Bleeds, Hydraulics, Air Con and Pressure Flashcards
Isol valve swx in AUTO, where will the valve be?
‘4 corners’ If both bleeds on and both packs in auto the isol valve will be closed. If any one of the 4 corners (bleeds or packs) is swithced off, the valve will open (based on swx posn logic, not actual air pressure)
Where is the bleed system presseure gauge?
Fwd o’head panel
What could cause BLEED TRIP OFF, how to restore?
Overtemp or over pressure, iaw the QRH press the trip reset
What are the sources for the bleed air system? (3)
Engines, APU, gnd starter cart
What services use bleed air?
- Aircon
- pressurisation
- wing and engine TAI
- eng start
- hyd resevoir pressure
- potable water pressure
- aspirated TAT probe
- NGS
Where is bleed air drawn from?
High power = 5th stage compressor
Low power =9th stage compressors
What functions does the Pressure relief shut off valve, PRSOVs have?
Pressure relief shut off valve, regulate pressure and shut off bleed air from the engine at times of critical flight
Which duct is external (pneumatic) air connected?
The right bleed air manifold (don’t confuse with pre conditioned air)
If starter air is connected to the right manifold, which engine do you start first?
The left. The air cart sits on the right away from pax boarding so you have to start the left via the open isolation valve, remove the cart then start the right
Why don’t we select bleeds off for TO to preserve power in critical flight?
They auto switch off
What causes DUAL BLEED?
Left or right bleed being selected on with the APU bleed selected on (swx logic only, not based on pressure)
What is the thrust limit with DUAL BLEED on and why?
Not above idle on the engines to avoid over back pressure damaging the APU
Where are the sensors for the left WING BODY OVERHEAT?
Engine strut, inner LE, air con bay, keel beam and APU duct (right doesn’t have keel or APU)
If a pack fails with the swx in auto what happens?
The other pack goes to high, unless flap not up, in which case it stays in norm to preserve bleed pressure for critical flight
With bleed off what do engine and wing TAI do?
Engine TAI stays on, wing TAI goes off
What does amber OFF SHED DESCENT mean?
You’ve started to descend before reaching your selcted crz alt on the pressurisation panel
From where is conditioned air for the flt deck supplied from?
Normally direct from the left pack, but if failed, from the right pack via the mix manifold
Max height on a single pack?
Boeing 41000ft Company limit FL250
How many packs can an engine run?
1
How many packs can the APU run?
2 on gnd, 1 in flt
How many packs can a ground air cart run?
2
When should packs not be set to high?
Flap not up, critical phases of flight (TO and app)
What does the ram air system do?
Provides extra cooling for the heat exchangers when cold temps are selected
What happens if a primary pack controller fails?
Its run by the stby pack controller in the opposite controller
What do the recirc fans do and what does it do for the Pack?
Pump air from the pax cabin, filter it and return it to the mix manifold. Reduces pack load by 50%
On the gnd where is Electronic & Equipment bay air sent?
Overboards
Is the E&E bay exhaust duct always closed in the air?
No it works on differentail pressure so may be open at low speed
In flt where is E&E bay air sent ?
Around the forward cargo bay liner (not into it) to heat it
If an equip cooling fan fails what can you do?
Follow QRH. Select the alternate
What do you do with a PACK amber fail?
Follow the QRH. Increase all zone temps, then try to reset (PACK – UP)
What do you do if you get a ZONE TEMP warning?
Follow the QRH. Reduce that zone temp and try a reset (DUCT – DOWN)
What does the slosh flap do?
Only open on ground, deflects wheel slosh in bad weather away from the ram air doors
When do the RAM DOOR FULL OPEN blue lights come on?
When ram air doors fully open at high cold demand
Where is pre-conditioned air plugged in?
Direct to the mix manifold (don’t confuse with starter air)