Focke-Wulf Fw 190A poor high-altitude performance

[kennethklee]

Originally Posted by Graham Boak

The power drop is due to the drop in pressure above full throttle height, not to a shortage of oxygen in particular.

Even a single stage supercharger requires power to drive it.

A turbocharger takes energy from the exhaust that on mechanically supercharged engines can be used to provide thrust from angled and ducted exhausts, though this is less than that needed to drive the supercharger. However, a turbocharged radial would not be able to benefit from the engine/airframe integration that was so cleverly devised on the Fw 190 - which is the example under discussion. The extra power would therefore be counteracted by greater configuration drag - the precise tradeoff depending upon the actual design.

The P-47 found the turbocharger's stainless steel ducting valuable as pilot armour for the ground attack role, but I think that can be described as a fortunate result rather than a planned feature. However, all advantages count.

Graham-

I thought that basically piston engines provided power by oxygen igniting fuel and creating little explosions within the cylinder walls, the force of which pushed the pistons up and down. By this reasoning, I surmised that the lower power at altitude was due to the relatively lower oxygen concentration, which would lead to mismatched stoichoimetry in the combustion of fuel and oxygen and therefore lower power. By the same token, I thought superchargers compressed air, which therefore increased oxygen content and therefore restored power.

You mentioned the power drop was due to drop in pressure above full throttle height. Pressure of what? Could you kindly elaborate some more on this? I readily admit my ignorance here, I'm not following the reasoning here.

Thanks!
Kenneth