Originally Posted by
chornedsnorkack
The performance of aircraft deteriorates in thin air - in "hot-and-high" conditions. Wings have less air for lift, and engines have less air for thrust.
But is there any difference between hot and high? Do aircraft perform differently in low-but-hot conditions and cold-but-high conditions? Or is the air density all that matters, with temperature and pressure being irrelevant for performance at a given air density?
No, temperature also matters. Because often your engine thrust deteriorates significantly at high temperatures, due to internal temperature limits in the engine. Even at the same density/pressure altitude.
So a plane taking off at SL at ISA and one at SL at ISA+30 may have very different performance, because the thrust available is much lower, even though the aircraft aerodynamic conditions are identical.
Hot AND high is also worse than just hot OR high, for similar reasons.