lets be honest the chances of the issue being with the actual aircraft are quite slim i would imagine

Yes, hard to imagine why or how the aircraft itself would change, assuming you have not updated it. One never knows though whether some other add-on within FSX might somehow be affecting the 777. ASN itself is one possibility since it has been updated several times in recent months. Perhaps even a Windows update could be causing some kind of issue with the internal FSX processes.

 

I do recall seeing a recent thread where a couple of individuals seemed to be having a problem where the passage of time in the sim was running slower than the actual computer clock. That might be something to check. The next time you fly the 777, check the aircraft's clock. See whether the passage of time in the sim chronometer is in sync with an actual clock. Not really necessary to have the sim clock synced to current UTC, but see if 60 seconds in the sim = 60 seconds in real time. They should be very close.

 

I seem to recall that some brands of mother boards can develop CMOS clock problems that can have some strange effects on complex add-ons in FSX.

cruise alt was FL310 pretty much all the way through as PFPX didnt give me any step climbs

As for no step climbs in your OFP, this is an issue with version 1.23 and according to Judith at PFPX will be corrected in the next version. See this thread - http://forum.aerosoft.com/index.php?/topic/101834-no-step-climbs-on-flight-plan/. PFPX should calculate the fuel required for FL310 from KMEM to LFPG. It is obviously not doing that. So something is screwed up right now in PFPX. This only happens on certain installations. Thank god mine still calculates step climbs and the proper amount of fuel required. Until that issue is corrected, you will be short of fuel at the end. Doing step climbs per the FMC as JRBarrett recommended should help somewhat alleviate the issue. I always do step climbs per the FMC and not what the PFPX OFP indicates.

Thanks for pointing me at that! Good to know....so extra fuel in the meantime

 

I still find the steady decrease of the fob on the prog page a bit strange...same as the observed fuel burn not matching with what the FF on the displays shows..

 

Im gonna do a longer period on the next flight with my stopwatch and See...1min is a bit short but still 12000kgs/h is a lot

i just completed said flight to dubai and i had the exact same problem where the plane would use way too much fuel and the predicted fuel on the prog page would steadily decrease...here are all the numbers:

I used PFPX to calculate the fuel required for the LFPG-OMDB flight . Fuel Bias 100%. CI 85. Same payload and route as yours. PFPX weather server for forecast. The results were as follows:

 

Trip 47849

5% Cont 2392

Alt-OOMS 5319

Final Resv 3753

Taxi 517

Release 59831

Remaining 11207

 

Initial Altitude FL310 with two step climbs to FL330 and FL350. This was done using version 1.18.2 which is the one that I halfway trust. I won’t even bother to tell you what version 1.23 came up with.

 

Doing the whole flight at FL310 only resulted in an increase of 1147 kgs. of fuel consumed. These calculations were done in pounds and then converted to kilograms. So the column of figures may not add up.

I'd suggest the issue is not with PFPX. If the aircraft is burning 12 tonnes an hour, that has nothing to do with the PFPX fuel bias, the wind or step climbs, the aircraft itself is burning around 25% more fuel than it should be. That's independent of the paper flight plan, whether calculated in PFPX or on the back of a fag packet.

 

Incidentally, the issue with PFPX 1.23 is with the "optimisations" section. It defaults to "fuel" -- turn it off and your step climbs will return.

As mentioned 1.23 will not plan step climbs on some installations. However, there is a solution to this!

 

If you go to the optimization tab, you will see the default in 1.23 is "FUEL". Simply change this to NONE, and you are set! You now have your PFPX planned step climbs again.

 

Furthermore, depending on what aircraft performance file you use. Be it PFPX's or FlyPrecisely's B777 aircraft performance files for PFPX (I prefer the latter as they were put together with the latest B777 FPPM and performance data). This will of course determine the OPT/MAX altitudes and accuracy release fuel for the trip.

 

What I have been doing with great success (in terms of even better fuel planning) is to go to the speed/altitude tab and manually enter step climbs. If you have access to a B777 FPPM, the weight vs. optimum and maximum altitudes are listed on performance tables.

 

I know most operators want 500ft-1000ft of margin between their next step climb and MAX altitude. So for example, on my VHHH-KLAX yesterday I departed at 320,000Kgs. At that weight FL310 was planned initial and thus set in PFPX.

 

Using the latest B777-300ER FPPM, at 307,000kgs MAX is 33,500ft. Thus at waypoint KUDOS the aircraft at 307,000kgs or lighter and I set PFPX to plan the first step climb to FL330.

Next at 270,000kgs the MAX becomes FL355, and thus I set PFPX to plan the second step climb to FL350 at waypoint 39N170E at which point the aircraft will weight 270,000kgs or less.

 

Finally at 227,000kgs the MAX becomes FL375, and thus I set PFPX to plan the third and final step climb to FL370 at waypoint 40N140W at which point the aircraft will weight 227,000kgs or less.

 

How do you determine at which waypoint the aircraft will reach a given weight?

 

First off you compute the flight allowing PFPX to determine the initial and step climb points. Remember to set the "optimization" tab to NONE and not FUEL as it is currently defaulted too. When set to anything but NONE it is resulting in the no step climbs bug, present in version 1.23.

 

Looking at the result of that initial calculation I can now see how much fuel remaining I will have at each waypoint.

 

I re-plan the flight one more time doing the following:

 

I calculate and manually enter each step climb in PFPX as follows:

 

Using the -300ER as an example, at 270,000kgs MAX is FL355. Thus to determine the correct waypoint at which the aircraft weight will be at or below 270,000kgs you do the following:

 

270,000 - 223,500 = 46,500Kgs. Thus, the waypoint at which I will have 46,500kgs or less of fuel remaining is the waypoint at which I will set PFPX to step climb to FL350. (Same procedure for subsequent step climbs).

 

Finally hit compute one last time (this will 99% of the time result in a release with a few hundred kgs less of fuel required than what PFPX planned on its own.

 

The reason being that left to its own, PFPX tends to plan its own step climbs rather close to the MAX altitude, with only a 100-200ft margin at higher step climbs. Again, the typical safety margin for dispatch software, pilots and dispatchers is 500-1000ft and sometimes more if there is moderate/severe turbulence predicted (this having to do with buffet/stall margins).

 

Hope that helps!

 

 

I would also like to point out the following which has a very significant impact on PFPX planning:

 

Introduced with PFPX version 1.18 and still present as of 1.23 is rather significant bug which means PFPX is unable to correctly read the Active Sky next interpolation data.

 

This means that when you are using ASN as the weather source inside the PFPX tool, if ASN forecasts 234/150kts at waypoint XYZ, PFPX will most likely show you something like 126/63kts at the very same waypoint (the problem is worst on oceanic waypoints and in the polar region). This throws off time and fuel predictions significantly and makes planning 6+ hour flights a nightmare. The longer the flight, the worse the discreptancy between that PFPX will tell you you need and what you will actually need in the sim.

 

The solution? When PFPX weather source is set to the default PFPX weather source (requires valid PFPX server subscription), you will see that the winds are extremely close to matching with the winds you will see in your simulator using Active Sky Next as your weather source for the simulator! No issues whatsoever, as both are pulling winds from the same sources.

 

The problem is merely that PFPX is having problems reading ASN's WX file output if one sets PFPX to use the ASN file as the weather source for the planning stage.

hey leo thanks a lot for your input and how to "fix" PFPX...

 

now a couple of things happend today: flying from OMDB-EDDP, so westbound, with a headwind, and using a different airframe than the fedex one i used previously, here are the numbers:

 

ROUTE: DAVM1F DAVMO Y601 GABKO Q1 BONAM UG81 VAN UL852 UDROS L621

           REVDA UP193 KARIL DCT ABULI UL624 MAKAL DCT HDO UM748 RENDO

           Q230 BEBEX T234 GOBAX GOBA26

 

Weather is still ASN PFPX weather source is still their own server...now the interesting bit:

 

TRIP          61025  ........  05:50 
CONT 5%        3051  ........  00:22
ALTN EDBC      2843  ........  00:13
FINAL RESV     4169  ........  00:30
MIN T/O       71088  ........  06:55     
EXTRA          7904  ........  00:56       
TAXI            330  ........  00:10       
RELEASE       79322  ........  08:01   

all weights in KG as usual

 

heres the kicker: now it used LESS fuel than it should have, using a 124 bias, removing those 24% would make it pretty spot on again because my USED fuel from the FMC after parking is 51.8 

 

so my question is: what the hell happend? literally the only thing thats different today is the direction of travel and the repaint...to keep in line with testing no step climbs were performed....i'm baffled

 

hey leo thanks a lot for your input and how to "fix" PFPX...

 

now a couple of things happend today: flying from OMDB-EDDP, so westbound, with a headwind, and using a different airframe than the fedex one i used previously, here are the numbers:

 

ROUTE: DAVM1F DAVMO Y601 GABKO Q1 BONAM UG81 VAN UL852 UDROS L621

           REVDA UP193 KARIL DCT ABULI UL624 MAKAL DCT HDO UM748 RENDO

           Q230 BEBEX T234 GOBAX GOBA26

 

Weather is still ASN PFPX weather source is still their own server...now the interesting bit:

 

TRIP          61025  ........  05:50 
CONT 5%        3051  ........  00:22
ALTN EDBC      2843  ........  00:13
FINAL RESV     4169  ........  00:30
MIN T/O       71088  ........  06:55     
EXTRA          7904  ........  00:56       
TAXI            330  ........  00:10       
RELEASE       79322  ........  08:01   

all weights in KG as usual

 

heres the kicker: now it used LESS fuel than it should have, using a 124 bias, removing those 24% would make it pretty spot on again because my USED fuel from the FMC after parking is 51.8 

 

so my question is: what the hell happend? literally the only thing thats different today is the direction of travel and the repaint...to keep in line with testing no step climbs were performed....i'm baffled

 

Tobias,

 

That cruise BIAS of 124% is definitely way way off.

 

I have done close to 60 ULR's in the -300ER and have always compare actual to predicted burn etc. throughout the flight.

 

The PMDG -300ER is within 0.5-0.8% less than the values in the latest Boeing B777 FPPM (flight planning and performance manual). This represents the real world values of a factory fresh -200LR/-300ER or one that has recently undergone a heavy maintenance visit.

 

With that being said, I suggest you switch to these aircraft performance files for PFPX, created by FlyPrecisely who is highly respected in the PFPX community and has access to the latest Boeing FPPM's for the various Boeing aircraft types and builds his PFPX performance files off those official Boeing numbers.

 

http://forum.aerosoft.com/index.php?/files/file/2819-pfpx-boeing-777-performance-profiles-pack-part-one/

 

I have been using his -200LR and -300ER files pretty much since they were released in the summer of 2014. They are far more accurate than the default PFPX 777 profiles, and match the Boeing B777 FPPM numbers.

 

Having observed the actual burn over countless very long trips and even more 2-5 hour segments in the B777 family, I have made one and only one modification to FlyPrecisely's -200LR/-300ER values. Changing the "Cruise BIAS" to 99.5%. That is 0.5% less than book values. 

 

No changes whatsoever to climb, descent, drag etc.

 

I highly recommend you try these files and that very minor BIAS modification. You will never look back.

 

Furthermore, I would like to point out the importance of not only uplinking winds, but choosing the correct flight levels one uplinks.

 

If simply doing a wind request, the FMC will choose flight levels on its own. However, If for example your initial flight level on a long flight is FL300, the FMC will typically uplink FL260/280/300/350 or something along those lines. That is no problem of course, except for the fact that much of your flight on a 12-15 hour segment will be flown at FL320, FL340, FL360 and at lower payloads on the -300ER even FL380!

 

The problem is that with that uplink you are not giving the FMC any info. regarding the winds at the flight levels it will be spending lots of time at later in the flight. (It will interpolate to a certain extent). Unless you remember to uplink again after each step climb.

 

So what do I do in order to have the best possible fuel prediction at destination and for the various waypoints enroute?

 

I do the initial wind request letting the FMC choose the winds/flight levels it wants to uplink. Then, starting from the first waypoint on the RTE DATA page, I delete the 4 flight levels which were automatically selected during the uplink and then manually enter the 4 flight levels I will be cruising. (Or the first 4 if I will be cruising at 5 on a ULR).

 

So if I am starting off at FL300 and conducting steps to FL320, FL340, FL360 as I become lighter, I enter those 4 flight levels. Of course they will not be populated with winds, so you simple request the winds one more time, and just like that, the first waypoint and all subsequent ones will have populated wind and temperature data straight from ASN!

 

Just like PFPX, the FMC works under the garbage in = garbage out principle. So giving it as much data as it can take is essential! Doing this and the above (assuming one did not feed PFPX with garbage) is the best way to have the FMC and PFPX match each other.

 

And ultimately, as Kyle often reminds (for good reason) those who tend to forget or not realize!

 

Winds and temperatures used in the planning stage are forecasted. So when actual inflight conditions are less favorable than planned for (or more favorable than), the numbers can be off from a few kgs, to a few tonnes on a 15 hour segment!

 

Ultimately, the best one can do is to plan with the latest information, and in turn feed as much of that information as possible into the FMC while keeping your fingers crossed that inflight conditions are as close as possible to what you planned for.

 

Just to give a real world example:

 

On a few occasions the LIDO servers (LIDO being a very popular flight planning tool by Lufthansa Systems) have been unavailable, thus operators have been unable to access their latest wind/temp forecasts (updated 4 times per day). 

 

EK happens to be a major user of LIDO (there are countless other operators dispatching their flights with it), and as such was forced to dispatch many its flights on that day using historical wind figures (stored in its system for this very reason).

 

However, a handful of the ULR flights, such as the DXB-SFO and DXB-LAX flights, encountered less favorable conditions over much of the 15 and a half hour westbound segment to SFO and LAX. This forced both to land at YYZ and re-fuel before continuing. This happens on a daily basis even when the latest forecast models are perfectly available. Ultimately a forecast is just that, a forecast.

 

 

 

the 124% bias is manually entered by me to compensate for the initial higher burn that i observed in my original post. i do use the flyprecisley profiles. as stated in my previous posts.

 

i know how to operate the aircraft i know how to uplink winds and do all of that jazz, while i appreciate you trying to help me it doesn't ultimatley benefit me as my planning and performing routine is no different from yours until recently when pfpx stopped giving me steps because of the mentioned bug, which is not an issue anymore really

 

 

what i find VERY strange and what is my sole point is that the values seem to be back to normal on a westbound flight and a different repaint, compared to an eastbound one because that is literally the only change i made for testing purposes 

 

 

my numbers have been spot on ever since the 777 and pfpx came out and i started using both...my issues are VERY recent and for some reason seem to be conditional

http://forum.aerosoft.com/index.php?/files/file/2819-pfpx-boeing-777-performance-profiles-pack-part-one/

 

I have been using his -200LR and -300ER files pretty much since they were released in the summer of 2014. They are far more accurate than the default PFPX 777 profiles, and match the Boeing B777 FPPM numbers.

I wanted to get your comment on a discrepancy that I noticed in the DOW/ZFW between PMDG, PFPX, and FlyPrecisely. FP shows DOW of 318300 lbs. and PFPX and the PMDG FMC shows 311800 lbs. PFPX is DOW and PMDG is ZFW.

That difference doesn't matter if you just load the ZFW calculated by PFPX as the ZFW on the Payload page of the FMC.

the 124% bias is manually entered by me to compensate for the initial higher burn that i observed in my original post. i do use the flyprecisley profiles. as stated in my previous posts.

 

i know how to operate the aircraft i know how to uplink winds and do all of that jazz, while i appreciate you trying to help me it doesn't ultimatley benefit me as my planning and performing routine is no different from yours until recently when pfpx stopped giving me steps because of the mentioned bug, which is not an issue anymore really

 

 

what i find VERY strange and what is my sole point is that the values seem to be back to normal on a westbound flight and a different repaint, compared to an eastbound one because that is literally the only change i made for testing purposes 

 

 

my numbers have been spot on ever since the 777 and pfpx came out and i started using both...my issues are VERY recent and for some reason seem to be conditional

Apologies, I missed your initial posts on the previous page.

 

 

You mentioned FF figures are normal. Have you checked for any failures that are somehow enabled? There is a fuel leak failure in the failures menu. I also suggest trying a different panel state / creating a new one.

 

Are temperatures in the expected range at the respective flight levels?

 

Which specific repaint is this?

 

 

I wanted to get your comment on a discrepancy that I noticed in the DOW/ZFW between PMDG, PFPX, and FlyPrecisely. FP shows DOW of 318300 lbs. and PFPX and the PMDG FMC shows 311800 lbs. PFPX is DOW and PMDG is ZFW. 

 

 

To clarify,

 

DOW (Dry Operating Weight) will be different on each flight as it includes crew + bags + potable water + pantry. Just the pantry/catering on a 354 seat -300ER  DXB-SEA/IAD/BOS/ORD/GRU flight is weighed at ~4200kg by Emirates. All major operators have standard weights depending on the route flown and crew count.

 

The slightly higher DOW set by FlyPrecisely is taking this into account. Ultimately the DOW will vary flight to flight. Hence the ability to change it so easily in the planning stage of PFPX.

 

The weight you see in the PMDG B777 when completely empty (no payload/crew) is actually the OEW (operating empty weight). As in the flyable aircraft without any fuel, payload, crew, crew bags, pantry.

There is no baseline DOW for a B777 or really any other commercial aircraft for that matter. Different equipment options, configurations etc. all have different weights. In fact any B777 fresh off the line today will be ~100-150kg's heavier or lighter than the one before it. Overall the -300ER has shed close to 2,000kgs from when the first one rolled off the line due to various product improvements and weight reduction programs. Examples being the recent removal of the -300ER tailskid which saved ~130kg if I remember correctly.

 

As Marc mentioned the difference between the DOW of a profile in PFPX and the OEW of the B777  is pretty much irrelevant as you will be setting the exact ZFW from the PFPX release as the ZFW  in the PAYLOAD MENU of the B777. 

 

well you see thats the silly part....

 

failures and wear and tear are enabled yes however, my FSX-SE install of the plane is a fresh one so it shouldnt be aged, in addition to that no there were no failures armed or active on any of the flights...thats the first thing i checked 

 

 

i might try a new panel state yeah although i've been using the same one ever since really but thats a good idea actually 

 

temps are in their ranges, nothing out of the ordinary, neither engine, fuel or ambient temps...everything is perfectly within limits

 

repaints are the pmdg "default" fedex (regular, non panda) and aerologic ones....

 

fwiw the issue happend with the -300ER aswell, i havent flown that since to check if its gone, but as far as the F's go...the FedEx one was the one with all the problems, the aerologic one seems fine for some reason

 

 

i'm about ready to put this down to flightsim voodoo....

DOW (Dry Operating Weight) will be different on each flight as it includes crew + bags + potable water + pantry. Just the pantry/catering on a 354 seat -300ER  DXB-SEA/IAD/BOS/ORD/GRU flight is weighed at ~4200kg by Emirates. All major operators have standard weights depending on the route flown and crew count.

I understand that. But this profile is for a freighter so there would be at most be a couple of seats, netting, tie downs, additional reinforcement of the airframe, and maybe stuff I don't even know about. I have the profiles installed in 1.23 on a second computer. I think I will uninstall 1.18.2 and install 1.23 on the FSX computer along with the PreciselyFly profiles later today.

 

Your are a good salesman.

Tobias,

 

With that being said, I suggest you switch to these aircraft performance files for PFPX, created by FlyPrecisely who is highly respected in the PFPX community and has access to the latest Boeing FPPM's for the various Boeing aircraft types and builds his PFPX performance files off those official Boeing numbers.

 

I do the initial wind request letting the FMC choose the winds/flight levels it wants to uplink. Then, starting from the first waypoint on the RTE DATA page, I delete the 4 flight levels which were automatically selected during the uplink and then manually enter the 4 flight levels I will be cruising. (Or the first 4 if I will be cruising at 5 on a ULR).

 

So if I am starting off at FL300 and conducting steps to FL320, FL340, FL360 as I become lighter, I enter those 4 flight levels. Of course they will not be populated with winds, so you simple request the winds one more time, and just like that, the first waypoint and all subsequent ones will have populated wind and temperature data straight from ASN!

 

 

 

I am now using the FlyPrecisely profile in PXPX and requesting wind data per what you have outlined above. Both make a difference but in particular the levels set in the FMC make a significant difference compared to accepting the default levels in the FMC. The ETA is more accurate or maybe the forecasts are over the past several weeks has been closer to what is encountered in flight.

 

Thanks for the information.