737 Air Systems
(L) Maximum Cabin Differential Pressure?
(L) Maximum Differential Pressure for Takeoff and Landing?
• 236 feet below airport pressure altitude
(L) Normal operating differential pressure is allowed within the _______ band.
What's the Pack restriction when operating single-engine (or a single engine-bleed source)? (All Aircraft)
Do not operate more than one pack from one engine
Restriction if DUAL BLEED is illuminated?
Thrust must be limited to IDLE.
The DUAL BLEED light illuminates whenever the APU bleed air valve is open and the position of the engine bleed air switches and isolation valve would permit possible backpressure of the APU. Therefore, thrust must be limited to idle with the DUAL BLEED light illuminated.
Pack restriction with the Engine Bleed Air Switches ON?
If an Engine Bleed Air Switch is ON, do not operate the Pack in HIGH for takeoff, approach or landing.
• Non-Normal procedures accepted.
List the systems requiring Bleed Air?
The following systems rely on the bleed air system for operation:
1. Air Conditioning & Pressurization
2. Wing & Engine Thermal Anti-Icing
3. Engine Starting
4. Hydraulic Reservoirs Pressurization
5. Water Tank Pressurization
6. Aspirated TAT Probe
- See Side 3 of this Card -
Bleed Air comes from which sections of the Engine?
5th and 9th Stages.
- See Side 3 of this Card -
Engine Bleed Air Valves power source?
DC activated and Pressure Operated.
• The Engine Bleed Air Valve acts as a pressure regulator and shutoff valve. With the engine bleed air switch ON, the valve is DC activated and pressure operated. The valve maintains proper system operating pressure and reduces bleed air outflow in response to high bleed air temperature.
- See Side 3 of this Card -
Bleed Air Switch function?
Engine BLEED Air Switches:
OFF - Closes Engine Bleed Air Valve.
ON - Opens Engine Bleed Air Valve when engines are operating.
• Acts as a PRSV
• DC activated and pressure operated
• Valve maintains proper Pressure and Temperature
AIR 002 (001 Deleted)
Explain the meaning of an illuminated BLEED TRIP OFF light.
BLEED TRIP OFF indicates excessive:
1. Engine Bleed Air temperature, or
• Engine Bleed Air Valve Closes automatically
• Requires Reset.
Explain the function of the TRIP RESET Switch.
Push (if fault condition is corrected) -800
1. BLEED TRIP OFF,
2. PACK and
3. ZONE TEMP lights.
• Related engine bleed valve opens, or related pack valve opens.
• Lights remain illuminated until reset.
- See Side 3 -
Describe the function of the Temperature Selectors. (-800)
AUTO - provides automatic temperature control for the associated zones. Rotating the control toward C (cool) or W (warm) manually sets the desired temperature.
OFF - closes the associated trim air modulating valve.
Describe the function of the Control (CONT) CABIN and Passenger (PASS) CABIN Temperature Selectors? (-700)
AUTO - automatic temperature controller controls passenger cabin or flight deck temperature as selected.
MANUAL - air mix valves controlled manually. Automatic temperature controller bypassed.
Explain the function of the ISOLATION VALVE Switch.
Bottom Line: Isolation Valve Opens if any 1 of the 4 Bleed or Pack Valves are closed.
"...Isolates the left and right sides of the bleed air duct during normal operations."
CLOSE - Closes Isolation Valve.
• Closes Isolation Valve if all BLEED and PACK Valves are Open.
• Opens Isolation Valve automatically if any BLEED or PACK Valve is Closed.
OPEN - Opens Isolation Valve.
Note: Auto functions via the position of the four corner switches (bleeds and packs). If any of the four corner switches are off, the isolation valve opens, otherwise, it is closed.
How does the APU Switch affect the Isolation Valve?
"Isolation valve position is not affected by the APU bleed air switch."
Show where External Air connects into the Bleed Air System.
What's the Caution about APU and Bleed Valve use?
"Do not select a combination that will back pressure the APU."
APU bleed valve must be CLOSED when:
1. ground air connected and isolation valve open
2. engine no.1 bleed valve open
3. isolation and engine no. 2 bleed valves open.
Note: DUAL will be illuminated with the #2 & 3 configurations above.
Note: APU bleed valve may be open during engine start, but avoid engine power above idle.
Note: There is also the possibility that APU Bleed Air backpressuring the 9th Stage Modulating and Shutoff Valve causing it to close.
- Schematic on Side 3 -
Describe the meaning of an illuminated DUAL BLEED Light.
"Restricted Bleed Configuration"
DUAL BLEED indicates:
1. APU bleed air valve open and engine No. 1 BLEED air switch ON, or
2. No. 2 BLEED air switch ON, APU bleed air valve and Isolation Valve open.
Explain the meaning of an illuminated WING-BODY OVERHEAT light.
Left Light indicates overheat from bleed air duct leak in:
1. left engine strut,
2. left inboard wing leading edge,
3. left air conditioning bay,
4. keel beam or
5. APU bleed air duct.
Right Light indicates overheat from bleed air duct leak in:
1. right engine strut,
2. right inboard wing leading edge or
3. right air conditioning bay
What's the note regarding single pack capability? (All Aircraft)
"A single pack in high flow is capable of maintaining pressurization and acceptable temperatures throughout the airplane up to the maximum certified ceiling."
Describe the associated alerting with an E & E bay over temperature on the ground.
If an over temperature occurs on the ground, alerting is provided through the crew call horn in the nose wheel well.
Recall the function of the RECIRC FAN.
The purpose of the Recirc Fan is:
1. Reduce AC System Pack Load and,
2. Reduce Engine Bleed Air demand
Air from the passenger cabin and electrical equipment bay is drawn to the forward cargo bay where it is filtered and re-circulated to the mix manifold.
Explain the function of the Pressurization Mode Selector.
AUTO - pressurization system controlled automatically.
ALTN - pressurization system controlled automatically using ALTN controller.
MAN - pressurization system controlled manually by outflow valve switch, both auto controllers bypassed.
Recall what cabin altitude will cause the Cabin Altitude Warning Horn to sound.
Intermittent Cabin Altitude Warning Horn sounds when cabin reaches 10,000 feet altitude.
Note: The only indication that Cabin Altitude has exceeded 10,000 ft is the Intermittent Cabin Altitude Warning Horn. Other than the indication on the Pressurization Indicator itself, there are no other associated lights (such as a MC/SA).
Note: The Cabin Altitude and Takeoff Configuration Warnings use the same intermittent tone when activated.
Explain the function of the cabin ALT HORN CUTOUT Switch.
Push - cuts out intermittent Cabin Altitude Warning Horn.
Explain the function of the Air Temperature (AIR TEMP) Source Selectors.
SUPPLY DUCT - selects appropriate zone supply duct temperature.
PASS CAB - selects forward or aft passenger cabin temperature.
PACK - selects left or right pack temperatures.
Explain the meaning of an illuminated PACK light. (-800)
PACK Light indicates:
1. Pack Trip due to Excessive Temperature, or
2. Failure of both primary and standby pack controls
During MASTER CAUTION recall, indicates failure of either primary or standby pack control. Extinguishes when Master Caution is reset.
- See Side 3 -
Explain the meaning of an illuminated ZONE TEMP light.
CONT CAB indicates:
1. duct temperature overheat, or
2. failure of the flight deck primary AND standby temperature control.
FWD CAB or AFT CAB indicates:
1. duct temperature overheat.
During Master Caution light recall:
• CONT CAB indicates failure of the flight deck primary OR standby temperature control.
• Either FWD CAB or AFT CAB indicates failure of the associated zone temperature control.
• Lights will extinguish when Master Caution is reset.
Note: Trim Air Valve closes.
Explain the meaning of an illuminated OFF (Schedule) SCHED DESCENT light.
OFF SCHED DESCENT Light
• Airplane descended before reaching the planned cruise altitude set in the FLT ALT indicator.
Note: If a flight is aborted in climb and returns to the takeoff airport, the controller programs the cabin to land at the takeoff field elevation without further pilot inputs. If the FLT ALT indicator is changed, the automatic abort capability to the original takeoff field elevation is lost.
Recall the function of the TRIM AIR Switch.
ON - trim air pressure regulating and shutoff valve signaled open.
OFF - trim air pressure regulating and shutoff valve signaled closed.
Explain the function of the (Equipment) EQUIP COOLING SUPPLY Switch.
NORM - normal cooling supply fan activated.
ALT - alternate cooling supply fan activated.
Explain the function of the (Equipment) EQUIP COOLING EXHAUST Switch.
NORM - normal cooling exhaust fan activated.
ALT - alternate cooling exhaust fan activated.
Explain the meaning of an Equipment Cooling Supply OFF Light.
Illuminated (amber) - no airflow from selected cooling supply fan.
Explain the meaning of an Equipment Cooling Exhaust OFF Light.
Illuminated (amber) - no airflow from selected cooling exhaust fan.
Selecting the alternate fan should restore airflow and extinguish the OFF light within approximately 5 seconds.
Explain the meaning of a RAM DOOR FULL OPEN Light.
Illuminated (blue) - indicates ram door in full open position.
Describe the function of the Engine BLEED Air Switches.
OFF - closes engine bleed air valve.
ON - opens the engine bleed air valve when engines are operating.
Describe the function of the APU BLEED Air Switch.
OFF - closes APU bleed air valve.
ON - opens the APU bleed air valve when APU is operating.
Explain the function of the Air Conditioning PACK Switch
OFF - pack signaled OFF.
AUTO - pack signaled to operate in the AUTO mode.
HIGH - pack regulates to high flow, provides maximum flow rate on ground with APU BLEED switch ON.
Negative Relief Valve Location?
Positive Relief Valve Locations?
D is 1 of them... There are 2. ...somewhere on the Aft Right Fuselage...
What is the Cabin Altitude at Max Certified Ceiling of 41,000ft?
What inputs are necessary if after takeoff a return to the field is required?