Northrop YA-9

The Northrop YA-9 was a prototype attack aircraft developed for the United States Air Force A-X program. The YA-9 was passed over in preference for the Fairchild Republic YA-10 that entered production as the A-10 Thunderbolt II.

Northrop YA-9
Class Aircraft
Type Attack
Manufacturer Northrop Corporation
Origin United States of America
Country Name Origin Year
United States of America 1972
ManufacturerName Production From Production To Quantity
Northrop Corporation 2 View

Criticism that the U.S. Air Force did not take close air support seriously prompted a few service members to seek a specialized attack aircraft. In the Vietnam War, large numbers of ground-attack aircraft were shot down by small arms, surface-to-air missiles, and low-level anti-aircraft gunfire, prompting the development of an aircraft better able to survive such weapons. Fast jets such as the North American F-100 Super Sabre, Republic F-105 Thunderchief, and McDonnell Douglas F-4 Phantom II proved for the most part to be ineffective for close air support. The Douglas A-1 Skyraider was the USAF's primary close air support aircraft.


In mid-1966, the U.S. Air Force formed the Attack Experimental (A-X) program office. On 6 March 1967, the Air Force released a request for information to 21 defense contractors for the A-X. The objective was to create a design study for a low-cost attack aircraft. Discussions with A-1 Skyraider pilots operating in Vietnam and analysis of the effectiveness of current aircraft used in the role indicated the ideal aircraft should have long loiter time, low-speed maneuverability, massive cannon firepower, and extreme survivability; an aircraft that had the best elements of the Ilyushin Il-2, Henschel Hs 129 and Skyraider.

In May 1970, the USAF issued a modified, and much more detailed request for proposals (RFP). The threat of Soviet armored forces and all-weather attack operations had become more serious. Now included in the requirements was that the aircraft would be designed specifically for the 30 mm cannon. The RFP also called for an aircraft with a maximum speed of 460 mph (740 km/h), takeoff distance of 4,000 feet (1,200 m), external load of 16,000 pounds (7,300 kg), 285-mile (460 km) mission radius, and a unit cost of US$1.4 million. During this time, an RFP was released for A-X's 30 mm cannon with requirements for a high rate of fire (4,000 round/minute) and a high muzzle velocity. Six companies submitted proposals to the USAF, with Northrop and Fairchild Republic selected on December 18, 1970 to build prototypes: the YA-9A and YA-10A, respectively. General Electric and Philco-Ford were selected to build and test GAU-8 cannon prototypes.

While turboprops were considered in some designs for the A-X project, turbofans were selected for the flyoff prototypes. The A-9 used the Lycoming F-102 engine, while the A-10 used the GE TF34. The YA-9 took its first flight on 30 May 1972.


Apart from aircraft themselves, the A-X program was also developing a powerful cannon for the winning plane to carry. Eventually, this would result in the GAU-8 Avenger, but for trials, the YA-9 and YA-10 were both equipped with the smaller M61 Vulcan Gatling gun. By comparison, the A-10 engine location at the tail is less conventional, but offers greater survivability in the case of a hit on the engine area. The double tail of the A-10 also hides the engine infrared and noise signature, and incorporates redundancy in case one of the tails is shot away.

A fly-off of the two prototypes took place between 10 October and 9 December 1972, with the YA-10 declared the winner on 18 January 1973.

The two YA-9 prototypes were subsequently relegated to NASA for continued flight testing before being quickly retired. When retired, the YA-9s' custom-built engines were removed and were later mated to a C-8 Buffalo airframe as part of the NASA-Boeing joint Quiet Short-haul Research Aircraft (QSRA) study into a quiet short-haul commercial aircraft.

Role Attack aircraft
Manufacturer Northrop
First flight 30 May 1972
Status Canceled
Primary user United States Air Force
Number built 2

General characteristics

  • Crew: 1
  • Length: 53 ft 6 in (16.3 m)
  • Wingspan: 57 ft 0 in (17.4 m)
  • Height: 17 ft 10 in (5.4 m)
  • Wing area: 580 ft² (53.88 m²)
  • Empty weight: 23,076 lb (10,467 kg)
  • Loaded weight: 28,575 lb (12,961 kg)
  • Max. takeoff weight: 41,795 lb (18,958 kg)
  • Powerplant: 2 × Lycoming YF102-LD-100 turbofans, 7,500 lbf (33.4 kN) each


  • Maximum speed: 523 mph (837 km/h)
  • Thrust/weight: 0.33


  • 1x 20 mm M61 Vulcan Gatling gun (Substitute for GAU-8/A)
  • Up to 18,370 lb (8,350 kg) of ordnance

End notes