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davidzill

"Insufficient Fuel"

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Started flying the 777. I use the PFPX/Topcat/ASN Real weather combo. When planning flights, all seems well until I input the route into the FMC and activate it, at which point I quickly receive a prompt "Insufficient Fuel" message on the FMC display, followed by the same warning message on the EICAS. This happened while planning a flight from KSFO to VHHX. I didn't take the chance of executing the 15+ hours flight with those warning messages, so I planned a much shorted flight; KSFO to KDEN. The same message appeared again, however I checked the 'Progress' page on the FMC which indicated I would land with all of my 12,000lbs of reserve fuel. Is this a documented bug, or must I change something?

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Started flying the 777. I use the PFPX/Topcat/ASN Real weather combo. When planning flights, all seems well until I input the route into the FMC and activate it, at which point I quickly receive a prompt "Insufficient Fuel" message on the FMC display, followed by the same warning message on the EICAS. This happened while planning a flight from KSFO to VHHX. I didn't take the chance of executing the 15+ hours flight with those warning messages, so I planned a much shorted flight; KSFO to KDEN. The same message appeared again, however I checked the 'Progress' page on the FMC which indicated I would land with all of my 12,000lbs of reserve fuel. Is this a documented bug, or must I change something?

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Might have you forgotten to request and upload the appropriate winds that ASN created for you via the FMC?

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This happened while planning a flight from KSFO to VHHX.
This is essentially a westbound fight that will encounter strong headwinds, so even if you did what Stratox suggested you might not have enough fuel to complete the flight. PFPX might indicate you can make it on fuel but you need to make certain that all the data in PFPX agrees with the data for the PMDG T7 and what you enter into the FMC. Plus PFPX and the T7 don't do step climbs at the same time. I find that the initial altitude suggested by PFPX is almost always too high when compared to the FMC VNAV page 2 of 3 optimum altitude. PFPX is a good starting place but it is not the be all to end all.

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This happened while planning a flight from KSFO to VHHX
Which model of the T7 was this? What was you payload in pounds?

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WX data is loaded via FMC "Request." The KSFO-->VHHX flight had about 50,000+ of cargo. With some short-mid length flight experimentation, the insufficient fuel warning seems far inaccurate; I'd often times land with 12-15,000 lbs fuel on board. One thing I did take special note of is the difference in performance calculations between PFPX and the 777's FMC. During intermittent stages of flight, the 'Insufficient fuel' caution appears in yellow on the EICAS. I simply announce "Cancel EICAS" via FS2 Crew. At this point it is more or less an annoyance, however when planning a 20+ hour one way leg, I'm more than reluctant to commit to the flight with the message appearing during preflight.

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insufficient fuel
This warning is triggered when the estimated fuel at landing is less than the reserve figure entered on the PERF INIT page. See FCOM2, pages 11.32.5, 11.60.3 and 12.30.1.

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This warning is triggered when the estimated fuel at landing is less than the reserve figure entered on the PERF INIT page. See FCOM2, pages 11.32.5, 11.60.3 and 12.30.1.

 

Precisely.  I have had the same happen to me a number of times and recently discovered that reducing the value of the reserve amount stopped the issue.

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reducing the value of the reserve amount stopped the issue.

I don't know how you come up with the reserves but if you believe it is a valid figure, it should not be reduced to get rid of the warning. That aside, I do it from time to time. I get sick of looking at the message. The sim world is very forgiving. In the real world I think we would be looking for new jobs.

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I get sick of looking at the message

That's why I do it.

 

However, my default PFPX setting is to calculate the minimum allowable fuel needed for any flight. Changing this setting to Maximum allowable fuel will probably also avoid the message. (with all associated resulting weight implications)

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Precisely.  I have had the same happen to me a number of times and recently discovered that reducing the value of the reserve amount stopped the issue.

Thanks. This solved the problem.

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however when planning a 20+ hour one way leg, I'm more than reluctant to commit to the flight with the message appearing during preflight.

 

Thats really what the message is there for: should I continue or should I turn back?

 

Before I go into this, however, I must note that just because you do not understand a feature does not mean it is a bug.

 

Insufficient fuel means that, for the fuel numbers you have given the aircraft, the flight cannot be completed without dipping into your reserves. This suggests either you have not loaded enough fuel, or have misinterpreted the reserve value and have set it too high (or simply threw a random value in there).

 

I rarely, if ever get this message and I use PFPX. Sounds a lot like planning error to me. Sorry for the bluntness, but when "bug" gets thrown around, I need to be clear.

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rarely, if ever get this message and I use PFPX. Sounds a lot like planning error to me. Sorry for the bluntness, but when "bug" gets thrown around, I need to be clear.

Hi Kyle,

 

In my case I also use PFPX so I'm 'assuming' the reserve fuel value in the CDU is the final reserve amount within the PERF INIT uplink (which is a PFPX derived value?) I have never cross checked these figures though but will do on my next flight

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which is a PFPX derived value?

 

It's not. How do you suppose that PFPX data is getting into the the PERF INIT? There aren't any files saved out. The route is the route, and the weather is the weather.

 

Override the value with whatever value is planned on the paperwork.

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