Using Reserve Fuel (737NG)
 

Hi guys..

I have a quick question

When landing, I have once or twice come across the message "Using reserve fuel" in the FMC, without being below the amount entered in the Perf page.

I.e. getting the message when landing with 2,6 with reserve fuel of 2,4. Message comes immediately after touchdown..

Thank You

Note that you may be carrying an amount of fuel greater than the reserve value you have supplied to the FMC but it may have calculated that the fuel quantity will be lower than that value by the time you are on terra-firma and hence the message.

Just a speculation. I am not too sure about this...

Thank you for your reply. But the message does not show until I am on terra-firma... And can read of the instruments (and FMC), that the fuel is more than reserve!

henrik - I saw it happen quite a few times and just ignored it. I have no explanation other than a glitch in the great god 'software'. If your concern is to do with data monitoring I would forget it. Your tech log shut down fuel should silence any excitement.

It is 10.8. So the "mistake" should be gone I guess

The USING RSV FUEL alert from the FMC indicates that the PREDICTED fuel remaining at destination is less than the reserves entry on the PERF INIT page during preflight prep.

That's the way I know it...

Then of course, touchdown is not exactly at your destination as far as the FMC destination position is concerned, is it!

EW73

- I think only the software coder/FMS spec writer can answer that. Since the FMS has the touchdown lat and long for the selected runway I had assumed it knew where it was. If it is computing fuel remaining at airfield datum...............chocolate teapot?

I was always told on landing the fuel "sloshes" around therefore shows an inaccurate reading until you've stopped! Always works out that way.