A single-seat reconnaissance fighter developed from the two-seat HD.3, the HD.9 was placed in the broad category of Avions de Corps d'Armee (as the HD.9 Apl) and it was armament with a single synchronised 7.7mm Vickers machine gun. The airframe was basically that of the HD.3 and the installation of the 260hp (194 kW) Salmson 9Za radial engine was identical, but fuel capacity was considerably increased.
The first example of the HD.9, serial 3001, was completed in November 1918 as the initial aircraft built against an order for 10 machines with serials starting at 3001 and up. However, its career was cut short by the Armistice and there is no evidence that all nine remaining aircraft were completed.
Empty weight: 710 kg / 1565 lb