Rolls-Royce Exe
The Rolls-Royce Exe, or Boreas, was a 24-cylinder air-cooled X block sleeve valve aircraft engine intended primarily for the new Fairey Fleet Air Arm aircraft, particularly the Fairey Barracuda. The Exe was relatively powerful for its era, producing about . This is notable given the relatively small displacement, the Merlin requiring for approximately the same power level. The X-24 layout made this quite a compact engine. The Exe was named after the River Exe, although Rolls-Royce later transferred the use of river names to its gas turbine engines. Design and development. The Exe was  under development in 1939, having been started in the 1930s, along with the Peregrine and Vulture. Work on the Exe was suspended in August 1939, and stopped about August 1940. Ernest Hives, head of the Rolls-Royce aero engine division, wanted to stop work on the Exe, Peregrine, and Vulture to concentrate on the Merlin and Griffon engines. An enlarged version, the Rolls-Royce Pennine, was built later in the war, but cancelled as jet engines became the company's focus. Originally intended for the Supermarine Type 322 and Fairey Barracuda the Exe was only test flown in a Fairey  Battle, the first flight taking place on 30 November 1938. This aircraft continued in use for some time as a communications aircraft where the Exe was noted to be quite reliable in service.