What normally categorizes the max altitude an aircraft can fly?
Max allowable PD
What is the usual air source for pressurization in turbine engines?
Turbine engines typically use bleed air from the engine compressor for cabin pressurization.
This can place a demand on the engine
Bleed air is typically used directly or it may be used to drive a turbocompressor
How is pressurization accomplished?
By supplying more air to the cabin than required allows excess air to escape in a controlled manner by the cabin pressure controller.
(A constant supply of incoming air is balanced against a variable rate of outflow air.
What is the pressure controller?
- Controls the escape of excess air
- Through an outflow valve determined by a rate selector.
What is a positive pressure relief valve?
- Prevents over-pressurization by opening automatically at a predetermined pressure
- Set on the ground to reflect the maximum allowable PD
Negative pressure relief valve?
- Prevents cabin pressure from going below that of ambient outside air temperature
- Typically set for 0.5 psi
What is a dump valve?
- Dumps any residual cabin pressure on landing
- Often controlled by the LDG gear squat switch
- Can be selected by pilots for emergency use
What is a safety valve?
Incorporates the positive and negative pressure. relief valve and the dump valve to form the safety valve.
What is the desired cabin altitude?
8000ft or less
15000ft
What is the rate of change in psi allowable for ascending and descending?
- 26/min for ascending
0. 16 psi/min descending
What can a solenoid valve do in the pressurization system?
Dump pressure
