757 fuel burn issues

Two fuel issues that I have found when testing:

  1. The optimal altitude when cruising at .80 jumps from around 320 to around 390 in a very short period of time, at around 80 tonnes.
  2. For some reason the plane is more efficient at .85 compared to .80 (doubt this is accurate).

Are these issues known to the devs and will they fix it?

I don’t have an answer for the first one, but I have for the second one:

  • The Aircraft is designed to fly between 0.78 and 0.80, that does not mean it can be more efficient at higher speeds but the plane is not designed for higher speeds.

The 757’s Mmo is .86 though. Other planes that cruise at .78-.80 such as A320 and 737 have a much lower Mmo at .82

BTW, LRC simbiref uses fastest speed that uses 1% more fuel than optimal, and that gives up to .82 at lower altitudes and down to .78 at higher altitudes, never .85.

This is a known issue actually and is already noted internally. Thanks for the report!


As long we don’t pay for the fuel , I don’t care how much it needed 😅
I add extra 3 hours on a long haul

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I have the numbers too and can confirm this is true however the difference is quite small I don’t think it’s significant

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Well it starts to matter a bit when you try to range push (eg. use CSN 757 in place of A330)

There is another issue that might not have been noted though. If you have fuel in all three tanks, the aircraft would normally drain from the centre tank first followed by the wing tanks. This is done for structural reasons.

However, the aircraft in Infinite Flight appears to drain from all three tanks simultaneously.

Not sure ablut this, but don’t think this affects the flight dynamics significantly. Trim doesn’t affect fuel in IF at all.

It’s nothing to do with trim. I suppose it’s more of a realism thing really. In real life it would make a bit of a difference in roll characteristics etc but I don’t imagine that is simulated in IF due to being quite a complex and subtle thing.

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I would have to say that it’s more of a center of gravity issue if anything, Maybe even a trim issue depending on where the fuel tanks are located on the aircraft.Nothing to do with structural limitations I would say. Never flown the 757, many hours in the 737 which has a somewhat similar fuel system I believe. Just my thoughts though.🤔🤪

Having better fuel burn at .85 doesn’t make sense though (mmo is .86). I don’t think IF models CoG or trim for fuel.

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