-400F 635k MZFW no longer available?

[sosuflyer 30]

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?

[PLund 15]

William,

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

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

[sosuflyer 30]

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

[Captain Kevin 586]

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.

[Tony747-400 44]

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

[Captain Kevin 586]

1 hour ago, Tony747-400 said:

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

Not possible with the freighter.

[scandinavian13 5,192]

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.

[PinkPony 171]

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 January 15, 2019 by calzonister

[Ephedrin 418]

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 January 16, 2019 by Ephedrin

[Captain Kevin 586]

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.

[PinkPony 171]

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 January 16, 2019 by calzonister

[Captain Kevin 586]

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.

[PinkPony 171]

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 January 16, 2019 by calzonister

[sosuflyer 30]

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

[sosuflyer 30]

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 January 16, 2019 by sosuflyer