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

I do not think the 4.5" should be considered a mistake.

The US adopted the UK 4.5" projectile and ballistics because it offered an already proven capability. When the US Army evaluated the 4.5" vs the planned US 4.7" design, they found that their own experimental 4.7" offered no appreciable advantage. The UK 4.5" projectile showed superior ballistics & accuracy to the US 4.7" projectile design at the time of the evaluation.

While the story is that the US adopted the 4.5" shell for their own gun for ammunition compatibility with the UK 4.5", this is often misunderstood as being some arbitrary decision. While it is true the US built their own 4.5" guns beginning in 1942(?) that used the compatible ammunition, they had actually adopted the UK built gun in significant numbers before entry into the war (I think beginning in late-1939 or early-1940, but I may be off on that). While the common story mentions that the 4.5" M1 only amounted to "only" 16 Corp level Artillery Battalions, the US had another 14 Army(?)/Corp/Division level Artillery Battalions equipped with 4.5" guns supplied by the UK (I am not sure how many of these were stood up before the US entry into the war (possibly 10?) and how many early-war). They were used in the MTO and ETO until the end of the war.

The 155mm Long Tom is often mooted as an example of how the 4.5" design was a mistake, but the 155mm and 4.5" were designed to parallel but very different requirements. The 4.5" was intended to act as a relatively mobile (ie to be towed by the common trucks of the time) medium caliber counter-battery weapon (with a maximum shell weight of 60 lbs for ease of one man handling) - while the 155mm was intended as a heavy caliber long range general support weapon (it only developed into a de-facto counter-battery weapon due to its range capabilities after entry into service use).

ThomasP said:

they had actually adopted the UK built gun in significant numbers before entry into the war (I think beginning in late-1939 or early-1940, but I may be off on that).

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ThomasP said:

the US had another 14 Army(?)/Corp/Division level Artillery Battalions equipped with 4.5" guns supplied by the UK (I am not sure how many of these were stood up before the US entry into the war (possibly 10?) and how many early-war). They were used in the MTO and ETO until the end of the war.

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This is rather different than a few books/articles I have read. The British shells may well have had better ballistics than the US 4.7in.
However the only pre war British guns were mounted on old 60pdr carriages and some were lost in France. The remainders were used in North Africa and for training. Perhaps some American units used them for training in England? The whole plan to use the old 60pdr carriages fell through when the discovered there were only 76 (or 96 ?) available to convert. Which rather limited British pre war deployment, let alone giving any to the US.
The later British 4.5in guns were mounted on the 5.5in carriages. They went into production after the 5.5in guns, both being built at the same time. One account claims that only the British and Canadians used the British 4.5in MK II equipment. The 4.5 was not popular in British service either.
The US and British ammunition was not as interchangeable as was hoped. The US projectiles changed the threads for the fuse, You could fire it out of the British barrels but you had to have the right fuses. The powder charges were also different, they gave very similar performance and maybe you could use everything but the max charge? It might only be off by 100-200 yds? The Americans didn't offer the number of different powder charges the British did but then the US guns elevated much higher and could lob shells over obstructions better (although with decreased accuracy?)
The Barrels were off by a few inches in length and they used slightly different breech mechanisms. The British one being better, the breech block was turned and withdrawn in one motion while the US guns (and the 155 M1 Howitzer) turned the breech block and then withdrew it. two separate motions. These were not rapid fire guns in any case but they were different.
While much different and much lighter than the US 155mm M1 gun they were both just over 12,000lbs in weight and needed a bigger than average truck.
A quick search of the internet shows a common tow vehicle was the M5 tractor (M3 Stuart tank chassis, different engine) once it got into production. Although I have no doubt they were pulled by trucks many times. The older 155mm 1917/1918 howitzers stayed in service in Burma and other areas into 1945 but those guns went about 8,000lbs.

The US used quite a number of the old 1917 & 1918 155mm GPF guns in North Africa and Italy and in the Pacific in the early years.

Hey Shortround6,

Sorry, I misspoke(mistyped)/was unclear. I meant to say that the US had significant numbers of the UK built guns in service before they engaged in ground combat in the MTO and ETO (so 1943 to 1944), not before the US entered the war in December 1941 as my original statement implied.

re service dates

The 4.5" Mk I (60pdr carriage) entered service with the UK in late-1938, and the 4.5" Mk II entered service in early-1941.

The US purchased two UK built 4.5" Mk I guns for testing sometime in 1939.


re mobility and prime movers

US 155mm M1 howitzer_______________12,800 lbs
US 4.5" Gun M1______________________12,500 lbs
UK 4.5" BL Medium Field Gun Mk II____ 12,900 lbs

Although the US eventually ended up assigning the M5 High Speed Tractor for towing the 155mm Howitzer M1 and the 4.5" Gun M1, the original intent was to use a M967/M968 4-ton 6x6 truck as prime mover. The M5 High Speed Tractor was eventually chosen due to its increased mobility off-road and its ability to also serve as the crew carrier and ammunition carrier. But it should be noted that the M5 High Speed Tractor did not enter service until mid-1943, so 4-ton trucks were used as the prime mover for both guns until sometime after then. As an alternative, 6-ton 6x6 trucks were also used in various situations.

The British usually towed their 4.5" guns with the Matador 4x4 5-ton truck.

BarnOwlLover said:

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?

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GMC owned NAA and Allison.
There were no R-R engines available to NAA, had the blessing of GMC been given to replace Allison V-1710-39 as the NA-73 powerplant. The AAF did not express an opinion, but clear to NAA that the P-40F would receive Priority, had production been available.
NAA still hoping for AAF orders of P-51 in 1941. All AAF Pursuit figters with in-line engines were engined with Allison V-1710 making introduction of Packard spares, engine logistics problematical.
Allison/NAArelationship was soured for a multitude of reasons and NAA DID reach out to RR-US, which responded with technical docs and mount requirements and cooling system requirements for Packard 1650-1 in late through April 12, 1941.
The Packard agreement to deliver 50/50 to BAM and AAF consumed all potential production for Fy1942, and Echols CO of AAF-MC allocated US % to Curtiss.
NAA did a design layout for both 1650-1 and Continental VIV-1430 in attempts to examine increased Hp options, between Nov 1941 and Feb 1942.
R-R US kept Kindelberger appraised of Packard's progress on 1650-3.

Pause - IMO, the Februar 28, 1942 when Packard received drawings from R-R for the Series 60 Merlin marks the beginning timeline for 'the dream' of an earlier P-51B.
In February 1942 NAA completed specifications and performance estimates for "Low Altitude Ground Attack Airplane" which were presented to Arnold/Spaatz during their NAA visit late Jan 1942. The lobbying for Attack/Dive Bomber FY42 funding resulted in A-36 contract.
Until NA-83 AM 118 was modifed with wing omb pylons and fuel plumbing in anticipation of carrying ferry tanks on those pylons, there were no other NAA designs, or structural analysis applied to the Mustang.
The state of AAF-MC development of combat tanks was 'slow at best' when AM 118 first flew to test dive brakes in May 1942.
May 1942 marks R-R activity in UK and NAA activity in Inglewood to design airframe/Merlin 60 series powerplant requirements for Mustang.

Pause -
While R-R/RAF could contemplate airframe modifications of a portion of their NA-73/83 deliveries to install Merlin 61 - their was fierce opposition to diversion of Merlin 61 from Spit IX commitment. BPC/BAM requested NA propose building engineless airframes for delivery to UK for final assembly - NAA responded with estimates but indicated that it would take 18-24mo to build assembly centers in UK.
NAA was in middle of NA-101 XP-78 (later XP-51B) in late May.
XP-51B airframe was completed in early October. At that time Packard 1650-3 failed bench tests in July, redesigned portions of crankshaft, delivered engine number 2 to NAA, which installatio failed in early October. The next engine #3 wasn't delivered until mid November 1942 - for first flight one month after R-R - on November 30, 1942.
The next production engine (#4) was delivered in February 1943 for XP-51B #2
The first P-51B-1 was completed in late March 1943, but flight tests delayed until 1650-3 #5 was delivered late April.
AAF-MC/War Board rejected Curtiss request for 1650-3 to upgrade P-40L in June.

Major Point
The P-51B-1 with 1650-3 engine, 184 gal internal fuel with submersed pump for mains, but high altitude vacuum pump scheme stil not installed for external tanks.
Development of 85 gal fuselage tank began July 1943.
85 gal kits with production fuel cell, new O2 bottles, and larger oil tank, not begun until early September for US Depot install in November, and BAD2 in December 1943.

Conclusion
P-51B arrived earliest possible date - and largely associated with critical path of Packard implementation of Series 61 Merlin.

I think it was Galland who said that it became clear that they were only fighting over where the new border between east and west would be. If the US offensive was possible in full in 1943 that may have just meant. Russian and Western forces meeting up at Duisburg shortly after D-Day..

drgondog said:

Pause - IMO, the Februar 28, 1942 when Packard received drawings from R-R for the Series 60 Merlin marks the beginning timeline for 'the dream' of an earlier P-51B.

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Here is the RR/Ford/Packard offers worked out this way.

OTL Plans for Ford of France at the new plant at Poissy (West of Paris) to make a metric Merlin, fall apart with the fall of France

June 1940 RR offered the Merlin engine to the US, a deal setup by Edsel Ford, but Henry Ford didn't like the British, or the terms they offered for building the Merlin. Edsel Ford had got the Merlin plans and drawings, but Henry told his crew to make a better V12 in that bore and stroke size for the Navy. Contract went to Packard, who had been offered Merlin subassemblies (crankshafts) in 1939, but passed at that point. Packard, like FMC, didn't like the RR engine but unlike Ford, was allowed to modify it for US processes, but not thread patterns.

Henry Ford still wanted to build aero engines for the war effort, and agreed to build P&W R2800s instead, building a new factory for that in September 1940, and that plant was producing by December 1941

Ford still wanted that 1650 c.i. Aero engine built, so it was developed in house.
Called the GG, a turbocharged test mule with direct fuel injection was rated to 1800HP on 100 octane gas, estimated from going from twin cylinder mule to real V12engine

The USAAC wasn't interested in untried engines(and were in the tank for GM's Allison anyway) and the Navy wanted to stick with radials.

But the US Army was having supply problems with Tank engines, and wanted those.

GAA engine was born, 4 cylinder chopped off from the original V12 dream to a V8, with twin carburators in 1941, ready for production in just over a year

Best way for earlier US built Merlin, is to have Henry Ford have a Stoke in 1939, and Edsel Ford is running FoMoCo.
That way Ford makes Merlins a little sooner, and maybe gets a Meteor offshoot for tank engines

marathag said:

Best way for earlier US built Merlin, is to have Henry Ford have a Stoke in 1939, and Edsel Ford is running FoMoCo.
That way Ford makes Merlins a little sooner, and maybe gets a Meteor offshoot for tank engines

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Assuming that Ford signs the deal in Early June that buys you 3-4 weeks at the other end (1942/43) assuming that Ford can build the Engine factory at the same speed that Packard did.
Packard engineers were looking at the drawing and the sample engine in either the end of June or beginning of July. Actual contract was signed in Sept but actual work began earlier.
Packard got two RR engineers, one of which died from overwork several years into the project.
Ford sent a team of engineers to P & W East Hartford to examine the P & W factory and essentially copy their layout. Liaison between Ford and P & W was much easier than between Packard and RR due to distance/travel. Ford didn't have to redo the P & W drawings.

marathag said:

…..
Best way for earlier US built Merlin, is to have Henry Ford have a Stoke in 1939, and Edsel Ford is running FoMoCo.
That way Ford makes Merlins a little sooner, and maybe gets a Meteor offshoot for tank engines

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…and the U.S. avoids that '50's icon, the Edsel.

Shortround6 said:

Assuming that Ford signs the deal in Early June that buys you 3-4 weeks at the other end (1942/43) assuming that Ford can build the Engine factory at the same speed that Packard did.

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Never have been able to determine how far along the French plans for the Merlin went at Poissy. Edsel was involved with this, trying to get around Henry

It's overlooked, but English Ford made Merlins at the Trafford Park facilities at Manchester, unused, as Ford's main focus was on Dagenham after 1931), and Ford redid the RR plans to suit Ford's methods, and were making engines by May 1941, and 400 a month the following month.

But not what date Ford started working with RR to make engines at Trafford Park. I've got 'Late 1939' , and factory refurbishing done at Trafford Park in 'Spring 1940' but not exact date

Ford's plant really wasn't a true Shadow Factory like RR had at Glasgow, Derby, Hillington and Crewe. Glasgow took five months to start production, with RR heavily involved.

RR wasn't nearly as involved with Ford

SaparotRob said:

…and the U.S. avoids that '50's icon, the Edsel.

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Referring to Marathag's post, the new Edsel would appear in 1946 offered between the Ford and Lincoln lines competing with the Mercury.

The absolute critical path was the development of the two speed/two stage supercharger, followed by early bench faliures at Wright Pat in summer 1942.
The Bench failures delayed the XP-78/51B Flight Test initiation by seven weeks. Packard production deliveries after #4 was delayed two months including the time the union was on-strike.

Early delivery by Ford for XX or 1650-1 equivalent would have assisted RAF but not assisted Curtiss or NAA in US.

special ed said:

Referring to Marathag's post, the new Edsel would appear in 1946 offered between the Ford and Lincoln lines competing with the Mercury.

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I thought the Edsel was Henry's idea.

The Edsel line was a corporate idea and was launched in 1956 but cancelled by the 1960 model year.

marathag said:

RR wasn't nearly as involved with Ford

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Ford of England was using the British style of drawings. 3rd order projection (?) while the US used 1st order projection (?). or the other way around?
In any case Ford of Dearborn would have to redraw any drawings obtained from Ford of England. That was almost a 12 month job for Packard. Might well have been going on while the factory was being re-equipped and added to.


"Packard--Today" was in 1944.
Note the space/s for "Marine Engines" the V-2500 PT boat engines. Something like over 4000 built?
The Ford plant for the R-2800 was built on a bare plot of ground.

pbehn said:

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.

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Cornish clotted cream dear boy. Cornish, and with strawberry jam put on first then the cream as God intended. Not like those benighted Devonian heathens……..

yulzari said:

Cornish clotted cream dear boy. Cornish, and with strawberry jam put on first then the cream as God intended. Not like those benighted Devonian heathens……..

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You are an obvious heretic, God made blueberries and Devon purely for use on scones. What other use do they have?

pbehn said:

You are an obvious heretic, God made blueberries and Devon purely for use on scones. What other use do they have?

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Eus mona dhedha?

Lew ow lostek yw agas eeli.

SaparotRob said:

I thought the Edsel was Henry's idea.

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Edsel, before he died, tried to get Old Man Henry to Modernize, and, well, not act like Henry Ford so much.

Edsel was given control of Lincoln Motors, after Henry bought up that failing company in Detroit for $8M in 1921 , and was allowed to create the Mercury Division in 1938. This was for fancier and sporty vehicles, nicer than the Ford Line

He died of stomach cancer during the War.

But Edsel failed pretty much in changing the direction of FoMoCo, and Henry really wasn't up to the task anymore of running everything


Enter Henry Ford II, brought back from Naval service to run Ford in 1945, after Senior was getting too erratic.


HF II and the 'Whiz Kids' like Bob McNamara, wanted to shake up FoMoCo, and decided a new division was needed, to better compete with GMs mid range line up

and M-E-L was born
Mercury
Edsel
Lincoln

Similar as GM was doing with BOP
Buick
Oldsmobile
Pontiac

With 'Edsel' being a brand new.

Edsel Ford, had be been alive would not have gone with this

Ford: Entry Level and Trucks

Mercury: More powerful and nice than Ford

Lincoln: compete with Cadillac

Continental: compete Packard and Rolls Royce

This could (and maybe should) be spun off as a separate topic, but what about the XP-51F/G Mustangs in the interceptor role? Namely, how good might they have been, and what would their armament be in Interceptor trim (type of guns and ammo capacity)?

AAF contemplated 4xOldmobile 20mm with 125rpg, 205 gal internal fuel, no fuselage tank but capability for bot bombs/fuel tanks external stores. At the end of 1943, the AAF decided a.) not to buy the P-51F, b.) reject NAA offer to supply Aussies P-51D wing kits with 2x20mm plus 2x50 cal to meet the Australian Spec for nA-107, then NA-110.

The primary reason for abandoning the P-51F was that AAF was locked into fuse tank for extended range in both ETO and Pacific. No fuse tank could be installed in P-51F production - for both structural and CG reasons. Ditto XP-51G, hence the reason for P-51H to achieve both performance AND Range.

Also at this time AAF ordered that effctive January 1,1944 - that all Mustangs delivered by NAA should have 85 gal fuselage tank - which killed the P-51D-1-NA as it was originally P-51B-1 fuselage with 6 gun wing For some reason not yet known by me, the 55gal fuse tank could be fitted (and was in 42-106540) but something about the wing/fuselage of B-1 Fuse with production 6 gun wing would not work. The 85 gal tank Would work w/four gun wing - as noted due to all the kits installed from Nov 43 forward to B/C-1 and B-5s.