I've just spent a while trying to figure out some algorithm or process to distribute weight in the same ratio received when setting the FMC Payload to MAX. The following is the method I have worked out. It's a bit of work but it feels good to realize it works when it does.

 

I use PFPX to get a random cargo load then my own math to create weights to input into the FMC. I hope you find this method useful and if you find it to not work please let me know, but I've tried it at least 5 times with different weights and have everything matched. 

 

Please note: This is my way not a professional way.

 

Firstly, here's my PFPX Setup for the 777LR (Pax model, not 77F) The aircraft weights are crucial for this to work. 

 

 

Required: PFPX for weight, unless you create your own random weights. 

Here's my PFPX Weight Settings:

1 PAX (Adult and Child)= 195 lbs

Baggage (per pax) = 24 lbs (all 4 settings)

 

When set at MAX the FMC has the FWD/AFT Cargo set at 39090/27030.

 

 

If you  break those numbers down they reduce to a simple ratio of 1303:901 <----- Important Number

 

Now, here's a random payload, courtesy of PFPX:

 

 

Note the # of Pax=230 (Infant is set to 0 weight).

Note the Baggage=5520

Note the Cargo=25591

 

Now, time for some math.

Multiply 230*195=44850

I check Payload=44850+5520+25591=75961 and that checks with PFPX!

 

Remeber our 1303:901 ratio? I can't remember my mathematical thinking behind this, but there was a little voice from high school algebra inside my head that said add the two numbers and divide the cargo.

 

1303+901=2204. <--- Important

 

Now, take the Cargo (applies to FWD/AFT, not Bulk. Bulk will be used for given baggage weight), 25591 and divide that by 2204. 25591/2204=11.6112 (rounded to 4 decimals)

 

Because the 1303 and 901 are the lowest whole numbers you get with the FWD/AFT cargo ratio, multiply 1303 and 901 by 11.6112

 

1303*11.6112=15129.3936 <- round to nearest whole number

901*11.6112=10461.6912 <- round to nearest whole number

 

15129/10462..... WHAT!! 15129+10462=25591, that's the weight of the Cargo #!

 

Here's how I load the FMC

 

 

The PAX are set to 230

The FWD/AFT Cargo is set to 25591, broken down into the ratio of 

15129/10462

I place the Baggage number from PFPX in the Bulk Cargo.

The ZFW in the FMC matches the ZFW from PFPX setup above!

 

I sincerely hope you guys work with this, see if there are any mistakes in my calculations. I have it written up in a non tutorial way, more of a checklist. If you want me to post that too, I can. Thank you so much and please let me know your feedback!!!

 

EDIT: I just made a quick Spreadsheet. Input the numbers in the gray boxes and Yellow under AFT and FWD will you give you the Cargo load. Cheers!
https://www.dropbox.com/s/opmgpcmxqla08i3/PMDG%20777X%20Weight%20Spreadsheet.xlsx

What a genius , you are, Nick. Much appreciated. I'm sure others who use PFPX will also, likewise, thank you. Going to use this from now onwards.

Or you could just put 420.2 into ZFW and the FMC will figure it out for you.

Or you could just put 420.2 into ZFW and the FMC will figure it out for you.

But if you do this, the FMC automatically inputs PAX numbers and Cargo. Not the same according to PFPX. My method allows the use of inputting specifics for people like myself who enjoy inputting specific PAX numbers and cargo. To each their own I guess.

Good job Nick. Here are the formulas and the algebraic solution.

 

1303/901 = fwd/aft

aft = 1.4461709fwd

 

fwd + aft = total

fwd + 1.4461709fwd = total

2.4461709fwd = total

fwd = total/2.4461709

 

Using your total cargo value of 25591:

 

fwd = 25591/2.4461709

fwd = 10462

 

aft = 25591 - 10462

aft = 15129

 

Mike

 

 

Good job, Nick!! One question from another "specific numbers" lover: where did you got the Cargo Capacity data?? I've been looking for that in everywhere on internet and no way

 

Thanks!

Only question here is the baggage weight, 24lbs? that not very much. It would normally be that amount in KGs so around 51lbs with some airlines giving around 30kgs (66lbs)

/shrug

 

Weight is weight.

ZFW is ZFW no matter if you onload bags, ppl, cars, cows, or water beds.

But good job anyway!

But if you do this, the FMC automatically inputs PAX numbers and Cargo. Not the same according to PFPX. My method allows the use of inputting specifics for people like myself who enjoy inputting specific PAX numbers and cargo. To each their own I guess.

This is true but if you don't focus on how it actually distributes weight then it isn't a big deal. Don't get me wrong as we are flying in our virtual world we like to know how many virtual bags, passengers or crates of live virtual lobsters we are carrying but as AJ stated weight is weight no matter how the FMC distributes it. To each their own. Good job on the math though. I hate numbers.

 

 

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Yes agree weight is weight, but its distribution does matter all those pigs, cows in wrong place effects handling, fuel burn etc...

 

So when distributing it you need to understand the amounts used in order that adding another pig you put it in the right place, and if you are using other tools to simulate your pigs, then in order it all matches up you need to set right numbers. If I use 24kg not lbs for bag weight, it likely be too much to go in bulk, so think distribution not quite right with that