When at cruise in the flight levels (transition altitude FL180) and setting up for the descent, I set my altimeter preset to the landing field altimeter.   The FO automatically switches it from IN to HPA QNH setting equal to the IN value.  For example i'm cruising at FL290 from KLAX to KLAS (shorthaul haha).  I start setting up my descent and enter the preset altimeter to 29.97.  When I call for the descent procedure the first officer automatically switched 29.97 to 1015. How do I prevent him from switching to QNH?  

 

Thank you as always, 

Matt

Hi Matt,

When the Descent Procedure is run, FS2Crew scans for the nearest airport to determine what country you're in.

If the ICAO starts with a K or a P or a C it assumes you're in the US or Canada, and the FS2Crew FO should set the altimeter scale accordingly.

However, I'm thinking it might be picking up some small little airport that doesn't start with the usual K or P.  Like some private airport.

I just tested it sitting on the runway at KORD and the selector stayed in IN when I ran the descent procedure.

So I'm thinking that's it.

I'll see what I can do about this scenario.

 

Hi Bryan,

I think you found the root cause of this issue.. I ran 2 tests based on the altimeter selection logic, on the active runway at R33 (Wakonda Beach State ) and at KPDX (Portland Intl). As you predicted, the altimeter scale remains set to IN at KPDX but is switched to HPA when at R33 (nearest airport with K/P/C located 11.7 NM away).

Can you change the logic to check for the arrival ICAO code from the flight plan or FMC?

-thanks,

Scott

 

 

I did some research.  We can narrow the nearest airport scan using runway length to filter the  results.

That way we can exclude all the little private airports by only scanning, say, airports with a runway over 2000 meters or some such value.

This will be in V1.2.