Fuel burn way off from Simbrief recommendations

[Parksandtech]

In order to even be near using the recommend trip fuel, and having enough to make it to the alternate airport I have to set fuel factor to P30. This seams really extreme. To be honest I've only tested as high as P30, and it's not enough to match Simbrief recommendations. With P30 I usually arrive somewhere between FINRES and ALTN fuel quantity recommendations. I'm not pausing, no assistance options are on. I'm using the iniBuilds provided Simbrief profile. For cruise profile I've used M80 and LRC, and didn't see much of a difference. I've tried cost indexes of 40, 60, 100.  I set my cruise altitude no higher than the FMC recommendation.

[Deleted Account]

This is very weird as that profile was very accurate during testing. Are you by chance pausing the sim during the flight? There currently is a bug that fuel gets consumed during a paused sim.

[Alexair]

I just discovered that I have a fuel issue as well. Not quite the same though.

At the end of the flight my FMS is off by 4000-5000 lbs (less than actual) compare to what I have left in the tanks. I saw that on several long haul flights (8h and more).

[Deleted Account]

50 minutes ago, Alexair said:

I just discovered that I have a fuel issue as well. Not quite the same though.

At the end of the flight my FMS is off by 4000-5000 lbs (less than actual) compare to what I have left in the tanks. I saw that on several long haul flights (8h and more).

Yup, there are current weight calculation errors when using lbs. That´s already on our radar 🙂

[Parksandtech]

4 hours ago, gumbyger said:

This is very weird as that profile was very accurate during testing. Are you by chance pausing the sim during the flight? There currently is a bug that fuel gets consumed during a paused sim.

No, I'm not pausing. Sorry, I forgot to mention that I am using lbs. Which I wasn't tracking was already an issue. Didn't compare the FMS with the overhead. I assumed they were correct because when the low fuel warnings went off on a flight the overhead low fuel warnings were on as well.

[Aburek]

Real world planning accounts for 2500-3000 lbs extra that gets trapped in the center tank.  After each landing we have to transfer that fuel out as its not usable.

[Alexair]

Oh that's an interesting point !

Can you develop/explain a bit more? (why, how you transfert and who, etc...)

Thanks !

[Aburek]

Fuel transfers to the trim tank for cruise CG control its a rather sensitive (and pretty unreliable) system which doesnt allow for long range flights when inoperative.  Some A300s didnt come with it actually, but all the A310-300s did.  A310-200s did not.  Anyway, when it transfers back to the center tank around 2200-2500 remains in the center and is not used.  When you account the fuel in the manifold, it accounts for nearly 3000 lbs.  

Fuel is transferred by ground personnel.  Its basically turning the center fuel tank pumps on and transferring the fuel to the wing tanks from the refuel panel below the right wing.

Edited November 19, 2022 by Aburek

[Alexair]

Thanks a lot for this explanation !

So, wouldn't ge great to simulate all of that ? (via the tablet when on the ground and with an option for AUTO for those who doesn't want to bother).

Maybe I'm asking too much here 🤣

[Aburek]

Well when you set up your next fuel load it should properly distribute it so it sort of does.

[alex192]

Hi, I noticed very high fuel burn on my flight today. I noticed it right after using the drone camera, and it is reproducible by doing the following:

- Switch to drone camera, move far away from the plane -- i.e. if cruising move the drone down to ground level (I mapped 'increase drone translation speed' to help speed up -- not sure if this is relevant to the bug).

- Re-centre drone (drone will fly back up to cruise altitude very quickly

- Notice that the plane does a sort of nose dive to try to recapture the cruise altitude, as though the autopilot wasn't being followed when far away with the drone

- The fuel burn totaliser will read much higher

This doesn't happen in any other plane, so my guess is that either fuel burn is linked to how the camera is moved, or fuel burn / the aircraft systems do not behave the same when the camera is far removed from the aircraft.