tatin

747 V3 Fuel consumption problem

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Hi,

lately it happens that in some flights the airplane has excessive fuel consumption. When I takeoff, I have 22000kg of estimated fuel on destination. But after taking off, that number drops 0,1kg every 4 or 5 minutes. 

I use PFPX, I load the winds to the legs page via the uplink, so I don´t know what could be wrong. 

 

Thanks,

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no luck on you you got that with 777 and 744...

 

could you post your results including your flightplan and your report found?

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But after taking off, that number drops 0,1kg every 4 or 5 minutes. 

 

Since you crossposted this, I noticed you're seeing it in multiple aircraft. Sounds like you're suffering some sim pauses. Try lowering the settings in P3D for a flight to see how it handles it then. It may also be a BIOS issue.

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Since you crossposted this, I noticed you're seeing it in multiple aircraft. Sounds like you're suffering some sim pauses. Try lowering the settings in P3D for a flight to see how it handles it then. It may also be a BIOS issue.

I am using fsx. It is weird because it only happens with the 777 and the 747v3. I own the 737 and ir Never happened such a thing.

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I am using fsx. It is weird because it only happens with the 777 and the 747v3. I own the 737 and ir Never happened such a thing.

 

Lower the settings in FSX then. Something is causing your sim to hang, and fuel is being drawn during this time.

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Lower the settings in FSX then. Something is causing your sim to hang, and fuel is being drawn during this time.

ok. I Will give it a try. But I dont think that is the cause. Seldom does fsx hang. And if it does, it is just 2 ir 3 seconds.

Lower the settings in FSX then. Something is causing your sim to hang, and fuel is being drawn during this time.

The fuel prediction drops at a constant rate. It doesnt happen when it hangs.

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ok. I Will give it a try. But I dont think that is the cause. Seldom does fsx hang. And if it does, it is just 2 ir 3 seconds.

The fuel prediction drops at a constant rate. It doesnt happen when it hangs.

 

If I may...

 

You're here because you don't understand why your sim is behaving oddly. I support our products daily to know generally where to look. Sometimes it doesn't always make sense, but bear with me a bit and humor me.

 

Your computer's processor processes things so fast that it could finish things before you even knew it started. If some of that stuff is getting jammed up in the processor, you wouldn't even have to notice it for it to have an effect over time.

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Now that is an answer with enough information to understand.  Often we get told do this and it seems to have no relevance.  Sometimes it is because the poster has misundertood the problem.  while lower the settings makes sense to you it does help that you have observed this as a problem.

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I tried lowering the settings, but it keeps happening. 


If I may...

 

You're here because you don't understand why your sim is behaving oddly. I support our products daily to know generally where to look. Sometimes it doesn't always make sense, but bear with me a bit and humor me.

 

Your computer's processor processes things so fast that it could finish things before you even knew it started. If some of that stuff is getting jammed up in the processor, you wouldn't even have to notice it for it to have an effect over time.

I tried lowering the settings, but it keeps happening. 

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The first thing I would do now is do a flight with clear skies and calm winds and check your fuel consumption. Take winds completely out of the equation.

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Did anyone get this issue sorted? The same thing happened to me yesterday on a Delta flight from RJAA to PHNL. When I left Narita I had an estimated reserve of 55,000lbs and halfway through the flight, I had to divert because there was no way I'd make to Honolulu. When I landed in Guam I had a TOTAL of only 17,000lbs of fuel remaining. I followed the weights, altitudes, and speeds given by PFPX, yet the fuel reserve prediction continued to drop by 0.1 every 2-3 minutes. I doubt the cause was the 148kt tailwind I had, but that was the only anomaly (other than almost running out of fuel) throughout the flight.

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Hello, yes, I do have the feeling we have an overconsuption of fuel too on each long-range scenarios, and I had not this problem with other aircraft, because the discrepency between calcuted expected fuel and actual fuel at destination is very big, not the same order of number. But I don't have a metric to report pinpoint and normalised data.

Geoffrey Fernandez

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5 hours ago, daguerreotype said:

Hello, yes, I do have the feeling we have an overconsuption of fuel too on each long-range scenarios, and I had not this problem with other aircraft, because the discrepency between calcuted expected fuel and actual fuel at destination is very big, not the same order of number. But I don't have a metric to report pinpoint and normalised data.

Geoffrey Fernandez

 

It's not just long-haul flights, I had an expected reserve of 42,000lbs of fuel on my flight from Taiwan to Tokyo, but when I arrived I had only 3,500lbs remaining. I don't know what's causing this, but PMDG needs to look into it.

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29 minutes ago, Kyle94 said:

It's not just long-haul flights, I had an expected reserve of 42,000lbs of fuel on my flight from Taiwan to Tokyo, but when I arrived I had only 3,500lbs remaining. I don't know what's causing this, but PMDG needs to look into it.

for anyone to reproduce your problem, you need to post a lot more details. is this 100% reproducible on your system? does it happen with no weather just ISA? what weather engine do you use?

also more details about which flight? what was the exact route and altitude? what was the load weight and fuel weights and predicted weights from pfpx? which model and engine type? what cost index was set, and what planning values did you use for the climb and cruise speeds? which pfpx profile are you using, is it the one that comes with pfpx or the updated ones that have been posted around?

it seems like what you guys are describing is pretty unusual !!!  so eliminating variables will be important in the long run. i glanced at this thread earlier while i was debating what flight to sim tonight and i'm flying RJAA->PHNL right now ...i set my fuel so pfpx predicts 55.8k lbs...and my FMS fuel prediction, rather than dropping, has gradually increased from 54.0 to 54.9 over the course of a few hours. i am using the 400F version with ge engines and ZFW of 602.5, original fuel load of 207259. that is with FSX-SE, AS2016 weather.

if this was a widespread issue there would probably be a lot more posts...it seems like there's something going on if it's more than a few people but i dunno... all my flights so far end up within around 5% of what was planned.. so i'm pretty sure that if you have found an issue it will be something specific to your settings or maybe some unique combination of factors.. hopefully the guys in this thread who have the problem can identify whatever it is they have in common. maybe post your hardware specs, OS, which version of fsx or p3d you are using, stuff like that too.

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

good luck!

cheers, andy crosby

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I have no problem at all with this.

Yesterday I did a flight from SBGR (Sao Paulo, Brazil) to FACT(Cape Town, South Africa), trip was estimated by PFPX to 3505 nm and minimum fuel 118683 Kg. Around 7 hour flight. It was with the 747-400 Virgin Atlantic Airways (G-VROM | 2009) with General Electric CF6-80C2B1F
PFPX also predicted that I would have 37.9 metric tons left on arrival.

But I did have ~40 metric tons left after TD. Also checked at some navpoints and fuel was very close to predicted.
I have also seen on shorter flights that PFPX is very close about fuel.

So there is something weird going on on your system, nothing wrong with the 747 and fuel.

PFPX 1.19, Yes old but works perfect, tried the later versions but had a lot of problems with them.
Win7 64 Professional, i5 3.8 Ghz 16Gb mem. Nvidia Gforce GTX 960 2Gb
FSX:SE, got it for only 70 Skr around $8. Better memory handling, not seen any OOM since upgrade. VAS goes up and down during flight, as it should. And better performance, FPS.

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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.

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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

 

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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

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10 minutes ago, PerWel said:

What version of PFPX do you use? I use 1.19

1.28

blaustern

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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.

 

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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.

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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. 

 

 

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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 

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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.

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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. :happy:

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.

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