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Chintito
5th Jun 2004, 18:48
Pitch angle during decent at a constant mach number will:

a) Increase.
b) Decrease <--- answer given
c) Increase at first then decrease.
d) Stay constant.


Descending below the tropopause from FL370 to FL250 at a steady M#, then FL250 to FL100 at a constant CAS. What happens to descent angle?

a) Increase Increase
b) Increase - Constant <--- answer given
c) Decrease Decrease
d) Constant Constant


2 questions from the same schools feedback.

am i going wrong in my understanding of pitch angle and descent angle being the same thing ?

In a constant Mach descent the TAS increases which would mean the planes nose going upwards i.e angle reducing. thats been my understanding so far. Am i not seeing something?

Keith.Williams.
5th Jun 2004, 21:27
The problem with this type of question is that the answer all depends on how you interpret the terms "pitch increase" and "pitch decrease".

To carry out a constant mach decent in the ISA troposphere you must increase your CAS. If you are gliding you can only do this by pushing the nose down. So you must increase the nose down pitch.

But if you assume that nose level is zero pitch, then you might argue that nose moving up is an increase and nose moving down is a decrease.

You might however argue that increasing your nose down pitch is still an increase in pitch (albeit negative pitch). This appears logical in that the angle of the aircraft is becoming steeper.

The second problem is that different schools take different views. Some teach that pushing the nose down below zero in a glide is an increase in pitch. But others teach that this is a decrease in pitch.

This situation has been a problem for a long time, but like most such problems , each school simply assumes that the others are wrong. This does not help the students, but it does make the instructors feel more comfortable (superior).

I asked the CAA examiners to broadcast a definitive statement on this matter less than two weeks ago. Their reply was that "the existing questions are safe". When I pointed out this was not possible, they reiterated their statement that "the existing questions are safe within the contexts used" This may mean that other aspects of the options are sufficient to eliminate any ambiguity.

The examiners also said that they would take the matter to the SETs (the multi-national committees) to get a final answer.

All I can suggest is that if you find such questions in your exams you should look very carefully at all of the options. If you find that two or more options may be correct depending on the definition of "pitch increase" then you must select one option and lodge an appeal. You should also inform your CGI immediately so that he can also appeal.

The first of your questions should be appealed because options a or b may be true, depending upon the definition used.

But your second question should not be appealed because only option b can be true. This is becuase the constant CAS part of the descent requires a constant pitch attitude.

But if option b is true in question 2, then option a becomes true in question 1.

I appreciate the fact that this is all very frustrating, but it is often the only way of resolving this type of problem.