Could Mustang have had 2nd stage Super/Turbo without Merlin

[gruad]

The Mustang was designed to use the Allison V-1710 engine without an export-sensitive turbosupercharger or a multi-stage supercharger, resulting in limited high-altitude performance.

From wiki.

Surely with the similarities in size and possibly superior strength Allison could have come up with something that worked.

Didn't the P38 use this engine with Turbo? Surely mustang could have been adapted like the P47 with Turbo in the rear fuselage?

Hope the experts in the forum can chip in...

 

[ThomasP]

Two problems I can think of:

1. The 'smaller' turbocharger installations were having reliability problems at the time the P-51 was being designed.

2. Drag of the turbocharger installations on 'smaller' airframes - ie anything smaller than a P-47 or P-38.

 

[Shortround6]

See the P-43 for a 1940/41 1200hp turbo installation. Or the early P-38s but remember, the early P-38s used the wing leading edge as the intercooler and that limited growth/performance. As power was increased the rated altitude decreased because the too small intercooler could not handle the needed airflow.
US supercharger design was behind RR supercharger design. Hooker in his prototype test rig used a first stage impeller from a Vulture engine to get the needed airflow.
Allison at first tried using two identical sized impellers. Had to change after months of testing (Allison was also busy with other projects, at US gov requests)

Turbo in bottom of rear fuselage. Much like the P-47 the intercooler was in the fuselage above the turbo. Air was ducted from the cowl back though the belly to rear of the fuselage.
Long exposed exhaust pipe was cool the exhaust gases before entering the turbo to avoid turbine failure.
P-43 didn't have to deal with liquid cooling radiators for the engine.

 

[gruad]

See the P-43 for a 1940/41 1200hp turbo installation. Or the early P-38s but remember, the early P-38s used the wing leading edge as the intercooler and that limited growth/performance. As power was increased the rated altitude decreased because the too small intercooler could not handle the needed airflow.
US supercharger design was behind RR supercharger design. Hooker in his prototype test rig used a first stage impeller from a Vulture engine to get the needed airflow.
Allison at first tried using two identical sized impellers. Had to change after months of testing (Allison was also busy with other projects, at US gov requests))

Could RR Supercharger technology have been licensed to the US?

 

[Shortround6]

Could RR Supercharger technology have been licensed to the US?

Well, it was in 1942. The single stage supercharger (Merlin XX) was licensed to Packard in Sept 1940.
Interesting factoid. At Dieppe in Aug 1942 The British had just about the same number of Squadrons of Spitfires using two stage Merlins as the had of Allison powered Mustang Is.
Part 2 of this Factoid. P-40s with single stage US Merlins were just starting to be delivered to Egypt the same month.

The Allison supercharger was just a bit behind the Merlin III supercharger and was better than some other countries superchargers in 1939/early 1940. Hooker made some major improvements in the spring/summer of 1940 with the Merlin XX and 45 (same supercharger, different drive system). Allison never really changed the main supercharger, just some minor tweaks. Now with the turbo Allison didn't really need to. The Turbo converted the exhaust gasses to several hundred HP to drive the aux supercharger. Problem was cooling the intake air. The turbo could supply enough air in both pressure and volume (weight of air) but it was inefficient and heated the air more than a more efficient design.
Now in 1941-42 how much time do you want to loose while testing different designs?

 

[Engineman]

Hooker made some major improvements in the spring/summer of 1940 with the Merlin XX and 45 (same supercharger, different drive system).

Hi, The Merlin 45 was single-speed supercharger, the Merlin XX was two-speed supercharger with the Farman drive that added 3 inches to the length of the engine.
Sir Stanley Hooker had done quite a lot of work on modifying the intake and supercharger airflow of the early Merlins and this was initially incorporated into the Merlin XX (an upgrade of the initial two-speed Merlin X). For the Spitfire, the airframe could not easily accept the longer engine, so the intake and supercharger redesign features were built into the single-speed engine as the Mk 45. This gave some reasonable increase in performance for the resulting Spitfire Mk V that was rushed into production.

Eng

 

[RCAFson]

Hi, The Merlin 45 was single-speed supercharger, the Merlin XX was two-speed supercharger with the Farman drive that added 3 inches to the length of the engine.
Sir Stanley Hooker had done quite a lot of work on modifying the intake and supercharger airflow of the early Merlins and this was initially incorporated into the Merlin XX (an upgrade of the initial two-speed Merlin X). For the Spitfire, the airframe could not easily accept the longer engine, so the intake and supercharger redesign features were built into the single-speed engine as the Mk 45. This gave some reasonable increase in performance for the resulting Spitfire Mk V that was rushed into production.

Eng

I initially thought that no Spitfires ever received Merlin XX engines but I posted this over a decade ago:

"I ran across an interesting paragraph in Price's The Spitfire Story:

"...in 1943 some 50 MkIIs were fitted with the more powerful Merlin XX and operated in the air-sea rescue role as the Mk IIC." (p.109)

I never knew that Spitfires were used operationally with the Merlin XX!

Morgan and Shacklady confirm this on page 108 of Spitfire the History."

 

[Engineman]

I initially thought that no Spitfires ever received Merlin XX engines but I posted this over a decade ago:

"I ran across an interesting paragraph in Price's The Spitfire Story:

"...in 1943 some 50 MkIIs were fitted with the more powerful Merlin XX and operated in the air-sea rescue role as the Mk IIC." (p.109)

I never knew that Spitfires were used operationally with the Merlin XX!

Morgan and Shacklady confirm this on page 108 of Spitfire the History."

That quote exists but more original detail would be interesting.
Of course, the Merlin XX could "fit" with modification, they later fitted the Merlin Mk 61 etc. The point is, in 1939/40 the Air Ministry chose not to put the Merlin X or later the Merlin XX in the Spitfire(s) because of the pressures on production, so the Merlin X/XX were built with .42 reduction gear. They didn't even go ahead with the RE-ENGINEERED Spit III, just moved to the Mk V with the single speed Merlin Mk45, so even then it didn't seem to be worth fitting the two-speed engine.
The ASR conversions sound like a fairly simple later use of resources.

Eng

 

[MIflyer]

Not without the Mustang looking like this. And they'd have to add a liquid cooled aftercooler, which no one but RR thought to do.

 

[tomo pauk]

The Mustang was designed to use the Allison V-1710 engine without an export-sensitive turbosupercharger or a multi-stage supercharger, resulting in limited high-altitude performance.

I'd offer some ... unpacking there.
The turbocharging was exported on the B-17s the British bought in Spring of 1941, and they also signed a deal for such outfitted Lightnings in 1940.
(a small issue was that there was no such P-38 between March of 1939 and September of 1940, and even then just as the YP prototype)
Stipulation that Mustang was desinged without the multi-stage supercharging might suggest that there was such a supercharger to choose in the 1st place. That was not the case, it will not be until well into 1943 for the V-1710 was available with a mature enough 2-stage supercharging system.

Surely with the similarities in size and possibly superior strength Allison could have come up with something that worked.

At the end of the day, they did come up with a workable 2-stage S/C system (even if the RR system was a better one). It was installed on the P-63s and P-82s (bar the prototype).

For the Spitfire, the airframe could not easily accept the longer engine, so the intake and supercharger redesign features were built into the single-speed engine as the Mk 45. This gave some reasonable increase in performance for the resulting Spitfire Mk V that was rushed into production.

Spitfire V, outfitted with 1-speed Merlin, when up-engined with not just the engine that was with a 2-speed S/C, but that engine itself was a longer and heavier one, resulted in the Spitfire XII.
A lot of Spitfires IX started out with the 1-speed Merlin.
Spitfire III 1st prototype started it's life as a Spitfire I on the production line.

My point is that the notion, that a 'normal' Spitfire in 1940-41 somehow could not be powered by Merlin XX, is well past it's sell date.

 

[Shortround6]

Guessing by looking at production histories, basically an overview of which engines were made where, it may have been a supply problem?
1940 and 41 saw the Glasgow and Ford factories come on line but some times full production took almost a year.
RR was also operating a 3 tier system.
Derby was where most/all of the development work happened with initial production being sorted out in small batches (200-300? engines) before transferring production to Crewe and Glasgow. Glasgow was mass production of a few types at a time and Crewe somewhere in-between. Ford came in later.
Glasgow, while construction started in June of 1939 and first buildings occupied in Oct 1939 didn't build complete engines until Nov 1940(?) although parts had been shipped to Derby and Crewe.
Ford plant construction began in the Spring of 1940 and first parts for use by Crewe was in Aug 1940 first Ford engines didn't show up until May-June 1941.
The Merlin 45-56 all seem to have been built at Derby and Crewe. While the Merlin XX was built (in the UK) by all four factories I don't know how fast they came on line.
In the the summer of 1940 the Hurricane needed the Merlin XX more than the Spitfire did. Derby built 1104 Merlin XIIs for the Spitfire II.
The British could have built better Spitfires in the Fall/Winter of 1940 but only by building less capable Hurricanes, like using Merlin XII engines instead of Merlin XXs.
And then in the late fall using Merlin 45s instead of the Merlin XX engines.

Now how truthful the claim of the Merlin XX not fitting into the Spitfire was I don't really know. Apparently not that hard if they could fit them into 50 several year old airframes at a repair facility. However it also appears that it took a number of months to do this and there may have been a shortage of airworthy Merlin XII engines in 1943. What is unknown (without archives) is the extent of the modifications (like amount of ballast) needed to make it work.
Criteria in 1943 to keep 50 airframes serviceable may have been different than the Criteria in the summer/fall of 1940 to avoid disruptions in production.

What is the difference between won't fit at all and it will fit but needs XX hours of modification per airframe? At least to start.

 

[Shortround6]

At the end of the day, they did come up with a workable 2-stage S/C system (even if the RR system was a better one). It was installed on the P-63s and P-82s (bar the prototype).

True but it took until the summer of 1943 to do it. There was still a problem in the P-63s, There was no intercooler which hurt high altitude performance.
Allison wanted an intercooler but the contractor failed to deliver so Allison had to resort to a fall back position. Using water injection to lower the intake mixture temperature.
The P-82E s did use an Allison with a liquid cooled after-cooler along with many other changes. but since they don't show up until several years after the war (although the XP-51J used it, first flown in 23 April, 1945).
The aftercooler used (different than original design?) blocked the normal carburetor location and needed the Bendix "speed density" system which took a long time to sort out. Perhaps changed could have been made but R&D funds for piston engines in 1945-46 might have been scarce.

 

[tomo pauk]

Now how truthful the claim of the Merlin XX not fitting into the Spitfire was I don't really know. Apparently not that hard if they could fit them into 50 several year old airframes at a repair facility. However it also appears that it took a number of months to do this and there may have been a shortage of airworthy Merlin XII engines in 1943. What is unknown (without archives) is the extent of the modifications (like amount of ballast) needed to make it work.
Criteria in 1943 to keep 50 airframes serviceable may have been different than the Criteria in the summer/fall of 1940 to avoid disruptions in production.

What is the difference between won't fit at all and it will fit but needs XX hours of modification per airframe? At least to start.

The elephant in the room is the dire need for making the Hurricane to match the performance of the Emil, all while making as much of Spitfires in the same time. In 1940, the Merlin XX, with it's excellent S/C, that was also with the 2-speed drive, was the ticket for the needs of Hurricane, while not messing with Spitfire was the ticket for the later problem.
British were not swimming in the Merlin XX engines in 1940.

 

[GregP]

Joe Yancey is now out of the Allison V-1710 business but, when I worked for him, he had in his possession several letters dated a few years apart from Allison to the USAAC/F asking for funds to develop an integral, 2-stage supercharger for thr V-1710. The USAAC/F declined to fund it and Allison was a small enough shop that just building the production orders was more than enough to take up their engineering department. Had the USAAC/F accepted, they would have had to hire the team to develop said 2-stage unit.

As it happened, they developed in-house an auxiliary second-stage unit that we all now know about but, yes, they COULD have done better. The issue was never lack of ability; it was very much lack of commitment and funding for the actual effort.

The 2-stage Rolls-Royce unit COULD have been adapted, but nobody ever took that seriously enough to pursue it past the "wouldn't THIS be neat?" stage. Perhaps, in retrospect, they should have. But the "what ifs" never came to pass, so it's sort of moot at this late date. The Merlin was a great engine and I, for one, like it better than the Griffon. Perhaps that is because it turns in the "right" direction ... another can of worms ...

 

[Geoffrey Sinclair]

The following is a mixture of Rolls Royce and Ministry of Aircraft figures, they measured production slightly differently, and can have slightly different totals, Merlin XII, RR 1,102 Sep-39 to Sep-41 (but only 5 to end March 1940, peak 165 in January 1941 and only 9 Jul to Sep 41), MAP 1,104 total.

The British tried to have the ending in production before the airframes, for example the Merlin 60 from November 1941, admittedly mostly for the high altitude Wellington. Sabre production began in the final quarter of 1940, first Gloster Typhoon production June 1941. However Manchester airframe production outpaced Vulture production in 1941, the same would happen with the Typhoon and Sabre in 1942/43.

One point to note is the RAF had hedged its heavy bomber engine bets, Manchester Vulture, Halifax Merlin, Stirling Hercules, as of mid 1941 there was a "sudden" need for lots more Merlin for Lancaster, which came into production in October.

The British had 23 Merlin XII waiting end May 1940 for the first Spitfire II production in June, had 100 more engines built than airframes by end September, 216 surplus by end February and 181 (or 183) by end of Spitfire II production in October 1941 (a laggard, 3 months late), giving a 20% engine reserve. As of end February 1943 there were 439 Spitfire II on strength including 29 operational with Fighter Command, the number of Merlin XII available in the repair and storage systems is small enough the MAP figures do not count them by mark, just under Merlin others or not at all and this starts as early as February 1942. By end June 1944 there were still 337 Spitfire II on strength.

1939
January Derby: Merlin II, III and X in production, Kestrel XXX production/conversion, 169 engines built/converted for month
February, Derby: end Merlin II,
April/May, Derby: test batch of 4 Merlin VIII
May, engines built/converted for the month passes the 200 mark
June, Crewe: first production, 3 Merlin III
September, Derby: first Merlin XII production (2)
October, Crewe/Derby: Merlin X production transferred to Crewe which temporarily ceases Merlin III production (3 more Merlin X from Derby Nov/Dec), engines built/converted for the month passes the 300 mark
November, Derby: production of Merlin VIII resumes (7)
December, Derby: first Vulture II production (2) but no more until March 1940.

1940
February, Derby: first Peregrine production (3) (24 by end May, first Whirlwind production in June)
March, Crewe: Merlin III production resumes (36).
April, engines built/converted for the month passes the 400 mark
June, output surge, engines built/converted for the month passes the 900 mark but back to under 800 in August.
July, Crewe: first Merlin XX production (14)
November, Derby: first Merlin 30 production (30), Glasgow: first production, 3 Merlin XX
December, Derby: last Merlin VIII production, first Merlin XX (1).

1941
January, Derby: first Merlin 45 (12)
February, Crewe: first Merlin 21 production (2) (but none produced June to August plus October)
March, another output surge, engines built/converted for the month passes the 900 mark but back to under 800 in April.
April, Crewe: first Merlin 45 production (22), Merlin III production ends.
May, Derby: Merlin III production ends.
July, engines built/converted for the month passes the 900 mark
August, Ford: first production, 13 Merlin XX
September, Derby: Merlin XII production ends, engines built/converted for the month passes the 1,200 mark
October, Derby: first Merlin 46 production (8), engines built/converted for the month passes the 1,400 mark
November, Derby: first Merlin 60 production (13)
December, Derby: first Merlin 47 production (26)

Crewe reached the more than 100 engines per month in February 1940, Glasgow in July 1941, Ford output was 91 in December 1941. Derby was running at just under 200 engines a month in early 1939.

Yearly / Crewe / Derby / Glasgow / Ford
1939 / 208 / 2,583 / 0 / 0
1940 / 3,097 / 4,537 / 6 / 0
1941 / 5,076 / 5,330 / 1,711 / 184

Using Jane's, Merlin III 1,375 pounds, XII 1,425 pounds, XX 1,450 pounds, Merlin 45 1,425 pounds.

338 Merlin XX to end 1940, for 171 Hurricane II.

 

[Shortround6]

Thank you for that detailed listing.

 

[Mustangtmg]

Mustang was designed to use the Allison V-1710 engine without an export-sensitive turbosupercharger or a multi-stage supercharger, resulting in limited high-altitude performance.

From wiki.

Surely with the similarities in size and possibly superior strength Allison could have come up with something that worked.

Didn't the P38 use this engine with Turbo? Surely mustang could have been adapted like the P47 with Turbo in the rear fuselage?

Hope the experts in the forum can chip in...

The Mustang was designed to use the Allison V-1710 engine without an export-sensitive turbosupercharger or a multi-stage supercharger, resulting in limited high-altitude performance.

From wiki.

Surely with the similarities in size and possibly superior strength Allison could have come up with something that worked.

Didn't the P38 use this engine with Turbo? Surely mustang could have been adapted like the P47 with Turbo in the rear fuselage?

Hope the experts in the forum can chip in...

I tried to reply a couple hrs ago and I think that my words "went away," then I got busy doing something else.

Your questions don't involve a lot of words, but the answers would take a TON of words. I use too many words anyway, but having worked as a hospital pharmacist for over 45 yrs before retiring, my fingers still move pretty quickly (faster than my brain at times ).

I'll try to be short...as far as putting a GE Turbo (or any OTHER appropriately-sized turbo) anywhere in the rear half of the Mustang's fuselage, the resulting aircraft, even without my being an aeronautical engineer/aerodynamicist, I can say for sure that the Weights and Balance would put the center of gravity waaaaaay too far behind the wing, and there would be NO way in the world, short of moving the wing a foot or more to the rear, or making the "nose part of the fuselage" put the Corsair's nose look short by comparison.

A "bare" GE Type B Turbosupercharger, which is the size that'd work with an engine in the displacement category of the Merlin, weighs 135 lb (or) so and that does not include the ducting, intercooler, etc etc ... and you add that much weight in the rear half of a Mustang fuselage and THAT would be what'd make the whole fuselage and wing VERY different (it would be a "new" aircraft - no longer ANY kind of Mustang)...

I hear that there may be a new book on the horizon that will address such things, but I'm not 100% sure.

Well, that was boring if you read the whole thing ... sorry. (And this is the SHORT version!).

 

[MIflyer]

By the way, the USAAF was correct in its conclusion that turbosupercharging was superior to mechanical supercharging in terms of ultimate performance. Compare the performance of the XP-41, with much the same engine as the F4F Wildcat, to the Seversky AP-4, the same airplane as the XP-41 but with a turbo. The AP-4, not the XP-41, led to the production of the XP-43 and ultimately scaling it up to the XP-41. And compare the performance of the P-61A, with the same supercharging as the F4F and F4U, to the P-61C, which had turbos.

But while the turbosupercharger provided superior performance it was much harder to implement, and also made the need for a effective Inter/aftercooler more important.

 

[tomo pauk]

By the way, the USAAF was correct in its conclusion that turbosupercharging was superior to mechanical supercharging in terms of ultimate performance. Compare the performance of the XP-41, with much the same engine as the F4F Wildcat, to the Seversky AP-4, the same airplane as the XP-41 but with a turbo. The AP-4, not the XP-41, led to the production of the XP-43 and ultimately scaling it up to the XP-41.

The turbo pointed out that the 2-stage R-1830 was with a meh 2-stage supercharger. Able to deliver how much, 45.5 in Hg at 18000 ft? A single stage S/C on the Merlin XX did 48.2 at 18250 ft. The 2-speed Sakais were making about the same power there as the 2-stage R-1830s, while requiring much lower boost, being okay with the lower octane fuel, with lower cubic capacity, and while being 300+ lbs lighter.
The installation of the American radials before 1943(?) was also to blame for not taking advantage of the exhaust thrust, robbing the F4F and the XP-41 by 10-15 mph of speed.

And compare the performance of the P-61A, with the same supercharging as the F4F and F4U, to the P-61C, which had turbos.

Different generations of R-2800s.
The P-61A have had the 1942-vintage engine (B series) and supercharger (good, but not great), while the P-61C used the C series of engines and the new-gen turbo, a powerplant that some of the the P-47Ns gotten.
Installing the brand new 2-stage R-2800 on the P-61s, like the engines the F4U-4 had, let alone what the -5 had, would've also provided a major boost to the performance of these P-61s.

But while the turbosupercharger provided superior performance it was much harder to implement, and also made the need for a effective Inter/aftercooler more important.

Agreed 100%.

 

[MIflyer]

The turbo pointed out that the 2-stage R-1830 was with a meh 2-stage supercharger

But the F4F's best speed was at a higher altitude than the A6M. And the two speed and two stage feature meant things could get better at over 15,000 ft, unlike the V-1710 equipped P-39 and P-40. Admittedly, the two stage of the F4F likely was inspired by the need for the USN to intercept the B-17 in war games and therefore win "The Battle of Washington" that every weapons system has to face. The FM-2 with a lighter and more powerful engine seems to have been a much deadlier foe than than the original Wildcat - with only a single stage supercharger.

I still think that the relatively complex supercharger controls on the F4F, F6F and F4U must been a pain the the butt for the pilots.