Page 199 - The Jet Engine

Vertical/short take-off and landing

Fig. 18-3 V/STOL fighter aircraft.

exhaust system from the engine turbine. In this way (3) Driving a lift system, which is remote from the
the first ducted fan lift/propulsion engine (the engine, either from the engine or by a
Pegasus) evolved (fig. 18-2). separate power unit.
(4) Swivelling the engines.
5. Subsequent experience with the Pegasus engine
in the Harrier V/STOL fighter aircraft (fig. 18-3), lead (5) For STOL aircraft, using bleed air from the
to the development of the short take-off and vertical engines to increase circulation around the
landing (STOVL) operational technique. In this way wing and hence increase lift.
the additional lift generated by the aircraft wing, even In several of the projected V/STOL aircraft a
after a short take-off run, provided a large increase in combination of two or more of these methods has
the payload/range capability of the aircraft compared been used.
to a pure vertical take-off. Vertical landing had
several operational advantages compared to a short Lift/Propulsion engines
landing and so was maintained. 7. The lift/propulsion engine is capable of providing
thrust for both normal wing borne flight and for lift.
METHODS OF PROVIDING POWERED LIFT This is achieved by changing the direction of the
6. Although the Pegasus engine is the only V/STOL thrust either by a deflector system consisting of one,
engine in operational service in the Western World two or four swivelling nozzles or by a device known
there are several possible methods of providing as a switch-in deflector which redirects the exhaust
powered lift, such as; gases from a rearward facing propulsion nozzle to
(1) Deflecting (or vectoring) the exhaust gases one or two downward facing lift nozzles (fig, 18-4).
and hence the thrust of the engine. 8. Thrust deflection on a single nozzle is accom-
(2) Using specially designed engines for lift only. plished by connecting together sections of the jet

Fig. 18-4 Thrust deflector systems.

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