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sosuflyer

-400F 635k MZFW no longer available?

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I was trying to do a short flight at the highest ZFW option of 635k, like i have in the recent past, and noticed I could only go to 610k. I opened the 400F CFG file and saw that there was no optional 635k zfw listed. I tried different airframes, same result. Usually PMDG models the highest available weights so the user can then dictate what they want, but it seems I'm being forced to limit myself to 610k. ( I know, only 25k difference, not the biggest deal). Why the change on the update?

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William,

Are you sure you didn´t use the -400ER in the past ?.

The -400ER has a higher MTOW than the -400.

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Yes I know about all variants weight limitations.   I'm talking about the zfw of the 400f. 

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2 hours ago, PLund said:

Are you sure you didn´t use the -400ER in the past ?.

The -400ER has a higher MTOW than the -400.

Higher take-off weight for the -400ERF, but also a lower zero fuel weight of 611,000 pounds.

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1 hour ago, Tony747-400 said:

Have you got the STAB Fuel Tank option selected in the options menu?

Not possible with the freighter.

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20 hours ago, sosuflyer said:

Why the change on the update?

I don't recall this ever being an option. In fact, we have a very strong stance against people modifying files directly, because of the mess it can cause. If it were an option, it would've been in the CDU MENU.

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On 1/14/2019 at 9:22 AM, sosuflyer said:

I was trying to do a short flight at the highest ZFW option of 635k, like i have in the recent past, and noticed I could only go to 610k. I opened the 400F CFG file and saw that there was no optional 635k zfw listed. I tried different airframes, same result. Usually PMDG models the highest available weights so the user can then dictate what they want, but it seems I'm being forced to limit myself to 610k. ( I know, only 25k difference, not the biggest deal). Why the change on the update?

The 635k MZFW is a customer option. It enables operators to carry larger payloads at the expense of MTOW (when needed on a specific sector). As the ZFW increases linearly from 610k to 635k, the MTOW decreases linearly from 875k to 811k.

Personally, I cannot confirm/deny if the PMDG -400F ever allowed us to load past 610k (pre-update). I certainly never tried. However, what did change is the MTOW decreasing from 875k to 850k* in the PMDG -400F. I know they re-did the entire W&B so that the CG now remains within limits when selecting payload/fuel (on the -400/-8)

850k happens to be the MTOW for the -400 when you do not option the STAB tank. So PMDG may just have ported the new W&B model for that specific -400 model (no STAB tank) to the -400F. 

*Note, you can still load the -400F to 875k without any problems. The CG limits for a -400F at MTOW (875k) are 18.3% to 23.5%. 

 

Edited by calzonister

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I would understand the max amount of fuel to drop with the MZFW being increased. But why should the max TAKEOFF WEIGHT decrease while the amount of cargo goes up?? 20 Tons more of cargo means 20 tons less fuel at take off... but if the MTOW decreased it would mean for +20t cargo  --> -40t fuel?!

I guess I'm stuck... or took the wrong exit xD

Edited by Ephedrin

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2 hours ago, calzonister said:

The 635k MZFW is a customer option. It enables operators to carry larger payloads at the expense of MTOW (when needed on a specific sector). As the ZFW increases linearly from 610k to 635k, the MTOW decreases linearly from 875k to 811k.

Where are you seeing this. I'm looking at the Boeing documentation I have here, and it's showing the opposite of what you say. With the maximum zero fuel weight at 610,000 pounds, the maximum take-off weight ranges between 800,000 to 850,000 pounds. With a maximum zero fuel weight at 635,000 pounds, maximum take-off weight is 870,000 or 875,000 pounds.

On 1/14/2019 at 4:48 PM, Captain Kevin said:

Not possible with the freighter.

I will retract this statement, though. I was incorrect. The -400ERF doesn't give you the option of a stabilizer tank, but it appears the -400F does, as reflected by the options for maximum zero fuel weight.

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29 minutes ago, Captain Kevin said:

Where are you seeing this. I'm looking at the Boeing documentation I have here, and it's showing the opposite of what you say. With the maximum zero fuel weight at 610,000 pounds, the maximum take-off weight ranges between 800,000 to 850,000 pounds. With a maximum zero fuel weight at 635,000 pounds, maximum take-off weight is 870,000 or 875,000 pounds.

Source: Latest Boeing B744/8 FCOM Vol. 1

Your source is incorrect. The 610k lbs MZFW is a hard limit if you want to have a MTOW above 811k. This is a structural limitation!

Simply put, the penalty for using the MZFW of 635k is limiting the MTOW to 811k, when physically operating at that MZFW.

The relationship between the >610k MZFW and MTOW reduction are linear (as outlined clearly in any Boeing -400F FCOM Limitations chapter.

 

29 minutes ago, Captain Kevin said:

I will retract this statement, though. I was incorrect. The -400ERF doesn't give you the option of a stabilizer tank, but it appears the -400F does, as reflected by the options for maximum zero fuel weight.

Boeing never offered a STAB tank option on the -400F. There simply waa no need for it, and that is why the -400ERF and -8 don’t have it either. 

Edited by calzonister

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14 minutes ago, calzonister said:

Source: Latest Boeing B744/8 FCOM Vol. 1

Your source is incorrect.

My source came from Boeing's own website. It was under the airplane characteristics for airport planning for the Boeing 747-400, though it was dated 2002, so if anything changed since then, I wouldn't know. In any event, it also seems to mention the stabilizer tank on the -400F.

https://www.boeing.com/resources/boeingdotcom/commercial/airports/acaps/747_4.pdf

I don't have access to the FCOM, so I don't know what it says in there, though I would find it unusual that Boeing gives conflicting information in two different sources if that's the case.

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1 hour ago, Captain Kevin said:

My source came from Boeing's own website. It was under the airplane characteristics for airport planning for the Boeing 747-400, though it was dated 2002, so if anything changed since then, I wouldn't know. In any event, it also seems to mention the stabilizer tank on the -400F.

 

The ACAPS you linked merely shows a high MZFW/MTOW optioned -400F and is purely a airport planning document. Boeing is only showing that a operator who options the maximum 875k MTOW may also want to option the MZFW of 635k (which in fact most did), as this would reflect the most capable -400F. What that does not mean, is that you can actually operate at 635k MZFW and 875k MTOW simultaneously. Does that make sense?

Its either or "As the ZFW increases linearly from 610k to 635k, the MTOW decreases linearly from 875k to 811k" 

FYI, you do have access to the FCOM, thanks to PMDG 🙂 \Prepar3D v4\PMDG\PMDG 747 QOTS II\Flight Manuals

You will see the PMDG -400F FCOM shows a 610k MZFW limit for the 875k MTOW. Because it reflects a airframe with the highest MTOW, optioned without the 635k MZFW (and the MTOW limitations associated with using it).

 

Interesting to see the ACAPS mention the horizontal stabilizer option for the -400F. First time I have seen it in any official Boeing document. Once Either way, no -400F was ever optioned with it. 

Edited by calzonister

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5 hours ago, calzonister said:

The ACAPS you linked merely shows a high MZFW/MTOW optioned -400F and is purely a airport planning document. Boeing is only showing that a operator who options the maximum 875k MTOW may also want to option the MZFW of 635k (which in fact most did), as this would reflect the most capable -400F. What that does not mean, is that you can actually operate at 635k MZFW and 875k MTOW simultaneously. Does that make sense?

Its either or "As the ZFW increases linearly from 610k to 635k, the MTOW decreases linearly from 875k to 811k" 

FYI, you do have access to the FCOM, thanks to PMDG 🙂 \Prepar3D v4\PMDG\PMDG 747 QOTS II\Flight Manuals

You will see the PMDG -400F FCOM shows a 610k MZFW limit for the 875k MTOW. Because it reflects a airframe with the highest MTOW, optioned without the 635k MZFW (and the MTOW limitations associated with using it).

 

Interesting to see the ACAPS mention the horizontal stabilizer option for the -400F. First time I have seen it in any official Boeing document. Once Either way, no -400F was ever optioned with it. 

This guy knows what I'm talking about. I remember specifically doing 635k MZFW flights (which limit MTOW to 811k) from KATL-KDFW before the latest updates. Now, no matter which airframe I load, I can only get up to 610K on the -400F.  I know they changed some cg stuff, but I really enjoyed doing heavy short flights landing at MLW.  Wish it hadn't been changed

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Also just loaded up the sim and so far, all of my -400F variants have the 850K MTOW barrier in the FMC even though Boeing 2010 documentation says that the 610 MZFW option can have a MTOW of 875K. Just confused why all of this changed. I had my fleet planned out on pfpx, and all related weight options on a notepad on my desk, and now everything is mixed up.

Edited by sosuflyer

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9 hours ago, calzonister said:

Does that make sense?

Not really.

9 hours ago, calzonister said:

FYI, you do have access to the FCOM, thanks to PMDG 🙂 \Prepar3D v4\PMDG\PMDG 747 QOTS II\Flight Manuals

Yes, I'm aware of that. However, I'm not sure where you're seeing the various weight options. I'm only seeing the weight limitations for each airplane.

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Gents,

First, MTOW is pay-to-play, so whatever the operator pays for is what they get to use. There is a max certified weight by the regulatory authority, but any variation under that is simple a paper chase, and explains the different values.

If the assertion is that we provided a method by which someone could alter cfg files, I'm inclined to disagree. Again: we make it a point to either do the work for you, or provide alternative config files (like the alternative panel.cfg files) so that people cannot go digging into things and creating hassles for support because they changed the wrong value such that a 744 turns into an Extra 300.

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5 hours ago, scandinavian13 said:

Gents,

First, MTOW is pay-to-play, so whatever the operator pays for is what they get to use. There is a max certified weight by the regulatory authority, but any variation under that is simple a paper chase, and explains the different values.

If the assertion is that we provided a method by which someone could alter cfg files, I'm inclined to disagree. Again: we make it a point to either do the work for you, or provide alternative config files (like the alternative panel.cfg files) so that people cannot go digging into things and creating hassles for support because they changed the wrong value such that a 744 turns into an Extra 300.

That doesn't fully answer the question asked in the OP. The MZFW of the PMDG -400F used to be the higher figure (635,000 lb). Now it is 610,000 lb. I had setup the weights of the PMDG -400F in TOPCAT so everything matched properly. My TOPCAT setting hasn't changed so I have no doubt the higher MZFW figure was in the standard configuration previously (there was no option). It appears something has changed, but it isn't mentioned in the change list. Can you confirm this was intended and why it was done?

Edited by kevinh

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16 minutes ago, kevinh said:

That doesn't fully answer the question asked in the OP. The MZFW of the PMDG -400F used to be the higher figure (635,000 lb). Now its reduced, and is the same as the-400ERF. I had setup the weights of the PMDG -400F in TOPCAT so everything matched properly. My TOPCAT setting hasn't changed so I have no doubt the higher MZFW figure was in the standard configuration previously (there was no option).

That wasn't the aim of my post. I'd already answered the OP's question, and then - as has been happening a lot more, recently - people took a sharp left turn into Tangentland, and I wanted to cut the side chatter off because people were getting animated with each other in the face of the actuality of the situation by citing random conflicting sources that are going to naturally be in conflict as a matter of fact. I stated the fact because I got tired of watching the quarrel over inane details that don't help the original discussion.

So...I'll go back (again - this is the third time, for the record) :

5 hours ago, scandinavian13 said:

If the assertion is that we provided a method by which someone could alter cfg files, I'm inclined to disagree. Again: we make it a point to either do the work for you, or provide alternative config files (like the alternative panel.cfg files) so that people cannot go digging into things and creating hassles for support because they changed the wrong value such that a 744 turns into an Extra 300.

 

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19 minutes ago, scandinavian13 said:

That wasn't the aim of my post. I'd already answered the OP's question, and then - as has been happening a lot more, recently - people took a sharp left turn into Tangentland, and I wanted to cut the side chatter off because people were getting animated with each other in the face of the actuality of the situation by citing random conflicting sources that are going to naturally be in conflict as a matter of fact. I stated the fact because I got tired of watching the quarrel over inane details that don't help the original discussion.

So...I'll go back (again - this is the third time, for the record) :

 

Your answer to the OP was that there was no MZFW option available in the sim (which was and is true) but that didn't address his observation that he used to be able to use a ZFW of 635,000 lb, now the maximum is 610,000 lb.

Your latest reply doesn't answer the question I asked, has something changed that wasn't in the changelog? You just repeated the warning not to edit aircraft.cfg. I can only assume you don't realise this has changed either.

Edit: I see the MTOW remains as 850,000 lb (as per the higher MZFW option). If MZFW is 610,000 lb MTOW should be 875,000 lb.

Edited by kevinh

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Yes, I was not talking about editing. CFG files, I was just wondering why the Max zero fuel weight option had been changed from 635 to 610.  That's all.  Would like to see it changed back though.  

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10 hours ago, Captain Kevin said:

Not really.

Yes, I'm aware of that. However, I'm not sure where you're seeing the various weight options. I'm only seeing the weight limitations for each airplane.

I hope the Boeing document I have linked below, helps you understand the relationship between either using the 635k MZFW or 875k MTOW. Loading the aircraft up to both limits simultaneously is prohibited due to structural limitations. 

https://m.imgur.com/a/QDgWtFn

 

8 hours ago, scandinavian13 said:

Gents,

First, MTOW is pay-to-play, so whatever the operator pays for is what they get to use. There is a max certified weight by the regulatory authority, but any variation under that is simple a paper chase, and explains the different values.

If the assertion is that we provided a method by which someone could alter cfg files, I'm inclined to disagree. Again: we make it a point to either do the work for you, or provide alternative config files (like the alternative panel.cfg files) so that people cannot go digging into things and creating hassles for support because they changed the wrong value such that a 744 turns into an Extra 300.

Hi Kyle,

I only tried to provide a explanation based on my assumption as to why the MTOW in the -400F may have changed post update. It is a fact that the limit was originally 875k and now is 850k in the freighter. Which also happens to match the non-stab tank equipped -400 limit. I would think if this was intentional, it was done because the revised CG model for the -400 without stab tanks (850k MTOW)  would also work with the -400F which cant be optioned with stab tanks to begin with.

13 hours ago, sosuflyer said:

Also just loaded up the sim and so far, all of my -400F variants have the 850K MTOW barrier in the FMC even though Boeing 2010 documentation says that the 610 MZFW option can have a MTOW of 875K. Just confused why all of this changed. I had my fleet planned out on pfpx, and all related weight options on a notepad on my desk, and now everything is mixed up.

You can still load the -400F to 875k without any problems/restrictions 🙂

 

20 hours ago, Ephedrin said:

I would understand the max amount of fuel to drop with the MZFW being increased. But why should the max TAKEOFF WEIGHT decrease while the amount of cargo goes up?? 20 Tons more of cargo means 20 tons less fuel at take off... but if the MTOW decreased it would mean for +20t cargo  --> -40t fuel?!

I guess I'm stuck... or took the wrong exit xD

The reason is quite simple! By loading up to the optional 635k MZFW, you are placing a lot more stress on the wing/body joints. The penalty for doing this, is limiting the overall weight of the aircraft to 811k. 

A similar concept applies to the Boeing BBJ family. The standard pressurization schedule is identical to that of the passenger -700/800/900. Typically 8000' of cabin altitude at FL410. 

For a substantial price, Boeing offers an alternative pressurization schedule option. With this, the cabin will maintain 6500' at FL410. 

The consequence of choosing this option is that the 50,000 cycle air-frame economic life is reduced for obvious reason to 26,000 cycles. (extendable by 50% with additional inspection intervals, at a even greater cost 😄

Edited by calzonister
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4 minutes ago, calzonister said:

you are placing a lot more stress on the wing/body joints

oooookay, thank you for that reminder. I absolutely missed the material point.

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4 hours ago, calzonister said:

I hope the Boeing document I have linked below, helps you understand the relationship between either using the 635k MZFW or 875k MTOW. Loading the aircraft up to both limits simultaneously is prohibited due to structural limitations. 

Copy. I see what's going on now. A little surprised that the ACAPS wouldn't point this out.

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