TopCat + PFPX + 737NGX / Weights (How To)

[Seme 6]

Dear Al Jordan,

 

What a remarkable topic - many many many thanks for this! Amazing we have such people here ready to help fellow simmers. This answers to my question I came up during the weekend, when trying to make the weights match between PFPX/TOPCAT/PMDG738.

 

Super!

Cheers

Thomas Schmiedeke

[jordanal 70]

Al, I cannot thank you enough for sharing your work.  As a longtime TOPCAT and NGX user, I was always wishing for a proper NGX specific profile, and now we have it!  We were previously limited to the PMDG profile for the FS2004 addon. 

 

Not a knock against you, but I just wish there was a way for the payload screen in the NGX FMC to match 100% what we see in the payload manager in TOPCAT, in terms of the passenger and cargo distribution.  The zero fuel weight is correct of course, but there will be a big difference in CGs, and I would think, trim settings between the two.  I know Tabs had said weight is the important figure, but what about cg?  See screenshots below:

 

I have, and will continue to disregard the CG setting recommendation in TOPCAT.  We have always been instructed not to trust TOPCAT in this regard, just use the FMC as it is really the best app for this purpose.  But I just wish the FMC would match the passenger/cargo numbers of TOPCAT, perhaps it's my OCD and also a FSX limitation, or custom coding by PMDG that TOPCAT or any external load program is not equipped to handle.

 

Any thoughts?

 

A.J.,

I completely agree and never gave TopCat's CG much consideration.  Like you, I always double-punched the CG button on the FMC and let it auto-populate.  I  don't know if the CG difference in TopCat comes from the values in (Trim) section of the config files above, or if it's hard-coded in the TopCat aircraft profile (aircraft.0=B737-700_GE), also referenced in the above configs.  Personally, I always just duplicated the seats and cargo weights in the FMC as displayed in the TopCat payload, double-checked that the ZFW, Fuel, and TOW all agreed and moved on.  It might be a worthy question for Christian over in the TopCat support forum - why the CG differs.

[merlin61 0]

Hi Al Jordan

        thanks for all the above info on PFPX and aircraft data for Topcat. Will now see if I can put it all into practice! :unsure:

Cheers Patrick

[Anteater 4]

Al,

 

This has been very helpful. I do have questions about max landing weight. How did you use the FMC to figure this out? Also, the MLW values are different in your text files and the PFPX screenshot. For example, the B736-M text file is 128,928 and the screenshot is 120,500.

 

Your post and files have made this so much easier. Thanks again!

 

Greg Moore

[jordanal 70]

Al, This has been very helpful. I do have questions about max landing weight. How did you use the FMC to figure this out? Also, the MLW values are different in your text files and the PFPX screenshot. For example, the B736-M text file is 128,928 and the screenshot is 120,500. Your post and files have made this so much easier. Thanks again! Greg Moore

 

Hmmm, that doesn't seem quite right, does it....  It's a MLW value issue for both 736's actually.  I honestly don't know which one is correct.  My guess is, one came from TopCat or PFPX, and the other came from the NGX FMC or aircraft.cfg.  I'll look at it more closely when I get home tonight.

[jordanal 70]

OK, with regard to the B736/7 MLW differences, this is what I've discovered so far.  All TopCat B737 config files, regardless of vendor (PMDG, iFly, Ariane, etc) has the MLW set to 128,928.  This is why all my TopCat B736 and B737 config files above have this value.

 

Now PFPX on the other hand had some 'basic' (non-template) profiles for the B736 and B737 airframes including separate MLW values as can be seen above, in my PFPX Aircraft Editor Screenshot in the OP.  I'm sure these MLW values are somewhat generic in natures as well, but they seem a bit more realistic than the B737 TopCat value/128,928.  The TopCat B739 MLW is off as well.

 

At this point, I'm inclined to update my B736, B737, and B739 TopCat config files above, with the MLW values from PFPX - if for no other reason, so they match.

 

Oh, and FWIW, I looked through the PMDG B736 and B737 aircraft.cfg files and could not find any MLW values or comments - no joy there...

[jordanal 70]

Just a quick reply in the midst of the 777 release pandemonium.  I did find a boeing pdf 737 performance summary doc earlier this afternoon and it listed the same MLW values noted in the PFPX Aircraft Editor screenshot above.  I've already changed my TopCat configs files accordingly.  If you're so inclined, just open each of the B736, B737, and B739 TopCat configs files and change the MLW= value to the same as PFPX.

[Anteater 4]

Thanks!

 

Greg Moore

[lfishe 2]

Are these the numbers for the winglet or for the non-winglet models, and does it matter?

Thanks,

Lynn

[jordanal 70]

To the best of my knowledge, these numbers are for both Winglet and non-Winglet - the FMC ZFW, DOW, MTW, etc., did not indicated a difference when either model was loaded; just the cabin configuration (1 class vs 2 class).  Winglets are more for fuel-economy and don't make a big difference in takeoff or landing performance (i.e., topcat).  PFPX however, does have different winglet vs non-winglet -800 templates, so you might chose the appropriate template for your flight and link it via the Reg # and takeoff performance module to a TopCat aircraft.

[lfishe 2]

Thanks

[MikeHenke 1]

Awesome! Thank you for these clear instructions! Just finished setting everything up and it is spot on!

[Bman2006 6]

I do appreciate all of this information.  I am a GA guy at heart but I do like the change of pace and a differnet type of complexity when it comes to big tin flying.   I finally broke down and picked up PFPX last night.  Great planning tool.   I need to keep on reading and keep on investigating to fully understand the planning concepts. 

 

The one thing that has always bugged me is trying to determine if my aircraft profiles are correct "enough" to provide somewhat accurate fuel burn predictions.  It's always felt like a black box mystery to me.    A year or two back when I first picked up the NGX, I changed some weight values (from a thread found here in AVSIM) but as I recall, all of the configuration information was in one large .txt file, not separate aircraft .txt as I see in Topcat Configuration folder. I can't seem to find that file now.   Does any one know which file I am talking about?  Maybe I am out to lunch.

 

Any way - the questions are or at least verification

 

1) TopCat .acft and the configuration .txt files.  Is it that the .acft calcualtes the v speed and the .txt handles the derate and fuel burn?

 

2) When I make a new plane profile in TopCat:

- Should I use the B737-800" For type selection with the PMDG 737-800 configuration?

- Are the engines correct model CFM56-7B23 or is there something I need to change there also?

 

I will follow the steps listed at the front of this thread and download the .txt configuration files.  Thanks for those.   I am concerened that what ever I changed 1.5 years ago will be lingering around somewhere when I changed some weight values.  Just not sure where that was and not sure they will be nulified when I use these .txt configs from this thread and generate new aircrafts.

 

I need to get a grip on how this all works so I can do it correctly for the T7 as well. 

 

Benjamin

[Jetman67 517]

Hello Jordanal

 

I seem to have this working with all the correct weights thanks for the instructions, I cant seem to get the topcat v speeds and N1 settings to match the 737 NGX FMC, is this normal or should they exactly match for full power and any derates, thanks

 

Wayne

[jordanal 70]

I don't think mine ever matched exactly, but they weren't extremely different either.  I always trust the FMC in the end, it has my virtual pilot life in it's hands, LOL...