Helio AU-24 Stallion

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AU-24 Stallion
Helio AU-24A Stallion in storage at Davis-Monthan AFB, July 1972.jpg
Helio AU-24A Stallion in storage at Davis-Monthan AFB, July 1972
Role Armed gunship, counter-insurgency, utility transport
National origin United States
Manufacturer Helio Aircraft Company
First flight 5 June 1964[1]
Primary users United States Air Force
Khmer Air Force
Number built 20

The Helio AU-24 Stallion was an American armed gunship, counter-insurgency, and utility transport developed for the United States Air Force. A total of 20 were built during the Vietnam War. Most aircraft were later sold to the Khmer Air Force.

Design and development[edit]

The Helio HST-550 Stallion was an STOL utility aircraft developed in the United States in 1963. The prototype flew in July 1964. Initially conceived by the Helio Aircraft Company as a turboprop-powered variant of the Helio Courier, it eventually emerged as a completely new design of the same general configuration and much of its design was initiated from components used in the Helio H-500 Twin. It was a much larger aircraft than the Courier, and Helio soon discovered that it was too expensive for the market.

The United States Air Force however, emerged as a buyer for the design, purchasing the aircraft for the Credible Chase programme as the AU-24A. This was the gunship version of the Stallion, with a PT6A-27 680 shp (510 kW) turboprop, equipped with a General Electric M197 three-barrel 20x102mm rotary cannon mounted in the left cargo door. It also had five underwing and fuselage hardpoints.

Of the 18 aircraft purchased, fourteen or fifteen were eventually sold to the Khmer Air Force.


  • H-550 – prototypes (2 built)
  • AU-24A Stallion (H-550A) – production version (18 built)
  • H-634 Twin Stallion – version with twin Allison 250 turboprops mounted on a beam across the nose of the aircraft (not built)
  • H-1201T Twin Stallion – version with twin engines in underwing nacelles, retractable undercarriage, tiptanks, and underwing cargo pods (not built)


 United States

Specifications (H-550A)[edit]

Data from Jane's All The World's Aircraft 1976–77[2]

General characteristics

  • Crew: One pilot
  • Capacity: 9 passengers
  • Length: 39 ft 7 in (12.07 m)
  • Wingspan: 41 ft 0 in (12.50 m)
  • Height: 9 ft 3 in (2.81 m)
  • Wing area: 242 ft2 (22.48 m2)
  • Empty weight: 2,860 lb (1,287 kg)
  • Gross weight: 5,100 lb (2,313 kg)
  • Powerplant: 1 × Pratt & Whitney Canada PT6A-27, 680 hp (507 kW)


  • Maximum speed: 216 mph (348 km/h)
  • Cruise speed: 160[3] mph (257 km/h)
  • Range: 641 miles (1,031 km)
  • Service ceiling: 25,000 ft (7,620 m)
  • Rate of climb: 2,200 ft/min (11 m/s)

See also[edit]

Aircraft of comparable role, configuration and era



  1. ^ Taylor 1965, pp. 242–243.
  2. ^ Taylor 1976, pp. 301–302.
  3. ^ Econ cruise


  • Simpson, R. W. (1995). Airlife's General Aviation. Shrewsbury: Airlife Publishing. pp. 208–10. 
  • Taylor, John W. R. (1965). Jane's All the World's Aircraft 1965–66. London: Sampson Low, Marston. 
  • Taylor, John W. R. (1976). Jane's All the World's Aircraft 1976–77. London: Jane's Yearbooks. ISBN 0-354-00538-3. 
  • Taylor, Michael J. H. (1989). Jane's Encyclopedia of Aviation. London: Studio Editions. p. 506. 
  • World Aircraft Information Files. London: Bright Star Publishing. pp. File 896 Sheet 28. 

External links[edit]

Media related to Helio Stallion at Wikimedia Commons