75 Engine Air Flashcards
What are the 3 sources of engine engine air used for?
Bearing compartment sealing, cooling air, compressor bleed valve and airframe services.
What bearings is air utilised to seal?
1,2,3
What components is air used to cool?
compressor and power turbine disks and compressor turbine stator.
As the cooling air and oil from the bearings enter the accessory box what happens to it?
separated by the centrifugal breather impeller and bled overboard.
What is the purpose of your compressor bleed valve?
Automatically opens ports in the gas generator case to spill interstage compressor air (P2.5) and prevent compressor stall.
How is the operation of the bleed valve controlled?
P3 pressure taken from the vicinity of the no 2 bearing air.
Explain the process of engine start up for the bleed valve.
On start up at low speed valve is open as 2.5 is greater than p3, as p3 overcomes p2.5 the valve closes.
What air is supplied for airframe services?
P2.5 and P3
What is the purpose of the swing check valve located on the end of the compressor bleed valves via a hinge.
To relieve excess 2.5 on start up.
Compressor interstage air (P2.5) is utilized to provide a pressure differential across the labyrinth seal located in front of the
No. 1 bearing.
