From: Old Los Angeles
increasing performance at altitude
Turbo/Super/Twin charger technology allows a piston engine to generate horsepower that will approach sea level performance ... but you cannot exceed that. Jet/rocket technology is completely different and so excluded from this discussion.
Now, as you increase altitude, air density drops. Thus, for the same engine output, some performance characteristics can potentially improve (climb rate), but in practice rarely do. Others though that rely on control surfaces (roll, turn, etc) generally degrade as altitude increases.
The net effect for this era is that theorectical maximum plane manouverability degrades as altitude increases. Now, by judicious use of twin chargers and design you can come ever closer to these maximums. P51 is the standard against which all air frames of this era are measured. That is why it was used in racing even into the 70's as the very best aircraft.
I'm late to comment on this, but - and as a matter of fact, having worked on this part of the game - I can tell you without reservation that some WWII piston engine aircraft CAN and indeed DID make more horsepower and produce greater speeds at higher altitudes than at sea level.
I am not responsible for the final MVR Ratings in the game, the head of the Air Team was directly responsible for choosing those - though he did have a consistent methodology.
I therefore cannot state with certainty that some aircraft in the game have higher MVR ratings at high altitude than they do at Low Altitude (for reasons beyond this discussion), but there certainly ought to be.
For example, the maximum speed of the above mentioned P-47D is 333MPH @ 2,110 HP at sea level, increasing as altitude climbs to 390MPH @ 2335 HP at 15,000 feet; maxing speed to 435MPH @ 31,000 feet (though HP drops a bit). Look HERE for aircraft test and acceptance documents.
< Message edited by Big B -- 4/4/2013 11:26:55 PM >