Hi,I get this message "using rsv fuel" upon loading all take off data into the FMC.Why?(In the FMC I enter all info required including of course adequate fuel quantity for my flight) Thanks,Christos

This means the fuel you've entered in the reserves section on the init data page is the same as the total fuel in the tanks.

Your estimated remaining fuel at destination is lower then FMC's reserved value. You can go back the PREF page and change the RESERVE.Next time, take some extra fuel :)

Your estimated remaining fuel at destination is lower then FMC's reserved value. You can go back the PREF page and change the RESERVE.Next time, take some extra fuel :)

That would throw up a Insufficient fuel message

hhmmm Interesting... I never got the "Insufficient fuel" msg... only "using rsv fuel".

Using rsv fuel is when the fuel remaining is less than what you have set as the reserve fuel in the init ref page

As far as I have learned. Using rsv fuel simply means that the airplane is going to dig into the reserve fuel entered into the fmc. So if you lower the reserve in the performance init page you could be able to fly without any further messages. The Insufficient fuel message is if the fuel onboard is not enough to reach the destination! I could be wrong :)

You've entered a value for reserve fuel at PERF FMC page, like 3.5 for example. According to FMC calculations, when you arrive at your destination, your remaining fuel will be less than 3.5, and youraircraft will be using your fuel reserves. (in this example) Simple like that.

FCOM v2 "The FMC continually estimates the amount of fuel that will remain when the destination airport is reached if the active route is flown. The CDU message USING RSV FUEL is displayed if the estimate is less than the fuel reserve value entered on the PERF INIT page. The CDU message INSUFFICIENT FUEL is displayed if predicted fuel at destination will be 2000 lb. (900 kg) or less."

FCOM v2 "The FMC continually estimates the amount of fuel that will remain when the destination airport is reached if the active route is flown. The CDU message USING RSV FUEL is displayed if the estimate is less than the fuel reserve value entered on the PERF INIT page. The CDU message INSUFFICIENT FUEL is displayed if predicted fuel at destination will be 2000 lb. (900 kg) or less."

Thanks for this post... Never got the 'insufficient fuel' message yet... This clears up the difference though...

Using rsv fuel is when the fuel remaining is less than what you have set as the reserve fuel in the init ref page

Blonde moment number 2?

That's correct though? So I'm assuming you're now having a blonde moment for thinking that's wrong.

FCOM v2 "The FMC continually estimates the amount of fuel that will remain when the destination airport is reached if the active route is flown. The CDU message USING RSV FUEL is displayed if the estimate is less than the fuel reserve value entered on the PERF INIT page. The CDU message INSUFFICIENT FUEL is displayed if predicted fuel at destination will be 2000 lb. (900 kg) or less."

Sorry quoted wrong bit...your first statement was wrng about insufficient fuel and setting reserve at same amount as in tanks.The quote above is correct statement to answer the ops question - is fuel figure at dest is going to be beneath the figure he set in reserve, but isn't such that it will genererate an insufficient fuel as it still more than 900kg.Of course to de blonde you it could be because he set reserve at same amount as he as onboard - which would generate that, but doubt that was the case.Common error here is where people mix up kgs and lbs especially when setting smaller values as they look less out of place.