Re: Focke-Wulf Fw 190A poor high-altitude performance
 

Jim,

Do you have Peter Rodeike's Focke Wulf book?
If not, that one certainly deserves a place with these three works.

Re: Focke-Wulf Fw 190A poor high-altitude performance
 

There is also:

Kurt Tank: Focke-Wulf's Designer and Test Pilot
Wolfgang Wagner
ISBN 0-7643-0644-8

Re: Focke-Wulf Fw 190A poor high-altitude performance
 

Ruy-

Thanks for the book recommendations. I have Jerry Crandall's (Focke Wulf Fw 190 Dora Vol 1" on order and I am hoping it will cover the altitude issues that led from the Fw 190A to the Fw 190D. I'll see if I can find Dietmar Hermann's Fw 190 books.

Kenneth

Re: Focke-Wulf Fw 190A poor high-altitude performance
 

Thanks to everyone who posted on this thread. I gained more insights into why the Fw 190A had poor performance above 20000 feet, why it was not initially considered a problem, and more books to read.

Kenneth

Re: Focke-Wulf Fw 190A poor high-altitude performance
 

Guys:

Say can anyone define what an 'exotic' metal is? Also, does the power drop off to an engine due to lack of oxygen at high altitudes or to another reason?
Thanks ahead of time;

nm

Re: Focke-Wulf Fw 190A poor high-altitude performance
 

I'll take a shot at answering. However, if I am wrong, please, more knowledgeable members do not hesitate to correct me!

1. Exotic metals - I think what Graham Boak was referring to were metals for higher-strength alloys, which Germany sorely lacked. These are needed for high-compression engines and I think this is the reason the Bf 109 and Fw 190 relied on chemical boosters such as GM-1 and MW-50 to increase power output. I suspect these were needed for superchargers as well and thus a reason the Fw 190A did not have an effective supercharger for its BMW radial engine.

2. Oxygen - yes, the lower oxygen at higher altitudes results in lower piston engine (both radial and inline liquid-cooled) power output. This is the reason superchargers are needed for high-altitude performance; they compress the air and thus increase oxygen concentration, then the compressed air is injected into engines to ignite with fuel.

Kenneth

Re: Focke-Wulf Fw 190A poor high-altitude performance
 

Kenneth, one needs exotic metals in turbo superchargers because of the hot exhaust gases used to spin the turbine wheel. Mechanical superchargers sucked in 'cold' air. Even in the 2 stage superchargers, the air from the first stage was not that 'hot'.

The Jumo 004A used exotic metals but the Jumo 004B did not, which reduced its TBO from 100 hrs, in the 004A, to 25hrs.

MW-50 was used below the engine's FTH and GM-1 was used above the engine's FTH.

Re: Focke-Wulf Fw 190A poor high-altitude performance
 

Regarding 1, the German engines were of typically high compression ratio engines (starting at 6.7:1 and increasing 8.5:1 during the war) against the typical Merlin/Allison 6:1.

Regarding 2, lack of oxygene that can no longer be provided by the supercharger as it runs out of air (get it?) above its rated altitude is one of the reasons for the drop of power with altitude. The other cause is the supercharger itself - unless we talk of single stage superchargers, the second high altitude speed/stage of the supercharger always takes away more power from the propeller to drive the supercharger harder.

There is some inherent handycap with the radial engines themselves, as typically radial engined fighter require more power to develop the same performance as inline ones, it also means the engine needs to develop more power - and thus it also needs more air to burn more fuel, and thus having greater need for a high capacity supercharger than an inline engine.

Re: Focke-Wulf Fw 190A poor high-altitude performance
 

You should have mentioned Kurfurst that German engines used less boost. The highest boost, except for the penny pocket of 109ks using 1.98ata, was 1.80 ata. 1.80ata being a little less than 11lb.

Re: Focke-Wulf Fw 190A poor high-altitude performance
 

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.