So this is my first flight with the PMDG777. I'm going from KJFK --> CYVR and inputed 11040lbs of fuel before takeoff. While i'm in cruise, I monitor the PROG page to see how much fuel I will have left at my destination and it keeps dropping. It dropped from 64 to 5 in a time frame of 2 hours~. I've asked many VATSIM users that fly the PMDG777 and they can't seem to figure it out. I dont suspect any fuel leak/dump because it doesn't give me any warnings. Has anyone had the same problem or knows the fix to this?

Thanks,

Bryan Cheung

Do you have flight level winds entered in the legs pages in the FMC so it can properly calculate fuel at destination?

This is the LEGS > RTE DATA page. http://gyazo.com/a121dada615f45ddffd69a17241a9256

The page in your screenshot does not shown if winds were entered or not. You need to click to the right of Wind Data Request on line 6. It will then say wind data requested. Next is Request Sent. When you receive the winds you see a message Load. Click to the right of that on line 6. When the light comes on above Execute, press that key.

 

If you have not followed this procedure you have no winds entered in the FMC.

In that case, Yes, I have flight level winds loaded. The fuel quantity still keeps dropping

And are they correct? I mean, have you crosschecked the winds in the LEGS page and made sure they roughly tally with the currecnt winds? Because obviously a 100kt headwind will greatly increase fuel consumption compared to calm winds aloft

I have monitored the forecast fuel remaining provided by the PROG page to actual fuel values in a PFPX flight plan for quite a few flights.  On some flights, the FMS forecast error diverges (becomes worse than predicted) and more likely it will converge (error starts large and gets smaller) and it all depends on actual winds verses forecast.  Conversely, I've had several RJAAKDFW flights where everything happened as planned, quite an experience for an experienced aviator.

 

My advice is to use a good flight planner instead of the FMS for long flights.  Update winds in the FMS at least once every six hours. Keep track of actual elapsed time vs. estimated at key waypoints (the time in the air is the primary determinate of fuel consumption).  Be ready to execute enroute diversions if the fuel required numbers at key waypoints or redispatch points are not satisfied.  Be careful during flight planning that you are using the best wind forecasts available, which often means resetting ASN from custom historical time to simulator time as required to get the desired forecast window.

So the problem is most likely headwind? I understand that you require more fuel into a headwind. I thought it was just a bug or something with the controls because it is my first time using the PMDG777 and I've had no problems with the PMDG737 in the past year.

Not contradicting Dan, of course, because he's made valid points as usual. I personally, however, have found PFPX to be extremely accurate and I mainly do flights from London across the atlantic. Presuming you're using ASN, Dan's resetting advice is very good. Also, there may be a discrepancy between real-world PFPX weather data and ASN data in PFPX, so make sure you have ASN weather selected in PFPX, otherwise you may find the calculated required fuel figure differs. I can't imagine the discrepancy is very big, but it could make a difference. Given the accuracy of PFPX, I would say there's something up with the winds that you're not quite getting, especially as there is no reported technical fault with the aircraft.

 

 

I personally, however, have found PFPX to be extremely accurate and I mainly do flights from London across the atlantic.

 

We agree, I guess I should have been clearer.  The converging and diverging values were those of the aircraft and not the flight planner.

 

 

 

I understand that you require more fuel into a headwind.

 

Sorta.  You are using more fuel because you are in the air longer and that is due to the headwind.  As far as your fuel rate lbs/hr is concerned, winds have no impact.  It's the hours that get you.

KJFK --> CYVR and inputed 11040lbs of fuel before takeoff.

This is obviously a typo. What fuel did you enter in the FMC?

 

 

It dropped from 64 to 5 in a time frame of 2 hours~.

Is this 64000 to 5000 and was the two hours real time or accelerated time?

 

Where do you get your weather from?

64000 to 5000 lbs/kg in two hours seems a bit excessive for unprecise fuel planning.

 

Which simulator are you using? If FSX, have you set AffinityMask in the fsx.cfg? Do you get freezes of a few minutes during cruise (sounds keeps running but sim seems frozen)? Because these freezes will have you end up with less fuel in the tanks each time they happen. Using the newest version of the T7 and AffinityMask should cure this issue.

 

 

So this is my first flight with the PMDG777. I'm going from KJFK --> CYVR

 

For your first flight, you should really be doing the tutorial. We (specifically Ryan) walk you through all of the main knowledge items that you need for flying the plane, in addition to more knowledge items to help you fly it better.

 

Tutorial #1.5 (on our website's downloads page) goes through a lot more background knowledge, some fuel planning, and the NATs. This, of course, goes into more advanced knowledge to help you get even more out of the 777.

 

Fly at least the first one and report back. While the fuel number will adjust as the flight goes on, it shouldn't be terribly significant as long as you're doing everything properly.

This is obviously a typo. What fuel did you enter in the FMC?

 

 

Is this 64000 to 5000 and was the two hours real time or accelerated time?

 

Where do you get your weather from?

Yeah my bad, it was a typo. I get my weather from ASN. I came to a final decision and concluded that it was the headwind that was causing really heavy fuel use.

64000 to 5000 lbs/kg in two hours seems a bit excessive for unprecise fuel planning.

 

Which simulator are you using? If FSX, have you set AffinityMask in the fsx.cfg? Do you get freezes of a few minutes during cruise (sounds keeps running but sim seems frozen)? Because these freezes will have you end up with less fuel in the tanks each time they happen. Using the newest version of the T7 and AffinityMask should cure this issue.

I use P3D. I do not get any freezes during cruise. I concluded that it was the headwind that was causing heavy fuel use.

For your first flight, you should really be doing the tutorial. We (specifically Ryan) walk you through all of the main knowledge items that you need for flying the plane, in addition to more knowledge items to help you fly it better.

 

Tutorial #1.5 (on our website's downloads page) goes through a lot more background knowledge, some fuel planning, and the NATs. This, of course, goes into more advanced knowledge to help you get even more out of the 777.

 

Fly at least the first one and report back. While the fuel number will adjust as the flight goes on, it shouldn't be terribly significant as long as you're doing everything properly.

Yeah everything is fine now. I think it was the headwind that was causing heavy fuel use. I'm currently making a hop from CYYZ --> VHHH with 272,420lbs of fuel and so far, its been stable. I'm halfway there too

I have found that, during more than 240 long haul flights, the PFPX fuel burn figures are extremely accurate, taking account of winds encountered en route. But you have to follow the described planning and flying procedures as has been mentioned.

HTH