Weight Discrepency (Checklist/ ME vs Loadout menu)

[Shadow KT]

Seems like this classic of a bug from time past has returned.

 

Loadout menu and Checklist weight/ ME (small difference between Checklist/ ME) do not match.

 

Discrepency changes based on loadout and weapons used/ re-fueling (air). I've seen from +2K LBS to -3K LBS.

 

I've attached quick few tracks that display the issue at its basic, by demonstrating the difference in weight on a hot start with different loadouts.

 

In all the tracks, the checklist weight shows higher weight than the loadout screen, which is not that bad. The real trouble is when your checlist page shows a lower weight than your actual.

 

Was flying an op (shoutout to CVW-69), had to hit the tanker on the way back, before recovery, emergency fuel state (Was down to 1200LBS). Fueled up 35000 LBS indicated on the Checklist page. This put me at around 6K LBS fuel, which did make me rise an eyebrow for a moment, but checklist shows we are at 35000 LBS (will burn at least 1K by the time I get to the deck; CASE III), so we should be good.

Well, ended up with a bent gear on landing, thankfully I trapped first try. I was rather surpsied that I damaged the gear, taking into consideration that this is a Hornet we are talking about, made to land on carrier, random failure must be was my first thought, even shut down the jet... 

 

Then again... started the right engine just to check:

 

Checklist page shows 33.8K with 5.4K internal, two fuel tanks and a HARM on the jet..... Yeah, it is not adding up.

 

Opened up the fuel rearming panel, which shows your current fuel level percentage, removed what was not on the jet from the starting loadout and the weight indicated near 3K above, what the checlist was showing.

Reduced the fuel until I matched what was currently on the checklist page hit rearm and sure enough, crew started taking off fuel. Ended up with 2.4K fuel to match the previously shown checklist weight and as suspected the checlist page now showed 30.9K:

 

Weight 1.trk Weight 2.trk Weight 3.trk Weight 4.trk

Edited July 22 by Shadow KT

[Tholozor]

The rearming menu doesn't take the wing and centerline pylon weights into account (although it does in the editor). I did a breakdown over here: 

 

[Shadow KT]

13 hours ago, Tholozor said:

The rearming menu doesn't take the wing and centerline pylon weights into account (although it does in the editor). I did a breakdown over here: 

 

Then it would show less weight than the Checklist page, which as shown in the screenshots it did not.

Also the answer by Vader in that post makes no sense to me... can someone elaborate? How does that work, is the checklist weight programmed, or is it an actual weight reading on the gear?

If it's a sensor on the gear, how does it differentiate between pylons and actual "cargo", i.e. weapons? If the pylon is not part of the aircraft, then it's cargo as well.... what?

[Tholozor]

48 minutes ago, Shadow KT said:

Then it would show less weight than the Checklist page, which as shown in the screenshots it did not.

That's because his aircraft's actual internal fuel (in the screenshots in the linked post, specifically) was less than 100% (I broke this down as well in the second half of my linked post).

Regarding the pylons, some OFPs have stores management codes for them. I'm not sure whether or not it applies to this version if the weapons insertion panel behind door 14R needs the codes or not.

Edited July 23 by Tholozor

[Tholozor]

Looking at this a little closer, there's definitely an error regarding the fuel slider and the actual fuel level when external fuel tanks are involved.

In these screenshots, you can see in the initial setup the aircraft's fuel level is set at 50% (cold start, de-fueled from 100% and on ground power). After the installation of the centerline fuel tank, the internal fuel level is still the same, yet the fuel slider has increased to 71%, leading the rearming menu (after the rearm is complete) to read an increase in weight by an amount approximately double the amount of the external fuel tank.

Edited July 23 by Tholozor

[Fresh]

Be advised, the fuel mass changes with temperature... and also with spawn altitude. (Since that changes temperature)..

The rearming window assumes full external tanks when you add them: 2535 lbs total mass with 2244 lbs fuel mass at 15°C. The empty tank weighs 291 lbs. The slider has no effect on the external fuel tank content (unless you run them dry first).

I've been working on a loadout calculator, check it out below. (Credit to @kengou for his original I used to start with).

This bug report may be interesting/relevant:

 

Public F_A-18C Loadout Editor - 20240723 - Fresh.xlsx

Edited July 25 by Fresh

[Q3ark]

Fuel volume would change with temperature, but the mass shouldn’t change I think. If I have 50% fuel and it gets hot the fuel will expand and take up more space in the tanks, but the mass will remain the same, I won’t all of a sudden have less or more fuel.

[Fresh]

@Q3ark I fully agree... but if you set 100% fuel in the mission editor, you expect a full tank. Which is 1589 gallons volume. The temperature determines the density of the fuel. Cold fuel is denser than hot fuel. DCS then calcules what mass the 1589 gallons has, but unfortunately they got it the wrong way round, making cold fuel less dense and vice versa.

Once the mission starts the fuel mass should stay constant (minus fuel burned).. the volume can vary, hot fuel expanding. If DCS were to simulate a float type sensor in the tank and displaying that as pounds, the full tank would always show the same mass, but it doesn't.  

Basically with hot fuel and a full tank there should be less than 10803 pounds indicated. With cold fuel and full tanks there should be more than 10803 pounds indicated. (10803 lbs is the mass for JP-5 at 15°C). DCS at the moment inverts the density effect. (If you agree, please make a comment in my bug report, link is above..)

Edited July 25 by Fresh