American purchase programs, alternatives and reality, 1937-43

z42 · Mar 23, 2025

What about a next generation heavy bomber to replace the B-17 using 4 R-2800, and generally less technologically ambitious compared to the historical B-29? That could have shown up in numbers over Europe before VE?

And yes, a good 2-stage SC for the V-1710. With such a thing, would there even be a need for the Packard Merlins?

Make a good 20-25mm autocannon to replace the Browning HMG in fighters. Use it for defensive armament in next gen bombers too (the above suggested B-17 replacement, for instance).

Speaking of license producing British engines, what about equipping Liberty/Victory/T2 etc merchants with heavy fuel using Doxford marine diesels?

tomo pauk · Mar 23, 2025

z42 said:
What about a next generation heavy bomber to replace the B-17 using 4 R-2800, and generally less technologically ambitious compared to the historical B-29? That could have shown up in numbers over Europe before VE?

FWIW, Martin company was mooting the (X)B-33A Super Marauder, that was to be powered by the turbocharged R-2600 engines. Weight- and size-wise, R-2800 is as easy upgrade as possible there.

z42 said:
And yes, a good 2-stage SC for the V-1710. With such a thing, would there even be a need for the Packard Merlins?

The more the merrier?
Plus, Merlins produced ended up in many British-made aircraft.

z42 said:
Make a good 20-25mm autocannon to replace the Browning HMG in fighters. Use it for defensive armament in next gen bombers too (the above suggested B-17 replacement, for instance).

Americans managed to bungle u many automatic weapons' projects. So I'd suggest a 2-pronged approach - scale-up the .50 BMG to 20mm, and buy 20mm stuff at Oerlikon. Whatever is found to work better, have it manufactured, while keeping the .50 BMG also in production as insurance.

MIflyer · Mar 23, 2025

tomo pauk said:
FWIW, Martin company was mooting the (X)B-33A Super Marauder, that was to be powered by the turbocharged R-2600 engines. Weight- and size-wise, R-2800 is as easy upgrade as possible there.

And then there was the NAA XB-28, a high altitude medium bomber with two R-2800. As it turned out, the main value of Mediums was at low altitudes, exemplified by the A-26, and they did not need a high altitude Medium.

SaparotRob · Mar 23, 2025

tomo pauk said:
Vitally important? As decided by whom?

Methinks a touch of sarcasm may have been intended, sir.

tomo pauk · Mar 23, 2025

SaparotRob said:
Methinks a touch of sarcasm may have been intended, sir.

My 1st sentence in the reply box was actually 'Is this a tongue-in-the-cheek joke?', but I've scrubbed that and wrote what you've quoted

Howard Gibson · Mar 24, 2025

tomo pauk said:
The more the merrier?
Plus, Merlins produced ended up in many British-made aircraft.

Americans managed to bungle u many automatic weapons' projects. So I'd suggest a 2-pronged approach - scale-up the .50 BMG to 20mm, and buy 20mm stuff at Oerlikon. Whatever is found to work better, have it manufactured, while keeping the .50 BMG also in production as insurance.

How many Merlins were shipped west across the Atlantic to Canadians building Hurricanes, Lancasters and Mosquitos? Packard made Merlins because the British ordered them. Sticking them into Mustangs, another item originally ordered by the British, was an afterthought.

tomo pauk · Mar 24, 2025

Howard Gibson said:
How many Merlins were shipped west across the Atlantic to Canadians building Hurricanes, Lancasters and Mosquitos?

~~I'd say - thousands.~~ I've jumped the gun there.

Howard Gibson said:
Packard made Merlins because the British ordered them. Sticking them into Mustangs, another item originally ordered by the British, was an afterthought.

Installing the Merlins in the Mustangs was certainly not a part of original idea. However, up-engining a military aircraft with a much better engine was done perhaps a dozen times by the time Merlin Mustang was reality - most known probably being the Bf 109 when Emil emerged, but also the different Italian, Soviet, American, British, German or Japanese aircraft. There is a lot of logic in that undertaking.

Shortround6 · Mar 24, 2025

The main problem with sticking single stage Merlins in Early Mustangs was ownership.
The Americans owned 1/3rd of the first 9000 Merlins built. Most of these went into the P-40s.
The Americans only owned 2 of the first 622 Mustangs built,
They seized 55 of the 150 lend lease P-51s, which had been ordered in July 1941. They later gave the British 50 P-51As as repayment.
The British and Americans worked well together but not quite as well as some people may believe now. British were scrambling for every airplane they could get even in most of 1942.
Interesting factoid. At the time of Dieppe (Aug 19th 1942) the British have 4 squadrons equipped in Mustangs, which is just about identical to the number of squadrons using Typhoons and the number using Spitfire IXs. How much do you want to delay the supply of Allison powered Mustangs?
And where do you send them to compensate for the lack of P-40Fs???

By the time the US actually gets more than 2 Mustangs of their own (or actually orders their own, not lend lease) Both the British and NA are trying to figure out how to put the 2 stage engines in the Mustang airframe.

In fact the order for 400 P-51Bs with two stage Merlins was placed Aug 26th 1942, Several weeks before the first test flight of the first A-36.
A lot of programs were operating in parallel. You are not going to get single stage Merlin powered Mustangs at all until the 2nd half of 1942 and that is at the factory in California. It took 5-6 weeks (more/) to get the 2nd British Mustang to England by sea using the Panama canal.

How much engineering time and testing do you want to do in the Spring/Summer of 1942 trying to stick single stage engines into already contracted for P-51s, P-51As and A-36s?

marathag · Mar 24, 2025

Look at Allison, under GM.
Get Chrysler in he game with a V-12, and Ford two, with making one as well, before the rush in 1939 to make Merlins.
Made in the USA is still the goal.
Info on the Ford is out there, but not as much for Chrysler, so here is one paper for their tank engine that they developed in house to compete with Ford.

Make a bit bigger, rather than spinning fast like the Hyper projects engines that went nowhere

Geoffrey Sinclair · Tuesday at 6:55 AM

Howard Gibson said:
How many Merlins were shipped west across the Atlantic to Canadians building Hurricanes, Lancasters and Mosquitos?

tomo pauk said:
I'd say - thousands.

Try 0, which is closer to the number than thousands, definitely when only Canadian production is the criteria. Remember Canada needed to take 30 Merlin from Fairey Battle (plus propellers) for their early 1942 allocation of 30 Hurricane I. No Canadian built Hurricane I arrived in Britain with an engine and the minority of mark II that did had a Merlin 28, which were removed and fitted to Lancaster. The Canadian built Mosquito and Lancaster used US built Merlins. Why risk losing engines at sea only to return "soon"? Merlins were shipped to Canada as replacements for Merlin powered trainers.

UK columns are imports, 5,152 Merlin 28 shipped, 228 lost at sea, 30 Merlin 38 shipped, all still en route in the time period, Merlin 28 imports end in May 1943.

Month	UK P-51	UK M28	XP-51	NA-73	P-51	P-51A	P-40F	P-40L	M28	M29	M31	M33	M38	US 1 stage
Aug-41			1	1					2					2
Sep-41				6					3					1
Oct-41	1			25					3					2
Nov-41	7			37					7					3
Dec-41	24		1	67					17					9
Jan-42	10			84			5		74					35
Feb-42	50			84			42		22	79				48
Mar-42	57			52			55		57	160	1			115
Apr-42	118			86			104		334	1	2			168
May-42	97	220		84			104		406		2			194
Jun-42	42	289		84			130		458		2			242
Jul-42	85	297		10	66		135		528	36	13			224
Aug-42	57	289			22		130		505	82	23			190
Sep-42	42	397			60		130		476	71	63			190
Oct-42	7	578					153		502	20	43			235
Nov-42	32	746					136		418	28	105			245
Dec-42	37	312					160		430	3	135			281
Jan-43	23	287					27	131	439		128			283
Feb-43	1	297						158	519		43			302
Mar-43		188				70		270					568	44
Apr-43		454				120		141				119	487
May-43		570				120						147	1059
Total	690	4,924	2	620	148	310	1,311	700	5,200	480	560	266	2,114	2,813

2 P-51 became XP-51B, not counted here, 56 P-51 to USAAF. 21 Mustang I lost at sea, 1 more import in July 1943. 2,813 US 1 Stage Merlin for 2,011 P-40, with a one third allowance for replacement engines, about 2,680 engines needed. If you want single stage Merlin Mustangs they have to be done in Britain or lose P-40F/L, in any case look at when the Mustangs arrived in Britain in numbers and when Packard ramped up production, Merlin Mustangs of any type in numbers are mid 1942 at best.

As an aside to end June 1943, 7,685 O.50 Browning guns shipped to Britain, 334 lost at sea, 7,351 arrived.

Also be careful about what was ordered and when, the following is the list of USAAF contracts with North American in date order to end January 1943, what was actually built

serials	Site	Model	Qty	Contract	Date
41-038/039	Inglewood	XP-51	2	AC-15471	30-Sep-40
41-37320/37351	Inglewood	P-51	32	DA-140	25-Sep-41
41-37352/37352	Inglewood	XP-51B	1	DA-140	25-Sep-41
41-37353/37420	Inglewood	P-51	68	DA-140	25-Sep-41
41-37421/37421	Inglewood	XP-51B	1	DA-140	25-Sep-41
41-37422/37469	Inglewood	P-51	48	DA-140	25-Sep-41
42-83663/84162	Inglewood	A-36A-1	500	AC-27396	7-Aug-42
43-6003/6102	Inglewood	P-51A-1	100	AC-30479	24-Aug-42
43-6103/6157	Inglewood	P-51A-5	55	AC-30479	24-Aug-42
43-6158/6312	Inglewood	P-51A-10	155	AC-30479	24-Aug-42
43-6313/7112	Inglewood	P-51B-5	800	AC-30479	24-Aug-42
43-7113/7202	Inglewood	P-51B-10	90	AC-30479	24-Aug-42
42-102979/103328	Dallas	P-51C-1	350	AC-33940	28-Dec-42
42-103329/103778	Dallas	P-51C-5	450	AC-33940	28-Dec-42
42-103779/103978	Dallas	P-51C-10	200	AC-33940	28-Dec-42
43-12093/12492	Inglewood	P-51B-1	400	AC-33923	28-Dec-42
42-106429/106538	Inglewood	P-51B-10	110	AC-30479	5-Jan-43
42-106539/106540	Inglewood	P-51D-1	2	AC-30479	5-Jan-43
42-106541/106738	Inglewood	P-51B-10	198	AC-30479	5-Jan-43
42-106739/106978	Inglewood	P-51B-15	240	AC-30479	5-Jan-43

The next is the comparison with the above list to what the end January 1943 RC-301 says had been accepted (2 XP-51, 2 XP-51B, 148 P-51, 322 A-36) or were on order.

Site	Model	Qty Above	Qty RC-301
Inglewood	XP-51	2	2
Inglewood	P-51	148	148
Inglewood	P-51A	310	310
Inglewood	XP-51B	2	2
Inglewood	P-51B	1838	800
Dallas	P-51C	1000	400
Inglewood	P-51D	2	1040
Dallas	P-51E	0	600
Inglewood	A-36A	500	500
Both	Total	3802	3802

With another 150 Inglewood P-51D and another 350 Dallas P-51E not yet contracted for. USAAF contract quantities do not seem to shift that much but the models planned to be built kept changing. When the first P-51B were actually ordered is unclear, possibly 28 December 1942, given the block number and P-51C order from Dallas, with the earlier contract then being altered.

tomo pauk · Tuesday at 7:03 AM

Geoffrey Sinclair said:
Try 0, which is closer to the number than thousands, definitely when only Canadian production is the criteria. Remember Canada needed to take 30 Merlin from Fairey Battle (plus propellers) for their early 1942 allocation of 30 Hurricane I. No Canadian built Hurricane I arrived in Britain with an engine and the minority of mark II that did had a Merlin 28, which were removed and fitted to Lancaster. The Canadian built Mosquito and Lancaster used US built Merlins. Why risk losing engines at sea only to return "soon"? Merlins were shipped to Canada as replacements for Merlin powered trainers.

Yes, you are right.
I'll edit the post.

tomo pauk · Tuesday at 7:14 AM

Shortround6 said:
The main problem with sticking single stage Merlins in Early Mustangs was ownership.
The Americans owned 1/3rd of the first 9000 Merlins built. Most of these went into the P-40s.
The Americans only owned 2 of the first 622 Mustangs built,
They seized 55 of the 150 lend lease P-51s, which had been ordered in July 1941. They later gave the British 50 P-51As as repayment.
The British and Americans worked well together but not quite as well as some people may believe now. British were scrambling for every airplane they could get even in most of 1942.
Interesting factoid. At the time of Dieppe (Aug 19th 1942) the British have 4 squadrons equipped in Mustangs, which is just about identical to the number of squadrons using Typhoons and the number using Spitfire IXs. How much do you want to delay the supply of Allison powered Mustangs?

The V-1650-1 powered Mustang should've been produced instead of the A-36 and P-51A. That gives the service use from early 1943. There is no need to delay the supply of the V-1710-39 powered Mustangs.

Shortround6 said:
And where do you send them to compensate for the lack of P-40Fs???

North Africa, UK, helped out with having an early second source (Fisher body? - NAA was a good deal owned by GM, Allison and Fisher body were 100% GM's).

Shortround6 said:
By the time the US actually gets more than 2 Mustangs of their own (or actually orders their own, not lend lease) Both the British and NA are trying to figure out how to put the 2 stage engines in the Mustang airframe.

Take advantage of the 1-stage Merlin being far easier to install on the P-51.

Shortround6 said:
In fact the order for 400 P-51Bs with two stage Merlins was placed Aug 26th 1942, Several weeks before the first test flight of the first A-36.
A lot of programs were operating in parallel. You are not going to get single stage Merlin powered Mustangs at all until the 2nd half of 1942 and that is at the factory in California. It took 5-6 weeks (more/) to get the 2nd British Mustang to England by sea using the Panama canal.

All good. It is 1943 for the Merlin Mustang to prove it's mettle.

Shortround6 said:
How much engineering time and testing do you want to do in the Spring/Summer of 1942 trying to stick single stage engines into already contracted for P-51s, P-51As and A-36s?

All the time, resources and testing that went into the A-36.
Change the contracts for the A-36 and P-51A to cover the V-1650-1 powered Mustangs. Make the 'A-40' (= P-40 modified into a dive bomber) for all I care.

Shortround6 · Tuesday at 8:02 PM

tomo pauk said:
All good. It is 1943 for the Merlin Mustang to prove it's mettle.

Problem is that the P-40F was in production (slow) in Jan 1942. First overseas shipment was put on the Ship July 1st 1942.
To show production time lines, The order for 700 P-40Ls was placed June 15th 1942, so there were over 1300 P-40Fs on order for months before that.
The Prototype P-40F flew in June 1941. By August 1942 Curtiss had built 699 P-40Fs with August seeing the changeover to the P-40F-5 with the long fuselage.

The difference in timing is not huge but at times even a few months mattered. In 1942 months did matter. Curtiss built about 600 P-40Fs from Aug to end of Dec of 1942. They built about 600 P-40Ls from Jan though April 1943.
NA was not building Mustangs in those numbers in 1942/early 1943. NA production expanded about 3 times during 1943. But 1942 production was a real case of sorting out what could be made the quickest. Not always what was best.
A Merlin -1 powered Mustang was certainly better than the P-40F. But 1300 P-40Fs built in 1942 is a lot better than 500-600 Merlin Mustangs.

tomo pauk · Wednesday at 8:23 AM

Shortround6 said:
Problem is that the P-40F was in production (slow) in Jan 1942. First overseas shipment was put on the Ship July 1st 1942.
To show production time lines, The order for 700 P-40Ls was placed June 15th 1942, so there were over 1300 P-40Fs on order for months before that.
The Prototype P-40F flew in June 1941. By August 1942 Curtiss had built 699 P-40Fs with August seeing the changeover to the P-40F-5 with the long fuselage.

Contracts can be changed, and were often changed in ww2.
Production of the P-40F will now be even slower, and that of the V-1710-powered versions faster.

Shortround6 said:
The difference in timing is not huge but at times even a few months mattered. In 1942 months did matter.

P-40F was too late to matter for the ETO in 1942, since seasonality of the air war in the ETO mattered a lot (a brave new fighter needs to be there for spring and summer; if you have it available from mid-October means that fighter does not matter for that year). It is too late for 1942 battles at Solomons. It will not do much if anything before late 1942 (Op Torch), where the 'normal' P-40s (together with Spitfires) are more than a match for what Vichy can throw in.
Leaving it to make it's mark from very early in NA and spring for ETO (where it is even less capable vs. the German best than the Spitfire V), meaning that the Mustang with same engine is just weeks later, while being much more of a performer and with the longer range.

Shortround6 said:
A Merlin -1 powered Mustang was certainly better than the P-40F. But 1300 P-40Fs built in 1942 is a lot better than 500-600 Merlin Mustangs.

Math does not stay there.
I've suggested that AAF gets on the Mustang bandwagon ASAP (1941), not in 1942. Historically, AAF wasted last 5 months of 1941 to even test the XP-51. Meaning that production at Inglewood gets higher on the priority list, improving the delivery timetable by 1942. So we can have indeed 500-600 of Merlin Mustangs, but also 200-300 Allison Mustangs, plus hundreds of P-40Fs.
Add there another suggestion, like Lockheeds' heavy fighter second source, and odds look much better for 1943, and no worse for 1942.

ChrisMcD · Wednesday at 4:44 PM

marathag said:
Look at Allison, under GM.
Get Chrysler in he game with a V-12, and Ford two, with making one as well, before the rush in 1939 to make Merlins.
Made in the USA is still the goal.
Info on the Ford is out there, but not as much for Chrysler, so here is one paper for their tank engine that they developed in house to compete with Ford.
View attachment 822900
View attachment 822898

Make a bit bigger, rather than spinning fast like the Hyper projects engines that went nowhere

The Ford tank engine was their V12 'Merlin' cut down to a V8 tank engine after Henry pissed off just about everyone!

The Ford's, the Merlins and Maurice Olley

Origins of Ford Aero and Tank Engines, the American Merlin, and the writings of Maurice Olley. Before the entry of the United States in the Second World War,…

thunderboats.ning.com

tomo pauk · Wednesday at 4:53 PM

One half of the Chrysler IV-2200 engine turned into a tank engine would've been suitable for the US armor, IMO. Perhaps easier to do than the 30 cyl multibank, and certainly lighter.

Elan Vital · Wednesday at 5:10 PM

tomo pauk said:
One half of the Chrysler IV-2200 engine turned into a tank engine would've been suitable for the US armor, IMO. Perhaps easier to do than the 30 cyl multibank, and certainly lighter.

Considering it was designed as two V8 banks it might work. The end result would be a 1110 cu-in V8.

SaparotRob · Wednesday at 5:11 PM

And tail fins. Big ones.

Shortround6 · Thursday at 8:44 AM

tomo pauk said:
One half of the Chrysler IV-2200 engine turned into a tank engine would've been suitable for the US armor, IMO. Perhaps easier to do than the 30 cyl multibank, and certainly lighter.

Timing and production facilities.
The 30 cyl multi bank was five 6 cylinder car engines connected/geared together. There was a common "crankcase" that housed the 5 crankshafts.
There were a few modifications from the parent car engine. Distributers were moved to

The engines were the original cast iron.
The V-16 aircraft engine was aluminum and there were initial problems with alloy strength as supplied by Alcoa.
A large, aluminum V-8 engine fully sorted out would have been a huge advantage in 1940-41. It didn't exist and would not exist for several years.
Engines of this size/power needed large cooling arrangements although the Chrysler arrangement seems compact for what it was asked to do.

special ed · Thursday at 1:40 PM

Chrysler flathead six, times five, should be reliable if the gear train is.

American purchase programs, alternatives and reality, 1937-43

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