Folks,

I was wondering if any of you know of any WW2 aircraft designs which flew using this engine arrangment. I know that the Avro 684 Stratospheric Bomber design used this engine layout (1 Master Merlin in the fuselege driving a very large intercooled supercharger, which supplied compressed air to the 4 wing mounted Slave Merlins), but this design was never built. It had truely amazing performance but i'm wondering if the Master-Slave concept is a viable propulsion option, as i've not heard of it being used in any operational aircraft.

Sbiper.

The only WWII airplane I know using this configuration is the Pe-8.

A few of the early Pe-8s (Soviet bomber) used a 5th engine, located in the fuselage above the bomb bay, which was feeding the 4 wing engines with compressed air, acting like a sort of centralized supercharger.

This outfit was not retained, and 4 diesel supercharged engines were favored in the production series, even if the performance was worse, because it allowed for more range.

I think this was a viable and smart solution, as long as you had issue with producing good high altitude supercharged engines, which was the case for the USSR.

As soon as you had good supercharged high alt engines, adding an additional engine to the design would just mean more weight and more fuel to lift and haul.

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The Germans also tried this, specifically in the Henschel HS 130E. This aircraft used the HZ-Anlage, which used two DB603B engines (wing-mounted) that were supercharged by a DB605T engine mounted in the center of the fuselage.

http://www.airwar.ru/image/i/spyww2/hs130e-i.jpg

My source is the book "Warplanes of the Third Reich (Green) and this web page:

Translated version of http://www.airwar.ru/enc/spyww2/hs130e.html

tom

The whole concept was necessary for one of two reasons, and often for both.

The first reason was most nations could not produce either individually or enmasse turbochargers running on engine exhaust. Outside the US, who was the leader in this particular niche, no other nation made extensive use of exhaust driven turbochargers on aircraft.
The alternative was a mechanical supercharger run off the engine. As these grew in size their parasitic load grew with them. For very large systems it was more efficent to just have a dedicated engine running the supercharger compared to each engine running its own compressor.
The US also ran into this problem with the P-47 being the classic design case. Here you have an aircraft with such a large turbocharger supplying the engine that there is not enough exhaust to provide power to run it alone. So, the designers added a drive shaft making the system a turbosupercharger that combined the "something for nothing" exhaust turbocharger with the necessary make up by parasitic load of supercharging.

The Germans, Japanese, and Russians really had little choice but to go with supercharging. They lacked the metallurgy to build more than a handful of turbochargers. In the Japanese case they actually built one prototype fighter (a take off of the Ki 84 Hayate) using captured B-29 superchargers from shot down aircraft! This hardly bodes well for mass production.
Outside the Fw 190C the Germans pretty much stuck to the supercharger system. The Hs 130 was mentioned. I believe there was a Do 217 with a similar system that was tried also. Most of the time, using just the supercharger was sufficent for typical altitudes reached.
In any case, these systems had a practical limitation of about 45,000 feet in any case. Much above this piston engines just were not going to get enough air regardless of the system used. Going higher demanded jet engines.

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