Wednesday, March 28, 2012

Vertical/short take-off and landing - AIRCRAFT CONTROL

Fig. 18-18 Reaction control system.
29. The low forward speeds of V/STOL aircraft during take-off and transition do not permit the generation of adequate aerodynamic forces from the normal  flight  control  surfaces,  it  is  therefore necessary to provide one or more of the following additonal methods of controlling pitch, roll and yaw.
Reaction controls
30. This system bleeds air from the engine and ducts it through nozzles at the four extremities of the aircraft (fig. 18-18), The air supply to the nozzles is automatically cut off when the main engine swivelling propulsion nozzles are turned for normal flight or when the lift engines are shut down. The thrust of the control nozzles is varied by changing their area which varies the amount of airflow passed.
Differential engine throttling

31. This method of control is used on multi-engined aircraft with the engines positioned in a suitable con- figuration.  A rapid response rate is essential to enable the engines to be used for aircraft stability and control. It is usually necessary to combine differ- ential throttling with differential thrust vectoring to give aircraft control in all areas.
Automatic control systems
32. Although it is possible for the pilot to control a V/STOL aircraft manually, some form of automation can be of benefit and in particular will reduce the pilot workload. The pilot's control column is electronically connected to a computer or stabilizer that receives signals from the control column, compares them with signals from the sensors that measure the attitude of the aircraft, and automatically adjusts the reaction controls,  differential  throttling  or  thrust  vectoring controls to maintain stability.

No comments:

Post a Comment