correct as-is Checklist weight page is incorrect!

[Paarthunax]

So as seen on the images, the fuel and payload showing my weight on my stores page and IFEI display do not match up with my checklist aircraft weight page and the loadout ground crew page, tested with two different loadouts and had two different errors. A track file is also attached to the same aircraft I used for this test.

weight problem.trk

[Lord Vader]

Hi @Paarthunax

In the Checklist page, the A/C WT is calculating the Aircraft Gross Weight, meaning the airframe and cargo (loadout) rounded to the nearest pound. It does not take into account items like pylons and other small items. In the DCS rearm page, that is the actual total weight of the aircraft. That explains the discrepancy you're seeing. 

[Paarthunax]

14 hours ago, Lord Vader said:

Hi @Paarthunax

In the Checklist page, the A/C WT is calculating the Aircraft Gross Weight, meaning the airframe and cargo (loadout) rounded to the nearest pound. It does not take into account items like pylons and other small items. In the DCS rearm page, that is the actual total weight of the aircraft. That explains the discrepancy you're seeing. 

Understood, but shouldn't these two be the same? I understand the difference, but there shouldn't be one. Why would one account for it and not the other?

[Tholozor]

Here's what I found from my own tests using ground power to keep the internal fuel level full for all tests (displayed as 10,840 lbs internal on the IFEI @ 20°C, 29.92 inHg), full gun ammo on HEI-T rounds:

- A slick Hornet with the wing/centerline pylons removed: CHKLST shows A/C WT as 36,396 lbs and rearming menu showing 36,229 lbs. My presumption is that this ~167 lbs discrepancy is accounted for as the weight of the pilot (LAU-116 ejectors on stations 4 and 6 would attribute to ~130 lbs together, and LAU-7 rail launchers on the wingtips would account for ~180 lbs together, so neither of these seem likely).
- Adding the centerline pylon (SUU-62) does not change the weight on the rearming menu (stays at 36,229 lbs). A/C WT increases to 36,535 lbs (SUU-62 weighs ~139 lbs, so A/C WT is correct).
- Adding all 4 wing pylons (SUU-63) does not change the weight on the rearming menu (stays at 36,229 lbs). A/C WT increases to 37,775 lbs (each SUU-63 weighs ~310 lbs * 4 is ~1,240 lbs. 37,775 - 36,535 = 1,240. A/C WT is again correct).

Right off the bat, any payload that does not remove any pylons will automatically have a difference of 1,379 lbs between the rearming menu and the A/C WT, plus the 167 lbs discrepancy.

Adding ATFLIR has the A/C WT properly accounting for the removal of the LAU-116 on station 4. The A/C WT will decrease by 65 lbs when the pod is initially added and the LAU-116 removed, then increased by 430 lbs once the rearm is complete. However, the rearming menu does not account for the removal of the LAU-116, and only shows the difference of the weight of the ATFLIR itself.

External fuel tanks are accounted for properly by both rearming menu and A/C WT calculation. A full FPU-8 tank accounts for ~2,535 lbs (~2,244 lbs for JP-8, if calculating at 6.8 lbs per gallon, plus 290 lbs for the tank itself).

The LAU-115+LAU-127 launcher combo racks for AIM-120/AIM-9 are also accounted for correctly (~357 lbs for each AIM-120, ~120 lbs for the LAU-115C/A, and ~191 lbs for both LAU-127A/A attached to the side).

 

The only issue I see in the screenshots lies in your internal fuel weight. The rearming menu sliders are set to 100%, but the internal fuel level is below that. Given the above regarding the weight discrepancies between the rearming menu and the A/C WT on the CHKLST page, we can determine if the jet is calculating correctly.

Using the screenshot of the aircraft loaded with AIM-120s and three external tanks, internal fuel at ~7,530 lbs:
- Starting at 46,983 lbs on the rearming menu, we add the weight of the discrepancy between the menu weight and A/C WT if the aircraft had nothing loaded and pylons removed (+167).
- We add the weight of the SUU-62 centerline pylon (+139).
- We add the weight of the four SUU-63 wing pylons (+1,240)
- We subtract the weight of the missing internal fuel (-3,310)

This gives us a total of 45,219 lbs, only ~12 lbs off from the A/C WT.

Same thing applies to the second screenshot with AGM-65s:
- Starting at 43,096 lbs on the rearming menu, adding the discrepancy (+167).
- Centerline pylon (+139)
- Wing pylons (+1240)
- Removed LAU-116 for the ATFLIR on station 4 (-65)
- Subtract the missing fuel (-1130)

Total of 43,447 lbs, only ~3 lbs off the A/C WT.

 

I'd say CHKLST is doing a better job than the rearming menu.

Edited June 11, 2023 by Tholozor

[Lord Vader]

On 6/11/2023 at 2:20 AM, Paarthunax said:

Understood, but shouldn't these two be the same? I understand the difference, but there shouldn't be one. Why would one account for it and not the other?

That's just the way that McDonnell-Douglas/Boeing designed this particular calculation versus how the Total Weight in our rearm menu was designed.
When operating the aircraft to comply with operational procedures, just rely on the A/C WT value in the plane. 

[Fresh]

@Tholozor I agree with your testing. The armament page doesn't account for the mass of the pylons. Also the mission editor has a unknown "Weapon" of 130 lbs, and I reason that is for the two LAU-116 on the cheeck stations (2x 65 lbs)

Missing masses:

2x LAU-116 = 130 lbs

1x SUU-62 = 139 lbs

4x SUU-63 = 310 x 4 = 1240 lbs

For a total of 1509 lbs

See attached image.

Here is a Google Table to use to compare/test:

https://docs.google.com/spreadsheets/d/1HhVtqnUz6esMMMACH5DuwJJswHPZbkYqfmfESMM7hF4/edit?usp=sharing

BRGDS,

Fresh

[Fresh]

On 6/10/2023 at 12:53 PM, Lord Vader said:

Hi @Paarthunax

In the Checklist page, the A/C WT is calculating the Aircraft Gross Weight, meaning the airframe and cargo (loadout) rounded to the nearest pound. It does not take into account items like pylons and other small items. In the DCS rearm page, that is the actual total weight of the aircraft. That explains the discrepancy you're seeing. 

Hi @Lord Vader, @Paarthunax, I think it is the other way around, the rearm page is not accounting for pylons, but the aircraft is.. see above.

BRGDS,

Fresh

Edited October 11, 2024 by Fresh