Focke-Wulf Fw 190A poor high-altitude performance

[kennethklee]

The poor performance of the Fw 190A above 20,000 feet is well-known. As best I could ascertain, the reason for this limitation was ineffective superchargers for the Fw 190's BMW radial engine. The Republic P-47 Thunderbolt had excellent high-altitude performance with its radial engine, which was attributed to a large degree to its supercharger. The Germans seem to have effective superchargers for their inline Daimler-Benz and Junkers Jumo engines, so I am curious why an effective supercharger was not able to be developed for the BMW radial engine. (Searching on Google was fruitless for me.) Am I missing the real reason(s) for the poor performance of the Fw 190A at altitude?

Thanks,
Kenneth

[John Beaman]

The P-47 was the happy recipient of a lot of research and experiments by the USAAF with turbo-superchargers (exhaust driven) and was, therefore, ready for high-altitude combat.

The Germans, on the other hand, never anticipated the WWII high altitude combat that resulted from the USAAF’s high altitude bombing campaign. Recall, that the DB 601 engine was developed in the late 19030s when medium altitude combat was the expected norm. The DB engines were not that great over 20k feet, hence the eventual addition of GM-1 to the DB 601 and 605 for high altitude performance and eventually, the make-shift AS types. This was also true of the RR Merlin which did not have effective high-altitude performance until the Merlin 61(?) in the Spitfire IX. Superchargers for in-line liquid cooled engines were much simpler to develop than for radial engines, hence all the work by the US on the turbo superchargers—it was tedious work. The Germans never made that much effort for radials until the Fw 190 experiments which resulted in nothing for the BMW radials. It was simpler, easier and quicker to do the D-9, pending the Ta 152.

Bottom line: the need was not anticipated and money for experiments was always a big issue for the pre-war Luftwaffe. Goering and Hitler wanted a strong air force, now, not a few years down the road.

[kb]

IIRC US Navy/USMC radial engine fighters (F4F, F6F, F4U) had similar performance drop offs to the 190A at high altitude.

[Graham Boak]

It is not a function of radial engines. It is largely a matter of superchargers and the maximum compression ratio. All single-stage supercharger engines begin running out of power around 20000ft. The radial BMW 801 was no different to the inline Sabre, hence the problems with accepting the Typhoon into a Fighter Command that increasingly emphasised high-altitude performance. For performance at higher altitudes the US went to turbochargers, the UK to two-stage superchargers, the Germans to exotic fuel additives. This was partly a matter of available materials, turbochargers requiring exotic metals the Germans lacked; and available expertise, RR being particularly good with superchargers.

For additional altitude, aerodynamic advantage can be gained from larger wings, either by increased span or greater aspect ratio (span divided by mean chord, or span squared over wing area). The Fw 190 has a low aspect ratio wing, so loses out here. Consider the Ta 152H.....

[Harri Pihl]

Focke Wulf and BMW planned to add the turbo charger but these developements never went beyond experimental stage. IIRC the only plane which reached more or less experimental service with the BMW turbo charged engine was the Ju 388.

[Harri Pihl]

Originally Posted by Graham Boak

For performance at higher altitudes the US went to turbochargers, the UK to two-stage superchargers, the Germans to exotic fuel additives. This was partly a matter of available materials, turbochargers requiring exotic metals the Germans lacked; and available expertise, RR being particularly good with superchargers.

The Germans were going towards two stage mechanical superchargers as well. There were numerous such projects, the development was just slow. The Jumo 213E was the only such engine to reach the service in some degree.

[Graham Boak]

And Allison did a two-stage supercharger, which saw production in the P-63, and postwar in the F-82.

It is worth pointing out that phrases such as "poor high-altitude performance" is only meaningful comparated to those aircraft with turbochargers or two-stage superchargers. The Fw 190 was superior to the Yaks and Lavochkins it faced on the Eastern front, although curiously it does not seem to have gained the same reputation in the East that it had in the West. A supercharger design is set to a given pressure, and hence a given fixed throttle height. Witness the "cropped" LF series of Merlins, which gave the Spitfire LF Mk.V possibly the highest low-level climb rate of any WW2 service fighter, but reached its maximum power at only 5000ft.

[Ruy Horta]

Kenneth,

I suggest you take a look at:

Focke-Wulf Fw 190A
Die Ersten Baureihen
Dietmar Hermann, Ulrich Leverenz & Eberhard Weber
Aviatic Verlag, 2002
3-925505-72-5
Laminated, 222p

Focke-Wulf Fw 190 "Long Nose"
An illustrated history of the Fw 190 D series
Dietmar Hermann
Schiffer Publishing, 2003
0-7643-1876-4
Hard Cover, 206p

Focke-Wulf Höhenjäger
Vom ersten Höhenjäger zur Fw 190 H
Jet & Prop Typen-Chronik 6 Spezial
Dietmar Hermann
VDM, 2002
3-925480-XX-X
Softcover, 132p

The first title is also available in English as published by Schiffer (I usually by original German if I have a choice).

These three books cover your questions regarding the Fw 190 and high altitude performance.

Issues as design philosophy, impact of the RLM, engine and supercharger research are all covered. The Fw 190 was seen by Tank as a flexible frame for a work horse.

[Jim Oxley]

Thanks for those book recommendations Ruy, I've been looking for quality books on the Fw190 for ages.

Btw, what does IIRC mean?

[John Beaman]

Originally Posted by Jim Oxley

Thanks for those book recommendations Ruy, I've been looking for quality books on the Fw190 for ages.

Btw, what does IIRC mean?

"If I Recall Correctly"