When I set my altimeters and the FO responds "xxxx set, passing altitude xxx descending xxx" I always get to hear a wrong passing altitude, which mostly is about 300-400ft off compared to the correct altitude.

My FS units are set to imperial already, so a metric setting there is not the issue.
This happens regardless of the actual QNH, even if I just reset it from 1013 to 1012 I get some 300-400ft difference, so the QNH can't explain the issue either.

Any ideas what may be wrong here?

When having the FO read the altitude (passing 8000 feet or whatever), we have to guess at the passing altitude value he reads out because that value can very a lot depending on how fast you are descending.  Due to the way the code works for the audio que, we have to feed the FO the passing altitude the second the call is made.  At the moment we just approximate it by subtracting so many feet from the altitude you passed when the call was triggered.

Make sense?

 

Yes, this certainly makes sense and explains why it can't always be spot on!

May it be possible to adjust the "guess" of the passing altitude a little based on the vertical speed?
It could possibly become more accurate if you'd take the actual VS of the aircraft and predict the passing altitude since you know how long it will take the FO to say his words.

At least in my experience you seem to assume a far greater rate of climb/descend than what I typically fly.
Any chance for some input of other users here? Do the calls match (approximately) for you other guys out there?

Lucky for you I'm a math expert :-)

I think I can improve the math a bit to generate a more accurate call 

1 hour ago, Emi said:

At least in my experience ......

more please !!

1 hour ago, byork said:

Lucky for you I'm a math expert :-)

I think I can improve the math a bit to generate a more accurate call 

 

Haha, you're the greatest Bryan ;)