View Full Version : Min TO Fuel and unusable fuel

mona lot
1st Mar 2009, 19:42
Our company CFP calculates minimum TO fuel including 30 min final reserve in ISA condtions etc. There is no account for unusable fuel. So if we land with Final reserve fuel we would have considerably less than 30 min holding available.

Why does the final reserve not take into account the unusable fuel? Is this normal?

1st Mar 2009, 21:19
What aircraft type are you refering to?

When useable fuel is exhausted, what will the fuel qty gauges say? I would have thought that they would be calibrated to read zero.

1st Mar 2009, 21:23
Declared empty (operating etc.) weights (from the load data sheet - or whatever named document you might use) include unusable fuel. When you add in your tanker-delivered 20,000 lb, that's all usable unless you are starting from a bone dry aircraft.

As an aside, be aware that unusable fuel is a flight test determined quantity and, generally, is not the same quantity as you might get by draining the aircraft on the ground ...

1st Mar 2009, 21:44
Unusable fuel is included in the dry op mass.

mona lot
3rd Mar 2009, 22:58
What aircraft type are you refering to?


Does zero on the flight deck fuel guages include unusable fuel?

4th Mar 2009, 09:25
Sorry mate, dunno. Im not a 73NG pilot.

4th Mar 2009, 12:18
I am curious as to where you are getting information that the CFP is not accounting for unusable fuel.

Unusable fuel is exactly that, unusable and is not, by certification standard on FAR 25 aircraft to be displayed on the fuel quantity indicators. The exact process for determining the unusable fuel is not perfect, but also defined.

The CFP in all the flight planning systems I have looked at does not in any way consider unusable fuel and plans for Final Reserve to be usable fuel. So if you land with Final Reserve in theory it is all usable. In practice we can all accept that 100% of fuel on an aircraft is not usable and no prudent pilot would ever assume that you can take the quantity all the way to zero.

4th Mar 2009, 13:13
The only time unusable fuel may be indicated on a PLOG is via an F-3 message relating to tankering do to an MEL or DDPG item relating ot the fuel system.

4th Mar 2009, 13:15
Captjns, thanks for adding that item.

However, it is still considered unusabel and cannot be considered by the Flight Planning system for any reason.

4th Mar 2009, 13:18

You are one hundred percent correct. It was merery a message to crews when appropriate that such fuel can not be considered as flight plan fuel.

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