Hey!

 

I keep getting an FMC message that I am "Using RSV Fuel" when I have plenty of gas. Anyone?

 

Thanks in advanced!

 

 

I keep getting an FMC message that I am "Using RSV Fuel" when I have plenty of gas. Anyone?

 

Add more fuel or lower your reserve amount. If you receive that message, you are eating into your reserves.

The message isn't related to the amount of fuel you have on board now, that is to say, you actually are using reserve fuel now, no, it means that according to the fmc predictions you may start eating into your reserves by the time you are overhead the destination

When you are setting up the flight in the Perf Init page, there is a section to enter your reserves.

 

When the FMS is flying along and predicts that you will arrive at your destination with less fuel than the number you entered into this section, it will throw up that warning.

 

If you have 6000kg of fuel on board and are going to use 3000kg to get to where you want to go, you might be tempted to put 3.0 into that reserves number.

 

If you get a headwind which means that you will now arrive with 2900kg, the warning will come up.

 

2 options, Load more fuel to begin with, or reduce the number you enter into the FMS reserves to 2.8 or something.

While the above answers are technically correct, I want to provide more detail as to what's happening.

 

This fuel message is indicating that your fuel plan is...well...not going to plan.

If you get this before departing, it means that you should contact dispatch and verify the numbers.  In your case, it means you need to recalculate how much fuel you think you are going to need (see tutorial #2).  If you get this in the air, it means that you should take a look at the en route wind and destination weather so you can determine if it is safe to proceed to the destination with less than what you had originally set aside as reserve.

 

Remember that reserve fuel is the fuel that is meant to be set aside for various reasons: you can't land at the destination for weather/wind/demand and must fly elsewhere, extra fuel for other contingencies (en route holding), and so on.  The main point is that you have route fuel, which is the fuel to get you from departure to destination; and you have reserve fuel, which is extra fuel for those reasons I've already mentioned.

 

In order to make it easier to enter, and less susceptible to fat-fingering, the aircraft calculates how much it has on board, and then all you do it tell it how much you are planning on not using between the two airports (the spot where you can enter your total fuel is there in case you want to run your numbers, but the fuel truck hasn't shown up yet, as an example - it does not need to be entered if there is a calculated value there).  If it detects that you will be cutting into the amount of fuel you've told it that you will not touch, it will alert you (as you've noticed).  You could be only using 0.1 of it, but it's going to let you know that your numbers are off.

 

Now, in order to get it to stop telling you about it, you can use what they've mentioned above, though I'd advise a different strategy:

The point of the alert is to let you know that the fuel numbers are off (either by poor planning, or unforeseen circumstance).  The alert is still worth having, so if you get the alert and decide to press on to your destination, set the reserve to a lower amount as determined by your PROG page.  If you get the alert, look at the PROG page.  If your original reserve amount was 5, and it now says you'll be landing with 4.9, you should set your reserved to 4.8 or 4.9.  This way, you'll get alerted again if the prediction changes.  Setting reserves to 1 or 0 (or some other random number) basically renders the alert worthless.  What if you encounter stronger headwind in 30 minutes that wasn't planned?  What happens if there's really a leak somewhere, and that's why the original alert popped up?

 

Part of being a pilot isn't just sitting up front making the plane do what it's supposed to do.  It's about knowing what to do when it's not - or won't - do what it's supposed to do.  Don't put yourself in a bad spot by either lacking that knowledge (proper fueling and reserve values), or not utilizing the tools in front of you to their fullest potential (FMC fuel planning, and other pages; in addition to its alerting features).

 

 

 

You should take a little more of a look at Tutorial #2, because it gets into fuel planning.  It's very helpful.

The point is the FMC needs to be told how much fuel you want in the tanks before it tells you something. Generally this is used to prompt you into a decision to do something, like divert, call a fuel emergency, or similar. As such if you plan to arrive with enough fuel to hold for an hour plus enough to divert to an airport 20 minutes away and a little extra as a contingency of say, 30 minutes.. then you enter the value of the "Divert + contingency" and NOT the "enough to hold".

 

This is because the "hold for an hour" is actually part of your fuel plan (probably put there due to notams or expected high volumes of traffic and not carried every day just incase the other 1 airplane that operates to boondocks faraway airfield on Tuesdays happens to show up 2 hours early and gets in front of you, causing you a 5 minute delay.)

 

The FMC reserves number should be set so that the alert only comes on when the fuel plan means that you will be down past that "Diversion & contingency" fuel level if you flew the whole LNAV track to the runway. And if that is the case, something may need to change (ie either the airport you are going to land at, or the squawk code to 7700 or something).

 

 

This is because the "hold for an hour" is actually part of your fuel plan

 

haha - like at sEWaRk...