FMC Fuel Warning ?

[mbiggins 0]

Hi

 

Running PMDG B777 with FSX and fly regularly with a good general knowledge of the sim/aircraft.

 

For some reason I keep getting an "Insufficient Fuel" warning from the FMC. I have had this occur on short and long haul flights.

I always carefully calculate loads and fuel and I fly with real weather software. This has never happened before! I have noticed that if I turn off the fuel tank

cross-feed switches the warning resolves. This warning occurs prior to departure and continues regardless of my loads and fuel.

This is a new occurance that I have never experienced before after many hours in this sim.

 

Any ideas?

 

Thanks Marc Biggins

[PinkPony 171]

Hi

 

Running PMDG B777 with FSX and fly regularly with a good general knowledge of the sim/aircraft.

 

For some reason I keep getting an "Insufficient Fuel" warning from the FMC. I have had this occur on short and long haul flights.

I always carefully calculate loads and fuel and I fly with real weather software. This has never happened before! I have noticed that if I turn off the fuel tank

cross-feed switches the warning resolves. This warning occurs prior to departure and continues regardless of my loads and fuel.

This is a new occurance that I have never experienced before after many hours in this sim.

 

Any ideas?

 

Thanks Marc Biggins

 

 

1. Why are either of your crossfeed valves set to OPEN at any point? This is not required under any point during normal operation of the B777 (assuming no failures etc).

2. You mentioned real weather: Are you requesting/loading accurate en-route wind/temp data and descent winds? 

3. How are you determining the fuel figure which you believe to be sufficient for the flight? (Specifically, the TOTAL FUEL/RAMP FUEL figure which will see you arriving with more than the 'reserve fuel' figure entered on the PERF INIT page).

 

Remember the data the FMC outputs is only as accurate as the data that was inputted. Based on the ZFW/TOTAL FUEL/WIND (or lack thereof)/RESERVE FUEL, it is currently telling you that you will be arriving with insufficient fuel.

 

There are various other entries or lack thereof which could be resulting in a incorrect fuel at destination calculation (prediction).

 

If you plan 3-4 step climbs on a long haul and yet your FMC does not have a single populated step climb, it will be making a significantly less optimistic fuel at destination prediction than whatever you used to plan the flight and arrive at a required takeoff fuel figure. 

[mbiggins 0]

Thanks.

 

1, The open crossfeed valves may have been an inadvertent error on my part . I noticed when I closed them on the flight I am conducting now the error has resolved.

2. Yes on downloading en-route weather to FMC.

3. Fuel calculations have been calculated as mentioned and I have landed with plenty of reserve still showing a fuel warning . Oddly this has only just started happening over the last 4 flights.

$. Yes I let the FMC calculate my step climbs.

[jtsjc1 3]

Also check the cost index.

[downscc 1,327]

It's easier than all that... , just decrease the reserve fuel value on the PERF page. It is this value that triggers the advisory message.

 

It's normal for the first few hours of a long trip to underestimate fuel remaining on the PROG page if there are significant wind changes along the way. I've found the values usually converge as flight progresses. It's not a problem, the message is advisory only.