Brewster has top speed at all alts.
Heh, funny way to put it.
Other way is to say that it's equally slooow at all alts.
Seriously tho, G5-Cyclone looses power quite rapidly after it's first gear's very low critical alt of 4000ft. Good way to see this is to look at the climb chart. So as the air gets thinner Cyclone looses power fast...so as drag gets smaller the power gets smaller aswell...+/-=0. Most planes are able to sustain their sea level power to much higher alts which enables them to get faster as the drag decreases.
One suprise might be to some that if the starting speeds are the same you can out run/climb an La-7 with 109K-4 or even with a G-14 by doing a very shallow climb (+/- 1000ft/min). At those high speeds the 109 has a hair more excess thrust even at sea level and the difference gets bigger as the alt increases. As everyone knows, La-7 will catch K-4 on the deck easily at level flight so the shallow climb is about the only way to disengage from the angry mob with La-7 leading the pack.
As Grizz mentiones after reaching 6k you are safe at level too with K-4, for G-14 the safe alt is naturally higher.
