Oral Prep - Anti-Ice Flashcards
What is the bleed air source for the wing and cowl anti-ice?
14th stage bleed air
With the APU deferred what procedures need to be used when operating in icing conditions?
Since both 10th and 14th stage bleed air cannot be extracted from the engine at the same time, if anti-ice has to be used for takeoff or landing, the unpressurized takeoff or landing procedure must be accomplished.
What is the difference between the Wing Anti-Ice switch NORM and STBY positions?
- NORM modulates the wing valve to maintain a constant wing L/E temperature
- STBY opens or closes the wing valve to maintain a lower L/E temperature
What does the red OVHT light in the wing OVHT/DUCT FAIL Switch indicate?
Associated with a EICAS warning message and indicates an overheat condition in either the left or right wing anti-ice duct.
Describe a satisfactory wing or cowl anti-ice test.
First flight of the day when both engines are operating:
* L and R 14TH STAGE bleed air CLOSED.
- L and R CLOSED lights come on and L and R 14TH SOV CLSD status messages come on.
* L and R 14TH STAGE bleed air OPEN.
- L and R CLOSED lights and L and R 14TH SOV CLSD status messages out.
* ANTI-ICE, LH and RH COWL switches ON.
- Check that both engines’ ITT indications increase.
* ANTI-ICE, WING switch NORM.
- Check that both engines’ ITT indications increase and N2 gauges amber band appears.
* 14TH STAGE ISOL switch OPEN.
- ISOL OPEN light and 14TH ISOL OPEN status message comes on.
* 14TH STAGE ISOL switch CLOSE.
- ISOL switch light and 14TH ISOL OPEN status message go out.
* ANTI-ICE, WING switch OFF.
* ANTI-ICE, COWL switch as required.
(Reference previous question) What causes the ITT to rise? What could prevent this from happening?
By bleeding air from the compressor section of the engine to supply the wing and cowl in this case, the amount of air passing through the engine is reduced resulting in an increase in ITT. If there is no increase in ITT the most likely cause is that the 14th stage bleeds are not opened or for some other reason the system is not allowing the high pressure air to go from the engine to the wing and or cowl
In the event of a wing overheat condition, in addition to completing the QRH procedure, what very important detail should be included in the write-up and the first question you expect Maintenance to ask you? Which side is it? How would you know?
Synoptic page
Why is this so important to Maintenance? The wing anti-icing system uses a single overheat loop in the fuselage and thermal sensors in the wing leading edges. The bleed air ducts are constructed of stainless steel, then insulated and encased in an outer cover for protection. Holes are drilled in designated locations through the outer cover with the overheat detection loop installed at those points in case of a leak. There are many of these detectors in each wing and each has to be checked to see if it is the one that triggered the warning. If they do not know which side caused the warning, there is a good chance they will ‘guess’ the wrong side, thus wasting time checking the good wing.
When are you required to test the crew oxygen mask? How do you complete the test? Is harness inflation part of the test?
How do you know the harness inflation worked? Why is this important? What is the purpose of the NORMAL / 100% MANUAL CONTROL LEVER (red tab) on the front lower right side of the mask and when would you select the 100% mode?
The crew O2 mask check is part of the Before Start Check. The inflation and deflation of the harness is what holds the mask in place and seals it against your face. Without this it will leak and will not seal out ambient air/smoke when set to 100%. In NORMAL mode it provides a mixture of ambient air with oxygen, much like the overhead passenger mask in the cabin. This would not be what you want with a flightdeck filled with smoke. The 100% mode provides nothing but O2 without any ambient air; therefore you are not breathing any smoke so long as the mask is properly sealed with a good harness.
What is the function of the wing OVERHEAT/DUCT FAILURE switch/light?
To allow for testing of the normal mode of the overheat system and to indicate an overheat condition in the wing leading edge (OVHT), to indicate a bleed leak (duct failure) in the wing left or right anti-ice ducts (DUCT FAIL).
