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## CPL Performance Finding The Maximum Fuel

• Posts: 45

### Sofeopka created the topic: CPL Performance Finding The Maximum Fuel

CPL Performance Finding The Maximum Fuel

Greetings all,

I'm referring to CPL Performance Book (most recent edition) Page 143 and page 13 of the supplement.

I have included photos of the pages.

I'm not sure if I'm reading too much into it, for the practice exercises in the book, but don't want to "not read enough into the questions" when I sit the exam.

In the example the answer is given as 121 gallons. I understand this answer and how it is derived.

However, according to the data on aircraft fuel capacity (page 13 supplement) the Empty A/C includes 10 gallons of unusable fuel.

In the example the question is asking find the maximum full that can be on board at start-up.
So if 10 gallons of fuel has already been incorporated into the listed Empty A/C weight of 1980Kg given what the question is asking should the answer not be 131 gallons?

I think I'm reading too much into it maybe.

##### Attachments:

• John.Heddles
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• ATPL/consulting aero engineer
• Posts: 477

### John.Heddles replied the topic: CPL Performance Finding The Maximum Fuel

In Australian practice, per CAO 100.7, unusable fuel is part of the empty weight and plays no further part in pilot calculations. As an aside, in some aircraft, some of the unusable may be able to be used in cruise but that is a sideline issue and the declared unusable is not able to be planned for consumption.

As a general consideration, any request for "total" fuel should be read as "usable" fuel unless the question makes it painfully obvious that the total fuel, including unusable, is required. There really should be no occasion when this occurs as it doesn't make all that much sense.

Engineering specialist in aircraft performance and weight control.

• Posts: 45