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asymmetric fuel burn

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greetings.

 

i've had 2 flights in the past few days where one of the wing tanks depleted a bit faster than the other... starting at around 8000 lbs each, by the end of a 2.5 hour flight there was almost a 400lb difference between the two.

 

it was kind of cool having an excuse to mess with the cross feeds to balance them out a bit, but i'd never seen that before until now, usually they stayed within pretty close range to eachother. any ideas what could cause this? as far as i know the only thing different on my system is AS2016, could that be related somehow? (previously using ASN. this is on FSX:SE).

 

cheers

-andy crosby

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any ideas what could cause this?

 

Running the APU for a while on the ground (or in the air) and not realizing it's pulling from only one side, most likely.

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Kyle, you beat me by a second, I was about to say the same!

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Running the APU for a while on the ground (or in the air) and not realizing it's pulling from only one side, most likely.

 

thanks for the reply.

 

when i noticed it i indeed thought possibly i had forgotten to turn the APU off, but it wasn't running..

 

if it was just usage from the ground, wouldn't it require quite a bit of time for it to use 400lbs of fuel?  i usually use the ground power during pre-flight, so the apu is typically running for maybe 5 minutes during pushback+start..  

 

i will keep a closer eye on the numbers next time. maybe was just a fluke, but i thought it was odd to see it twice in a row after never seeing it before in many flights. 

 

cheers

-andy crosby

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The FCOM puts a fuel imbalance limit at 1000 lbs for landing or takeoff.  In reality, a 400 lb difference out of a total fuel burn of 16,000 lbs is only 2.5% and I've observed there is a small difference between NGX engines for fuel and oil consumption.

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The FCOM puts a fuel imbalance limit at 1000 lbs for landing or takeoff.  In reality, a 400 lb difference out of a total fuel burn of 16,000 lbs is only 2.5% and I've observed there is a small difference between NGX engines for fuel and oil consumption.

 

i did another flight last night looking very carefully at the tank levels and everything seemed normal. there was maybe a 10-20lb difference over the course of 1.5h. 

 

i did notice that a 30sec delay between starting engine 1 and 2 was enough to introduce a 50lb difference. i'm guessing that is where it happened, i may have been messing around with settings or otherwise distracted during pushback and had a few minutes of time in there..

 

cheers and thanks 

-andy crosby

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