@iniKyle The issue isn't poor fuel burn calculations; it's the drag and the fact that the aircraft really struggles to climb above FL300. This will only become worse if carrying additional fuel, so I'm not sure what the solution is here.

The proposed workaround seems to be increasing the fuel consumption figure during flight planning, but that doesn't actually address the underlying issue. It simply means planning for a higher fuel burn than the aircraft should realistically be consuming, which isn't an accurate representation of how much fuel the aircraft should be burning.

Are we therefore expected to carry more fuel and cruise at a lower flight level instead? Neither seems like a particularly satisfactory solution to the underlying performance issue.

1 hour ago, Gungnir said:

Which fuel factor (Pxx) in simbrief?

P05, but the Plane needs more fuel as Simbrief calculated, i try it later with P11 or Higher

1 hour ago, MasterLorenzo said:

@iniKyle The issue isn't poor fuel burn calculations; it's the drag and the fact that the aircraft really struggles to climb above FL300. This will only become worse if carrying additional fuel, so I'm not sure what the solution is here.

The proposed workaround seems to be increasing the fuel consumption figure during flight planning, but that doesn't actually address the underlying issue. It simply means planning for a higher fuel burn than the aircraft should realistically be consuming, which isn't an accurate representation of how much fuel the aircraft should be burning.

Are we therefore expected to carry more fuel and cruise at a lower flight level instead? Neither seems like a particularly satisfactory solution to the underlying performance issue.

The underlying performance issue is a simulator bug, it seems.

Is someone on the beta branch 1.9.23.0 and can verify that drag/fuel flow is fixed there? Are the dev team confident that is the case @iniKyle ?

Actually reading the inibuilds discord threads about the fuel issue is not particularly reassuring.

Edited 4 hours ago4 hr by Gungnir

I wrote in the discord thread but I'll post it here too:

First evidence that something is wrong: if you try to recreate https://en.wikipedia.org/wiki/Longest_flights in simbrief with the new profiles at P11, they are all impossible. For example: for new york to manila in the a35k simbrief says I am lacking 17 tons of fuel/range.

TEST 1: airspawned a a359 and compared it to this SAS jet in the FR24 youtube video. I refuelled to match the GW at 231 T, matched the temperatures at -1 degree ISA and climbed to the same level and speed. in the sim the FF is 3350 kg/h at around 85% thrust. In the real jet, by looking at several times in the video, it looks very steady at 3050--3100 kg/h at 80--81% thrust. clearly either there's a thrust issue or a drag issue in the sim.

TEST 2: If I match the thrust figures instead then?

At 81--82% like they have, my FF is even a bit lower than theirs.

TEST 3: in this video https://www.youtube.com/watch?v=jOe9nZ3qYkk, they take off at FLEX +72 and their FF reaches about 8600 kg/h.

I spawned an aircraft also at sea level, set the SAT to match. If I go FLEX 72, my thrust goes to 81% (no idea why it's not 65% like theirs actually), but if I set my thrust manually to 65% it matches well.

So these findings are consistent with too high drag or too low thrust, since FF seems to be similar at similar thrusts, rather than too high fuel flow at given thrust.

I also note that the cruise figures above, 3400 vs 3100 kg/h, is about 10% off, which matches the P11 figure. On a long flight, and if those numbers are representative of the whole cruise (it's just one altitude), I would expect the inibuilds aircraft to require P10 if the real aircraft could use P00 in simbrief.

Edited 2 hours ago2 hr by Gungnir

Yep, definitely a drag issue.

What I don't know is if Microsoft have 'fixed' drag with these updates and are expecting devs to adjust their aircraft to these 'correct' drag profiles or if Microsoft/Asobo have just got it wrong and they need to make a change

Asobo are not expecting anyone to change, like I posted earlier in the thread

But it's not clear to me if the a350 even is affected by this bug. Rich over on the discord said that they had made various tweaks:

"1.2.7 actually tweaked the cost index and fuel burn
1.2.8 tweaked the fms estimation logic under certain specific conditions."

So they did change the fuel burn in 1.2.7 without mentioning it in the patch notes (which is a strange decision to me). This together with the fact that the reports of high fuel burn started coming after 1.2.7, not a week earlier when SU7.1 was released makes it quite frustrating that there's all this speculation in this thread.

Some of us are acutally spending quite a lot of our free time to make the a350 better here. It would be great if the dev team could just say "oh yeah, that's because we increased the fuel burn".

Anyway, as my tests show above, P11 is unrealistic (you fall into the sea instead of make it to manila) and the fuel flow / required thrust in cruise is unrealistic compared to actual cockpit footage.

Edited 2 hours ago2 hr by Gungnir

Of course, if someone is in the 7.2 beta we could check instantly

5 hours ago, MasterLorenzo said:

@iniKyle The issue isn't poor fuel burn calculations; it's the drag and the fact that the aircraft really struggles to climb above FL300. This will only become worse if carrying additional fuel, so I'm not sure what the solution is here.

The proposed workaround seems to be increasing the fuel consumption figure during flight planning, but that doesn't actually address the underlying issue. It simply means planning for a higher fuel burn than the aircraft should realistically be consuming, which isn't an accurate representation of how much fuel the aircraft should be burning.

Are we therefore expected to carry more fuel and cruise at a lower flight level instead? Neither seems like a particularly satisfactory solution to the underlying performance issue.

As I, and many others in this thread have spoken about, this is a core sim issue ATM.

I will ask if any of the team members can try the newest SU7 Beta, to confirm whether this has been fixed or not.

Thanks for your understanding and patience 🙂