Accessory Gearbox
Accessory gearbox provides the power for hydraulic, pneumatic and electrical systems which are used on both the engine and in the aircraft. It is also used to drive fuel pumps, oil pumps and tacho-generators and various other devices necessary for efficient engine operation.
The drive for the accessory gearbox is usually taken from the high pressure compressor shaft, via an internal gearbox. It is then passes to and external gearbox, which provides mounting for the accessories and the engine starter motor.
Accessory gearbox provides the power for hydraulic, pneumatic and electrical systems which are used on both the engine and in the aircraft. It is also used to drive fuel pumps, oil pumps and tacho-generators and various other devices necessary for efficient engine operation.
The drive for the accessory gearbox is usually taken from the high pressure compressor shaft, via an internal gearbox. It is then passes to and external gearbox, which provides mounting for the accessories and the engine starter motor.
Allowing for Expansion of the compressor shaft
Axial movement of the compressor shaft would case the teeth of the bevel gears to move apart and the drive would be interrupted.
Axial movement of the compressor shaft will occur due to expansion and contraction during the working cycle.
Axial movement of the compressor shaft would case the teeth of the bevel gears to move apart and the drive would be interrupted.
Axial movement of the compressor shaft will occur due to expansion and contraction during the working cycle.
Stub Shaft Drive
In the compressor shaft is splined, then stub shaft, which has teeth cut internally that conform to the pattern of the grooves in the compressor shaft, can be fitted around the compressor shaft. The fact that the splined shaft can move axially while the stub shaft is held firmly in the correct position by the location bearing tell us that the gear teeth will not lose contact with each other. |
Spreading the load
To spread the load of driving accessories, some engine divide the gearbox into two smaller separate gearboxes. A second radial shaft is taken from the LP compressor shaft and used to drive a second external gearbox.
These two gearbox system allows the accessories to be divided into two smaller groups, thus overcoming the difficulties of limited space around the engine.
During engine start, instead of gearbox being driven by the engine, the gearbox drives the engine and the starter motor rotates the HP compressor shaft and LP compressor shaft is rotated by air being sucked/drawn through the engine.
Accessories which are specific to the engines operational needs, such as oil pumps and fuel pumps, are grouped on the gearbox which is driven by the high compressor shaft.
To spread the load of driving accessories, some engine divide the gearbox into two smaller separate gearboxes. A second radial shaft is taken from the LP compressor shaft and used to drive a second external gearbox.
These two gearbox system allows the accessories to be divided into two smaller groups, thus overcoming the difficulties of limited space around the engine.
During engine start, instead of gearbox being driven by the engine, the gearbox drives the engine and the starter motor rotates the HP compressor shaft and LP compressor shaft is rotated by air being sucked/drawn through the engine.
Accessories which are specific to the engines operational needs, such as oil pumps and fuel pumps, are grouped on the gearbox which is driven by the high compressor shaft.