Pressurisation Flashcards
What altitude must pax not be subject to?
15000ft
Effect of differential pressure on stresses
Greater Δ PSI, greater hoop stresses.
A cabin pressure controller maintains a pre-set cabin altitude by regulating the:
Position of the outflow valve(s).
Pressurisation Requirements
15000’
14000’
10000’
8000’
15000’ max cabin altitude (emergency)
14000’ oxygen masks will automatically drop
10000’ Cabin Altitude warning system
8000’ Maximum Cabin Altitude
Passenger comfort rate of climb and maximum
CLB 500fpm, DES 300fpm
Maxmium 1800fpm
Maximum Differential Pressure for a Jet
9 psi
Pressurised Areas
Cockpit, cabins, fwd/aft cargo
Unpressurised Areas
Radome, nosecone, torque box, main undercarriage, tailcone
Safety Valve
Simple outwards pressure relieft value to releive pressure when maximum diff psi has been exceeded.
Valve will open if pressure exceeds max diff by 0.25 psi
Inwards Relief Valve
Will deploy to prevent excessive negative differential pressure if cabin psi is smaller than outside.
Dump Valve
Manually operated dump valve allows the crew to dump all cabin pressure.
The operation of manual pressurisation control
Achieved by a second circuit operating the outflow valve.
The purpose of the cabin pressure controller in the automatic mode is to:
- Control cabin altitude.
- Control rate of change of cabin altitude.
- Limit differential pressure.
In the event of excessive cabin pressure, a normal transport aircraft will relieve this by:
Opening a positive pressure relief valve
The main function of an air cycle machine
The main function of an air cycle machine is to cool the charge air (bleed air).
Turbine drives the compressor, which makes the second heat exchanger more effective.
