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MD12
17th Jan 2010, 17:08
Hi,

Im reviewing some stuff, to keep my "atpl knowledge" up to date, and just got stuck on the following exercise:

The second segment requirement for a twin engine aircraft is 2.4%. If the total drag of the aircraft at V2 is 18500lbs and each engine produces 22000lbs of thrust. The maximum permissible take-off weight will be:

a) 145800 lbs
b) 1062500 lbs
c) 91700 lbs
d) 90300 lbs

According to the book, the correct answer is A, but still I cannot get it (I know, monkey stuff).

Climb gradient=(T-D)/W

so,

Climb gradient = (44000-18500)/W

2.4/100=25500/W

From above: W=1062500 (answer b)

What am I doing wrong? Your help is really appreciated. Enjoy the rest of the weekend.

WaterMeths
17th Jan 2010, 17:22
Hi...

Try the calc again with the single engine (i.e. 22000 lbs thrust) as the 2.4 gradient is to be achieved with an engine failure.

Cheers

WM

MD12
17th Jan 2010, 17:26
Thank you! I found it out myself and was just about to post the solution. You are absolutely right.

Now its all clear. Tnx