Page 174 - The Jet Engine

Thrust reversal

11. The clamshell doors are operated by pneumatic Cold stream reverser system
rams through levers that give the maximum load to 15. The cold stream reverser system (fig. 15-4) can
the doors in the forward thrust position; this ensures be actuated by an air motor, the output of which is
effective sealing at the door edges, so preventing converted to mechanical movement by a series of
gas leakage. The door bearings and operating flexible drives, gearboxes and screwjacks, or by a
linkage operate without lubrication at temperatures of system incorporating hydraulic rams.
up to 600 deg. C.
16. When the engine is operating in forward thrust,
Bucket target system the cold stream final nozzle is 'open' because the
12. The bucket target system is hydraulically cascade vanes are internally covered by the blocker
actuated and uses bucket-type doors to reverse the doors (flaps) and externally by the movable
(translating) cowl; the latter item also serves to
hot gas stream. The thrust reverser doors are reduce drag.
actuated by means of a conventional pushrod
system. A single hydraulic powered actuator is 17. On selection of reverse thrust, the actuation
connected to a drive idler, actuating the doors system moves the translating cowl rearwards and at
through a pair of pushrods (one for each door). the same time folds the blocker doors to blank off the
cold stream final nozzle, thus diverting the airflow
13. The reverser doors are kept in synchronization through the cascade vanes.
through the drive idler. The hydraulic actuator incor-
porates a mechanical lock in the stowed (actuator Turbo-propeller reverse pitch system
extended) position. 18. As mentioned in para. A, reverse thrust action is
affected on turbo-propeller powered aircraft by
14. In the forward thrust mode (stowed) the thrust changing the pitch of the propeller blades through a
reverser doors form the convergent-divergent final hydro-mechanical pitch control system (fig. 15-5).
nozzle for the engine. Movement of the throttle or power control lever

Fig. 15-5 A propeller pitch control system.

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