During conventional flight, the lift engines would be shut down; before beginning the transition from horizontal to vertical flight, they would be started using compressed air from the single cruise engine. The compressed air provided the initial rotation of the engine but a pressure drop from intake to exhaust had to be present also as the compressed air alone was not adequate for reaching idle speed. Considerable wind-tunnel and flight development of the air intake was required because at the start of transition from horizontal flight vertically-mounted engines have to tolerate a crosswind equal to the forward flight speed without surging or excessive vibrations. The required uniformity of flow was achieved with the help of a set of 7 hinged gills which opened to a forward-facing position to direct air into a plenum which supplied the engines. The behaviour of a vertically-mounted RB.108 in terms of re-ingestion and ground erosion had been investigated with an installation representative of that intended for the SC.1 during ground operation in a Meteor at Hucknall Aerodrome. Initially, a series of scuttles were fitted to the exit nozzles of the lift engines to maintain a low-pressure environment beneath the engines to ensure that the engine rotor would be "windmilling" in the correct direction prior to supplying the compressed air for starting; due to the effectiveness of intake and engine design changes, the scuttles became unnecessary.