R-1830 2-stage supercharging for high altitude fighters?

[gjs238]

An often lamented subject is the US lack of high altitude fighter capability, particularly in the early years of the war (P-40, P-39, P-38 issues, etc.)

However, the F4F fielded the R-1830 w/2-stage supercharging.
If not in the F4F, might the R-1830 w/2-stage supercharging been somehow utilized for high altitude fighter use?

I imagine the aircraft would have to be small, light, or double-engined to achieve the range performance necessary.

 

[tomo pauk]

Grumman Skyrocket, P-40, Yak-1, Hurricane, all main Italian types, D.520 (that one would've ruled prior 1941).

 

[Shortround6]

I am not sure just how good it was.

There were reported surging problems.

It was the first of it's kind (in aircraft).

Air cooled engines, as a general rule of thumb (talking WW II aircraft engines here, not modern race cars) would not take the level of manifold pressure a liquid cooled engine would.

That said it did provide some altitude capability over Guadalcanal that other US fighters of the time could not match.

A smaller lighter airframe than the F4F would have given better performance but it wasn't going to match the Merlin 60 series.

It also wasn't going to match the Turbo Allisons in the P-38.

 

[Markus]

If not in the F4F, might the R-1830 w/2-stage supercharging been somehow utilized for high altitude fighter use?

I imagine the aircraft would have to be small, light, or double-engined to achieve the range performance necessary.

Most Curtiss Hawks had R-1830 engines but with single-speed SC. The top speed of the last versions was 320mph@15kft. And engine with a 2-stage SC should have permitted a decent speed at 25kft. And by the way, at GC Wildcats routinely climbed to 25-30kft, that should make them high altitude fighters.

 

[davebender]

I expect so. The improved IJN A6M3 entered service during April 1942. Without an altitude advantage the USN F4Fs were pretty well out classed.

 

[Shortround6]

Grumman Skyrocket, P-40, Yak-1, Hurricane, all main Italian types, D.520 (that one would've ruled prior 1941).

Grumman Skyrocket was built with turbocharged Wright Cyclones, see p-50.

The Army had a shot at the P-36/P-40 with the R-1830 two stage supercharger.

see:Google Images

Duct under the rear of the wing was the Intercooler. It was at the 1939 Army fighter trials. An early version of the engine used in the Wildcat. BTW don't believe Wiki caption.

The two stage R-1830 was over 1500lbs WITHOUT the intercooler.

It needed 100 octane fuel (which rather rules it out for the Italians and French)

Hurricane doesn't need it once it gets the Merlin XX in Aug 1940.

Yak-1?

 

[Colin1]

However, the F4F fielded the R-1830 w/2-stage supercharging.
If not in the F4F, might the R-1830 w/2-stage supercharging been somehow utilized for high altitude fighter use?

Historically, no
Pratt Witney's first attempt at 2-stage supercharged 1830s began in 1935 with the efforts being concentrated on two methods

The first model had both impellers fitted on a common shaft and driven through a fixed-ratio gear. Performance turned out to be less than expected.

The second model concentrated on an intermediary and 2-speed drive. This too had its problems and it would be 1939 before a model came together that was decent enough to be tested, the R-1830SB-2. This offered 1,050hp @ 17,500ft. The design team kept adding improvements and the R-1830SC2-G gave a normal rating of 1,050hp @ 22,500ft on 100-octane fuel.

It suffered badly from surging at altitude so Pratt Witney went back to the drawing board and completely re-designed its own supercharger and modified the inlet and diffuser. The R-1830-19 (R-1830-SC2G) was the first all-Pratt Witney 2-stage supercharged powerplant and featured C-type cylinder heads, new-type cylinders, an NA-V12A carburettor and lead-coated silver master-rod bearings. The supercharger itself had an air intercooler. Unfortunately, all of Pratt Witney's travails did not solve the surging at altitude problems; they persisted with the type and produced the R-1830-76 and -86 but the problem never completely went away.

 

[tomo pauk]

Grumman Skyrocket was built with turbocharged Wright Cyclones, see p-50.

Indeed

The Army had a shot at the P-36/P-40 with the R-1830 two stage supercharger.

see:Google Images

Duct under the rear of the wing was the Intercooler. It was at the 1939 Army fighter trials. An early version of the engine used in the Wildcat. BTW don't believe Wiki caption.

Thanks for the link, but it only opens a Google Images home page

The two stage R-1830 was over 1500lbs WITHOUT the intercooler.

About same as pre-60 series Merlin (dry). And only 500 lbs lighter than R-2600 , or 7-8% for F4F's empty weights (while reaching parity in power-to-weight category only above 20 kft, in 1942).

It needed 100 octane fuel (which rather rules it out for the Italians and French)

Yep, that's very true.

Hurricane doesn't need it once it gets the Merlin XX in Aug 1940.

It's tough to find a replacement for Merlin

Yak-1?

Surely.

 

[Shortround6]

Thanks for the link, but it only opens a Google Images home page

Sorry try:

http://upload.wikimedia.org/wikipedia/commons/6/61/Curtiss_P-36_Hawk.jpg

 

[Markus]

How difficult would have been to put an R-1820/30 with a 2-speed SC into a Curtiss Hawk? Could it be done in the field or were the dimensions of the engines so different, that the airframe needs to be modified?

 

[Shortround6]

How difficult would have been to put an R-1820/30 with a 2-speed SC into a Curtiss Hawk? Could it be done in the field or were the dimensions of the engines so different, that the airframe needs to be modified?

What do you mean?

Curtiss Hawks with R-1820s or R-1830s already had two speed superchargers, I doubt any were built with single speed superchargers.

If you mean switch from one engine to the other then the actual airframe doesn't need modification but you do need the appropriate engine mount, cowl, exhaust system, etc. The engines did not come as "power eggs".

If you meant two STAGE supercharger see the photo list in previous post.

 

[Markus]

What do you mean?

Curtiss Hawks with R-1820s or R-1830s already had two speed superchargers, I doubt any were built with single speed superchargers.

I meant single stage, two speed SC like the F2A had. And I was not aware any Hawk had them. To be honest the info about max speed/horespower look like 1-stage, 1-speed as the optimum performance was at app. 12,000 to 15,000ft. Or were these radials also designed for use at low altitudes and required 2-speed SC to meet the V-1710´s performance at medium altitudes?

 

[Shortround6]

I meant single stage, two speed SC like the F2A had. And I was not aware any Hawk had them. To be honest the info about max speed/horespower look like 1-stage, 1-speed as the optimum performance was at app. 12,000 to 15,000ft. Or were these radials also designed for use at low altitudes and required 2-speed SC to meet the V-1710´s performance at medium altitudes?

My apologies Markus. It appears I was in error

From what I can find the Hawks fitted with P&W R-1830s had single speed superchargers while the Hawks fitted with Wright R-1820s had two speed superchargers, except for the fixed landing gear ones.
It does appear though that the P&W engines were set up so that their critical altitude was close to the critical altitude of the Cyclone when in high gear.

You are correct in saying that these engines were originally intended for use at low altitude.
With the commercial market in mind in the 30s (and the Cyclone dates back to the 20s) cruising altitudes were on the order of 4-8,000ft except in mountainous regions. Airlines could order engines with supercharger gears (choice of several ratios but still single speed) optimized for their routes. With improvements in both fuel and engines things got much better but both engines are only a bit bigger than the Allison and turn fewer rpms. They need as much manifold pressure (boost) if not more to make about the same power. The extra gear was used to improve take-off and low altitude performance (low gear used less power, heated the intake charge less and had less pumping losses than high gear) as much or more than to extend operating altitudes.

 

[Markus]

From what I can find the Hawks fitted with P&W R-1830s had single speed superchargers while the Hawks fitted with Wright R-1820s had two speed superchargers, except for the fixed landing gear ones.
It does appear though that the P&W engines were set up so that their critical altitude was close to the critical altitude of the Cyclone when in high gear.

P-36A: R-1830-13, 900hp@10kft, [email protected]
P-36C: R-1830-17, [email protected], 311mh@10kft

H-75A-1/-2: mostly a Twin-Wasp rated at 900hp@12kft, 300mph top speed(from memory)
H-75A-3: R-1830-SC3-G, [email protected], 311mph@10kft
H-75A-4: R-1820-G205A: 1,000hp@15kft, 323mph@15kft

To be honest I would not have expected the perfomance numbers of the Cyclone to be with a 2-speed SC but now that you mention it I see the difference.

 

[hrandy]

There was an Army Air Corps bias for turbosuperchargers and against mechanical superchargers in the 1930s that meant no AAC funding for mechanical two stage superchargers.

The U.S. was the only country to mass produce turbosuperchargers during the war - so in one respect this policy was a success especially with large aircraft with multiple podded engines. On the other hand it was very difficult to incorporate a turbosupercharger and its' associated intercooler in small single engined aircraft.

Pratt Whitneys' efforts at two stage two speed superchargers for the USN were not very good in my opinion. I would argue that the Cosair, Hellcat and Black Widow would have been better aircraft with a simple single stage two speed supercharger. The Hellcat could have been a Bearcat three years sooner.

 

[tomo pauk]

US never went 'small single-engined fighters' alley, so their F4U F6F were tried tested with turboed engines. Stuff worked just fine, but was not needed.

Any sentence vs. R-2800 is blasphemy - Hellcat needed to loose 1 ton in order to became Bearcat anyway.

 

[gjs238]

re-turbo: How did F4U F6F deal with plumbing issues without "growing" like the P-47?

 

[Shortround6]

There was an Army Air Corps bias for turbosuperchargers and against mechanical superchargers in the 1930s that meant no AAC funding for mechanical two stage superchargers.

On the other hand there were TWO fighters tested in the 1939 fighter trials that had two stage mechanical drive superchargers.

Pratt Whitneys' efforts at two stage two speed superchargers for the USN were not very good in my opinion. I would argue that the Cosair, Hellcat and Black Widow would have been better aircraft with a simple single stage two speed supercharger. The Hellcat could have been a Bearcat three years sooner.

Would you care to expand on this or explain it further?

I am do not understand how chopping 6,000 ft from the altitude rating of an engine turns the planes it powers into better aircraft.

What are the differences between a Hellcat and a Bearcat?

 

[Shortround6]

re-turbo: How did F4U F6F deal with plumbing issues without "growing" like the P-47?

For a photo see:
http://www.aero-web.org/database/aircraft/getimage.htm?id=9259

The navy planes did not use GE turbos but rather a pair of Bierman ones. At least on the F4U-3 they apparently used two. They also proved rather unreliable, perhaps they needed more plumbing?

 

[hrandy]

The AAC wanted to go with small single engine pursuits as late as Circular Proposal CP39-770 in the late summer of 1939. Curtiss proposed the XP-46 and Republic the Allison powered P-47 for this RFP. Fortunately information on the war in Europe nixed the light fighter concept and Republic was allowed to redesign P-47 as the R-2800 powered P-47B.

The two stage charge cooled versions of the R-2800 used in the Corsair and Hellcat had a lot of weight and bulk associated with the second stage supercharger, its' gearing and charge cooling. It was not as heavy and bulky as the turbo stage in the P-47, but close.

The Bearcat was a simple lightweight single stage R-2800 powered fighter almost a ton lighter than the Hellcat. Elimination of the second stage supercharger and the associated charge cooler was key to this reduction. In my opinion single stage power was more than adequate for the low level war in the Pacific. All the pilots (many of them Pacific war veterans) who flew the Bearcat at the October 1944 Joint Fighter Conference at Patuxent River in Maryland were thrilled with the performance of XF8F-1 prototype.

I do not have any information on the 1939 fighter trials. I assume at least one of the two stage pursuits you mentioned was a Curtiss Hawk. There were so many iterations of the basic Hawk airframe I can't keep track of them all. The Hawk image you posted in June of last year looks to me like it is turbocharged, but I can't find anything on this model. I also can't find much info on the evolution of the two stage R-1830. Colin1 seems to very knowledgeable about this branch of the R-1830 family. I wonder if he would share his sources with us?