EDIT: as we say in Oz, the “problem” turned out to be a Furphy.
I was measuring RPM with the aircraft braked on the ground, which meant the prop was under load and hence not reaching max. revs. Once I started taxiing and in particular flying the prop unloaded and rpm increased, in most cases to the red, in a couple well into the yellow.
The only two that still couldn’t get to the red or yellow lines (Optica and Savage Cub) both seemed to hit airframe aerodynamic limits before they could get fast enough.
So… the simulator is in fact AFAIK accurate, but I used to be able to get all piston aircraft to the redline static. So it’s a simulation bug that was fixed at some stage, SU7 perhaps?
As for the ones that do go to the redline under brakes, they appear to be the more powerful and some may have variable pitch or CP props.
I’ve further investigated the problem where the 152, 172 and Optica would no longer reach full throttle by testing throttle response of all aircraft and the great majority are fine!
All jets and turboprops are OK.
The only problem aircraft, all piston-engined, are:
Cessna 172 and 152: max 2400, redline 2500
DR400: 2340/2600
CT: 4300/5800 (!)
Icon A5: 5100/5800
Savage Cub: 4700/5800
Savage Shock: 5460/5700
Optica (Orbx): 2300/2700
I can’t see anything these aircraft have in common, apart from high rpm engines more likely to be affected.
Any ideas?
Thanks!