Hi Bob.
How are you.

I just have a few question. I just have some triple with question on the practice exams while i'm studying.

question form the book P 3.18 says.

*yellow band on carby air temperature gauge indicates ice is:

a) about to start . b) well advance c) possible. d) unlikely.
Could you explain it to me why the answer should be C.

*application of carburettor heat when ice is present on an engine fitted with CSU is accompanied by?
the answer is : an initial drop, then an increase in MAP at constant RPM.
but why the second chose wrong, it says : a drop in MAP with constant RPM .

...SNIP...

thanks..

EDIT: Hi Pilot, I have removed these other questions from your post as we do not want full questions posted here in the forums. Please see the posting guidelines here . Don't worry, Bob and I saw your questions and will get back to you shortly...

Hi Pilot,

Here you go....

Yellow band on carby air temperature gauge indicates ice is: possible.
The CAT gauge gives an indication of the risk of carburettor ice occurring. It doesn’t actually tell you if carbie ice is present or not. The yellow range warns you that carbie ice is theoretically possible at the current temperatures measured in the inlet manifold. Whether ice actually forms is dependant on the atmospheric conditions of the day.


application of carburettor heat when ice is present on an engine fitted with CSU is accompanied by: an initial drop and then a rise in MAP with a constant RPM
Applying carburettor heat will cause a reduction in the MAP but the governor will ensure the RPM stays the same. If ice was present, this ice will melt and clear with carbie heat on and the “throttling” effect of the ice will be relieved so the MAP will increase again to a reading you would expect from a normal engine with carburettor heat on. If no ice was present, the MAP will simply stay at a lower MAP.

Again, in both cases, the governor will keep the RPM constant.

Fuel injected versus carburetted fuel systems
Fuel injected systems are less susceptible to induction icing. Fuel injected engines do not have a carburettor and as such are not susceptible to fuel evaporation and throttle ice. They can still suffer from impact ice problems though.

Leaning mixture for a take-off from a high density altitude airport
If taking off at a high density altitude airport, the engine may need to be leaned out to get smooth running. If the mixture was left fully rich, the engine would not be producing expected take-off power so it would be a good idea to lean the mix somewhat and find a balance between power output and the cooling effect you get from a richer mixture which you will need during the climb.

Indicators for low oil quantity
Low oil quantity means the heat generated by the engine is having to be carried away by less oil i.e. that engine heat is being distributed to less oil and the oil will start to heat up despite the work of the oil cooler. Initially oil pressures will remain normal but hot oil is less viscous than cooler oil i.e. it is very runny and thin. The oil pumps expect oil to be within a certain viscosity range and they will soon find it hard to maintain pressure in the line with hot, thin oil. Therefore high oil temperature and low pressure are the best indication of abnormally low oil levels.

Initial effect of clear icing
Any ice/damage/contamination disrupts the smooth airflow over the wing so laminar flow and lift production will suffer. Anything that affects the amount of lift you need or the amount of lift you can produce is going to affect your stalling speed. Therefore, the initial effect of accumulating clear ice will be an increase in the stalling speed of the aircraft. Some of the other options may occur as the icing progresses but the question explicitly asks for the “initial” effect.

Cheers,

Rich

Hi Richard.

Thank you indeed for your clarification Rich.

Cheers,