RAF Search and Rescue Sycamore helicopter at Sylt - Jun58.   (Thanks to Jack Goldthorpe.) Bristol Type 171 Sycamore The Bristol Type 171 Sycamore was Britain's first post-war commercial helicopter.   The first protoype flew on 27 July 1947 powered by a 336kW (450hp) Wasp Junior radial engine, and a 410kW (550hp) Alvis Leonides powered all subsequent versions. (Thanks to The Encyclopedia of Aircraft from Silverdale Books.)