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Exercise 5.11 answers

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Simathawk77 created the topic: Exercise 5.11 answers

Hi guys,

With my Perf exam fast approaching I'm slightly concerned about correct rounding/decimal places etc, especially as some questions will apparently require answers to be entered (vs multiple choice). I've read that the actual exam question may specify whether it requires whole number or not but I'm coming across a few instances in the textbook where answers don't make a lot of sense.
Re Ex 5.11, q 3, 6, 7, and 10, the answers provided on pg 214-217 have a ballast weight to be added, yet the final line of explanation has a figure which differs, albeit by only 1kg. Is this a typo or have I missed something?


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  • John.Heddles
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  • ATPL/consulting aero engineer
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John.Heddles replied the topic: Exercise 5.11 answers

There are various posts by Bob and Stuart on this subject for reading.

However, as a general rule -

(a) read the question and give the examiner what he is asking for

(b) carry calculation to, at least, one more decimal point that you require the final answer

(c) make use of the calculator accumulator to keep the precision running

(d) round off at the end of the calculation to the precision required for the answer.

(e) please avoid inappropriate precision eg a CG calculated to the 5th decimal of a mm is ridiculous when the accuracy of the starting data is around 5-10 kg (or considerably worse) and around 5-10 mm (or somewhat worse).

Engineering specialist in aircraft performance and weight control.

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