Armstrong Siddeley Deerhound
Armstrong Siddeley Deerhound
The Armstrong Siddeley Deerhound was a large British aircraft engine built by Armstrong Siddeley between 1935 and 1941. It was a triple‑row, 21‑cylinder air‑cooled radial engine with inline cylinder banks and overhead camshafts (one camshaft for each bank of three cylinders).
Flight testing began in 1938 using an Armstrong Whitworth Whitley II (serial K7243). Early on, engineers found cooling problems in the rear row of cylinders, which were solved by a reversed‑flow cooling system that drew air in from the rear of the cowling and sent it forward to exit behind the propeller.
The Whitley crashed on takeoff in March 1940; the crew were fatally injured, but the accident was not blamed on the Deerhound engine.
Only 11 Deerhound engines were built. A single Deerhound III prototype ran and survived into the late 1970s before being scrapped. Development of the early engines was cancelled on 23 April 1941, and all records were handed over to Rolls-Royce by 3 October 1941.
A larger variant called the Boarhound was planned but never flown, and a much bigger design named Wolfhound existed only on paper. The Wolfhound would have six banks of four cylinders (24 cylinders total), about 61 litres displacement, and a projected takeoff power of 2,600–2,800 hp. The Hyena arrangement of cylinder banks continued in later designs, but with little commercial success.
The Deerhound’s only aircraft use was in a modified Armstrong Whitworth Whitley used as a testbed.
This page was last edited on 2 February 2026, at 14:26 (CET).