Chapter 3: Anti-Ice, Rain

Question 1

Explain the function of the WINDOW HEAT Test Switch.

Answer 1

OVHT – simulates an overheat condition.

PWR TEST – provides a confidence test to verify operation of the window heat system.

Question 2

Describe the operation of the four WINDOW HEAT Switches.

Answer 2

ON – window heat is applied to selected window(s).

OFF – window heat not in use.

Question 3

Explain which equipment is electrically heated with the PROBE heat switches ON.

Answer 3

• associated PITOT PROBE(s).
• TEMP PROBE (Total Air Temp probe). Not heated on the ground unless TAT Test switch is pushed.
• associated ALPHA VANE(s).

Note: Static ports are not heated.
Note: In AUTO, probe heat is powered automatically when either engine is running. We normally move these switches ON after engine start & AUTO during the Shutdown Checklist.

Question 4

Explain the logic of the wing anti-ice L VALVE OPEN, R VALVE OPEN and the engine anti-ice COWL VALVE OPEN lights on the overhead panel.

Answer 4

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. (switch OFF)

Note: Dim = valve agrees with switch and light nomenclature. (open)
Bright= valve in transit or opposite of light nomenclature. (closed)

Question 5

Explain the meaning of an illuminated OVERHEAT indication on the window heat panel.

Answer 5

An overheat condition is detected.

Note: OVERHEAT lights also illuminate if electrical power to window(s) is interrupted.

Question 6

Explain the meaning of an illuminated Probe heat light.

Answer 6

-The related probe is not heated.

Note: If operating on standby power, probe heat lights do not indicate system status.

Question 7

Describe the circumstances that would cause the illumination of a COWL ANTI-ICE light.

Answer 7

Overpressure condition in duct downstream of engine cowl anti-ice valve. (Not temp related)

Question 8

Describe the area of the engine that is heated when anti-ice is used.

Answer 8

Engine cowl lip.

Question 9

Describe the indication when engine anti-ice is in use.

Answer 9

TAI is displayed above N1 digital display.

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.

Question 10

Describe how setting takeoff power and liftoff affects the wing anti-ice system.

Answer 10

• Left and Right control valves close if either engine thrust is above takeoff warning setting or thermal switch is activated in either distribution duct. Switch remains ON.
• Switch trips OFF at lift-off.

Note: Wing anti-ice control valves open if thrust on both engines is below takeoff warning setting and temperature inside both distribution ducts is below thermal switch activation temperature.