Incorrect fuel consumption

[Roman5018]

A serious mistake in fuel consumption. I've only tested it on one platform, but I think it's massive. Two F/A-18A+ were taken for tests. One with a standard set of weapons (2 AIM-120 C, 2 AIM-9M and 3 outboard fuel tanks), the second with exactly the same set plus 2 additional AGM-88C HARM. Now we look at their fuel consumption. At a speed of 480 knots, aircraft number 1 has a fuel burn rate of 41.76 kg per minute, number 2, with two additional HARMs, has 47.92 kg per minute. However, after the AGM-88s leave their pylons, the fuel burning rate drops sharply to 35.56 kg per minute. Thus, it becomes even lower than that of the number 1 aircraft, but this is impossible, since now they have exactly the same set under the wings. The interesting thing here is that after firing only one HARM, the burning rate becomes 41.74 kg per minute, that is, almost correct. It's like the game counts every missile fired as 2, and as a result, the drag becomes even lower than that of empty pylons on plane number 1.

While the topic of fuel consumption is not closed, I would like to talk about another possible problem. If I understand correctly, the game model calculates fuel consumption only based on the additional drag created by the outboard armament. After all, if the fuel consumption was also affected by the weight of the aircraft, then it would decrease as the fuel burned. But this is not happening. With both full and empty tanks, fuel consumption remains the same. I can agree with this simplified model, but one question remains. Why is fuel consumption also affected by weapons placed in the internal bays of the aircraft? This is especially felt on the example of the P-3 Orion patrol aircraft, for which the duration of the patrol is one of the main parameters. According to my tests, an empty P-3 can barrage for 12 hours at an altitude of 1000 feet, but with an additional 3.5 tons of payload (placed in internal bays), this time is reduced to 8 hours. It looks unfair, because the drag remains the same. For a four-engine aircraft with a maximum weight of 60 tons, a load weighing only 5% of this mass is unlikely to increase fuel consumption by 60%. I suspect there is some kind of mistake here too, as in the first case
Build 1328.18

[Quark73]

IMHO it's not a problem of fuel calculation. It seems to me that there is an inconsistency in DB.
Your HARM loadout (#1269) has a PayloadWeightDragModofier value of 0.0621 whereas your A2A loadout has a value of 0.108, which is almost double. It seem CMO makes a transition to the later one after the the HARMS are consumed.
Regarding the distance between both loadout ID numbers I would guess fuel consumption calculation has been changed in between and (not all) legacy loadout were adapted to this change.

So someone should write a DB request for fixing.

[Roman5018]

So someone should write a DB request for fixing.

I think that the problem should be solved at a higher level, since it is global in nature and is observed on many other platforms. I conducted additional tests by taking random loadouts with close numbers #26972 and #26981. The problem is exactly the same. After dropping bombs, the difference in fuel consumption is 10% on exactly the same loads. The theme on the Github will look like "Check 30 thousand loadouts so that they all have the same effect on fuel consumption." I believe that the problem should be thoroughly investigated by the developers in order to make a comprehensive solution.

[blu3s]

Thank you for the detailed report, we are looking into it.


Logged 15865

[Quark73]

Hmm, the PayloadWeightDragModifier seems to have much less, if not no, impact than I initially expected.
I made a test-file with my beloved Eurofighter and chose the loadout with the highest drag value (# 13967, Austrian Standard CAP !?, 0.2166) and the one with the lowest beside ferry (#30991, British GBU24 with 4 GBUs !?, 0.0239). The consumption on the heavier plane is significantly higher (61 kg/min vs 39 kg/min) what is expected.