De Havilland DH.15
The de Havilland DH.15 Gazelle was an engine testbed for the Galloway Atlantic engine, converted from a de Havilland DH.9A for flight trials in 1919–20.The DH.15 Gazelle, more often known just as the DH.15, was a standard DH.9A, complete with original armament, converted for use as an engine testbed.This replaced the DH.9A's standard 400 hp (300 kW) Liberty 12, although without a great change in appearance, as the Atlantic was mounted behind a similar large rectangular radiator.Both engines were upright V-12s, both with crankshafts near the base, and in each case, the propeller was mounted low on the nose.The exhaust pipes on the DH.15 were longer than the usual DH.9A set, running straight back from the upper sides of the engine, ending at the observer's cockpit.