6 hours ago, spesimen said:

i still think finding a perfectly reproducable case on your system would be the first priority for identifying a solution

Bingo. Thanks Andy.

PFPX occasionally does not process the weather (winds aloft) which will cause the problems that folks are describing.  The problem is a PFPX problem.  What I do is compare the average winds generated by the AS16 Briefing with the average winds generated by the PFPX flight plan. 

I have found that PFPX and PMDG will be within about 5 minutes on long haul flights and the fuel consumption less that 5 percent of planned on an 8 hour flight.  YMMV

blaustern

 

1 minute ago, Bluestar said:

PFPX occasionally does not process the weather (winds aloft) which will cause the problems that folks are describing.  The problem is a PFPX problem.  What I do is compare the average winds generated by the AS16 Briefing with the average winds generated by the PFPX flight plan. 

I have found that PFPX and PMDG will be within about 5 minutes on long haul flights and the fuel consumption less that 5 percent of planned on an 8 hour flight.  YMMV

blaustern

 

What version of PFPX do you use? I use 1.19

10 minutes ago, PerWel said:

What version of PFPX do you use? I use 1.19

1.28

blaustern

8 minutes ago, Bluestar said:

1.28

blaustern

I tried a couple of the later versions but there was many strange problems, like calculations and so on. Do not recall exact but by going  back to 1.19 things started to make sense again.
And fuel is almost on spot now for my FSlabs 320 and all three latest PMDG planes. I'll stay on that one for now, works OK for how I use it.

About wind so have I seen different calculations when I forgot to start AS16 first and start PFPX, and when after started AS16 and done a refresh of weather and re-calculate flight, fuel and times have changed.

My experience anyhow. Try an older one if you still have it and can. Just to test.

 

As a guy who was educated as a scientist I fully understand the need for accurate data sampling to increase the resilience to bootstrap tests on the observation. Just can't provide the information for the moment, due to IRL duty. Stay tuned. I use only the 747-400 ERF.

I have encountered the same issue after using the auto-turnaround function and accelerating time via FSX (not auto cruise) while auto refuelling before the return flight. The first leg (Amsterdam to Nairobi) was fine and my arrival fuel was within a ton.

I am using AS16 weather and PFPX (AS16 weather) for planning. PFPX is normally spot on as it was on my first leg. 

 

 

Having had the experience with the earlier version of the PMDG 747, after installation and a quick look around inside the cockpit, I started the United 747 in a cold and dark configuration at KORD, planned the infamous KORD - VHHH route using PFPX, and then set the ZFW to 220 tonnes (485016.9 pounds), Crammed all the fuel i could get at that ZFW, and the FMS estimated 13,000 kgs+ upon arrival, with the STAR programmed, step climbs and wind data imported.

I have never made this flight with such load with enough fuel with the previous version, ever.

But surprisingly, the estimated fuel 13.5 hours into the flight is now up to 16.4 metric tonnes... something that made me think this much be a glitch!

Fuel burn seems adequate and PMDG must have made sure that the fuel burn is realistic.

I agree with what some guys are propsing that the sim hands momentarily without you seeing it, amounting to severl minutes per flight.

I've had that with the PMDG 777, and noticed while flying online that my timer is off by over 10 minutes after a few hours, while fuel burn remains constant, resulting in the loss of 10 minutes of fuel for nothing.

The second clue was those flying with me at slower speeds breezing through and passing me by tens of nautical miles, showing that i've been frozen many times.

I've managed to reduce that effect by finding the proper affinity mask and adding it to the sim .cfg file.

If you wanna see what's going on, fly real time (sim clock/cockpit clock = PC clock). leave it flying for a few hours and check if there is a time difference.

 

Cheers 

It's strange to talk about this, but i have the same issue, BUT... on both versions of B747. In "inverse" mode.

My example. I've just finished a flight from Frankfurt to São Paulo. 11 hours and 38 minutes (i always use real time, and flying in real time). My ZFW was 215.2 tons (metric) and my FOB calculated by PFPX was 123.9 tons (profile by Fly Precisely). Estimating São Paulo with 14.7 tons on board. Until here, pretty normal, i'm used to land with around 12 tons in T7, in real, despite the diferences. I've just arrived with 22.9 tons... 8 tons above the flightplan. If this happens in real, i could be promoted due to such a wonderful economic flight.

But.. If you do a short or medium flight (Dubai to Frankfurt, for example), the diference between the calculated by PFPX and the FOB on airplane is 500 kilograms more or less... In this case, extreme accurate.

This behavior is also noticeable using the "Old" B747.

48 minutes ago, Renato Roberto Dos Santos said:

I've just arrived with 22.9 tons... 8 tons above the flightplan. If this happens in real, i could be promoted due to such a wonderful economic flight.

Or blamed for having taken too much fuel which is a waste of weight and fuel consumption in turn. 

I have done a couple of 8-10h flight with the -400F (GE), -400M (GE) and -400 (RR), with a various range of ZFW, planned flight with PFPX 1.28 with AS16 and never got more than 1 or 2 tons difference at arrival between the flight plan ROB and the actual ROB. I have seen the predicted ROB on the FMC changing for a couple of tons too during some flights but at the end, at landing the ROB was always consistent with the flight plan.

18 hours ago, Renato Roberto Dos Santos said:

I've just arrived with 22.9 tons... 8 tons above the flightplan. If this happens in real, i could be promoted due to such a wonderful economic flight.

But.. If you do a short or medium flight (Dubai to Frankfurt, for example), the diference between the calculated by PFPX and the FOB on airplane is 500 kilograms more or less... In this case, extreme accurate.

This behavior is also noticeable using the "Old" B747.

I have resumed the flight on the following day, and the FMC was still showing around 16.2 tonnes for the arrival fuel. Arriving into VHHH took a bit more power and i ended up touching down with 14.9 Tonnes (Good for such a long flight) and about 2 tonnes above the PFPX estimated figure.

Did you by any chance edit the Fuel Burn bias for your aircraft in PFPX? I kept the default (Blank) value for my calculation.

I used a fuel policy that I've created previously to use with the 777 with contingency fuel up to 20 minutes max.

I will experiment with shorter routes this weekend and see if I could get close to the estimations.

It was fun flying the queen after such a long time!

Has anyone found a solution to the fuel problem? I am still suffering it. I can´t even make a flight without having this issue.

I don't have any problems with fuel usage. I use SimBrief for planning and the results are always accurate. Looks to me like PFPX is the problem.

On 6/26/2017 at 7:33 PM, tatin said:

Has anyone found a solution to the fuel problem? I am still suffering it. I can´t even make a flight without having this issue.

I wasn't having this problem, until yesterday when ONCOR shut off the power to do some maintenance. NO words can express HOW furious I am right now as ALL I want to do is be able to enjoy My flights. I was nearing the end of a PERFECT 15 hr flight, from Sydney and was finally back over Texas Soil headed to DFW.

I'm using FSX real world weather and it's done this 2/2 flights since yesterday morning.

I set the cost index to 34, Cruise alt was FL345. from take off to FL200 I was climbing at 1800fpm, then dropped to 1500 until FL250, then 1000 until FL300, then 500 after that. I found Myself at 24% fuel left just south of hawaii.

Unlimited fuel is not an option as My flights are all tracked.

1 hour ago, Cory Collier said:

I set the cost index to 34, Cruise alt was FL345. from take off to FL200 I was climbing at 1800fpm, then dropped to 1500 until FL250, then 1000 until FL300, then 500 after that. I found Myself at 24% fuel left just south of hawaii.

Sounds like a planning/understanding issue.

1. Nobody cruises at FL345 - ever.
2. Decreasing VS is normal for a heavy load.
3. 24% according to what? FSX or something else?