Author Topic: P-38 with radial engines  (Read 14688 times)

Offline Steve Pace

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P-38 with radial engines
« on: October 26, 2009, 10:37:40 am »
I wonder why they never attempted to propel the P-38 with P&W R2800 radial engines?...

Offline AeroFranz

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Re: P-38 with radial engines
« Reply #1 on: October 26, 2009, 11:09:04 am »
My guess is that the P-38 powerplant was highly integrated into the airframe. As far as I know, the twin boom layout was sthe direct result of having to use the given engine, the given radiator, and turbocharger. As Kelly Johnson put it, by the time they had stacked everything, they were so far back behind the wing that they just added five feet to the booms and put an elevator across them.

Re-engining with such a different powerplant would have entailed a complete redesign of the booms at the very least.
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Offline airman

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Re: P-38 with radial engines
« Reply #2 on: October 26, 2009, 11:57:43 am »
must be ask us if there was an alternative to Allison engines : an answer of one bilion dollars !  ;D

Offline pometablava

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Re: P-38 with radial engines
« Reply #3 on: October 26, 2009, 02:39:47 pm »
In 1939 Ward Beman from Lockheed completed report No.1462 "Comparison of Two Engine Interceptor Pursuit Proposals". He compared 6 different engines as optional poweplants for the XP-38: four Allison V-1710-F series, the Wright Tornado X-1800 and the P&W R-1830.

Warren M. Bodie "The Lockheed P-38 Lightning" Pg 51-52

In 1939, the liquid cooled engine was considered the future in terms of high performance aircraft powerplants. And the XP-38 was US most advanced fighter aircraft at that time.

C.L. Johnson proposals to install RR Merlin engines in the P-38 faced opposition from the War Production Board. Any change that would seriously reduce production even a short time was not admited.

Warren M. Bodie "The Lockheed P-38 Lightning". Prologue Pg XIV

I think that information can give some help to understand why the P-38 never received an alternative powerplant




Offline pometablava

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Re: P-38 with radial engines
« Reply #4 on: October 26, 2009, 11:32:38 pm »
Quote
Grumman proposed a V-1710-powered twin

Drawing and/or details about it?

Thanks in advance

BTW, was this V-1710 a previous proposal to the XF5F?
« Last Edit: October 27, 2009, 12:19:29 am by pometablava »

Offline Tailspin Turtle

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Re: P-38 with radial engines
« Reply #5 on: October 27, 2009, 05:32:06 am »
Quote
Grumman proposed a V-1710-powered twin

Drawing and/or details about it?

Thanks in advance

BTW, was this V-1710 a previous proposal to the XF5F?

I haven't seen anything on the Grumman V-1710 twin yet. I did post a couple of Grumman V-1710 singles from that period. The XF5F was the successor to the twin V-1710 proposal submitted in response to the 1938 competition which also resulted in the XFL-1 and XF4U.

Offline SaturnCanuck

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Re: P-38 with radial engines
« Reply #6 on: October 30, 2009, 03:31:52 pm »
I wonder why they never attempted to propel the P-38 with P&W R2800 radial engines?...

Three reasons -- frontal area, frontal area, frontal area.

Although radials are lighter due to their lack of radiators, inlines always have less frontal area.  On a small plane like the Lightning, this was key.

On the P-47, however, the power-weight ratio allowed for the massive radial.  In fact, the plane was designed around the biggest radial and to accommodate the turbo-supercharger.
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Offline airman

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Re: P-38 with radial engines
« Reply #7 on: November 02, 2009, 08:07:14 am »
So could be that radial engines of P-38 could be lose  the good aerodynamic ?  ???

Offline elmayerle

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Re: P-38 with radial engines
« Reply #8 on: November 02, 2009, 09:58:51 am »
So could be that radial engines of P-38 could be lose  the good aerodynamic ?  ???

Quite possibly.  Getting an aerodynamically clean installation that also works functionally and isn't a maintenance headache would be a challenge and would definitely require some wind tunnel work to get right.  If I was going to re-engine the Lightning, I'd go with a late-model Merlin (perhaps even the low-profile ones from the Mosquito) or a Griffon.

Offline joncarrfarrelly

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Re: P-38 with radial engines
« Reply #9 on: November 02, 2009, 04:43:34 pm »

 In fact, the plane was designed around the biggest radial and to accommodate the turbo-supercharger.

While of greater displacement the P&W R-2800 is actually smaller in diameter than the Wright R-2600 and
the fuselage shape has as much to do with the P-47's ancestry as it does the engine and turbo installation.

Offline Skyblazer

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Re: P-38 with radial engines
« Reply #10 on: November 02, 2009, 05:01:47 pm »
While of greater displacement the P&W R-2800 is actually smaller in diameter than the Wright R-2600 and
the fuselage shape has as much to do with the P-47's ancestry as it does the engine and turbo installation.

Probably so... but the ancestry of the P-47 was made solely of radial engines! Not a single inline design at Seversky... Like the Grummans or the Brewster Buffalo, the Severskys had a barrel-like shape, very wide at the front and narrowing dramatically beyond the cockpit... So probably the type of engine used MUST have had its importance in the general lines of the Thunderbolt...

Offline joncarrfarrelly

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Re: P-38 with radial engines
« Reply #11 on: November 02, 2009, 05:16:50 pm »

Probably so... but the ancestry of the P-47 was made solely of radial engines! Not a single inline design at Seversky... Like the Grummans or the Brewster Buffalo, the Severskys had a barrel-like shape, very wide at the front and narrowing dramatically beyond the cockpit... So probably the type of engine used MUST have had its importance in the general lines of the Thunderbolt...

Well, yes that is what I said, my point was that the R-2800 was not the biggest available US radial of the period.
I said nothing about inline versus radial.

Offline Steve Pace

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Re: P-38 with radial engines
« Reply #12 on: November 02, 2009, 06:50:05 pm »
Wondering: Could they have counter-rotated the props (crankshafts) of the R-2800s if used. I know the Allisons had counter-rotation...

Offline elmayerle

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Re: P-38 with radial engines
« Reply #13 on: November 02, 2009, 09:00:25 pm »
Wondering: Could they have counter-rotated the props (crankshafts) of the R-2800s if used. I know the Allisons had counter-rotation...
I believe you mean "handed engines".  I don't see why not as it's primarily a change of gearbox, though I seem to rememeber that contra-props on the R2800 were one variation tested on the XP-47J.

Offline SaturnCanuck

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Re: P-38 with radial engines
« Reply #14 on: November 03, 2009, 02:11:50 pm »

 In fact, the plane was designed around the biggest radial and to accommodate the turbo-supercharger.

While of greater displacement the P&W R-2800 is actually smaller in diameter than the Wright R-2600 and
the fuselage shape has as much to do with the P-47's ancestry as it does the engine and turbo installation.

Yes, this is pretty much true.

When I researched my book on this, I found that Alexander Kartveli essentially designed the aircraft around the largest engine he could find mated to the turbosupercharger.  This dictated the size and dimensions of the P-47, as the radial engine made the fuselage circular and the ventrally mounted TSC giving the depth of the fuselage. 

Kartvelli was making up for the unsuccesssul P-43 "lightweight" fighter before the Thunderbolt.

This idea would later be repeated in the P-47's namesake, the A-10 Thunderbolt II, when the aircraft was designed around the largest gun -- the Vulcan!
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