Pneumatics Flashcards
What does the pneumatic system provide HP air to?
- air conditioning
- pressurisation
- de-icing
Where is bleed air taken from?
Low pressure and high pressure stages of the compressor
What is air from the HP stage used for?
De-icing of the engines and air frame
When is low pressure air available?
Anytime the engine is running
It flows through a one way check valve
How is the high pressure air controlled?
High pressure valve - electrically controlled, pneumatically operated butterfly valve
Requires electrical power to remain open and will close or remain closed in the event of loss of electrical power
Powered by the associated DC bus
What is the high pressure air temperature limit?
Sensor will allow high pressure valve to open provided the temperature is less than 270 degrees
If the va,Ve is open and the temp is exceeded the valve will automatically close
It will automatically reopen after a cooling period
When will the high pressure valve close?
Anytime the low pressure exceeds 22 psi
What is the bleed air valve?
Bleed air will flow to the air conditioning pack through a bleed air valve (regardless of HP or LP)
Electrically controlled and phneumatically operated
If electrical power is lost a solenoid will lock the bleed air valve closed
Powered by the DC ess bus
Automatically close if bleed air pressure is not available
When will the bleed air valve automatically close?
- if the temperature exceeds 274 degrees (HP valve will also close)
- if a bleed leak is detected
- if fire handle has been pulled
- if the associated engine fails
- if uptrim signal has been generated by the ATPCS
- left will close if the prop brake has been selected ON
- for 30 secs during engine starts to ensure normal starting
What is the purpose of the crossfeed valve?
One engine can supply both packs when the engine is on the ground only
Solenoid controlled shut off valve, spring loaded closed, requires electrical power to open
Automatically close in the event of loss of electrical power
When will the crossfeed valve close?
When the engines are operating and the prop brake is disengaged
How is the bleed air duct cooled?
By ram air in flight by a NACA air inlet located on the top of the engine nacelle
Air exhausted through a vent on the landing gear fairing
Where does the leak detection system monitor?
- wing leading edge
- wing to fuselage sidewall
- upper/lower fuselage floor
- air conditioning pack area
When will you get a leak alert?
Above 124 degrees
What happens if a loop overheat is sensed?
- pack valve, high pressure valve and bleed air valve are latched in the closed position
- FAULT light on the pb
- affected bleed air system is inoperative for the rest of the flight
- if leak detected in the left system, the ground crossfeed valve will close automatically
