Insufficient Fuel Reading

[fautleyj 1]

Hi Folks. In my FS2004 747-400, I use a fuel planner. I load the correct fuel. My FMC says I will have 23,000 Lbs on arrival, yet I get a message in the FMC 'insufficient fuel', but there is enough fuel. Does anybody know why this message comes up please?

Thanks

John

[shamrockflyer 647]

This is a common issue with the PMDG 747. Its ok we all experience it...

[PHXMD-11 86]

 

 

My FMC says I will have 23,000 Lbs on arrival, yet I get a message in the FMC 'insufficient fuel',

 

If the FMS is indicating that you have an insufficient amount of fuel on board, you are dipping into your reserve fuel. Increase the amount of fuel on board.

[ajpongress 467]

Or lower the reserve amount in the CDU.

[Boomer 1,619]

It is actually looking at your reserve fuel setting, decrease it in the FMC.

[ajpongress 467]

That's what I just said.

[PHXMD-11 86]

 

 

That's what I just said.

 

It drills the point in further...

[Paul_Smith 92]

FMC USER’S MANUAL 12 - 21:

 

RESERVES: The reserve fuel weight is
displayed in line 4L. Prompt boxes alert the
crew that a reserve fuel weight in thousands
of pounds must be entered. If no weight is
entered, a default value of 4000 pounds will
be assumed.
The value entered for fuel reserves is used
by the FMS to determine an insufficient fuel
condition, and will also be used to calculate
performance predictions for the flight.

[GregL 26]

Either, as stated above, the reserves are too high or, some extra reasons for the message can be (but not limited to):

 

1: You have set a lower cruise altitude other than that flight planned resulting in an increased fuel burn.

 

2: There is a discontinuity somewhere on the flight plan increasing the distance to be flown on the progress page.

 

3: There is a duplicated waypoint on the route which adds distance as the aircraft flies past and then wants to route back to the errant waypoint.

 

4: A waypoint is in the wrong position eg. 54S instead of 54N.

 

This is why we always check through the route thoroughly before take off and correlate the flight plan distance against the FMC calculated distance and ensure any errors are accountable. Generally the aircraft will be +/- 25 Nm.

 

Upshot, check the distance on the progress page, if it's wrong you have a flight plan error, check the planned cruise altitude and stick to it. Otherwise reduce the figure in the reserves box in the FMC as detailed above.

[scandinavian13 5,192]

 

 

Does anybody know why this message comes up please?

 

In addition to the other responses (with the exception of Post #2, as this is not an FMC issue, it is one of data entry or planning), you should take a glance at the Cruise/Fuel Planning chapter of the manuals.  It describes how to properly plan your fuel for your route, and what the different values mean.

 

As many have noted here, it seems you've entered a reserve value that's higher than it should be.

 

In plain English, the reserve fuel is the amount of fuel that you are telling the FMC that you will not be using for the planned route of flight.  It is being set aside for abnormal situations, particularly for any possible legs after the planned route of flight.  If the FMC notes that you will not be able to get to the destination without cutting into the amount of fuel you said you were setting aside:

*BING* INSUFFICIENT FUEL

 

Why?  Because you need to know that you're off plan, and must consciously do one or two things:

Ensure the aircraft is in its planned econ configuration (this should be the same configuration you planned your fuel for - altitudes, cruise speed, etc); or

If you're sure you're operating the aircraft as the fuel plan dictates, then you need to consciously understand you will now reach your destination with less fuel.  As such, you can go to the INIT page and lower the reserve amount to clear the message.

 

In the United States, as a US operator, the latter does not force you to divert to an alternate, though you should be increasingly aware of how much extra time you have in case something happens at your planned destination.  If you reach it, but have to go somewhere else, your options have become increasingly limited, depending on how off your fuel calculations were.

 

 

 

This is a common issue with the PMDG 747.

 

Please be careful, either in your wording, or your assignment of blame.  This is not an issue with the plane, rather it's an issue with the person properly planning or entering the right values.

 

If you were going for "it's a common question," then you are correct.

[shamrockflyer 647]

Please be careful, either in your wording, or your assignment of blame.  This is not an issue with the plane, rather it's an issue with the person properly planning or entering the right values.

 

If you were going for "it's a common question," then you are correct.

My apologies on that part... 

 

There's me thinking it was an error as I haven't got that message up until recently. Guess I will have to read back over the manuals and reconfigure my brain to the 747  -_-

[scandinavian13 5,192]

 

 

My apologies on that part... 

 

No apologies necessary, really.

 

It's a common message in most FMC-equipped aircraft (those that include fuel tracking, anyway), and the message means the same thing for all of them - Boeings, Airbuses, and the rest.

 

Just means you need to plan your fuel better, and/or give the FMC the proper data.

[fautleyj 1]

Thanks Guys, for your time and effort, and the great advice.

Regards

John