Max Design Speed limit for prop planes?

[Pseudonym]

No matter what I set the mmo overspeed warning to in my .air file, it gives me the max speed warning before 500 mph. Do I need to switch my plane to a jet to get a max speed over 500 mph?

 

[hairyspin]

I expect you're running up against an entry in the Reference Speeds section in your plane's aircraft.cfg, but the people who actually know are to be found at the Flight Dynamics forum:- http://www.sim-outhouse.com/sohforums/forumdisplay.php?f=42

All you need to view (or edit) aircraft.cfg is Notepad. BTW, the number of prop planes capable of exceeding 500mph in level flight was, and still is, exceedingly small.....