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About Flap extension reduce the stalling speed

  • Mido
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Mido created the topic: About Flap extension reduce the stalling speed

See the pic as attached,
I got confused, why "flap extension" is incorrect for the question?
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  • John.Heddles
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John.Heddles replied the topic: About Flap extension reduce the stalling speed

A silly question - the answer to which revolves around logical semantics rather than anything of direct interest to the pilot.

Often, this sort of question is better attacked by looking at the basics of the question, then the alternatives and then the details of the question.

The question has something to do with stall speed variation with an increase in several parameters, so first off let's consider each alternative - an increase in

(a) power will decrease stall speed

(b) flap extension will decrease stall speed

(c) load factor will increase stall speed

(d) ambient temperature isn't going to do much at all to the stall speed

(e) aircraft weight will increase stall speed.

Looking back to the question, it asks which of the alternative parameters, when increased, will not increase the stall speed.

Now, that could mean one of two things - we are looking for an alternative/alternatives which

(a) causes the stall speed to remain the same only, or

(b) causes the stall speed either to remain the same OR decrease.

The question doesn't either implicitly or explicitly tell you which alternative is expected by the examiner which is why I suggest that it is a silly question and poorly defined.

Looking back at the answer alternatives,

(a) if our interpretation is (a), above, viz., the stall speed does not increase but remains the same, the answer is temperature Very clearly, from the information given with the answer, this was the interpretation adopted by the particular examiner on this occasion.

(b) if our interpretation is (b), above, viz., the stall speed does not increase but either remains the same or reduces, the answers will be power, flap, and temperature. Note that, if your preferred answer were flaps only, you are setting yourself up for a fail - you must, necessarily, include the other two options to be consistent in your reading of the question.

Which alternative is correct ? Beats me. The examiner could, very easily, have avoided the semantic difficulty by stating his requirement explicitly rather than leaving it to a confused guess.

Unless Bob indicates that the examiner is likely to ask such foolishness, in which case - quite obviously - you should learn and know the examiner's semantic expectations, I would just shrug your shoulders on this one and move on to the next question .... Main thing is that you understand how to go about isolating incorrect, as against potentially correct, answer alternatives.

Engineering specialist in aircraft performance and weight control.
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bobtait replied the topic: About Flap extension reduce the stalling speed

I agree with John. It is a silly question. However, would you believe something like it was presented in a CASA exam. A common comment I get from students regarding the CASA Aerodynamics exam is, "I spent a lot of time trying to work out just what the examiner was saying".

I included the question ( and one or two others like it) as a warning of what to expect.

If I told you that I am not a person who does not live in Brisbane, what would you take it to mean?
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