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PPL Video Lectures (10 Jul 2020)

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× Welcome to the CPL Performance question and answer forum. Please feel free to post your questions but more importantly also suggest answers for your forum colleagues. Bob himself or one of the other tutors will get to your question as soon as we can.

Maximum holding time

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lucasgozzard created the topic: Maximum holding time

Hi Bob,

I'm unsure as to how the answer is 51 minutes in the attached question. Are you able to explain?

My methodology was as follows:

1. Calculate flight fuel (Total distance x Fuel Flow/GS) = 500 x 28/180 = 78 gal
2. Calculate minimum fuel reqd with that flight fuel required = 78 x 1.15 + 15 + 3 = 108 gal
3. Actual fuel on board at startup = 125 gal. So, 125 - 108 = 17 gal margin
4. Maximum holding time = 17 / 17.2 = 59 mins

Lucas.
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Kaos replied the topic: Maximum holding time

The new CAAP has come into effect meaning 45 mins at 10% which changes things a little too

It looks like they used the 28GPH fuel flow to get the 51 mins. I get around 87 too
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lucasgozzard replied the topic: Maximum holding time

Hey mate,

Yeah I wasn't sure if the questions had been updated with new requirements. Stuart is still working through it. Not sure why they used 28 GPH for the holding as the supplement says holding is at 35% power?
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bobtait replied the topic: Maximum holding time

I can see nothing wrong with your working. 59mins is correct. I guess you would still have to choose 51mins since it is the only answer given that is correct. Also, if you use the new 10% variable reserve requirement, the answer comes out to 74 minutes which would still make 51mins the only choice.
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lucasgozzard replied the topic: Maximum holding time

Thanks Bob!

Unless the question stipulates a certain power setting for holding for the Echo, do we refer to the Echo datasheet where it says holding power is at 35%?

Cheers.

Lucas.
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bobtait replied the topic: Maximum holding time

No. The Echo data I have given will not be available in the exam. However, the examiner will have to give you any power settings and fuel flows with respect to holding. Also, you won't have to look up TAS tables or fue flow tables - all of that sort of information will be given in the text of each question.

Bob
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lucasgozzard replied the topic: Maximum holding time

Ok great. Thanks for clarifying Bob!

Cheers.

Lucas.
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