC Avionics wide-angle headup display, where it is integrated with the A-7's APQ-126 radar to give automatic terrain following plus target acquisition

Both Greece and Portugal operate A-7s, which could be upgraded to A-7 Plus standard

and weapon aiming. The alternative "full-up" avionics pack-

age would be much more in line with present-generation thinking on combat avionics systems and their presentation to the pilot. The cockpit would have the wide-angle Hud, but would also have full-colour multifunction CRT displays for navigation and weapon aiming, and liquid crystal displays for systems monitoring.

LTV has long been seeking more power for the Corsair. This 1977 proposal is the V-529D, with two 16,000lb-thrust GE F404s. It did not progress beyond the drawing board

The full fit has yet to be frozen, but the shopping list includes such goodies as ALQ-165 aircraft self protection jamming (ASPJ), Navstar and/or ring-laser gyro INS, maps stored on compact digital video disc for CRT presentation, Class II Jtids (joint tactical information distribution), and secure communications. All the space, power, and equipment-cooling require-ments have been designed with the full-up version of the A-7 Plus in mind, so there will be no problems in that field, whatever variant is chosen.

Weaponry The warload of the A-7 Plus will be 17,3801b, compared with the A-7D's maximum of 15,0001b. The A-7 Plus will have six underwing pylons and two fuse-lage-side weapon stations each capable of carrying a 5001b load. On the A-7 these stations are usually used to carry AIM-9 Sidewinder air-to-air missiles. The General Electric M60A-1 Vulcan 20mm rotary cannon will be retained. Mounted in the port side of the fuselage, the gun has 1,000 rounds of ammunition and select-able firing rates of either 4,000 rounds/ min or 6,000 rounds/min. The A-7 is cleared to carry most tactical weapons in the USAF inventory, including the latest laser-guided and imaging infrared weapons. The A-7 Plus should be able to navigate to the target at 200ft in bad weather and then hit with 5mil accuracy.

The flyaway cost quoted by Vought for each A-7 Plus is $6 2 million, including $3 million to $3 5 million for the engine, with the rest going on avionics and airframe modifications. The Fast Lana A-7 would be marginally cheaper, at an estimated $5-8 million unit flyaway cost. The Air National Guard is scheduled to receive its first A-7 Plus in 1991. D

21 FLIGHT INTERNATIONAL, 22 August 1987