Anti-ice, Rain

Question 0

Describe the operation of the four WINDOW HEAT Switches.

ON
OFF

Answer 0

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

OFF – window heat not in use.

Question 1

Explain the function of the WINDOW HEAT Test Switch.

 OVHT
 PWR TEST

Answer 1

OVHT – simulates an overheat condition.

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

Question 2

Explain what equipment is electrically heated with the PROBE HEAT switches ON.

Answer 2

• Pitot probes.
• Total Air Temperature probe. (not heated on the ground unless TAT Test switch is pushed, may be tested on the ground with the probe heat switch off)
• Alpha vanes.

Note: Static ports are not heated. Note: There is a -700, -800 retrofit in progress that replaces the OFF position with AUTO. In AUTO, probe heat is powered automatically when either engine is started. Preflight and after start procedures will not change. We will move these switches to ON after engine start and to AUTO during the Shutdown Checklist. All -900 aircraft have the AUTO function.

Question 3

Explain the logic of the blue wing and engine anti-ice lights on the overhead panel.

Bright
Dim
Extinguished

Answer 3

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)

Question 4

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

Answer 4

An overheat condition is detected.

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

Question 5

Explain the meaning of an illuminated PROBE HEAT light.

Answer 5

The related probe is not heated.

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

VOL 2 / 3.10

Question 6

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

Answer 6

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

Question 7

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

Answer 7

Engine cowl lip.

Question 8

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

Green
Amber

Answer 8

TAI is displayed above N1 digital display.

(Green)– cowl anti-ice valve is open.

(Amber)– cowl anti-ice valve is not in position indicated by related engine anti–ice switch.

Question 9

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

Answer 9

• 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.