Thursday, March 22, 2012

Vertical/short take-off and landing - Remote lift systems

 Remote lift systems

Fig. 18-12 Remote lift fan.
17. Direct lift remote systems duct the by-pass air or engine exhaust air to downward facing lift nozzles remote from the engine. These nozzles may be in the front fuselage of the aircraft or in the wings.  The engine duct is blocked by means of a diverter similar to that described in para. 10.
18. The remote lift-fan (fig. 18-12) is mounted in the aircraft wing or fuselage, and is driven mechanically or by air or gas ducted into a tip turbine, The drive system is provided by the main propulsion power plant or by a separate engine.

19. The advantage of the remote lift system is that it gives some freedom to the aircraft to position the propulsion system to the best advantage whilst still maintaining the resultant thrust near the aircraft centre of gravity in the jet lift mode. This freedom is achieved at a cost of increased volume, particularly with the gas driven systems, due to the size of the ducts to feed the gas to the remote lift system. Although  the  mechanically  driven  remote  lift-fan eliminates the need for these large gas ducts, it is done at the expense of long shafts and high power gearboxes and clutch systems.

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