Warbirds with turbocharged engines.

[Autografe]

I recently found some photos I took at an airshow at NAS Miramar in the early 1970's. I was stationed there in an F4J squadron. I had the opportunity to speak with the pilot of a P-47D razorback (pre-bubble canopy model). He told me that the turbine in the supercharger had been removed because as the turbines aged they became prone to explode. I had occasion to have a walk around of a B-17G recently and it now occurs to me these bombers had turbocharged engines also. My question is are these birds being flown with inoperative turbos? I would assume since they aren't flown at 25,000 ft anymore the turbo would just be a maintenance problem. Are these aircraft flown with a different model R-1820, possibly with a mechanical supercharger, or maybe just run naturally aspirated. I have to imagine the av-gas these engines use is becoming very difficult to find.

Just occurred to me. Did the engines as used in the B-17, B-24 and P-47 have have mechanical as well as turbo superchargers?

 

[tom slick]

I thought they all had mechanical superchargers. Some were exhaust driven turbochaged?

 

[Autografe]

Originally Posted By: tom slick
I thought they all had mechanical superchargers. Some were exhaust driven turbochaged?


Yes the heavy bombers, B-17,B-24 and B-29, were all turbocharged. I edit my original post to ask if their engines were also mechanically supercharged. The P-47 and the P-38 fighters were also turbo supercharged. I am sure there were others.

 

[A_Harman]

All of the radials in the B-17, B-24, and P-47 had mechanically-driven centrifugal superchargers, but they also had turbochargers mounted externally on the airframes. The turbos were used in WW2 for maintaining sea-level performance at high altitudes. They were designed and regulated only to deliver sea-level pressure to the inlet of the carburetors, which were mounted at the inlet of the engine's supercharger. Since warbirds still flying these days are not required to climb much above 10,000 feet, the turbochargers would not be needed. This would save hundreds (maybe thousands) of pounds in a B-17 by taking out 4 turbos, their oil systems, and controls.

 

[L_Sludger]

Why don't you post the photos?

 

[needsducktape]

What kind of oil did they use?

 

[Autografe]

Originally Posted By: A_Harman
All of the radials in the B-17, B-24, and P-47 had mechanically-driven centrifugal superchargers, but they also had turbochargers mounted externally on the airframes. The turbos were used in WW2 for maintaining sea-level performance at high altitudes. They were designed and regulated only to deliver sea-level pressure to the inlet of the carburetors, which were mounted at the inlet of the engine's supercharger. Since warbirds still flying these days are not required to climb much above 10,000 feet, the turbochargers would not be needed. This would save hundreds (maybe thousands) of pounds in a B-17 by taking out 4 turbos, their oil systems, and controls.

Thanks for the info!

 

[Autografe]

Originally Posted By: L_Sludger
Why don't you post the photos?

I don't have any way to scan photos at the moment but will work on that.

 

[Spazdog]

Interesting.

you can often see the stubby exhausts on planes of that era and I gotta' admit, I don't often think turbocharger.

The Japanese Zeroes had a two speed supercharger which is unusual when you think of who made that particular aircraft. One naturally thinks turbocharger when one thinks of Mitsubishis and Subarus.

 

[bruno]

Aircraft oils of the time were single viscosity heavy weight - 50 or 60 . The aircraft had oil dilution systems that were used after the engines had cooled down by idling when avgas would be added . The avgas rapidly evaporated when the engines were started . Very often portable heaters and canvas tents were put over the engines to preheat them . Starting one of those big radials was no simple task !

 

[bruno]

Mustangs also had two speed superchargers - originally the pilot controlled the speed but later a barometric device was added to lighten the pilots workload !

 

[Pablo]

Originally Posted By: needsducktape
What kind of oil did they use?


Decent petroleum oil for the time.

Check out the Seattle Air and Space museum someday. Really cool WWII building.

 

[Autografe]

Allison V-1710. I think it is interesting that much maligned Allison engine gave very good service at low to medium altitudes where it was at least equal to or even better than the Merlin. It had a better HP per CI than the MB engine used in German fighters. The German engine was however 400 CI inches bigger and had a superior supercharger and fuel injection. The Allison was originally designed as an un-supercharged engine for the Navy as a lighter than air ship power plant. The Army took it up in the 1930s and developed it with turbo supercharging in mind. The P-39 was originally designed to utilize a turbo. But with the pressing need for turbos for heavy bombers and a limited amount of materials needed to construct them Allison and the Army started researching mechanical superchargers for the V-1710. However they never achieved the success the Brits did with the two stage, two speed, intercooled unit used on the Merlin. By wars end Allison had developed a turbo-compund Allison for the P-63 successor to the P-39. It was rumored to be approaching 3000 HP and only limited by the need for higher temp materials to produce even more. Of course by that time jets were the future. Without its turbo the P-47 lacked any real high performance at all. It was a monster at high altitude for speed and there were few aircraft that could stay with it in a dive though it couldn't match the range and maneuverability of the Mustang.

 

[Shannow]

From what I've read, the turbine was mounted such that the turbine wheel was mounted virtually flush with the lower cowling, and the exhaust gasses passed straight down through it.

The turbine wheels were thus cooled by the passing airstream.

Supposedly these were top secret at the time, and were removed when crashed or otherwise shown.

As to the S/C, the story of Stanley Hooker, who designed the blower for the Merlin is an exceptionally good read.

Oils ?

Hadfield's Merlin powered '55 Chev was recommended to run on 4 stroke SAE 30 Mower oil by Caltex.

I've seen operating manual excerpts that recommend dumping fuel into the oil to get it started, and relying on it boiling off in service to get back to operating viscosity...I Think that's the logic for SAE 30 in the road going Merlin, which will never see full power for more than a few seconds.

 

[needsducktape]

This era is absolutely fascinating to me,
my grandfather was a engineer during that time period-

Its amazing how brilliant these machines were AND designed without computers or other modern technology.

 

[A_Harman]

That's true. I have spent much time reading books about the WW2 aircraft engines, and find that many of the technologies they worked with back then are still relevant today. The engineers back then understood the science of IC engines, but improvements in technology in the modern era have made it possible to build engines to better realize the theory.

 

[Shannow]

If you can find it, get "the High Speed Internal Combustion Engine", by Sir Harry Ricardo.

What they acheived in terms of fuel economy is still good comared to today's engines. twin cam, 4 valve pentroof chambers in the 1920s, we just have better metals and control technollogies.

 

[Shannow]

http://search.4shared.com/postDownload/U0NklsMH/The_High_Speed_Internal_Combus.html

 

[A_Harman]

Thanks Shannow,

That's one I didn't have.

 

[JetStar]

The plant that I work at, 2000 Taylor St. Fort Wayne, Indiana was completed in 1943 specifically to build Turbo Superchargers for aviation use and the war effort. It was built by General Electric. The P-47 T-Bolt had the largest turbo-supercharger of the time. It was actually situated behind the pilot with plumbing going fore and aft. Look at a cut-away of the aircraft.

I don't know about the others, but the B-17 even had intercoolers.