Speculative thread: Early Mustang envisioned for Merlin power, GP fighter/interceptor

[BarnOwlLover]

Now this is a big "what if". What if the Mustang was envisioned as a Merlin powered general purpose fighter and interceptor from the beginning? This would take some changes to the real world timeline (like North American being aware of the two-stage Merlin earlier, etc), but I do wonder what thoughts and speculations would be.

Now the parameters:

-Built to British or optimum mix of British and American loading standards
-Intended to be engineered to take a two stage Merlin from the start
-Answer to British (and later USAAF) criticism of the hinged and framed canopy (my solution would be a Typhoon type bubble canopy or a two-piece canopy similar to the Yakovlev fighters or the Lavochkin La-5/7, maybe even La-9 or -11)
-Carry suitable armament for a 1942-era interceptor
-Be open for future development

So in this alternate time line, what would it look like, how would it perform, and how favorable would it be to go on to fufil the role for bomber escort later on?

 

[Shortround6]

North American design team in the Spring of 1940.

At the Time the Mustang prototype was sitting outside the NA factory (ok they rolled it back inside at night) waiting for it's Allison (sept 1940) Hooker and team had just delivered the
First 2 SPEED Merlin supercharged Hurricane to a service squadron. It is also the month that Packard signs the deal to make Merlin's in the US.

In 1941 NA built 138 Mustangs and would build them at the rate of just over 80 month for the first 1/2 of 1942.
Packard built 45 Merlins in 1941and production ramped up quickly in 1942. However these were the two speed, single stage Merlins.

In in addition to the obvious time problem (calling Dr Who??) you have a few problems. The Mustang was designed and promised to be a better P-40 with minimum delay over tooling up a NA factory to build P-40s. Designing the thing around a non-existent (or shadowy at best) engine was not what the British wanted or needed at the time. Remember that Sept 1940 was right in the middle of the BoB.
Next was would the American government even OK production of a plane with lighter construction standards. The US was NOT giving the OK to whatever the French and British wanted in 1940. The British had tried to get British tanks produced in the US and that went nowhere. Same for artillery production. The US had been burned badly in WW I with much of their production tied up with French and British contracts and the Americans were forced to use those designs to equip their armies in 1917 with those weapons because there was no time to retool the factories. The US was not going to make that mistake again. The US was willing to sell planes, tanks and artillery to the British (and the French had they hung on longer) but they would be American designs built to American standards. The Merlin was one of the few exceptions. Maybe they would have OKed the British standard for the Mustang but it would have required negotiations and delays and your idea requires the least amount of delays possible.

You are also biasing your intentions further into the future than 1942.

"Carry suitable armament for a 1942-era interceptor"
The guns in the Mustang I were suitable for a 1942 interceptor, or were easily adaptable.
NA was offering four .50 cal guns and four .303s when Curtiss was offering two .50 cal and four .303s for planes delivered in 1940 and early 1941 and was offering four .50s and later six .50s in planes to be delivered in late 1941/early 1942.
Wasn't that hard to swap four .303s for two .50s in the A-36. Now the Merlin Mustang could not hold the .50s in the fuselage and indeed I am not sure that any Merlin was ever fitted fitted with synchronizing gear.
But again you need your crystal ball to foresee the engine/fuel improvements in 1940 that would happen in 1942 to pin down possible armament schemes (the 6 cannon Spitfire sure didn't happen)

 

[pbehn]

Now this is a big "what if". What if the Mustang was envisioned as a Merlin powered general purpose fighter and interceptor from the beginning? This would take some changes to the real world timeline (like North American being aware of the two-stage Merlin earlier, etc), but I do wonder what thoughts and speculations would be.

Now the parameters:

-Built to British or optimum mix of British and American loading standards
-Intended to be engineered to take a two stage Merlin from the start
-Answer to British (and later USAAF) criticism of the hinged and framed canopy (my solution would be a Typhoon type bubble canopy or a two-piece canopy similar to the Yakovlev fighters or the Lavochkin La-5/7, maybe even La-9 or -11)
-Carry suitable armament for a 1942-era interceptor
-Be open for future development

So in this alternate time line, what would it look like, how would it perform, and how favorable would it be to go on to fufil the role for bomber escort later on?

I would use my 20/20 hindsight and have all Muslang MkI Mk II/ P-51A that were taken by the USA after Pearl Harbour to be shipped to UK for fitting with two stage Merlins when avalable, cancel the A 36 and do the same until two stage Merlin production starts at Packard. Along with the Merlin, fit a Malcolm hood as was done to many P-51Bs. Job done.

 

[SaparotRob]

And build them out of birch, spruce and balsa.

 

[pbehn]

And build them out of birch, spruce and balsa.

Held together with blueberry jam and Devonshire clotted cream. Then instead of scrapping it, you eat it with a nice cup of tea.until you get proper scones delivered.

 

[GrauGeist]

Answer to British (and later USAAF) criticism of the hinged and framed canopy (my solution would be a Typhoon type bubble canopy or a two-piece canopy similar to the Yakovlev fighters or the Lavochkin La-5/7, maybe even La-9 or -11)

The first Typhoons had a car-door style cockpit entry (like a P-39) with a razorback style fuselage.
Summer of '41 saw the Typhoon's aft cockpit sheet metal replaced with a framed canopy and in 1942, more modifications were made to the canopy but it wasn't until 1943, that the afore-mentioned bubble canopy was fitted.

The La-5 (first flown 1942) had a framed canopy/turtleneck (as did the La-7, La-9 and La-11).

The Fw190 had a much better canopy for the proposed timeline, though foreward visibility was somewhat limited by the cowling.

Perhaps the Miles M.20 (1940), KI-43 (1939) or A6M (1939) would be better sources?

 

[EwenS]

The first Typhoons had a car-door style cockpit entry (like a P-39) with a razorback style fuselage.
Summer of '41 saw the Typhoon's aft cockpit sheet metal replaced with a framed canopy and in 1942, more modifications were made to the canopy but it wasn't until 1943, that the afore-mentioned bubble canopy was fitted.

The La-5 (first flown 1942) had a framed canopy/turtleneck (as did the La-7, La-9 and La-11).

The Fw190 had a much better canopy for the proposed timeline, though foreward visibility was somewhat limited by the cowling.

Perhaps the Miles M.20 (1940), KI-43 (1939) or A6M (1939) would be better sources?

Or the Westland Whirlwind in 1940.

 

[tomo pauk]

Or the Westland Whirlwind in 1940.

Already in 1938...

 

[GrauGeist]

Or the Westland Whirlwind in 1940.

Excellent example.

 

[Clayton Magnet]

Now this is a big "what if". What if the Mustang was envisioned as a Merlin powered general purpose fighter and interceptor from the beginning? This would take some changes to the real world timeline (like North American being aware of the two-stage Merlin earlier, etc), but I do wonder what thoughts and speculations would be.

Now the parameters:

-Built to British or optimum mix of British and American loading standards
-Intended to be engineered to take a two stage Merlin from the start
-Answer to British (and later USAAF) criticism of the hinged and framed canopy (my solution would be a Typhoon type bubble canopy or a two-piece canopy similar to the Yakovlev fighters or the Lavochkin La-5/7, maybe even La-9 or -11)
-Carry suitable armament for a 1942-era interceptor
-Be open for future development

So in this alternate time line, what would it look like, how would it perform, and how favorable would it be to go on to fufil the role for bomber escort later on?

The Mustang was a big airplane, so perhaps it could have accepted a Griffon engine better than a Spitfire?
The Griffon Spitfires needed external bumps and enlarged tail surfaces to squeeze in the big engine and manage it's increased torque, so could a Mustang have accepted it more gracefully?
A lightened Mustang fitted with a Griffon 61 could have been a fearsome beast. Since this is What-If anyway, throw a couple Mk.V Hispano's in each wing
(I realize that neither the 60 series Griffon, nor the Mk.V Hispano were available in 1942)

 

[BarnOwlLover]

I think for the sake of speculation/comparison here, that the Ki-84 had similar dimensions to the Mustang, but was little heavier than a Spitfire 8/9. Also, the proprosed Miles M23A interceptor was a bit shorter than the Mustang (by about a foot). Even the lightweight Mustangs had the same dimensions as the earlier ones (same span and length), and the P51H was a foot longer and had a taller tail.

Even early single stage Spitfires were dimensionally "big" compared to the Me-109 and the Yak and Lavochkin fighters, though they were just as light or lighter than some of the examples mentioned. Same applies to the A6M Zero and the Ki-43 as far as generous dimensions.

 

[Shortround6]

I would use my 20/20 hindsight and have all Muslang MkI Mk II/ P-51A that were taken by the USA after Pearl Harbour to be shipped to UK for fitting with two stage Merlins when avalable, cancel the A 36 and do the same until two stage Merlin production starts at Packard.

Now what do you use instead of those planes while you wait for the Merlins? Or do you swipe the Merlins from the MK VIII and MK IX Spitfires made in 1942 and early 1943?
Yeah the Mustangs may have better than the Spitfires but you are swapping Mustang XXs for Spitfire MK Vs. I don't think your overall power/strength is going to come out ahead.

Packard made 56 two stage engines in June of 1943, 184 in July, 371 in Aug and then it was off to the races.
The last A-36 came off the line in March of 1943. The first combat operation of the A-36 was June 6th 1943. A-36s fly 1000 sorties in the first 35 days after that.

At some point in July 1943 North American had only received 173 Packard Merlins while NA had 534 P-51B airframes completed.

 

[GrauGeist]

Just as an aside: the Allison powered Mustangs were quite capable at lower altitudes.

For some reason, the pre-Merlin P-51s get a bad rap as being helpless blunders.

 

[EwenS]

The Mustang was a big airplane, so perhaps it could have accepted a Griffon engine better than a Spitfire?
The Griffon Spitfires needed external bumps and enlarged tail surfaces to squeeze in the big engine and manage it's increased torque, so could a Mustang have accepted it more gracefully?
A lightened Mustang fitted with a Griffon 61 could have been a fearsome beast. Since this is What-If anyway, throw a couple Mk.V Hispano's in each wing
(I realize that neither the 60 series Griffon, nor the Mk.V Hispano were available in 1942)

No need for a What If.

Rolls Royce did look at putting the Griffon into the Mustang. But not in the front end of the existing aircraft, except as a possible test bed for a more radical aircraft design.. They took Mustang wings, rear fuselage, fin & tailplane, and put the Griffon engine in a P-39 mid-engined arrangement. It reached the mock up stage. That work really got going in Jan 1943. Wind tunnel testing revealed the need for a much larger tailplane and it was proposed to fit the tail from a Tempest to the prototype.

SECRET PROJECTS:Rolls-Royce’s own fighter concept

The involvement of Rolls-Royce’s Hucknall plant in fitting the North American P-51 Mustang with its Merlin engine...

www.key.aero

As for two stage Merlin options in Britain, RR began work in April 1942, with 5 Mustang I airframes being delivered for conversion as Mustang X. The first of these flew in Oct 1942. 2 were delivered to the 8th AF for evaluation.

 

[pbehn]

Now what do you use instead of those planes while you wait for the Merlins? Or do you swipe the Merlins from the MK VIII and MK IX Spitfires made in 1942 and early 1943?
Yeah the Mustangs may have better than the Spitfires but you are swapping Mustang XXs for Spitfire MK Vs. I don't think your overall power/strength is going to come out ahead.

Packard made 56 two stage engines in June of 1943, 184 in July, 371 in Aug and then it was off to the races.
The last A-36 came off the line in March of 1943. The first combat operation of the A-36 was June 6th 1943. A-36s fly 1000 sorties in the first 35 days after that.

At some point in July 1943 North American had only received 173 Packard Merlins while NA had 534 P-51B airframes completed.

I was just responding to the "what if". The Two stage Merlin Mk IX was first tested in April 1942. Any Mustang Mk I or II taken after Pearl Harbour by the USA would have arrived in UK around Feb March 1942, so build Mustang XX instead of Spitfire Mk IX. Obviously it means much fewer Mk IX spitfires and Allison Mustangs/ A 36 but the RAF USAAF would have had a long range fighter earlier.

 

[Geoffrey Sinclair]

The time line does not support the Mustang being designed from the start for a Merlin 60 series, the NA-73 was being developed in 1940, the engine in 1941, with first NA-73 production examples in August, Merlin 60 in November. The ex mark III Spitfire prototype made its first Merlin 60 flight on 27 September 1941.

A more direct line to the two stage Merlin Mustang would be the RAF deciding the ability of Allison to deliver enough engines was a big risk. Since the NA-73 was outside the US fighter system specify it use a Merlin. Like CCF in Canada North American is shipped a few engines for test purposes, with the airframes then sent to Britain. North American are given the full details needed for fitting a Merlin XX (Production from July 1940) and later Merlin 45 (from January 1941). A Merlin 45 Mustang would be a good match for the Fw190A, quite useful in the first half of 1942.

Upon arrival in Britain, October 1941 on, Mustangs soon show how good they are and in early 1942 North American are given the full details needed for fitting a Merlin 60 and sent a couple, preferably by air freight. Suitable adjustments then made to the mix of Merlins built in US and UK. While North American begin fitting wing racks for drop tanks.

 

[Shortround6]

We have the history (a bit sketchy) of Packard production of Merlin engines and of Allison production.
The US Army was willing to jump on the Merlin bandwagon in 1940 because Allison had no track record, and all the other US liquid cooled engines were still in the experimental stage.
Packard was looking at the drawings and a sample engine of the Merlin XX in July or early Aug of 1940 but the paper work was not signed until Sept. on the very same day that Ford got contract to build a factory to make R-2800 engines.

The problem becomes not just airframes but engines. Packard got a contract for 9000 engines to be delivered at 800 engines a month. It took them until until the end of 1941 to start delivering them in even handfuls and 2/3rds were going to Britain. Packard hits the 800 engine a month mark for Merlin XX engines in July of 1942 and maintains it or exceeds it except for 2 months until Jan 1944. The Merlin stage production was in addition to Merlin XX production, not in place of it, which meant more factory space, more machine tools and more workers. For the last 4 months of 1943 Packard was building 1675 to 1950 engines a month.
This was at a time when Buick, Chevrolet, Nash-Kelvinator and Studebaker were all tooling up and starting to make aircraft engines. So you all those factories along with every other war industry looking for machine tools, workers, structural steel and cement.
For all practical purposes any additional Merlin Mustangs in 1941, 1942 and 1943 are going to come from taking the engines out of another airframe and either doing without those airframes or substituting a lower power engine (or less capable engine).
Getting a few hundred Mustang XXs but the British trying to use Allison powered Spitfires doesn't seem like that much of gain?
British went with Merlin XX powered Hurricanes because they thought that would give them a higher number of effective fighters than building Merlin XX powered Spits and Merlin X powered Hurricanes. The Hurricane needed the better engine in order to hope to stay in the game. Germans "cheated" by bringing out the 109F and later the 190.

For the US maybe you could have stuck Merlin XXs in the Mustang, but that would be at the cost of P-40Fs and Ls.
So do you want the P-40Fs and A-36s/P-51As or do you want Mustangs with Merlin XX engines and more P-40Ks?

And lets remember, the P-40Fs just barely made El Alamein and the Torch invasion. They had flown the P-40F prototype in Dec of 1941.

 

[marathag]

The British had tried to get British tanks produced in the US and that went nowhere. Same for artillery production.

Because the British Tanks were awful. The best of the early British Tanks, the Churchill, still had lousy reliability at this point. The Matilda and the Cruisers did not impress at Aberdeen Proving Grounds, while the US saw many good points of the two Soviet tanks, the KV and T-34 they also tested
The Book _ Business of Tanks_ goes into that British Tank Mission

The 25 pdr really did nothing better that the 105mm was already doing. But did adopt the 6 pdr

 

[marathag]

And build them out of birch, spruce and balsa.

Duramold, birch and phenolic resin, pioneered by Fairchild before the War

'largest' use was with Hughes HK-1, aka Spruce Goose

 

[Shortround6]

Because the British Tanks were awful. The best of the early British Tanks, the Churchill, still had lousy reliability at this point. The Matilda and the Cruisers did not impress at Aberdeen Proving Grounds, while the US saw many good points of the two Soviet tanks, the KV and T-34 they also tested
The Book _ Business of Tanks_ goes into that British Tank Mission

The 25 pdr really did nothing better that the 105mm was already doing. But did adopt the 6 pdr

The British were asking in 1940-41. The best the Americans would do was change the turret on the M3 Medium to put the radio in the turret instead of the hull. The M3 Stuart light tank was pretty much take or leave it. The Soviet tanks didn't show up until much later.

The US realized that the American 37nn AT gun was pretty much obsolete and was looking for something better and were handed the 6pdr, a wonderful gun.
About the only thing the US took form British artillery was the design/ammunition for the 4.5 in gun which turned out to be a mistake.

Fit in the carriage/cradle of the 155mm howitzer and while it gave longer range they kept the British shell for compatibility and weighed 55lbs it carried little more HE than the American 105mm projectile and so was a poor return for effort/cost. There was also no range of ammunition types for different missions.