[RESOLVED] FM: Sinks to much during bank & groove.

If you take off from land, the flight performance is correct, even after landing and rearming on a carrier. Its starting on the boat that somehow adds additional unrealistic weight (and probably some drag too).

Yes, I can confirm that this seems to be the case.

Air start - fine.

Land start, trap on the carrier, rearm and launch - fine.

Spawn on the boat - not fine.

Yeah, this is unfortunate. I've stopped flying the jet off the boat (to MICH anguish) until this and the sliding with engines on gets fixed.

Feels bad man.

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It would be actually worth to test once and for all, if the spawn or launch loudout is defining for the carrier bug, that is, what if you spawn clean and empty vs spawning full and loaded. I'll see if I can get to that soon, but if any of you can chime in on this, it would help a lot ofc. Thanks!

The best way to test this would be at the exact same atmosphere (choose +15C and pick an altitude), loadout, fuel state, and aircraft configuration. Trim the aircraft for steady, hands-free level flight and check the airspeed, AOA, and engine power setting. If they are different with land vs carrier spawn, we have a problem.

Gentlemen,

Just tested this with the help of Tacview (recordings available on request), running the latest DCS Beta branch as of this posting.

Loadout: 2x ET's. Full internal fuel. No external stores. No pylons.

Configuration: Flaps DOWN, Gear DOWN, DLC DEPLOYED, Hook DOWN.

Then I pitch/power for level flight and ON SPEED in the E-bracket, or 15 units AoA. This corresponds in Tacview to 10 degrees AoA.

With an aircraft I've spawned in the air, it stabilizes around 140 KIAS. In Tacview, the Kinetic Energy readout shows ~260. Fuel flow is ~5000pph/engine.

With an aircraft I've spawned on the catapult, it stabilizes around 160 KIAS. KE readout in Tacview is ~360. Fuel flow ~7000pph/engine.

This discrepancy, subjectively, feels even worse when trying a Case 1-esque approach. Maintaining desired descent rate feels like it takes a lot of extra power when in the groove, and due to the extra speed I'm having to bank excessively which results in substantial sink and destabilization when rolling out on final. I've seen speeds in excess of 170kts in the turn and, again, around 160kts to stay on-speed during final approach.

Unraveling this mystery should be a top priority. If carrier launch is affecting the fundamental lift, drag, and/or weight of the aircraft, then this bug might manifest itself all over the flight envelope for any aircraft launched from the deck. Further tweaks to the flight model might be in error if they're predicated on an underlying glitch such as this.

Update

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Upon further experimentation, it seems this phantom drag or weight compounds with any existing stores. I tried a heavier loadout of full fuel, 2x ET, 6x AIM-54C, 2x AIM-9M (about 96% of MTOW). Level flight in the configuration specified above requires ~155kts for an aircraft spawned in the air, and ~170kts for one spawned from the carrier catapult. So, in essence, it may be a decent approximation to say any aircraft starting its mission from the carrier may be potentially performing the majority of its mission as if it were heavier than MTOW...

PG, latest OB. All tests on the same mission, ISA +15c. Hot-start on cat/runway.

Loadout: 2 x-tanks, 4xPH, 2xSP, 2xSD. Fuel- dependent on test.

Flew straight & level, on speed AoA at ≈500', the same direction on all 3 tests.

Test 1: Full fuel. Catapult-launch. Shot of all missiles. Dumped fuel to 4000Ibs, on speed AoA =147 IAS (pic 1).

Test 2: Fuel 4000Ibs on spawn. Catapult-launch. Shot of all missiles. On speed AoA =120 IAS (pic 2).

Test 3: Runway take-off. Full-fuel. Shot of all missiles. Dumped fuel to 3500Ibs. On speed AoA =120 IAS (pic 3).

Conclusion: 26 IAS faster On-speed AoA if launched from Carrier with full loadout & fuel.

The best way to test this would be at the exact same atmosphere (choose +15C and pick an altitude), loadout, fuel state, and aircraft configuration. Trim the aircraft for steady, hands-free level flight and check the airspeed, AOA, and engine power setting. If they are different with land vs carrier spawn, we have a problem.

The On-speed AoA IAS & engine power settings are different in my tests & pics. Compered to land vs carrier spawn. (F-18 might suffer from the same bug https://forums.eagle.ru/showthread.php?t=247311)

Thank you for these excellent reports.

I looked at this a bit, it seems like DCS is adding the internal fuel mass twice when on the carrier. Odd, to say the least :P DCS tells our FM what the mass of the aircraft is, as well as center of mass, moment of inertia etc. etc. When I set internal fuel to 0, the mass is identical on land and carrier. When I set it to non-zero, the extra mass on carrier is double the extra mass on land, and the extra mass on land matches the fuel weight as set in the mission editor.

I looked at this a bit, it seems like DCS is adding the internal fuel mass twice when on the carrier. Odd, to say the least :P DCS tells our FM what the mass of the aircraft is, as well as center of mass, moment of inertia etc. etc. When I set internal fuel to 0, the mass is identical on land and carrier. When I set it to non-zero, the extra mass on carrier is double the extra mass on land, and the extra mass on land matches the fuel weight as set in the mission editor.

Thank you for the info. Always good to know the cause. Then we've been flying overweight by 20.000Ibs from the boat? Hope you can fix it sooner than later ;).

Hope you can fix it sooner than later ;).

I don't think the error is on our side, it seems to come from DCS.

Thanks for looking into it, gentlemen. Now that we've established a pretty good idea what's going on, it should be pretty straightforward for ED to take care of it. Should be...

Really appreciate the reports on this guys! Currently trying to inform ED of the issue.

Did some testing of my own with the F-18 and F-14.

General Results, this bug didn't seem to affect the F-18; however, the F-14 was affected.

F-18 Test Scenarios:

F-14 Test Scenarios:

Thanks, good to know. The issue is still DCS side though, ED is currently investigating.

This explains a lot I've been experiencing in both the 14 and 18 last weekend... thought it was me. Good to know this has been hunted down already, now it's just the wait for a fix

They'll fix it after someone makes a video and spoon-feeds it to them. Oops, did I say that out loud?

Yes, unfortunately, you did just say that out loud.

I take it ED haven't got back to you about the issue yet guys?

I don't think the error is on our side, it seems to come from DCS.

It seems the error is not fully on DCS' shoulders, but a bit of both: DCS calls a certain init API (provided as callback by F-14) twice when starting on carrier, vs. only once on land. This was undocumented (and therefore unexpected by us), but upon investigation by ED (after we submitted a detailed bug report) it is apparently necessary because the carrier is moving and something to do with multiplayer... not 100% clear yet exactly the reasons, but bottom line is we need to re-shuffle some code around in the FM to init the fuel tank weight distribution elsewhere to avoid it being done twice cumulatively (and ensure with thorough testing that it doesn't break ground/air refueling etc.). This fix won't make it in the current update cycle unfortunately, so might be a week or two before it lands. Unclear how long this issue has been present, as we don't know when that init API started being called twice by DCS. For now, just be aware that if you spawn on the boat and take-off, your weight will be too heavy (up to 7348kg too heavy, if you had full internal fuel). The way the DCS catapult API works automatically takes care of this issue (otherwise it would of course have been noticed immediately), so it basically gives you the extra oomph to make you still take-off correctly, but the extra weight is noticeable when landing or just trying to fly on-speed etc.

Thanks for the update gyro.

Would it be a feasible workaround to launch with a very low fuel state, fill up from a tanker immediately, complete the mission, then come back and not have this extra fuel weight dragging us down?

Yep that works with empty tanks.

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Would it be a feasible workaround to launch with a very low fuel state, fill up from a tanker immediately, complete the mission, then come back and not have this extra fuel weight dragging us down?

Yes. I haven't confirmed, but I think it would also work to start with low internal fuel and full external tanks, I don't think those get added twice, they follow a somewhat different path in the API. Not 100% sure though.

I never took the risk with the full tanks just spent an extra couple of minutes

on the tanker.

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You can spawn cold with 0% fuel, which will add 0 weight like that, then refuel on the boat and rearm with tanks and you will have normal weight instead.