Winter Operations

Aircraft Ice Protection Systems

Anti-ice Systems• Engine Anti-ice• Wing Anti-ice

Window Heat• Front Windows• Side Windows

Probe Heat• Operation• Indication

Overview

In this module we will review the aircraft systems used to prevent ice accumulation.

System Overview

The outboard three wing leading edge slats and the Engine inlet cowls are anti-iced/de-iced. Probes are heated to prevent icing. Ice probe detectors detect ice formation as well as automatically control wing and engine anti-icing.

Wing leading edge slats

Engine inlets

Probes

Window Heat

Wing and Engine Anti-Ice

Both wing and engine anti-ice systems use bleed air for anti-ice protection.

WAI WAI

EAI EAI

Engine Anti-ice Control

Nose cowl anti-ice valves allow engine bleed air to heat the engine inlet. A three position switch controls valve operation; OFF closes the valves, AUTO allows the valves to open when ice is detected and ON opens the valves.

OFF ON

Nose Cowl Anti-ice valve

Engine Ignition

Whenever the engine anti-ice is on, engine ignition automatically turns on as long as the engine start selector is in AUTO.

ON

Engine Anti-ice Exhaust

After heating the inlet cowl, the bleed air exhausts overboard through a vent on the bottom of the inlet cowling.

Engine Anti-ice Indication

Thermal anti-ice (TAI) indications appear below the N1 primary engine indicators when the nose cowl engine anti-ice valve is open.

Non-Normal Indications

Notice the top two lights are general indicator lights related to ice detection, even though they are above the wing or engine switches. The bottom valve lights are associated with the wing or engine depending on which switch they are above. Let’s have a closer look.

Icing Detector failure

Icing Conditions exist and one or both systems is OFF

Wing valve disagree lights

Engine valve disagree lights

Engine Anti-ice Valve Failure

The L(R) ENG ANTI-ICE EICAS message appears when the engine anti-ice valve is not in the commanded position. The valve may be failed open or closed. You use the non-normal checklist to find out the position of the valve.

Engine Anti-ice Non-Normal

Notice after determining if the valve is failed open or closed, you either prevent damage to the engine by avoiding high power settings if the valve is open when the temperature is above 100 or avoid icing conditions if the valve is closed.

Valve Open

Valve Closed

Open or Closed?

Valve Open

Valve Closed

Wing Anti-ice

The wing anti-ice system provides bleed air to the three outboard leading edge slats on each wing. Wing anti-ice can be operated in-flight only. It is inhibited on the ground.

Wing anti-ice valve

Three outboard leading edge slats

Wing Anti-ice Control

Wing Anti-ice Exhaust

Holes on the underside of the three outboard leading edge slats exhaust the bleed air.

WAI In-Flight Operation

When the switch is ON, or AUTO when ice is detected, and you are in-flight, the wing anti-ice valve opens and bleed air heats the outboard leading edge slats.

Wing Anti-ice Non-Normal (In-flight)

Notice, that if the valve remains closed, avoid icing conditions. If the valve remains open, then you have some after landing items to remove bleed air from the wing anti-ice duct.

Note: Run remaining normal checklists from this non-normal checklist because the after landing procedure contains new items

WAI Ground Operation

After landing, the wing anti-ice valves automatically close, even if the switch is in the ON position to prevent structural damage to the wing. If you see a wing anti-ice valve disagree light on the ground, turn the wing anti-ice switch OFF. If the light remains on, then accomplish the AFTER LANDING items in the wing anti-ice non-normal checklist.

Automatic Ice Detection

• The ice detection system controls the engine and wing thermal anti-ice valves if the switches on the anti-ice control panel are in AUTO.

• If the switches are in OFF, the ice detection system provides an indication of icing conditions.

• There are no indications of icing conditions if the thermal anti-ice valve control switches are in the AUTO or the ON position.

• System inhibited on ground.

The ice detection system controls the engine and wing thermal anti-ice valves if the switches on the anti-ice control panel are in AUTO. If the switches are in OFF, then the ice detection system provides an indication of icing conditions.

Ice Detector Failure

When the ice detector fails, you do not use the AUTO position. In other words, turn the switches either OFF or ON as required.

ICING DETECTED

• If the selector is OFF then the icing light alerts you to manually turn on the heat

• If the selector is in AUTO the icing light indicates a fault during icing conditions

Let’s review the special case where icing is detected and a valve is closed. You will get the associated icing message that will tell you to put the switch to ON. The EICAS message tells you which system is off.

Icing Dectected Valve Failure

If, after turning the associated ANTI-ICE SELECTOR ON, the valve remains closed, then the associated anti-ice valve failure EICAS message we just reviewed appears. Recall that checklist said to avoid icing conditions.

Window Heat Overview

• All flight deck windows are electrically heated for anti-fogging

• The forward windows are also electrically heated for anti-icing

• Conditioned air flows over the forward windows for additional anti-fogging– Independent of window heat

switch

The window heat system provides anti-fogging protection for all windows and anti-ice protection for the forward windows.

Conditioned air for Anti-Fog

Electric heat to anti-ice & anti-fog

Electric heat to anti-fog

Window damage

If the window arcs or is damaged you should remove power to the window. Remove power to the left forward window.

Outer Window Pain Damage

Window damage due to de-lamination or shattering of the outer pain is not a structural problem. There is no need to modify the flight profile.

Window Heat Non-Normal

The INOP light appears for an overheat or a fault. Turning the switch off for 10 seconds allows the window to cool. If the INOP light is still on when you turn the window heat back on, then there is a fault. Notice there are no operational limitations with the window heat off.

Probe Heat Overview

The four pitot static probes provide dynamic and static pressure for airspeed, altimeter, rate of climb instruments and the air data computers. The angle of attack probes send angle of attack information to the warning electronics unit. The total air temperature probe provides temperature for flight deck display and input to the thrust management and air data computers.

Probe Locations

Here are the probe locations on the left and right side of the nose.

Ice Detector Probes

Aux Pitot Probes

AOA Probes

Capt/FO Pitot ProbesTotal Air Temperature

Probe Heat Indication

Two pitot tubes, two angle of attack (AOA) sensors and a total air temperature (TAT) sensor are electrically heated to prevent ice formation. Probe heat is on when either engine is running, except the TAT sensor heats only while in-flight. Indication of a loss of probe heat is on the overhead panel.

Probe Heat Failure Indications

If probe heat fails to a single probe, then the individual probe message appears. If more than one probe is not heated, then the EICAS PROBE HEAT message appears.

Probe Non-Normal

As you know, erroneous flight instrument indications, such as unreliable airspeed, are likely with probe heat failures.

Pitot Heat Failure

Notice that for either pitot tube failure, you are unable RVSM.

Water and Waste Heat

The water and waste drain lines are also heated to prevent ice from clogging the drains. Now for a short quiz.

What does the icing light indicate in this situation?

Question

a) The wing anti-ice valve failed

b) Engine anti-ice failed

c) Icing conditions exist

d) The ice detector failed

Please select the best choice.

Question

Please select the best choice.

You are over the North Atlantic on a track and you see this EICAS message. What communication do you make?

a) Unable RVSM due equipment

b) None is required

c) We are having a problem with our instruments

d) Houston we have a problem

Question

a) True

b) False

Select the correct answer.

In this situation, you must avoid icing conditions.

Question

a) The left side window area will become cold

b) The left side window will not have anti-fog protection

c) The left side window will have anti-fog protection but not anti-ice protection

d) The left side window will be prone to shattering, you need to land as soon as possible

Select the best answer.

If you select this switch OFF, what happens?

Module Complete

You have come to the end of this module.