Auster A.O.P.9 (Air Observation Post 9)
Archive Photos 
[Auster B-5 Auster AOP.9, XP281 Army, 1994 Imperial War Museum Duxford, Cambridgeshire, England [Ref. 1]]
The Auster AOP.9 was a British military air observation aircraft ("Air Observation Post") produced by Auster Aircraft Limited to replace the Auster AOP.6.
Design and Development 
The Auster AOP.9 was designed as a successor to the Auster AOP.6. Like its predecessor, it was a braced high-wing single engined monoplane with a fixed tailwheel undercarriage. Although having the same general appearance the AOP.9 was a new design with larger area wing and a more powerful engine. The wing and tail were metal skinned but the fuselage and ailerons fabric covered. The fin and rudder assembly were more angular in the new aircraft with a noticeable dorsal fillet. A combination of the more powerful 180 hp (134 kW) Blackburn Cirrus Bombardier engine, larger wings and large flaps gave it an improved take-off and landing performance compared with the AOP.6. It could operate from ploughed fields and muddy surfaces using low pressure tires and strengthened undercarriage.
The cabin held three seats, pilot and passenger side by side and the observer behind, facing either forwards or rearwards. The aircraft was also designed to be convertible into a two seat light transport with an interchangeable rear floor. In this configuration the observer sat alongside the pilot. The prototype (WZ662) first flew 19 March 1954. Auster Aircraft allotted their model designation B5 to the AOP.9 design.
Operational History 
Deliveries started to the Royal Air Force in February 1955, replacing AOP.6s in the regular AOP squadrons, the auxiliary squadrons disbanding in March 1957 before receiving AOP.9s. Until the formation of the Army Air Corps (AAC) in September 1957, Army personnel flew RAF aircraft based in RAF squadrons.
The aircraft were in action with No. 656 Squadron from September 1955, flying an average of 1,200 sorties per month. By the end of Operation Firedog in the Malaya on 31 July 1960, 656 Squadron's AOP.6 and AOP.9s had carried out 143,000 sorties. The AOP.9s were involved in several of Britain's other end of Empire conflicts; 653 Squadron AAC used them in Aden in the early 1960s, flying from Falaise, Little Aden. They stayed in service until 1966 and were the last fixed wing AOP aircraft used by the AAC, though their light transport role was taken over by Beavers.
In the 1970s 19 AOP.9s joined the UK civil register and in 2008 fourteen remain though only about three of these have a current certificate of airworthiness. The sole Beagle E3/Auster AOP.11 (G-ASCC) was flying until an accident in 2007.
Specifications (AOP.9) 
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