P-38 with radial engines

[Steve Pace]

I wonder why they never attempted to propel the P-38 with P&W R2800 radial engines?...

 

[AeroFranz]

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.

 

[airman]

must be ask us if there was an alternative to Allison engines : an answer of one bilion dollars ! ;D

 

[Antonio]

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

 

[Antonio]

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?

 

[Tailspin Turtle]

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.

 

[saturncanuck]

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.

 

[airman]

So could be that radial engines of P-38 could be lose the good aerodynamic ? ???

 

[elmayerle]

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.

 

[joncarrfarrelly]

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.

 

[Stargazer]

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...

 

[joncarrfarrelly]

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.

 

[Steve Pace]

Wondering: Could they have counter-rotated the props (crankshafts) of the R-2800s if used. I know the Allisons had counter-rotation...

 

[elmayerle]

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.

 

[saturncanuck]

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!

 

[Tophe]

Extract from my (free) book "Forked Ghosts" (downlodable at http://cmeunier.chez-alice.fr/Free_EoFG_MV.htm ):
"...the projects of Lightning with radial engines: the L-24.0001 was before 1939, but
the most powerful Lockheed L-106 with R-2160 engines was contemporary of the last P-38 versions."
(with drawing of the L-106/R-2160)
The L-24.001 was a P-38 Lightning, the L-106 was a XP-49 improved Lightning

 

[frank]

An F4U was tested with contra props as well.

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.

 

[airman]

http://cmeunier.chez-alice.fr/JCC_Mustang.JPG

I like P-51T ( version bi-engined of Mustang) B)

 

[airman]

P-38 like P-51 had good performance for their engines , for their aerodynamic , if p-38 or p-51 was with radial engines, surely or had a redesigned wings or not had good performance as in real events !
So think @ gull wings of Corsair !

 

[Justo Miranda]

Unknown source...

 

[Tophe]

Here is a drawing I made long ago for the radial derivatives of the Lockheed P-38 family: P-38 itself, XP-49, XP-58.
Just to illustrate, mainly from my imagination.

 

[Tophe]

Below is what I found in the great booklet MiniDoc #6 (American Naval Fighters), by Alain Pelletier, Editions Larivière, 1998 (I think it still can be ordered within the famous French magazine Le Fana de l’Aviation):

 

[Vietcong]

I don't know how the P 38 look like if it was equipped with contra rotating prop with the same pratt and whittney engines

 

[Tophe]

I am glad to help, but you know, this kind of question is more for the what-if site than for the serious SecretProjects one:
EDIT: At last, I have drawn 3 versions of it, crediting you, dear Vietcong, at the end of my dreamy site http://www.kristofmeunier.fr/#Sit (this is not Alternative History, this is not History at all, sorry...)

 

[sienar]

Found this on enginehistory.com


No idea about where this image comes from, but it appears to be wartime. Maybe someone can recognize the partially cut off logo in the corner?

 

[J.A.W.]

What were prop-disc diameter size limitations for P-38?

Would the ~13ft R-2800 size fit? Doubt it..

Anyhow, the R-2800s were gas hogs, the slim P-38 airframe could not accommodate enough fuel,
or the associated massive turbo ducting with air-to-air charge coolers..

The P-38 was very pricey, as was the R-2800-turbo powered P-47,both were ~X 2 price of P-51..
But Merlin Mustang did the job better..

IMO the real reason the Lightning did not get the paddle-prop/bubble-canopy/ADI advances allowed
even to the P-47 - was that it was past its best by date, & the P-82 was up when/if a twin was needed.

The P-38 was dumped in favour of P-51s by the US 8th AAF, ( as were most P-47s), but when
given G/A duties - like the cast off P-47s in the 9th AAF, they proved too vulnerable losses-wise.

'Droop Snoot' conversions ( over 100, more than total numbers of W.Whirlwinds built) were tried,
to give P-38s some utility as de-facto medium bombers, but they weren't much good at that either..

The P-38 had a reasonable record against the lesser forces of Nippon, but bang-for-buck-wise in the ETO,
they just didn't cut it, since with their lousy Vne, they could not out dive the 109/190..

To sum up, even if improvements to the P-38 were technologically feasible, up to & including the R-2800,
by the time C model hi-altitude R-2800s were available in numbers, the USAAF had been sold
on the Merlin Mustang, & all the Congressional lobbying bought by Lockheed could not change the fact.

 

[famvburg]

IIRC the PV-1 Ventura and PV-2 Harpoon used relatively short diameter wide- chord 3 blade props on their R-2800s. some of the later "hot rod" corporate conversions used shortened DC-7 props on their R-2800s and I think one used shortened Constellation props but I may be thinking of an A-26 conversion, so diameter isn't everything.

 

[J.A.W.]

Fair point re P-D diameter, F.

Thing is, P-38 was a high altitude optimised turbo-charged interceptor,
- just like the P-47,
& the R-2800 so equipped needed all the prop it could get..

 

[PabloSniper]

The R-2600, which was used in the B-25s, was already available in 1940.
It was lighter than the R-2800, and had more power than a V-1710.

 

[Michel Van]

So could be that radial engines of P-38 could be lose the good aerodynamic ? ???

i think it have fly like Fokker G.I fighter
That had two Bristol Mercury VIII with max 830 hp each

View: https://www.youtube.com/watch?v=1pr47_IfcDc

 

[tomo pauk]

The R-2600, which was used in the B-25s, was already available in 1940.
It was lighter than the R-2800, and had more power than a V-1710.
View attachment 744040

With good intercoolers, the V-1710s on the P-38 were good for 1400-1600 HP. The R-2600 will still require the good intercoolers, in order to make the 'book' horsepower at altitude (talk above 20000 ft).
Then there is still the question of the bulk, weight and consumption of the R-2600 vs. the V-1710. Also the question of CoG, since the heavier engines are in the front, while the coolant radiators (located towards the tail) are deleted.

The much lighter R-2000 might've been a better fit, it was supposed to make 1350 HP on the XF5U-1, and 1500 HP with water-alcohol injection.

 

[PabloSniper]

With good intercoolers, the V-1710s on the P-38 were good for 1400-1600 HP. The R-2600 will still require the good intercoolers, in order to make the 'book' horsepower at altitude (talk above 20000 ft).
Then there is still the question of the bulk, weight and consumption of the R-2600 vs. the V-1710. Also the question of CoG, since the heavier engines are in the front, while the coolant radiators (located towards the tail) are deleted.

The much lighter R-2000 might've been a better fit, it was supposed to make 1350 HP on the XF5U-1, and 1500 HP with water-alcohol injection.

The possibility of the R-2180 could also be considered, and the possibility of using one in the P-36 was even considered.

 

[tomo pauk]

The possibility of the R-2180 could also be considered,

It was supposed to be the engine for the (X)P-44 together with the turbo installation, while the non-turbo engines were used on the XA-21 and DC-4E. Unfortunately, the development of the R-2180A ended some time between 1939 and 1940(?).
The post-war R-2180E (roughly, one half of the R-4360) of 1800+ HP was also manufactured in very small quantities, but that is too late for the P-38.

There was one interesting engine project by Wright, that became still born (unfortunately, IMO). Tentatively called R-2170, a.k.a. short-stroke Cyclone (bore x stroke = 6.125 x 5.25 in), weighted between 1700 and 1800 lbs, supposed to do 1500 HP at 2900 rpm. 47 in diameter (favorably compares with the bulky, 55in diameter R-2600).

and the possibility of using one in the P-36 was even considered.

I'd appreciate the details ):

 

[Apophenia]

...
I'd appreciate the details ):

This unbuilt Hawk 75K variant was intended as an engine testbed for the 910 hp P&W R-2180 Twin Hornet rather than a fighter proposal.

According to No Short Days: The Struggle to Develop the R-2800 "Double Wasp" Crankshaft by Kimble D. McCutcheon, the R-2180 was plagued by master rod bearing failures. Pratt & Whitney abandoned further R-2180 development in favour of the related R-2800.
-- https://www.enginehistory.org/NoShortDays/Introduction.pdf


That unattributed clipping came from Bert Kinzey's 1999 Curtiss P-40 Warhawk (Detail & Scale 61, Part 1).