NORTHROP AX

USAF designation: YA-9A

Engines: 2 x 6,000 lbs. (26.7 kN) Avco Lycoming YF102-LD-100 (ALF 502) turbofans (7,500 lbs. or 33.4 kN each at maximum power)

First flight: May 20, 1972 (May 30?)

The Northrop A-9 was a single-seat prototype aircraft designed to compete for the U.S. Air Force's AX Close Air Support (CAS)/ground attack competition, which called for an aircraft capable of operating from short unimproved runways, have a long loiter time over the battlefield area, carry heavy armour, and have a relatively high cruise speed to get from the home field to the battle field. The Air Force issued a request for proposal (RFP) to 12 aircraft manufacturers: Beech, Bell, Boeing, Cessna, General Dynamics, Fairchild, Grumman, Lockheed, LTV, McDonnell Douglas, North American and Northrop. Six companies responded with specific designs and two companies were selected to build prototypes for a fly-off competition. Northrop was one company selected and Fairchild Republic was the other. The Northrop entry was designated A-9 while the Fairchild aircraft was designated A-10.

Northrop had designed its A-9 with much attention to cost reduction, as the Secretary of the Air Force had announced that he would not buy the aircraft if it cost more than $ 1.4 million apiece. The A-9A was a high wing, twin engine, single place aircraft. It was designed for exceptional maneuverability and had large flight control surfaces. The engines were specifically designed for the project by Lycoming. Each of the YF102-LD-100 turbofans developed 7,500 lbs. of thrust at maximum power. Offensive firepower consisted of a 20mm "Vulcan" cannon and up to 16,000 lbs. of ordnance carried on 10 external wing stations.

The A-9A featured a triple redundant hydraulic system, foam filled self-sealing fuel tanks and armor plating protecting vital systems including a titanium "bathtub" surrounding the cockpit (note: an aluminum "bathtub" was fitted in the prototype). Besides, the winner of the AX fly-off would incorporate the new powerful 30mm GAU-8 cannon into production aircraft (would result in the General Electric GAU-8 Avenger), but the gun was under parallel development during the AX competition and wasn't ready for flight testing during the fly-off, so a smaller 20mm M61 Vulcan Gatling gun was used for the actual testing in both of the aircraft.

Models underwent basic aerodynamic testing and evaluation in Arnold Engineering Development Center's 16-foot transonic propulsion wind tunnel in 1971, before the first flight took place in May 1972. The prototype A-9A had some rather unusual performance capabilities and is considered to have been a very good aircraft. Despite the fact that the prototype was smaller than the YA-10A prototype, both aircraft still more than met the Air Force AX performance specifications. Although the A-9's IR signature was probably larger due to the traditional arrangement of its engines, the high mounted engines of the A-10A still have an IR signature very much visible to any ground or air launched IR seeking missile of that era. The high fuselage mounting of the A-10A engines also was not optimal for lift and thrust - requiring larger engines, a larger aircraft and more fuel to keep the same level of performance and combat load. This is another reason why the A-10A was larger.

A fly-off of the A-9 and A-10 prototypes took place October 10 and December 9, 1972, and although the two aircraft were equally accurate in weapons delivery and in the gun tests, the YA-10A was declared the winner of the AX Fly-Off on January 18, 1973. The two A-9s had completed 123 flights, totaling 146.0 flight hours between the both of them. (while the YA-10As had completed 87 flights totaling 138.5 flight hours). After the fly-off was completed, the U. S. Air Force had no more use or interest in either of the two A-9As; they were transferred over to the NASA Dryden Research Center for continued flight testing before being quickly retired. The YA-9A's' custom-built engines were then removed and later mated to a C-8 Buffalo airframe as part of the NASA-Boeing joint QSRA study into a quiet short-haul commercial aircraft. the YA-9A lost to the Fairchild Republic YA-10A, which became the A-10A Thunderbolt II ("Warthog") in service, a capable but very maintenance intensive aircraft type.

The most unusual variant of the A-9A proposed was a desktop 1/48th scale model of a pusher propeller version of the A-9A,, with 3 tail fins arranged in a Y shaped configuration: one ventral fin, two angled dorsal fins. It is alleged that the YA-9 more strongly impressed the Soviets than the US Air Force, and the Sukhoi Su-25 was largely based on spy footage of this aircraft. However, actual resemblance is very superficial and at any rate, work on what later became the Su-25 began in 1968, four years before YA-9's first flight.

The first A-9 was once exhibited at the Castle Air Museum but was removed in the mid-1990s, then shipped to the Edwards AFB, where it still lies dismantled. The second example is still preserved at the March Field Air Museum at March AFB, Riverside.

Population: 2 [71-1367/1368]

Specs:
Length: 53 ft 6 in (16.31 m)
Wingspan: 57 ft 0 in (17.37 m)
Height: 17 ft 10 in (5.44 m) (or 16 ft. 11 in.?)
Weight: 42,000 lbs. max. takeoff
Wing area: ft² (m²)

Performance:
Maximum speed: 523 mph (837 km/h) (or 449 mph?)
Cruising speed: 322 mph
Range: 3,622 miles
Service Ceiling: 40,000

Armament:
one M61A1 20-mm cannon (Gatling gun)
18,370 lb (8,350 kg) bomb, rocket & missile capacity

Crew/passengers: 1 pilot

Main sources:
- John Heck gallery
- Alain Ratinaud