12. Pressurisation Flashcards
What is the normal working pressure differential?
6.5 +/-0.1 psi
At what ambient temperature is ambient airflow completely closed off and bleed air bypass section opened, as necessary, to allow more bleed air passed the fixed flow passage of the air ejector?
0 deg C
Where are the outflow valve and safety valve located?
On the aft pressure bulkhead
Can the aircraft be pressurised on the ground?
No. The left landing gear safety switch keeps the safety valve open on the ground
What provides negative pressure relief protection during rapid descents?
Both valves incorporate a negative pressure relief function which prevents outside pressure exceeding cabin pressure by more than 0.1psi
Does ambient air enter the cabin via the flow controller whilst on the ground?
No, only bleed air. On the ground the safety switch closes a valve which allows ambient air to mix with bleed air
Which ambient air valve opens first?
The left, then 6-8 seconds later the right. This prevents excessive pressure bumps during takeoff
What is the approx rate range of the RATE control knob?
200-2000fpm
How does the CABIN PRESSure TEST function work?
When held in the spring loaded TEST position, the safety valve is held closed, bypassing the safety switch to allow cabin pressurisation test on the ground
What cabin altitude causes an ALT WARN light?
12500ft
What should cabin alt selector be set to prior to takeoff?
500-1000ft about cruise pressure altitude
During descent what is cabin alt selector set to?
500ft above field pressure altitude
What are the 4 functions of the vacuum-operated safety valve?
- Provide positive pressure relief if the outflow valve malfunctions
- Allow depressurisation when the pressure switch is moved to DUMP
- Maintain unpressurised state while on the ground with left landing gear safety switch compressed
- Prevent negative pressure differential
