PFPX Wind Summary

[MFarhadi]

Hey y'all,

I hope everybody's doing fine.
I was practicing diversions to destination alternates the other day and came across an issue I thought would be worth discussing here.
Since the PFPX's wind summary does not include destination alternate route winds and also the frequency of the fixes in which their winds are depicted in the summary report is limited, are there any commands that could be inserted into the OFP template so that DEST alternate winds are mentioned at the end of the OFP? It would be helpful as PSX only reads winds from "Corridor" winds inserted by the user.

Best,
Reza

[Will]

I don't see an obvious way to do that, but you might post the question over at the PFPX support forum:

https://forum.aerosoft.com/index.php?/forum/592-professional-flight-planner-x-not-for-sale-anymore/

Maybe someone there can have a look?

[MFarhadi]

I don't see an obvious way to do that, but you might post the question over at the PFPX support forum:

https://forum.aerosoft.com/index.php?/forum/592-professional-flight-planner-x-not-for-sale-anymore/

Maybe someone there can have a look?

Thanks for mentioning the forum.
I had previously speculated that the termination of support for PFPX by FlightSimSoft meant that we were left on our own.

Regarding the wind summary: I dug into it and basically only 3 options were available and seemingly, the default one was the only option that was useful to me, as the wind summary is hardcoded into the software and cannot be extensively specifically tailored by the users.

[Will]

For wind corridor purposes, don't worry about payload or fuel, but just plan a flight all the way from ORIGIN via DESTINATION to ALTERNATE. Then copy and paste the wind section into PSX.

Then, re-plan the flight just from ORIGIN to DESTINATION and use this OFP to fly from.

That will get you pretty close.

[MFarhadi]

For wind corridor purposes, don't worry about payload or fuel, but just plan a flight all the way from ORIGIN via DESTINATION to ALTERNATE. Then copy and paste the wind section into PSX.

Then, re-plan the flight just from ORIGIN to DESTINATION and use this OFP to fly from.

That will get you pretty close.

Speaking of getting pretty close:
I've noticed (using Stephen's PFPX profiles) that PSX with 0.0% fuel penalty factor, uses between 2.5%(while being heaviest ~380 tons) and 9.2%(lightest I've tested: 225 tons), across all engine types, more than what PFPX has in its profiles. Also, the FMC, while having identical drag and fuel flow factors to the Model specification for the exact registry of the aircraft, falls short of the fuel calculations; meaning that the estimated arrival fuel progressively reduces as the flight continues.
Have you ever came across a similar behaviour? I'd be happy to disclose the testing methodology I've been following so far.

Edit:
I searched the forum and found many helpful threads. Disregard my post here

Well, I think the NGFMC system should take that into account.

I didn't write that PSX doesn't take it into account. In fact, PSX does. I wrote this line because your comment sounded to me you expected the NG FMC should compute an idle descent like the legacy FMC does.

The thing is simply this: The code in PSX is an FMC simulation. It doesn't contain the original Honeywell code. And in this example here we have again another case of a simulation not being as good as the real gear. There is a reason the real FMC costs over 30,000 EUR and PSX only 300. Performance prediction is a very, very complex, interactive can-of-worm task. Now you noticed the predicted destination fuel in PSX may vary by 1 to 2 tons during a flight of several hours. This slight variation has always been there in PS since 1996. I'm not able to make it as good as the real FMC, I'm sorry. (By the way, I doubt that the 787/777 FMC can achieve zero variation on all flights; this would require an absolutely perfect weather forecast on all flights.)


I don't think so. The Model page shows the physical, actual addition factors: A positive FF value means this aircraft model uses more fuel. A positive drag value means this aircraft model arrives later. If these values are also entered in the FMC, the FMC will predict a higher FF (re FF factor), and a lower TAS (re drag factor). Of course, the drag factor itself implies even more FF, regardless of the entered FF factor.


Yes. See page 372 in the PSX manual, the part in italic font.

When I load ...

Basic 004 - Cleared for takeoff.situ

... and enter 9.0% drag addition on the Model page, the EHAM ETA display in the FMC will increase by 3 minutes.

When I enter 9.0% FF addition on the Model page, the EHAM fuel display in the FMC will decrease by 8 tons.

This is the positive/negative logic that I expect.


Regards,

|-|ardy

Cost Index Cruise Tables at 0, 100, 500, .84, .85, LRC & .86 are included in Boeing GE & RR 744 FPPMs.

They are sufficient for PFPX conduct the necessary calculations to cover the majority of scenarios.

Only Cruise Tables at .85, LRC & .86 are included in the Boeing PW 744 FPPM.

Slightly more limited.

I have set the last known real CI that the actual operator used in each individual PFPX Aircraft Model File.

I suggest you leave your PSX PERF Factors at 0/0.

I did extensive PFPX APMS testing of the PFPX data (using the proprietary Boeing book numbers) against a vanilla PSX Engine PSX PERF Factors at set at 0/0 with of each type with wind data corridor conditions injected from the PFPX OFP.

Thus I extrapolated a bias value inside the PFPX Model Files to match each PSX engine type with PSX PERF Factors at 0/0.

To summarise:

After extensive PFPX APMS (set at PERF FACTOR 0/0) comparison with PSX Burn data (set to PERF FACTOR 0/0)

PSX GE Engines burn an average of + 0.2% more than Boeing FPPM Book figures across all flight regimes.
PSX RR Engines burn an average of - 0.6% less than Boeing FPPM Book figures across all flight regimes.
PSX PW Engines burn an average of - 1.1% less than Boeing FPPM Book figures across all flight regimes.

Its as simple as that (but it took me a year of testing & data entry in notepad from circa 3000 pages of FPPM Books).

When you download my PSX Model Files you might find some of them do have different PERF Factor set; that might be a legacy issue because once upon a time I may have been lucky enough to have had access to RW OFP data to test against - sadly no more.

Change them back to 0/0 & you will be good.

Use a realistic CI - right now 50-90 is a realistic & economical CI in real-world use.

[Will]

I'll see if I can post some examples tonight, but I've found the cruise portion to be very accurate (using Stephen's data for GE engines, passenger variant, CI=80 or CI=180, fuel and drag biases 1.0% in both PSX and PFPX, with wind corridor set to mild randomization). But the approach phase always seems to burn a few extra thousand pounds. I don't know enough to rule out pilot technique (or ATC directives) playing a role.

[MFarhadi]

I'll see if I can post some examples tonight, but I've found the cruise portion to be very accurate (using Stephen's data for GE engines, passenger variant, CI=80 or CI=180, fuel and drag biases 1.0% in both PSX and PFPX, with wind corridor set to mild randomization). But the approach phase always seems to burn a few extra thousand pounds. I don't know enough to rule out pilot technique (or ATC directives) playing a role.

Usually, airlines do have an approach segment addition for the fuel and time. We used to have 240 Kg and 6' for the A330-200 and 360 Kg and 6' for the A300-600 and A310-300. Unfortunately, I don't have an exact figure for the B747-400.

For the fuel predictions, I guess I had an extra door open or something else that has affected the fuel calculations negatively    . I'd check it one more time for any silly things I've missed (There must be something as You, Steve and Hardy have it all neat and tidy, and mine burns a bit more than usual).


Update:
Is it possible that CG Variation with fuel distribution would contribute to such results? I don't personally think so; as it shouldn't have that much of a significant difference (around 1% "at most") even though the correct value been inserted in FMC PERF INIT page.

[Will]

Going from memory, PFPX has an "Approach Time" section in the aircraft editor, but it's not specific to a particular approach; it's for a particular airframe. And it's time (minutes).

There is also "Circuit In," which is associated with an OFP, not with an airframe, and is distance (not time).

What's missing is something like an "approach bias," where we could multiply a standard approach burn by a certain factor on every flight.

[MFarhadi]

Going from memory, PFPX has an "Approach Time" section in the aircraft editor, but it's not specific to a particular approach; it's for a particular airframe. And it's time (minutes).

There is also "Circuit In," which is associated with an OFP, not with an airframe, and is distance (not time).

What's missing is something like an "approach bias," where we could multiply a standard approach burn by a certain factor on every flight.

Will,

I believe you're right.
Other flight planning software, such as SITA AIRCOM and LH Systems, do the same as PFPX.
Usually, Departure and Arrival procedures are included in for Time and Fuel calculations, but there would be a fixed Fuel & Time value for the approach. SITA used to call it "APPR MANEUVERING" and it was fleet-customizable by the airline flight ops.

[Hardy Heinlin]

Hi all, I justed posted a suggestion in this thread:

https://aerowinx.com/board/index.php/topic,6712.msg75057.html#msg75057


|-|ardy

[MFarhadi]

Hi all, I justed posted a suggestion in this thread:

https://aerowinx.com/board/index.php/topic,6712.msg75057.html#msg75057

I'll be recording my T/O to T/C and T/D to LND fuel and times from now on to have some idea about the matter.
Do you have any ideas on what I am missing that "Cruise" FF is anywhere between 2.5 and 9 percent off? something silly that I'm missing, maybe?

Note:
I calculate the figures using PSX's Instructor panel -> Services and try to accurately time the exact difference between ~500 KG fuel usage intervals while flying straight & level segments in cruise, alongside Flight Level, Mach Number, CI, TAS, TAT, and Average Gross Weight during the calculation.

[Hardy Heinlin]

Sorted by probability and relevance, most relevant first:

Big disagreement between FMC RTE DATA entries and actual weather?
Disagreement between drag/FF factors entered on Model page and factors entered in FMC?
Flight controls perfectly centered?
Spoilers fully retracted?
Icing?
APU running in flight?
APU door open?


|-|ardy


(Cosmetic sidenote: You need not quote a post when you reply to it directly :-))

[Will]

If I recall correctly, Steve Bell said the quantity and depth of the data he had varied by engine and airframe. I think he said he had the most complete data for GE engines, so perhaps PFPX/PSX discrepancies are more visible when using non-GE variants?

[MFarhadi]

...
(Cosmetic sidenote: You need not quote a post when you reply to it directly :-))

Sorry I had to quote this one
Sure; I'll give it a look to see where I made a mistake. I'm actually a bit skeptical right now about my method, and from now on I'll be trying the Embry-Riddle recorder for more precise calculations.
Thanks Hardy.

... so perhaps PFPX/PSX discrepancies are more visible when using non-GE variants?

You might be right, to be honest; the last time I had the "diminishing Estimated FOB at Destination" with the GE engine was more than 10 days ago and my last flights were with the PW4056, PW4062 and the RB211-524G2.
I'll take a further look into it.
Thanks Will.

[Hardy Heinlin]

I guess the Embry-Riddle recorder format won't provide any additional data on top of what you already get on the flight deck from the FMC prediction displays and the EFIS/EICAS wind/SAT/FF sensor indications etc.

[MFarhadi]

The purpose I went for the Embry-Riddle recorder is for the accuracy of the time and fuel flow. The Tenth-of-a-ton FF meter on the EICAS just wasn't cutting it.

[G-CIVA]

I'm going to change the Bias Factors in all the PSX aircraft files that I offer for download since its beginning to cause some confusion.

Some of my PSX model files that are available contain Real World FF Bias Factors (These will be adjusted NOW TO 0/0).

In the meantime set your PSX FF bias factors to 0/0 in any of the model files you have downloaded if you fly PSX with my PSX Model files & use my PFPX data to create your flight plans.

Do not adjust any of the FF Bias factors within any of the PFPX files you use for flight planning purposes. They were fixed by me over a long period of testing against the 3 PSX Engine types with a PSX FF Bias factor of 0/0.

After extensive testing the PSX engines burn at the following rates in comparison to real world FPPM data used within PFPX model files which is already accounted for in the PFPX data I offer:

PSX GE engines burn +0.2% MORE fuel than the FPPM Book figures

PSX PW engines burn -1.1% LESS fuel than the FPPM Book figures

PSX RR engines burn -0.6% LESS fuel than the FPPM Book figures

This additional fuel burn is taken into account by my PFPX Model Files.

I hope this clears up the confusion.

I am now editing all of the PSX Model Files I offer to a FF Bias value of 0/0.

[MFarhadi]

Dear Steve,

I'm now trying out PH-BFU with CF6-80C2B1F. With 375 tons of GW, I'm showing spot on FF factors anywhere between -0.2% to +0.4% (having both Drag and Fuel flow addition offsets to Zero). But when the weight is reduced down (say around 320 tons), FF is about 2.2 to 4.2% higher than the PFPX's nominal (0.0%) value. Why the variation? While keeping a constant Mach of .85, PFPX's calculated fuel bias is 4.2%, while if CI is adjusted to give the exact .850 and though TAS and TAT remain the same, FF bias is calculated at 2.2%.
I'm trying to complete a rather long flight to observe if the divergence continues as GW decreases with the mentioned engine option and will let you know of the further results.

[G-CIVA]

My averages were compiled over 8 months of testing.

Are you flying your PSX inside a PFPX generated Wind Corridor?

Have you adjusted the slider in the PSX Wind & OAT random deviations slider?

A direct quote from the PSX NG FMS Manual:

"When it is set to Min, the wind & OAT deviations will be nearly zero; when it is set to Max, the wind direction may vary by up to 40°, the wind speed by up to 40 kt, and the OAT may vary by up to 7°C."

Any adjustment to the slider away from the minimum setting (slider in the PSX Wind & OAT random deviations) can have a marked effect.

It is also unwise fiddle with the FF/DRAG bias numbers in PSX 'on the fly' - My testing used a set FF/DRAG setting of 0/0 inside PSX without any 'on the fly' adjustments for every flight that I did during testing.

[MFarhadi]

Yes, I am.

I use the built-in Embry-Riddle Recorder in 60 seconds intervals. Then, using Microsoft Excel, I try to calculate the average GW, FF, TAT and TAS for the 60,000 milliseconds recorder (in 20 milliseconds intervals) for the applicable flight regime, be it using a Cost Index or a fixed Mach Number.
The explained method I'm using doesn't care if the adjustment slider is moved or not; but I've never used the randomizer and in my previous tests, it was all the way to the left.