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## Incorrect fuel calculations in RPL/PPL study guide?

• jacobsa
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### jacobsa created the topic: Incorrect fuel calculations in RPL/PPL study guide?

I have the RPL/PPL Study Guide Volume 2, "last revised November 2018", and it
seems like every row but the first in the answers for exercise no 7 on page 211
are wrong.

For example, given:

* 30 mins fixed reserve at cruise rate required
* Start up and taxi allowance of 8 litres
* Variable reserve of 10%
* Cruise fuel flow of 44 lph
* EET of 57 minutes

Then we should expect the trip fuel is 44 * 57 / 60 = 41.8 litres, and the fiel
required at startup is 41.8 * 1.1 + 8 + 44 * 0.5 = 76 litres, correct?

But the book says the startup fuel is 90.5 litres. It makes different errors
(plus or minus) in different rows; only the first appears to be correct.

Is this an error in the book, or have I misunderstood the calculation? :-/

• bobtait
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### bobtait replied the topic: Incorrect fuel calculations in RPL/PPL study guide?

Perhaps you missed that the fixed reserve is different in each question. At 30 minutes at cruise rate you get a different fixed reserve in each case.

Question 1
35 x 206 ÷ 60 = 120.2 litres = 31.8 gallons
120.2 x 1.1 +17.5 + 8 = 157.7 litres = 41.7 gallons

Question 2
55 x 133 ÷ 60 = 121.9 litres = 32.2 gallons
121.9 x 1.1 + 27.5 + 8 = 169.6 litres = 44,9 gallons

Question 3
33 x 97 ÷ 60 = 53.4 litres = 14.1 gallons
53.4 x 1.1 + 16.5 + 8 = 83.2 litres 22 gallons

Question 4
44 x 57 ÷ 60 = 41.8 litres = 11.1 gallons
41.8 x 1.1 +22 + 8 = 76 litres = 20.1 gallons

Question 5
60 x 308 ÷ 60 - 308 litres = 81.5 gallons
308 x 1.1 +30 + 8 = 376.8 litres = 99.7 gallons

• jacobsa
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### jacobsa replied the topic: Incorrect fuel calculations in RPL/PPL study guide?

Those are the answers I got, so thanks for confirming. The book has different answers!

• bobtait
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### bobtait replied the topic: Incorrect fuel calculations in RPL/PPL study guide?

That's really strange, because those answers we taken directly from the book and there have been no changes to that page since the 10% variable reserve was introduced.

• jacobsa
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### jacobsa replied the topic: Incorrect fuel calculations in RPL/PPL study guide?

Wow, strange indeed. Here's photographic evidence! ##### Attachments:

• bobtait
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