737 Air Systems Flashcards
What is the meaning of the BLEED TRIP OFF light?
Excessive bleed air or temperature so that related engine bleed air valve has closed automatically.
* requires reset
Temperature Sensors
* AUTO?
* OFF?
AUTO - automatic temp control for the associated zones. Full rotation is between 65* and 85º
OFF - closes the associated Trim Air modulating valve
What does the ISOLATION VALVE switch do?
Isolates the two sides of the Bleed Air system
CLOSE - closes the valve
AUTO - closes automatically if both engine bleed air switches are on and both air conditioning PACK switches are AUTO or HIGH
OPEN - Opens isolation valve
Explain function of TRIP RESET switch
Push (if fault condition is corrected)
* resets BLEED TRIP OFF, PACK and ZONE TEMP Lights
* related engine bleed valve opens, or related pack valve opens, or related air mix valve opens
* light remains illuminated until reset
The trip switch does NOT reset a WING-BODY OVERHEAT light
What is the alert for an E&E bay overtemp on the ground?
Crew call horn in the nose wheel well
Explain the three functions of the Pressurization mode selector?
1. AUTO
2. ALTN
3. MAN
- AUTO - system controlled automatically
- ALTN - pressurization system controlled automatically using ALTN controller
- MAN - system controlled manually by outflow valve switch and both auto controller bypassed
What causes the altitude warning Horn to sound?
Cabin Altitude above 10,000 ft.
Explain the function of the cabin ALT HORN CUTOUT switch
Pushing it cuts out intermittent cabin warning horn.
What causes the WING-BODY OVERHEAT light to illuminate?
Left light means overheat in bleed air duct at:
- left engine strut
- left inboard wing leading edge
- left air-conditioning bay
- keel beem
- APU bleed air duct
Right light:
- RH engine strut
- RH inboard wing leading edge
- RH air-conditioning bay
Explain the function of the Air Temperature Source selector
Shows temp in various areas of plane.
What is the meaning of an illuminated PACK light?
Indicates pack trip off or failure of both primary and standby pack controls.
During MASTER CAUTION recall, indicates failure of either primary or standby pack control.
Explain meaning of ZONE TEMP light in:
- CONT CAB (control cabin)
- FWD or AFT CAB
CONT CAB - indicates duct overheat or failure of the flight deck primary and standby temp control.
FWD or AFT CAB - indicates duct overheat
What is the meaning of an illuminated OFF SCHED DESCEND light?
The airplane descended before reaching the planned cruise altitude set in the FLT ALT indicator.
What is the TRIM AIR switch used for?
Turns on and off the trim air system valve.
What does the RECIRC FAN do?
It reduces the AC pack load and bleed air demand.
Draws air from the pass cabin and electrical equipment bay (E&E) to the forward cargo bay where it is filtered and re-circulated to the mix manifold.
Explain function of EQUIP COOLING EXHAUST switch?
- NORM
- ALT
What happens if the OFF light is illuminated on the switch panel?
NORM - normal cooling exhaust fan activated
ALT - alternate cooling fan exhaust fan activated
Fan is no longer working and need to switch to alternate fan. Once switched the light should go off within 5 seconds.
What is the meaning of a DUAL BLEED light on the air systems panel?
The APU bleed air is open and there is back pressure in the ducts.
Configuration Left engine
- APU bleed valve open and engine NO. 1 BLEED air switch on or,
APU bleed valve open and engine NO. 2 BLEED switch on and isolation valve is open
What do the blue RAM DOOR FULL OPEN lights mean?
Ram air cooling doors are open position which happen only on the ground or in the air when the flaps are extended.
Describe function of BLEED air switches.
ON - opens the bleed air valve when engines are running. This valve can only open when there is bleed air pressure.
Describe function of APU BLEED air switch?
ON - opens the APU BLEED valve only when the APU is operating.
What are the three functions of the PACK switch?
OFF - pack off
AUTO - pack in automatic mode
HIGH - pack regulates to high flow which will provide max o rate on the ground with the APU BLEED switch ON
What four ways can air be provided to the aircraft interior?
- RH bleed air from engine
- LH bleed air from engine
- APU bleed air
- On the ground pressure air can be supplied through a high pressure air source connected to a duct on the bottom of the aircraft.
To which side of the system (LH or RH) does APU bleed air provide pressure?
How about the high pressure ground air source?
LH side - APU
RH side - ground air source.
APU bleed air provides enough air flow for _________ packs on the ground and ___________ packs in the air.
2 packs on the ground and 1 pack in the air.
APU bleed air can be used up to an altitude of ___________ ft.
17,000 ft
When will the blue APU GEN OFF BUS light illuminate?
Once the APU is started but the APU generator has not yet been connected.
When is it normal for the amber DUAL BLEED light to be on?
At engine start. (according to the CBT video)
When the aircraft is on the ground is it possible to get air-conditioned air into the cabin without using any of the bleed air sources or high pressure ground air source?
Yes, air-conditioned air can be fed directly into the mix manifold, so one could say there are 5 ways to get air into the cabin on the ground.
What will happen if only one pack is operational?
The operating Pack will automatically switch to high flow mode.
What valves do the Temperature Selectors directly affect?
The trim air modulating valves.
