Air/Pneumatic Systems Flashcards
What does window heat do? (2)
Provides ice protection for forward windows and fog protection for all.
What powers window heat?
L1 and R2 are AC XFR BUS1, L2 and R1 are AC XFR BUS2
When will window heat OVERHEAT illuminate?
Temperature controller determine temperature too high. Current stops flowing. Reset by waiting to cool then cycling switch.
MASTER CAUTION ANTI-ICE
How long may ON lights stay illuminated during window heat test?
70 seconds
When will AUTO probe heat start?
Either engine running.
What heating element do the alpha vanes have?
Independent 115V AC
When must be pitot heat be on by?
Takeoff
What may happen if captains pitot fails?
- May loose cabin pressurisation
- Cabin altitude and cabin differential pressure indicator
- Standby instruments
What will cause FEEL DIFF PRESS light to illuminate?
L or R elevator pitot blocked.
What does wing anti-ice heat?
3 onboard slats
Can one engine operate WAI?
Yes. ISOL valve to be open, or AUTO.
What will happen to WAI valves if loss of AC power?
Valves fail in position
Will WAI operate on the ground?
Yes, until thrust levers pass TO warning angle.
- 55%N1 if below freezing
- 40% above freezing level
Valves shut above this and WAI switch to OFF
What does WAI L/R VALVE light indicate? (2)
Over temperature situation detected. Valves close. Wait to cool.
Position of valve and switch disagreements
When is the WAI thermal switch bypassed?
Inflight, wings will not overheat with natural airflow in flight.
What happens to speed bar when WAI on for rest of flight?
Stick shaker logic and MMS bars are adjusted for icing conditions. Remain adjusted for rest of flight. (FMC VREF not adjusted)
Where does EAI prevent icing on airframe?
Cowl top and engine core
What bleed air does EAI use?
4th stage, supplemented by 10th stage. Ducted upstream of bleed valve.
How is the EAI valve operated?
Controlled by normal DC power but pneumatically operated.
What ignition switch is required for EAI to be on?
CONT
Where and when will amber TAI appear?
On engine display, when valve not in commanded position.
What does Amber COWL ANTI-ICE light mean
Pressure too high between valve and cowl tip (MASTER CAUTION).
When will ENG ANTI-ICE light illuminate?
System inhibited due to system failure or when engine core anti-ice valve fails closed (MASTER CAUTION).
What are the 2 EAI lights?
- COWL ANTI-ICE (pressure)
- ENG ANTI-ICE (failure)
What power does pressurisation modes use?
All modes use DC power.
When will the Overboard Exhaust Valve be open? (3)
- on ground
- low differential pressure
- Inflight with either pack in high flow or R RECIRC fan OFF (smoke removal)
Up to what altitude can cabin altitude be maintained to sea level pressure?
18,500FT (maximum differential)
What is the maximum differential pressure?
9.1PSI
What protects from negative pressure? (2)
- Negative pressure relief valves
- Door seals
Does the differential pressure and cabin altitude indicator require power?
No electrical power required
When does altitude horn activate?
Cabin altitude passing 10,000ft.
What is the maximum differential pressure for TO/LDG?
0.125PSID
When is Main Outflow Valve closed?
When throttles advanced, controller modulates valve to close slightly pressurising cabin.
What does the cabin controller sense?
Only senses PSI.
When will OFF SCHED DESCENT illuminate?
Begin to descend before cruise altitude. Controller programmes cabin pressure to return to TO field elevation. If FLT ALT changed, TO elevation data lost.
When does cruise pressurisation mode activate?
1000ft below cruise altitude (within 0.25PSI)
What is the cabin differential above FL370?
8.35PSID.
What is the maximum differential pressure during isobaric cruise?
8.45PSID
When will Main Outflow Valve open on landing?
When N1 decreased below 50%N1. This prevents equipment cooling fan pressurising aircraft to negative pressure.
When will AUTO FAIL light illuminate? (6)
- Loss of DC power
- Controller fault
- Outflow valve fault
- Excessive differential pressure (8.75PSID)
- Excessive rate of cabin pressure change.
- Cabin altitude above 15800ft.
What will happen if AUTO FAIL light illuminates?
Automatic transfer to ALTN pressurisation mode. Light will extinguish with ALTN selected.
How does Main Outflow Valve move in manual mode?
Moved by separate DC motor at a slower rate than AUTO modes.
How long does full range of movement of outflow valve take?
20 seconds.
What happens to bleed valve if ON but no bleed air available?
Valve remains closed.
What do bleed air valves function as? (2)
- Pressure regulator
- Shut-off valve
When will BLEED light illuminate?
When bleed valve closed because of over-temperature after pre-cooler. Can also happen due to overpressure downstream of 10th stage.
Incorrect configuration after no-bleed takeoff.
Can BLEED trip-off be reset?
Yes, by TRIP RESET button.
What is APU bleed valve powered by?
BATT BUS
What can APU bleed air cause with 10th stage bleed air?
Back pressure 10th stage. SOV closes this.
When will the ISOL valve open in AUTO mode?
If any bleed or pack switch is OFF. Allows all pneumatic users to receive air from either manifold.
Does APU bleed position affect ISOL VALVE position?
No
When will DUAL BLEED light illuminate?
When APU bleed valve open and possibility that engine bleed air could back pressure APU.
Will DUAL BLEED illuminate when no engines running?
Yes. Only monitors position of the switches - including ISOL VALVE (not valve position).
What are the requirements for the APU to supply bleed air? (2)
- RPM over 95%
- 1 minute delay for warmup
Why does DUAL BLEED illuminate on engine start?
If ISOL VALVE in AUTO, the packs will be off so the valve will be open.
Does APU bleed switch need to be returned to OFF before APU OFF
No. APU OFF signals bleed valve to close. APU then runs for 60 seconds before shutdown.
Does DUAL BLEED illuminate on ground air or crossbleed starts?
No, because there’s no APU bleed air.
Where is external compressed air supplied to?
Right side of pneumatic system. Start engine 2 first.
Where is PACK HIGH prohibited? (3)
TO, APP & LDG
What is the configuration for ground AC operations?
L pack uses APU bleed with engine 1 bleed off and ISOL VALVE closed. Engine 2 supplies R Pack. Both in HIGH.
During no bleeds takeoff, which pack is supplied by APU?
L PACK
What does WING BODY OVERHEAT mean?
Duct leak exists. Causes MASTER CAUTION and AIR COND to illuminate.
What are the areas monitored for WING BODY OVERHEAT? (4)
- Engine strut
- Wing leading edge
- AC bays for both systems
- APU bleed air duct (Left side overhead light only)
Is there automatic bleed shutoff for WING BODY OVERHEAT?
No, valves won’t automatically close.
How is WING BODY OVERHEAT tested?
OVHT TEST switch
Which PACK feeds AC to the cockpit?
L PACK
What are the limits of single pack operation?
In HIGH flow, capable of maintaining pressurisation and temperature to surface ceiling.
How many PACKs can the APU feed inflight?
1
What happens to the pack flow when APU sole source of bleed air?
Switch to HIGH flow.
Where is ground air provided too?
R PACK. With ISOL valve open, can feed both.
When will a 1 pack operation revert to LOW flow from HIGH?
When flaps selected to maintain engine power. This does not happen if APU bleed used.
Where does the cooling air for the packs come from?
RAM air system.
When will PACK light illuminate? (2)
Overheat detected in one of 2 temperature sensors. Causes PACK valve to close.
Primary or standby control failure.
What happens after turbine in PACK assembly?
Processed cold air and bypassed hot air are combined to get correct AC temperature.
What operates PACK standby controls?
The opposite pack for redundancy.
What happens if either PACKs primary OR standby control fails?
Illuminates PACK on RECALL.
If both fail, illuminates immediately.
Pack will still operate unless it trips due to overheat.
What is the temperature of the air that leaves the packs?
Temperature to satisfy area that requires most cooling.
When is RAM air inlet door fully open? (3)
- on ground
- inflight with flaps extended
- inflight and maximum cooling required
What are RAM air deflector doors operated by?
Air/ground sensor
What determines position of RAM inlet door?
Compressor Discharge Temperature
How many temperature zones are there? (3)
Control cabin, forward and aft cabin.
What temperatures are the COLD, AUTO and WARM selectors?
Cold - 18
AUTO - 21
Warm - 30
With TRIM AIR off, what do the packs supply?
L PACK supplies cockpit, R PACK controller provides average for both cabin sections.
How many controllers control TRIM AIR?
Right controller for FWD cabin and cockpit, left controller for AFT cabin and backup for cockpit.
What happens with TRIM AIR off and 1 pack operating?
Provides average temperature of all 3 zones.
If all temperature selectors are off and TRIM AIR off, what temperature is supplied by packs?
L PACK supplies 24 degrees. R PACK supplies 18 degrees (default).
What does ZONE TEMP illumination mean? (2)
Duct temperature overheat. Trim Air associated modulating valve shuts. May be reopened by TRIP RESET.
Primary or standby temperature control fails. RECALL if only one.
What does CONT CAB illumination mean?
Failure of primary or standby temperature control. If both, get MASTER CAUTION.
When will PACK light illuminate? (5)
- Pack trip
- Failure of both primary and standby pack controls
- failure of flow control valve to open when commanded
- incorrect pack configuration that would cause unpressurised state.
- excessive temperatures
What are the RECIRC fans powered by?
Normal AC power
Where does each RECIRC fan draw air from?
L RECIRC - air distribution compartment
R RECIRC - main cabin and E&E bay
What happens when both PACKs selected HIGH on ground to RECIRC fans?
Shuts down L RECIRC fan.
What happens in air if either or all PACKs are selected HIGH to RECIRC fans?
L RECIRC shuts down if one in high.
If both in high, both RECIRC fans shut down. Causes overboard exhaust to open in E&E bay.
What happens to E&E bay cooling if R RECIRC fan off?
Cooling maintained by automatic opening of overboard exhaust. Will only close to maintain cabin pressure.
How many fans are in the E&E bay?
4 fans, 2 operate at a time. Normal and Alternate fans.
What happens if E&E bay airflow not adequate?
Cooling fans OFF light illuminates, and OVHD MASTER CAUTION. Selection of ALTN causes airflow to restore.
On ground, horn sounds in nose gear well.
What happens if smoke detected in E&E bay?
EQUIP SMOKE illuminates. PACKs to high, E&E supply fans off for 5 mins, then again for 5 mins if smoke still detected.
Exhaust valve opens to smoke position and RECIRCs off.
Extinguishes 30 seconds after no smoke detected.
What side of the pneumatic system pressurises potable water?
L side.
Will anti-ice/rain systems operate on BATT power?
No.
What will 2 bleed lights illuminate after takeoff?
Incorrect configuration, 45 secs after takeoff, flaps up
What are packs controlled by?
IASC, backup from other one
Where does left pack provide air too?
FCC and then leftover to mix manifold.
What does 2 PACK lights after takeoff mean?
Incorrect configuration, 45 seconds after flaps up
What RECIRC will shut off inflight if one pack in high?
L RECIRC
On ground, what RECIRC fan will turn off if both PACKS in high?
L RECIRC
When is RAM door fully open?
On ground and slow flight
What is temperature range?
18-30 degrees
What IASC controls CONT CAB?
R IASC, which does FWD cabin. L IASC is backup and does AFT.
How long after no smoke will EQUIP SMOKE go off?
30 seconds
When does cruise mode start?
0.25PSI before cruise
When does outflow valve fully open?
Taxi in
Differentials at 28, 28-37 and 37000ft+?
28000 - 7.45PSI
28-37000 - 7.8PSI
37000+ - 8.35PSI
When will CPC fail?
Cabin ROC 2000fpm, cabin altitude 15800+, differential over 8.75PSI, loss of DC Power, controller failure or outflow valve failure
How many outflow valve motors?
3
Which windows are heated?
All, but only 1+2 have anti-ice
What does EAI COWL ANTI-ICE, COWL VALVE & ENGINE ANTI-ICE mean?
COWL ANTI-ICE - over pressure in duct
COWL VALVE - position disagreement or transit
ENG ANTI-ICE - valve failed to close
What does WAI L/R VALVE light mean?
Not in commanded position
