page_title: Airco DH.9
section_title: Variants
hierarchical_section_title: Airco DH.9 / Variants
caption_attribution_description: English: Handley Page HP17 in 1921, demonstrating slots
context_page_description: The Airco DH.9 – also known after 1920 as the de Havilland DH.9 – was a British single-engined biplane bomber developed and deployed during the First World War.
  The DH.9 was a development of Airco's earlier successful DH.4, with which it shared many components. These were mated to an all-new fuselage and the BHP/Galloway Adriatic engine, which promised increased performance. Anticipating its usefulness, the type was ordered in very large numbers for Britain's Royal Flying Corps.
  Upon entering service, the DH.9's performance was found to be unsatisfactory. The Adriatic engine was unreliable and failed to provide the expected power, which gave the DH.9 poorer performance than the aircraft it had been meant to replace. The performance deficit was blamed for the heavy losses they suffered over the Western Front. The redesigned DH.9A was fitted with a more powerful and reliable American Liberty L-12 engine which rectified the shortcomings of the original DH.9 model.
context_section_description: DH.9 – Revised version of the DH.4 with the pilot and observer/gunner placed closer together (3,024 production aircraft built with others built in Belgium and Spain).
  DH.9A – (also referred to as the Nine-Ack) was designed for Airco by Westland Aircraft to take advantage of the 400 hp (298 kW) American Liberty L-12 engine. Apart from the new engine and slightly larger wings it was identical to the DH.9. Initially it was hoped to quickly replace the DH.9 with the new version, but the shortage of Liberty engines available to the RAF limited the new type's service in the First World War, and it is best known as a standard type in the postwar RAF, serving as a general purpose aircraft for several years. 2,300 DH.9As were built by ten different British companies.
  DH.9B – Conversions for civilian use as three-seaters (one pilot and two passengers)
  DH.9C – Conversions for civilian use as four-seaters (one pilot and three passengers)
  DH.9J – Modernised and re-engined conversions using the 385 hp (287 kW) Armstrong Siddeley Jaguar III radial engine. Used by the De Havilland School of Flying.
  DH.9J M'pala I – Re-engined conversions carried out by the South African Air Force. Powered by a 450 hp (336 kW) Bristol Jupiter VI radial piston engine.
  M'pala II – Re-engined conversions carried out by the South African Air Force, powered by a 480 hp (358 kW) Bristol Jupiter VIII radial piston engine.
  Mantis – Re-engined conversions carried out by the South African Air Force, powered by a 200 hp (149 kW) Wolseley Viper piston engine.
  Handley Page HP.17 – A DH.9 experimentally fitted with slotted wings, tested 1920–1.
  USD-9/9A – DH.9s manufactured in the United States by the US Army's Engineering Division and Dayton-Wright. (1,415 ordered, only four built)
caption: Handley Page H.P. 17 showing slots
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