Fuel Scalar in T7 CFG

[Flamin_Squirrel 71]

Ehm,

 

WHAT is wrong with adjusting something for my own reasons?

 

Nothing. But the problem you're facing is akin to solving a difficult equation, and your solution is to simply ignore the bits you can't solve to get an 'answer'. We simply want to help you get to the bottom of the problem, rather than you using a fudge factor.

 

I've flown multiple PFPX flights and always ended up within a few hundred kgs of what was predicted, and I'm not the only one. If something isn't adding up for you there could be a multitude of reasons why. Do weights definitely match between PFPX and 777? Is the weather source you're using the same, both in terms of source and time frame?

 

Basically i know that a 777 burns almost 8000 kg per hour per engine, and i had something like  7000kg, no realistic.

 

At what altitude? Fuel flow will decrease as you climb; less air, less fuel required to maintain the same RPM. You can't use figures like that as absolutes as they'll change with respect to environmental conditions.

[HeronVA 0]

Thanks for the update!

 

Does anyone knows what PMDG says about fuel burn of the aircraft? Is it near to the actual factory figures?

 

 

I've flown multiple PFPX flights and always ended up within a few hundred kgs of what was predicted, and I'm not the only one. If something isn't adding up for you there could be a multitude of reasons why. Do weights definitely match between PFPX and 777?

 

So you are saying that PFPX and 777 calculations are correct, so i need to check the weight in pfpx. I need to tell that iam useing one of the templates stored in the PFPX program.?!

[Flamin_Squirrel 71]

So you are saying that PFPX and 777 calculations are correct, so i need to check the weight in pfpx. I need to tell that iam useing one of the templates stored in the PFPX program.?!

 

I'm simply saying that you should check the basics first. For example: ZFW. You have to enter it correctly in 3 places: PFPX, the FMC, and lastly in the payload menu, and make sure they all match. It's easy to make a mistake with data entry.

 

Also, weather. What's the weather source for PFPX, and does it match FSX? Again, one slight mistake here and you'll end up with predictions being out.

[xkoote 57]

Thanks Jordan for your input. I am a 6500 hour MD80 captain and been doodling in FS since FS5 ;-)  I still have an original "Precision Manual" from Mr. Randazzo lying around. The original product and explanation of the company name. I'm not trying to appear better than anybody else or anything. Just that I know already about all the things concerning planning. Step Climbs, Actual vs Forecast Winds, Landing Weight effects on trip fuel, approach fuel, increase or decrease of CI as compared to plan etc etc. Believe me I get it. What I'm trying to let everyone know is that what I have is not a "problem". It's just being aware that the FSX atmosphere is sometimes simplistic/unrealistic and adjusting the sim to meet my personal preference. 

As far as the variations in planning, there are indeed. And that is why you would expect extra fuel upon landing on some flights, and others where you have eaten slightly into you international reserves. It's why they're there. I haven't seen posts regarding landing with less than planned fuel. Constant extra fuel on all flights indicates a discrepancy between PMDG and PFPX. Since the PMDG is more frugal (Not the case usually on used airplanes as compared to factory figures) I decided to try out something. If it doesn't work I can always revert. 

 

Hope everyone understands what I'm trying to say without feeling offended. I'm just saying that for me.....it is more believable to (try to) match PMDG to PFPX than the other way around in this given scenario.

 

 

Cheers,

 

EDIT: Just want to let you guys know also that I'm not making a decision based on trip fuel etc., but by validating the actual flight parameters at any given point in time to the PFPX Database (Evaluation Tool). The extra remaining fuel on all my flights is just a confirmation of what the Evaluation Tool is telling me.

[HeronVA 0]

The weather source as i read in forum is noaa the same as opusfsx uses! so as far as weather concerne we are covered!!! :excl:

As for data input in fmc i use the exact fugures used in pfpx.... so we are done with that too!!!

if the above are correct then i have to check pfpx parameters over the choosen template i try to much the pmdgs . How i will do that any ideas?

[xkoote 57]

HeronVA,

 

I find that my PMDG 777 templates were set at 104% BIAS originally. I don't know if yours are set there too.

What you can do (For the PMDG 777 at least) is set Climb, Cruise and Descent BIAS for all the 777's you have added to your database to 100%. Do not change the template yet as you don't know if you like that setting. Say for example you fly N855FD FedEx 777 in your aircraft database. Go to your aircraft database and change all the 104% biases to 100% for this airplane. Then plan your flight with that same airplane. See if you like it better like that.

 

 

Cheers,

[HeronVA 0]

i will try to do what you told me and i will post the results!

 

If anyone else has i new or better idea kindly post it over and lets hope that something will come up!

 

Thanks

[scandinavian13 5,192]

If your performance isn't matching the PFPX planning, you're not doing something right.

 

My initial thought is that you're using a Cost Index in the plane, while PFPX is planning based on a constant speed (it defaults to this when you create a 777 profile).

 

In order to have the sim accurately follow PFPX, what you do in the sim has to match what PFPX was planned using exactly.  If PFPX used a M.83 cruise, you have to use a M.83 cruise.  If you planned the flight well before departure, you should replan it closer to departure to ensure the winds will match up.  Your weights should match closely.  You should plan to execute step climbs that closely follow the PFPX plan (the STEP SIZE should be updated accordingly in the plane).

 

People should really stop blaming the programming first and look to themselves, instead.  Most of the time, it's user error.  If you don't believe me, call your local help desk and ask them for their stats.  Look for discrepancies in your own actions, and if you can rule yourself out entirely, then it might be an issue.  Until that point, though, it's probably you.

[onduty 5]

Hi Dear 777 Pilots,

 

A lot have been said about the 777 fuel consumption. A lot of assumptions, opinion, feelings, remarks, mixing up terms like wind effect, CI, etc.

I think all of this boil down to one question: are the fuel flow figures of the PMDG 777 correct or not? PMDG advertises this product that it is 5% within real world (factory)figures.

I'm sure the only valid test is a test flight, recording the data and compare them to real performance figures.

I have a 777-200LR GE90-110B1L FPPM (performance manual) with all the detailed data reqired.

I will go out for a test flight, (Mid Weight, optiomum cruise altitude, etc, and will report back my findings in detail.  We'll see the result.

 

 

Cheers,

[Flamin_Squirrel 71]

I'm consistently getting to each waypoint on time and on fuel with no tweaks, when compared to PFPX predictions and FSX actuals. 

 

As Kyle and I have said, if you're not, something's wrong.

[scandinavian13 5,192]

 

 

As Kyle and I have said, if you're not, something's wrong.

 

Yeah.  I've been using dispatch sheets since the Beta and it's been spot on.  I have a few with written numbers back in if people are interested.  I can post screens of the evidence if people really need it.

[onduty 5]

Hi Again,

 

I’ve discontinued my test flight (very rarely doing this!) being so anxious to share my experience with you.

My basic figures: Brake release weight: 260t (all units in metric). OAT throughout the whole flight ISA +2-3C.

PMDG                                                                                                BOEING

OPT ALT :                            FL340                                                                                                  FL340

TIME TO FL340                  00:14                                                                                                   00:14

 

                                               CRUISE DATA FL340 ISA+3C M.84 WGH:255T

 

IAS:                                       294/M.84                                                                                          -/.84

N1:                                        81.4%                                                                                                 83.5%

EGT:                                      471C                                                                                                    -----

N2:                                        98.9%                                                                                                  -----

Fuel Flow:                          3.6-3.7  kgs/hr/eng                                                                       3660 kgs/hr/eng

 

I don’t know about PFPX or whatsoever but PMDG’s numbers are spot on. Well within the 5% tolerance. You can experience with different weights, MACH numbers, etc.,  I think the result will be the same.

Congrats for PMDG!

 

Cheers

[HeronVA 0]

Hi,

 

I did some testing over the past days and i came up quit close to the figures that PFPX is calculating!

I need to say that i changed my 777 template with bias of 100%, the other is totally wrong.

The thing is that when you plan a flight the program used for that should plan with forecasts winds aloft in order to much. In FMC i used both the file created from OPUSFSX & and the one that PFPX is creating now and can be exported to PMDG wx. Lastly i entered the wings manually from the wings information provided from PFPX briefing, i and up very close to the calculations with the third option. The problem is the wind OBS from PFPX is some times old and cant much the winds that wx engines provides such us OPUS.

 

Currently i perform  a flight using winds from opus text file and i noticed that the PFPXs wind information is OBS 071200 very old in terms of my flight with DEP time 2100z. prediction over destination from pfpx was 9.4 tones and mine from fmc 12.2 tones and i believe that this is due to weather OBS.

 

Kindly correct me if i'm wrong!

 

Thanks

 

 

I don’t know about PFPX or whatsoever but PMDG’s numbers are spot on. Well within the 5% tolerance. You can experience with different weights, MACH numbers, etc.,  I think the result will be the same.
Congrats for PMDG!

Thats good to know! :rolleyes:

 

The problem is PFPX not the profiles but the winds that is used for calculations!

 

Thanks mate for the info!

[Flamin_Squirrel 71]

Hi,

 

I did some testing over the past days and i came up quit close to the figures that PFPX is calculating!

I need to say that i changed my 777 template with bias of 100%, the other is totally wrong.

The thing is that when you plan a flight the program used for that should plan with forecasts winds aloft in order to much. In FMC i used both the file created from OPUSFSX & and the one that PFPX is creating now and can be exported to PMDG wx. Lastly i entered the wings manually from the wings information provided from PFPX briefing, i and up very close to the calculations with the third option. The problem is the wind OBS from PFPX is some times old and cant much the winds that wx engines provides such us OPUS.

 

Currently i perform a flight using winds from opus text file and i noticed that the PFPXs wind information is OBS 071200 very old in terms of my flight with DEP time 2100z. prediction over destination from pfpx was 9.4 tones and mine from fmc 12.2 tones and i believe that this is due to weather OBS.

 

Kindly correct me if i'm wrong!

 

Thanks

 

Thats good to know! :rolleyes:

 

The problem is PFPX not the profiles but the winds that is used for calculations!

 

Thanks mate for the info!

PFPX allows you to change your departure time.

[HeronVA 0]

Hi,

 

I will try to evaluate performance within the pfpx when flying in order to fix BIAS and let you know of my results. Started a new flight with 9000nm range for testing.

 

Can someone tell me if the evaluation is done only at specific altitude or need to check more than one!

 

Thanks!