V-1710 turbocharged plane w/turbo mounted in rear ala P43/P47

I'm wondering what if you made a V-1710 powered plane with a turbocharger mounted in the rear ala P-43/P-47.

I suppose you'd end up with a more streamlined and lighter Lancer/Thunderbolt.

Any of the talented armchair designers here care to take a stab at it?

Let's hope so. However I wouldn't bet on it. Most American fighter aircraft tended to be on the heavy side.

Was not the P-40N close to what the OP is descirbing?

I might suggest a similar airframe if such a turbo could fit aft the pilot. It might not be much more than a short range racer or interceptor, as i don't think the fuselage allowed for other fuel stores.

Afterall, thats why a lot fo US planes were so big and heavy, they needed fuel stores.


Bill

You've still got to get the ducting to and from the turbocharger and powerplant, this was negated in the unsuccessful P-39 attempt owing to the position of the engine.

The Thunderbolt actually started life, albeit in another form, powered by the V-1710
The XP-47A was eventually abandoned however, as it simply became too heavy for the V-1710 to lug around effectively. Lessons coming in from the ETO led to requirements for self-sealing tanks and armour, so you'd end up with around 1,000lbs shaved off the nose weight but a powerplant that wheezed like an old pot boiler trying to throw the massive aircraft it had been saddled with, around the sky.

Low-down performance would likely have been awful. One could speculate on the high-altitude benefits of the turbocharger but I can't think why it would have been better than the R-2800 arrangement; I don't recall a V-1710 getting anywhere near 2,000hp

In a P-40 the part of the wing under the fuselage held the fuel tanks with another overload tank behind the pilot. These take up space needed for ducting, intercoolers and the turbo itself.

The p-47 mounted it's fuel tank in fuselage ahead of the pilot and routed the ducts under the fuel tank and cockpit. The P-43 may have done the same thing.

Somehow you are going to need to run a couple of exhaust pipes (4" at a guess? take a look at P-38 engine pictures/drawings) and the intake air duct past/under the cockpit. Intercooler cooling air has to be gotten from somewhere. P-43 and P-47 used the bottom of the cowl and routed ALL air not directly cooling the engine from the bottom of the cowl so they added more ducts carrying the intake air and the intercooler cooling air to the cross section of the fuselage. Maybe you can use scoops behind the cockpit to eliminate these ducts but I have no idea how these extra scoops would affect the streamlining of the airplane. It does help if the engine combustion intake air comes from a high pressure area of the plane. Any rise in pressure from the speed of the plane only helps the supercharger/engine raise it's critical altitude.

gjs238 said:

I'm wondering what if you made a V-1710 powered plane with a turbocharger mounted in the rear ala P-43/P-47.

I suppose you'd end up with a more streamlined and lighter Lancer/Thunderbolt.

Any of the talented armchair designers here care to take a stab at it?

Click to expand...

How about a bigger P-40 or smaller P-47 (Cross section) with unknown drag attributes. The Beast P-40 would have been heavier, higher wing loading (unless you change the design entirely) and had less performance at both high and low altitude because of adding weight and cross section (parasite drag) than a P-47.

The entire airframe line for the Corsair, P-47 and F6F were predicated on the R-2800. That automatically dictated a big airframe - once there, the designers had to put on a big wing and therefore had room for more fuel (and turbo charger/ducting if they chose to do so). The Grumman and Vought designers did not choose that path because very high altitude performance was not deemed essential, but range was so they needed fuselage space that a turbocharger would occupy.

The P-40, P-39 and P-51 based on the Allison, had total flexibility of cross section design but had to keep the size and weight low enough for the Allison to deliver low to medium altitude performance.

Each of the latter was several thousand pounds lighter so the available Hp of the Allison was not so limited to prevent terrible performance comparisons (with P-47) at middle altitudes.

When you mount a turbocharger in the rear you have to increase the depth of the fuselage, add more weight, and complexity to the airframe and you still need a coolant system. This mandates a LOT of changes to the airframes of a P-40 or P-51 (probably minimum fuselage length and depth changes) and virtually impossible with the P-39 because of aft cg issues. that existed initially just becaiuse of engine location.

The primary criteria for turbochargers or two stage superchargers is high altitude performance. (as you know)

Nobody really had a concept of long range escort except perhaps the Japanese and they were not contemplating bombing from high altitude in any of their doctrines

In effect the only a/c designed early enough with your concept was the P-38 which needed two engines to get the performance to compete with single engine turbocharged a/c at altitude.

In looking at a cutaway side view of the P47, there is an enormous amount of ductwork that runs from the exhaust manifold back to the turbo charger and also ductwork for air to be routed to the turbocharger and then more ductwork which conducts the air to the intercooler and subsequently to the carburetor. The main fuel tank is mostly in front of the pilot but also under him and the auxiliary fuel tank is also under as well as partially behind the pilot. This all accounts for the deepness of the fuselage in cross section. The Hellcat also has a deep fuselage in cross section because the fuel is located under the pilot. In contrast the Corsair fuelage is only large enough in diameter for the R2800 because the main fuel tank is only in front of the pilot and not beneath him.

Interestingly, since we are all aware of the ruggedness of the P47 in the ground attack role, the oil cooler for the Jug is mounted underneath the engine right behind the air intakes which are visible in the lower cowling. There is no armor in that location and it makes me wonder why the P47 is considered by many to be the ultimate US gound attack plane in WW2 while the Corsair is considered to be vulnerable in the ground attack mode because it's oil cooler is mounted behind an intake in the port wing. The only reason I can think that a Corsair oil cooler would be more vulnerable from ground fire is that hits are more likely to be made further back on the airplane becuse of insufficient lead. I have hit a lot more doves in the butt than in the head. However the difference in vulnerability would seem to be small.

Some of members (DAVIDICUS?) provided info that P-47 had 3-4 times more oil available to engine then F4-U. Guess that's the reason P-47 could bring it's pilot above friendly territory, while Corsair's pilot would need to bail out over ocean or over enemy-held territory, in case oil cooler was punctured.

The P47 in all models carried 143 pounds of useable oil. The Corsair carried anywhere from 90 to 193.5 pounds of useable oil.

Me-109F4.
WW2 Warbirds: the Messerschmitt Bf 109 - Frans Bonn
1,350 hp engine.
6,393 lbs Normal take off weight.
.21 hp / lb.

P-40E.
Curtiss P-40 - Wikipedia, the free encyclopedia
1,150 hp engine.
8,280 lbs Loaded weight.
.14 hp / lb.

P-43A.
P-43 Lancer - Wikipedia, the free encyclopedia
1,200 hp P&W R1830 radial engine.
7,418 loaded weight.
.16 hp / lb.

It appears to me the P-43 shows some promise. But you need more engine power without drastically increasing aircraft weight and size.

The R-1830 engne had a decent size displacement of 30L. Can they squeeze another 400 hp from it (1,600 hp total) by thowing money at the R&D department? That should provide plenty of power as long as overall aircraft weight does not rise too much.

I think the P-40 is a dead end design as it's just too heavy. Things might be different if the U.S. had an engine equivalent to the 1,750 hp DB603 or Jumo 213. And if such an engine would fit in the P-40 without serious weight gain for engine compartment modifications

davebender said:

It appears to me the P-43 shows some promise. But you need more engine power without drastically increasing aircraft weight and size.

The R-1830 engne had a decent size displacement of 30L. Can they squeeze another 400 hp from it (1,600 hp total) by thowing money at the R&D department? That should provide plenty of power as long as overall aircraft weight does not rise too much.

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Air cooled engines never delivered the same power per liter as liquid cooled engines. You could throw a lot of dollars at the R&D department and not get that result. For your consideration 3 different P&W14 cylinder engines.

R-1830

Take off-1200hp/2700rpm/48in manifold pressure.
Normal (max continuous)-1050hp/2550rpm/7500ft. low gear
1467lbs-single speed supercharger,single stage.
91/98 octane gas
40hp/lt
1.22lb/hp.

R-2000

Take off-1450hp/2700rpm/49.5in manifold pressure.
Normal (max continuous)-1200hp/2550rpm/5000ft. low gear
Normal (max continuous)-1100hp/2550rpm/1400ft. high gear
11595lbs-two speed supercharger,single stage.
100/130 octane gas
44.3hp/lt
1.10lb/hp.

R-2180

Take off-1800hp/2800rpm/unkown manifold pressure. but wet(ADI)
Take off-1650hp/2800rpm/unkown manifold pressure. but dry.
Normal (max continuous)-1300hp/2600rpm/8000ft.
1870lbs-single speed supercharger,single stage.
100/130 octane gas
50,4hp/lt
1.04lb/hp.

The last engine was post war and used the cylinder assembles from a late model R-2800.

As a comparison here are similar numbers for CB series R-2800.

Take off-2500hp/2800rpm/60.8 manifold pressure. but wet(ADI)
Take off-2300hp/2800rpm/60.2 manifold pressure. but dry.
Normal (max continuous)-1900hp/2600rpm/7000ft.
2390lbs-two speed supercharger,single stage.
115/145 octane gas
54.5hp/lt
0.96lb/hp.

For a more fair comparison try using the max continuous power ratings per liter of displacement. This would max cruise or in may cases the power used for climbing. the numbers are 32.8-35.7-36.4 and 41.4 for the R-2800. even the last when multiplied by 30 liters gives 1241hp. If 1600hp was wanted in 1941 it was available from the Wright R-2600 which sort of shows what P&W needed to do, get 33% more power per liter than Wright was getting at the time.

davebender said:

I think the P-40 is a dead end design as it's just too heavy. Things might be different if the U.S. had an engine equivalent to the 1,750 hp DB603 or Jumo 213. And if such an engine would fit in the P-40 without serious weight gain for engine compartment modifications

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Whats the point? Both the German engines don't come into play until well after the P-40s " best used by date". Even the R-R Griffon is too late in timing. All three engines are around 500-600lbs heavier than the Allison WITHOUT the bigger prop, radiators, oil system and cowling. With enough redesign it might be done but there would be precious little left of the original P-40 and in 1941-42 when such engines are being promised (but not delivered yet) the P-40 airframe is already 5-6 years old. Why spend time trying to redesign such an old airplane when you could design a new one (Griffon Mustang?)

I thought about that. However the R-2600 is quite a bit heavier as well as being more powerful. By the time the P-43 is modified to accept the R-2600 it may be 635 kg heavier, as the Fw-190 was after modification to accept the BMW801 engine. So in the end you don't gain much in power to weight ratio.

davebender said:

I thought about that. However the R-2600 is quite a bit heavier as well as being more powerful. By the time the P-43 is modified to accept the R-2600 it may be 635 kg heavier, as the Fw-190 was after modification to accept the BMW801 engine. So in the end you don't gain much in power to weight ratio.

Click to expand...

Quite right, But how do you predict how long it will take to increase specific output (power per liter) of a given engine by 33%. 6 months? 1 year? 2 years? 4 years?

Remember that it took 4 years for the R-2800 to go from 1850HP to 2800HP. It also required going from straight 100 octane (not 100/130) to 115/145 or 100/150 fuel and water injection to do it in addition to some redesigning of the the engine itself.

engines generally took longer to develop than airframes. The R-1830 had already gone from 800-900hp to 1200hp. A good part because of better fuel but big increases in power over the 1200 hp rating might only come at a cost of major redesign and retooling. When tooling up some of the "shadow" factories gambles were made that wound up paying off, if they hadn't there would have been big problems. When one of the factory's tooled up to build R-2800s was set up to build forged heads instead of cast, the forged heads had not yet passed type test. had they failed a mad scrambled would have resulted in either redoing the forged heads or coming up with the equipment/facilities to cast cylinder heads by the hundreds of thousands. With tons of forging equipment either sitting idle or being shipped somewhere else.

Historical experience. This includes foreign as well as American made engines.

Ask your in-house U.S. Army Air Corps experts.

Pay some civilian technical experts to study the issue and submit a report.

Sift the above data and make your best guess. 8)

and if the report comes back that it will take 2 1/2 to 4 years?

Go to plan "B"?

Or while you are fooling around trying to get the R-1830 up to or beyond 1400hp as a first step what other projects aren't being worked on?

P&W dropped the original R-2180 (based off of Hornet cylinders) and several sleeve valve projects in order to concentrate on the R-2800 and the R-4360.

They had money to burn from about 1938 onward. And no enemy nations camped on the border. So you've got the resources and time to try everything until something works. Which is a good thing because our aircraft were generally inferior prior to 1943. By then the war was 2/3rd over.

No, they didn't. They weren't even paying their bills to Allison in 1939. The real money flood doesn't start until the middle of 1940 with the announcement of the 50,000 plane air force.

Which is just a bit late in timing for a highly uprated engine to make it into production in about a year to have any real impact in the beginning of 1942. You need time for the planes to assembled, delivered, pilots,crews trained on them and getting the planes deployed overseas. It is also a little early to predict what grade fuels would be available in 1943.
In 1940 they were just figuring out the real differences in American spec 100 octane and British spec 100 octane fuel.

And it is not just a question of money. It is a question of enough engineers and draftsmen and enough tests stands. There were not enough engineers and draftsmen to go around. Since every production engine had to be run for several hours, torn down, inspected, reassembled and then run again test stands were being built as fast as possible As has been mentioned before the R-2800 had 3000hrs of ground testing before it ever went into the air.

Why not? The American Government was shoveling money to ship builders as fast as they could spend it.

Battleship Photo Index BB-55 USS North Carolina
Oct 1937. BB North Carolina laid down.
Jun 1938. BB Washington laid down.
Jul 1939. BB South Dakota laid down.
Nov 1939. BB Indiana laid down.
Jul 1939. BB Massachusetts laid down.
Feb 1940. BB Alabama laid down.
Jun 1940. BB Iowa laid down.
Sep 1940. BB New Jersey laid down.

You could buy a lot of aircraft engnes for the price of 8 new battleships. Vessels that were of only marginal value during WWII. Something of serious value to the war effort like a decent liquid cooled aircraft engine shoudl have been given more money then they could spend.

without a crystal ball who Knew at the time?

Japanese, British, Germans, French and Italians were all building battleships at this time. A fair number of which accomplished even less than the American ships.

An illustration of planing/paying for something now that won't be used for 4-5 years in the future. with all the risks that the enemy may come up with a new counter weapon in the meantime.

The Navy budget was not the Army budget.

and unless your plan of throwing more money at the problem than they could spend includes collage and trade school scholarships starting in 1934-35 so you have a bunch of extra engineers and draftsmen in 1938-39 to actually do the work throwing money at the last minute won't change the schedule much.

Looking over all of the previous posts, what I see is the P-51 being quite possibly the best candidate. There was room behind the pilot to place a fuel tank in the later models, that space could be utilized instead for the turbo installation.

It would still require some big time modifications, but the general layout of the plane makes it easiest. The fuselage would be a bit wider , to accomidate the exhaust manifolds to run back behind the pilot. It would also get a bigger belly, to hold the return ducting. The lower radiator scoop would be wider as a result, maybe enough to both duct the radiator and to be used for intake air.

Because the fuel is carried in the wngs, they would be or could be left alone.

But with the added weight, the wing should be enlarged in total area, which if the spars of the wing were widened a bit more,( more distance fore and aft between the spars) it may increase the internal fuel carried enough to somewhat offset the loss of the rear fuselage tank.