The Napier Eland Convair liner was really more of a test bed. It was flying out of Luton's grass airstrip in the mid 50's . They used to start it up in their hangar and it would ,allegedly begin its take off roll from there. The Fairey Rotodyne had Elands of course. . The full saga is on Google( Wikipedia) if you put in "Napier Eland Engine".