Min TO Fuel and unusable fuel
Thread Starter
Joined: Sep 2008
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From: The Middle East
Min TO Fuel and unusable fuel
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?
Why does the final reserve not take into account the unusable fuel? Is this normal?
Fleet Manager
Joined: Apr 2001
Aviation Qualifications: ATPL
Posts: 7,447
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From: various places .....
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 ...
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 ...
Joined: Dec 2000
Posts: 141
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From: Canada
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.
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.
