As for myself, I have seen the center tank quantity fluctuate on climb out. This is most easily seen when shutting off the center for take off when quantity is less than 3000 lb.

 

Hi Preston, 

 

what exactly have you seen?

Scavenging is not the error meant here, is it? 

I'd expect that the indicated amount raises and falls due to attitude, not scavenging  (always really down). 

Hi Andreas, did you do a fuel check? = comparing the fuel used to the fuel remaining?

 

The capacity measuring error I see in reality is a missing fuel amount of up to 300-400kg after more than 4 hours of flight due to the fuel temperature change.

 

Berni

Hi Berni, 

 

ok, then in 737NGX there should be a difference between

- the displayed/indicated amount of fuel on the upper centre MFD and

- the 'true' amount of fuel in the centre tank according to the PMDG FMC convenience fuel page,

right? 

 

A temperature issue would contradict or add-up to the aircraft attitude discussion above... 

 

Ok, during the weekend I need to do another test flight... 

Hi Preston, 

 

what exactly have you seen?

Scavenging is not the error meant here, is it? 

I'd expect that the indicated amount raises and falls due to attitude, not scavenging  (always really down). 

As I said, I saw the error during climb out, because that's when you get the large attitude changes. And no, it wasn't scavenging, because the quantity was too high to activate those pumps and the error went up, something like from 2.8 to 3.0. 

 

 

As I said, I saw the error during climb out

 

Hi Preston, 

 

but what IS the error?

I assume you have the center pumps off and instead of 3000kgs you read something else. 

 

And I would assume that in the FMS you still have 3000kgs, (true?)

 

while the center MFD shows more or less than 3000kgs. 

How much kgs more or less? 

 

Thanx in advance.