737 Anti-Ice Flashcards
What is the function of the WINDOW HEAT OVHT test switch?
How about the PWR test switch?
Simulates an overheat condition
Verifies operation of the window heat system.
Which equipment is heated with the LH or RH PROBE heat switches on?
Associated PITOT PROBE, TEMP PROBE, ALPHA VANE
Static ports are not heated.
In AUTO the probe heat is automatically powered when either engine is running. We normally move these switches to ON after engine start and to AUTO during the Shutdown Checklist.
What is the Logic behind the Blue Valve lights?
Bright - related anti-ice valve is in transit, or anti-ice valve position disagrees with related ANTI_ICE switch position.
Dim - Related anti-ice valve is open (switch ON)
Extinguished - related anti-ice valve is closed
What does the OVERHEAT light on the window heat panel mean?
Either the window is overheating or electrical supply to the window has been interrupted.
What is meant by an illuminated probe light?
Can the probe status lights be relied upon when on Standby Power?
The related probe is not heated.
Note: No, If operating on standby power, probe heat lights do not indicate proper system status.
What would cause a COWL ANTI-ICE light to illuminate?
Overpressure condition in duct downstream of engine cowl anti-ice valve. (Not temp related)
What are the indications on the engine instruments when engine Anti-ice is in use?
TAI green - cowl anti-ice valve is open
TAI amber - cowl anti-ice valve is not in position indicated by related engine anti-ice switch.
Describe how setting takeoff power and lift-off affects the wing anti-ice system.
- when the throttles are advance beyond the takeoff warning setting the wing anti-ice automatically shuts off but the switches remain in the ON position during the takeoff roll. When the wheels leave the ground the switches go to the OFF position.
- When on the ground both the Left and Right control valves close if either engine thrust is above takeoff warning setting. The valves automatically reopen if thrust on both engines is reduced and both temperature sensors have cooled down. Switch remains ON even if valves close under these conditions.
If Wing Anti Ice is turned on when on the ground is there a danger of overheating the wing leading edges?
No, there is a thermal detection switch that will close the control valves so that no heat can get to the inboard leading edge slats.
What can the crew do to reset the window heat if there is an issue?
Turn the affected window heat switch off and then on again.
When is the temperature probe TAT heat test performed?
It is not usually performed by the crew but is a maintenance function.
