Performance Question.. HELP
Thread Starter
Joined: Aug 2001
Posts: 1,430
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From: FL390
Performance Question.. HELP
Have got this performance question in some feedback and wondered if anyone could explain why the answer is the one it is
and not answer B
How must an aeroplane be flown to achieve maximum possible speed ?
a. Flown at a speed corresponding to Vmp
b. Flown with maximum thrust and minimum drag
c. flown with maximum thrust and maximum drag
d. flown as the best lift : drag ratio speed
answer given = C
Cheers, Spitty
and not answer B
How must an aeroplane be flown to achieve maximum possible speed ?
a. Flown at a speed corresponding to Vmp
b. Flown with maximum thrust and minimum drag
c. flown with maximum thrust and maximum drag
d. flown as the best lift : drag ratio speed
answer given = C
Cheers, Spitty
Last edited by spitfire747; 23rd September 2003 at 18:38.
Why do it if it's not fun?
Joined: Jul 2001
Posts: 4,782
Likes: 12
From: Bournemouth
The answer lies in the drag curve. The faster you go, the more drag you have (assuming you are above Vmd, which is a safe assumption since we're trying to go fast). Or, to put it another way, the more drag you have, the faster you must be going.
In level flight, thrust=drag, so maximum drag requires maximum thrust. Answer: C.
There is an argument that Answer B could also be correct. If, by "minimum drag", they are refering to devices such as flaps, air-brakes, etc, then you would want the aircraft to be clean, i.e. minimum drag, if you were looking for maximum speed. The question would be much clearer if it specified whether configuration changes are being considered.
FFF
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In level flight, thrust=drag, so maximum drag requires maximum thrust. Answer: C.
There is an argument that Answer B could also be correct. If, by "minimum drag", they are refering to devices such as flaps, air-brakes, etc, then you would want the aircraft to be clean, i.e. minimum drag, if you were looking for maximum speed. The question would be much clearer if it specified whether configuration changes are being considered.
FFF
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Joined: Mar 2003
Aviation Qualifications: PPL
Posts: 225
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From: London, England
