Page 197 - The Jet Engine

18: Vertical/short take-off

and landing

Contents Page

Introduction 187
Methods of providing

powered lift 189

Lift/propulsion engines
Lift engines
Remote lift systems
Swivelling engines
Bleed air for STOL
Lift thrust augmentation 194
Special engine ratings
Lift burning systems
Ejectors
Aircraft control 197

Reaction controls
Differential engine throttling
Automatic control systems

2. Early in 1941, the late Dr A. A. Griffiths, the then
Chief Scientist at Rolls-Royce, envisaged the use of
the jet engine as a powered lift system. However, it
was not until 1947 that a light weight jet engine,
designed by Rolls-Royce for missile propulsion,
existed and had a high enough thrust/weight ratio for
the first pure lift-jet engine to be developed from it.

3. In 1956 the Bristol Aero-Engine Company was
INTRODUCTION approached by Monsieur Michel Wibault with a
proposal to use a turbo-shaft engine and a reduction
1. Vertical take-off and landing (VTOL) or short gearbox to drive four centrifugal compressors which
take-off and landing (STOL) are desirable character- would be situated two on each side of the aircraft.
istics for any type of aircraft, provided that the normal The casing of these compressors could be rotated to
flight performance characteristics, including change direction of the thrust (fig. 18-1). The concept
payload/range, are not unreasonably impaired. Until incorporated two original ideas i.e. the ability to
the introduction of the gas turbine engine, with its deflect the thrust over the complete range of angles
high power/weight ratio, the only powered lift system from the position for normal flight to that for vertical
capable of VTOL was the low disc loading rotor, as lift and a system where the resultant thrust always
on the helicopter. acted near to the centre of gravity of the aircraft.

187