747-400F Polar Air Cargo after update... MTOW/GW

[ahuimanu 50]

Hi,

Did some values on the 747-400F change after the update to include the 747-8F?  My PFPX values don't work correctly now.

Thanks.

[NBL648 3]

Use this link.

 

[ahuimanu 50]

Hi Paul,

That's a great thread and it was what I used to grab a 747-8F profile for PFPX.  However, what I'm talking about is changes to the 747-400F.  Before the 747-8 release, the numbers seemed to have allowed for greater weights.  Now, however, the numbers are lower.

Thanks.

[ahuimanu 50]

Hi, I'm near a computer and able to better illustrate with data.

On the Polar Air Cargo model I prefer to fly, the following engines are modeled: GE CF6-80C2-B1F at 56,500 lbs of thrust x 4.  

I made a table below based on this Boeing document - http://www.boeing.com/resources/boeingdotcom/company/about_bca/startup/pdf/freighters/747-400f.pdf - which shows that a "basic" 747-400F configuration will facilitate, and the values found in the .CFG file for the 747-400F as would be installed as of this writing:

Boeing B747-400F Values                                PMDG B747-400F Values

MTOW - 800,000 lbs (362,870 kgs)                   850,000 lbs (385,554 kgs)  <-- why is this value higher?

MLW - 652,000 lbs (295,740 kgs)                      652,000 lbs (295,740 kgs)

MZFW - 610,000 lbs (276,690 kgs)                   610,000 lbs (276,690 kgs)

So, I wonder why the MTOW numbers are higher?  I noticed this as values for flights that used to work just fine in the 744F (using PFPX and the FMC) have been wrong since the -8F was released (which caused the base product to be updated too).

I would just manually edit the max_gross_weight variable in the aircraft.cfg, but that doesn't seem like a good idea.

[Captain Kevin 586]

Looking at the Boeing documentation I have, I see five options for maximum take-off weight, 800,000, 833,000, 850,000, 870,000, and 875,000. So it just comes down to what the airline selected. Even on your Boeing documentation, it gives you the option for three maximum take-off weights, with 800,000 pounds being the lowest and 875,000 pounds being the highest.

[ph-cxz 28]

Plus there are two cf6-80 engines options available the b1f and the b5f. Of the b5f is not so common.

[Jetlinker 13]

If it’s of any help I can confirm with 100% certainty that the real world aircraft in question has the 875,000 (396893kg) MTOW. 

Edited November 21, 2018 by Jetlinker

[Jetlinker 13]

20 minutes ago, Captain Kevin said:

Looking at the Boeing documentation I have, I see five options for maximum take-off weight, 800,000, 833,000, 850,000, 870,000, and 875,000. So it just comes down to what the airline selected. Even on your Boeing documentation, it gives you the option for three maximum take-off weights, with 800,000 pounds being the lowest and 875,000 pounds being the highest.

This is correct, it’s really a matter of the options selected by the carrier. 

[ahuimanu 50]

Thanks gents.  What I am wondering is why this changed when the product was upgraded in conjunction with the -8 release.

[mfrantz 45]

Jeff,

During the update the whole W&B system of both the -400 and the -8 was revised to allow for more accurate cg effects/calculations. During this process base data, payload stations locations & numbers etc. were updated and results were verified against various airline companies trim sheets.

I can't recall what was it that led to the specific 747-400F MTOW change. Probably done for consistency in selecting similar MTOW options for the various 747-400 variants.

[ahuimanu 50]

Hello Michael,

Thank you for your answer. I'm guessing that this will now curtail the published/expected range with full load?  I ask because some variants are indicated in the livery downloader/manager as containing an aircraft config that was verified as being accurate (likely panel, options, systems).  However, it seems that all 747-400Fs are the same (this odd addition of 50,000 lbs).  I ask because the -400ERF numbers are what Boeing publishes, but these -400F numbers are modified.

With the change, many routes are no longer viable. 

I'll end with a question please:

If I manually change these values in the aircraft.cfg file, what would the negative impact be?  I think I hear you say that the plane is now "tuned" to these values in terms of the .air file.

I appreciate your reply.

Edited November 22, 2018 by ahuimanu

[LRBS 943]

6 hours ago, ahuimanu said:

Hi, I'm near a computer and able to better illustrate with data.

On the Polar Air Cargo model I prefer to fly, the following engines are modeled: GE CF6-80C2-B1F at 56,500 lbs of thrust x 4.  

I made a table below based on this Boeing document - http://www.boeing.com/resources/boeingdotcom/company/about_bca/startup/pdf/freighters/747-400f.pdf - which shows that a "basic" 747-400F configuration will facilitate, and the values found in the .CFG file for the 747-400F as would be installed as of this writing:

Boeing B747-400F Values                                PMDG B747-400F Values

MTOW - 800,000 lbs (362,870 kgs)                   850,000 lbs (385,554 kgs)  <-- why is this value higher?

MLW - 652,000 lbs (295,740 kgs)                      652,000 lbs (295,740 kgs)

MZFW - 610,000 lbs (276,690 kgs)                   610,000 lbs (276,690 kgs)

So, I wonder why the MTOW numbers are higher?  I noticed this as values for flights that used to work just fine in the 744F (using PFPX and the FMC) have been wrong since the -8F was released (which caused the base product to be updated too).

I would just manually edit the max_gross_weight variable in the aircraft.cfg, but that doesn't seem like a good idea.

I attached some info for you that might help to understand what's goin on, at the same time all these specs varies from a/c to a/c so there is no standard number.

Each airplane is different in many aspects. That's the reason why we have a/c differences book and normally we check before flight and the last resort is the flight plan release where most relevant data is outlined (especially in terms of weight).

 https://www.dropbox.com/s/pahj29pt0qd09a0/WEIGHTS.pdf?dl=0

 

[ahuimanu 50]

Thank you Alex,

I will review it and ask questions.

[Captain Kevin 586]

1 hour ago, ahuimanu said:

However, it seems that all 747-400Fs are the same (this odd addition of 50,000 lbs).  I ask because the -400ERF numbers are what Boeing publishes, but these -400F numbers are modified.

The Boeing documentation I'm looking at lists 850,000 pounds as one of the five options for maximum take-off weight, so I don't know where you get the idea that these numbers are modified.

1 hour ago, ahuimanu said:

With the change, many routes are no longer viable. 

Not really sure where you're getting at with this. The documentation I'm looking at lists the maximum payload weight, zero fuel weight, and fuel capacity as being all the same from the 800,000-pound variant and the 850,000-pound variant. Your limiting factor is the take-off weight, so it's a trade-off between carrying payload and carrying fuel. If you want to carry more fuel, you reduce the payload weight.

[ahuimanu 50]

Thanks Kevin,

 

If you look at Michael's response to me, there were changes from the pre -8F and post -8F versions of the 747-400 base.  The changes are actually a reduction from the previous max weights.  The increased weight meant that I could fly further with a full load.