P51 genesis

[Rick]

Old news to a lot, new news to a few, and another example of one man making a difference.

 https://www.militarytimes.com/news/your-military/2025/03/18/the-p-51-mustang-and-the-man-who-won-the-world-war-ii-air-war-with-it/?utm_source=sailthru&utm_medium=email&utm_campaign=marine-dnr

[Stuart Galbraith]

The problem is with that narrative, the Americans were not the first to put a Merlin in a Mustang. The British did it in October 1942, a month before the Americans did.

https://www.mustang.gaetanmarie.com/articles/harker.htm

Granted it was a lashup and not the same setup as the Americans made. But as a tech demonstratorvit worked, and it was a British test pilot that had the idea, and Rolls Royce that proved it could be done.

Its not particularly clear whether the Americans knew what the British were doing. But considering they were building the Mustang for the British Air Ministry, and considering Rolls Royce had close links with American industry, it would be truly remarkable if they didnt hear about it.

[Markus Becker]

Well, Edgar Schmued never worked for Messerschmidt or any other German aviation manufacturer that designed fighters. He emigrated in the 20s already when the Versailles Treaty was still enforced by an Allied Control Commission. 

WRT the engine choices. It was logical. The P-51's airframe was very low drag making the plane really, really fast despite the low altitude. Putting in an engine with a higher critical alternative was a logical next step. 

 

As far as the critical role of the P-51 is concerned, enter Greg. 

 

[Mikel2]

Lots of German DNA in the P-51.

(Schmued and Fokker)

[RichTO90]

6 hours ago, Mikel2 said:

Lots of German DNA in the P-51.

(Schmued and Fokker)

Schmued never worked for Messerschmidt. That myth simply refuses to die. Fokker never worked for North American Aviation, nor did Messerschmidt. That myth also simply refuses to die.

North American Aviation was an aviation holding company. The Depression enabled them to acquire a large number of companies cheaply. When formed on 6 December 1928, it had interests in: Curtiss Aeroplane and Motor Company, Curtiss-Robertson Airplane Manufacturing Company, Curtiss-Caproni Corporation, Wright Aeronautical, Travel Air, North Aircraft Corporation, and Keystone Aircraft Corporation. Did the P-51 have a lot of Italian DNA?

Between 1929 and 1933, it acquired: Sperry Gyroscope Co., Inc, Pitcairn Aviation Inc (which started Eastern Air Transport in 1930), Berliner-Joyce Aircraft Corporation, Ford Instrument, Transcontinental and Western Air (the TWA of today), Intercontinent Aviation Inc, and a substantial interest in the Douglas Aircraft Corporation. Did the P-51 have a lot of airline DNA? Or perhaps gyroscope DNA?

In 1933, General Motors acquired NAA as a subsidiary, along with holdings in: General Aviation Corporation (which had taken over the Fokker Aircraft Corporation four years after Anthont Fokker lost control of and two years after Anthony he resigned as head of engineering at Fokker) and the Dayton-Wright Corporation. Did the P-51 have a lot of automobile DNA?

The NA-75 was the brainchild of Dutch Kindelberger, J. Leland Atwood, Raymond H. Rice, Edgar Schmued, Larry Waite, and E. H. Horkey.

Yes, using the Merlin was initially the idea of Ronald W. Harker, a Rolls-Royce test pilot. Five Mustang I were converted and tested. However, it could have ended there. The problem was that Rolls-Royce was barely able to produce enough Merlins for RAF requirements, let alone for an American-produced aircraft. It was Major Thomas Hitchcock USAAC, who was told of Rolls-Royce's dilemma and knew that Packard was negotiating to license the Merlin and convinced North America to build two Merlin-engined testbeds for a project to build Packard-engined P-51. Rolls-Royce had no role in that conversion process, other than supply the two Merlin engines as reerse Lend-Lease to NAA.

[Stuart Galbraith]

I think it was always the expectation it would be the Americans that would do the work, since its somewhat nonsensical to ship airframes without engines and do the additional work here. What is no explained is if the Americans knew this was being done in Britain or not. Its really rather key, because it would explain whether this was dual track, with 2 countries having the same idea at the same time but no connection between them, or whether the P51 with a Merlin story starts in the UK.

Kind of reminds me of the time when the Americans boasted they could give the Spitfire the range of a Mustang. So we sent along an aircraft for them to conduct the conversion on, and when we got it back found they had cut through several structural members and the aircraft presumably had to be scrapped. So it goes...

[sunday]

11 hours ago, Mikel2 said:

Lots of German DNA in the P-51.

(Schmued and Fokker)

Indeed!

https://en.wikipedia.org/wiki/Atlantic_Aircraft

[RichTO90]

Like I said, that particular myth refuses to die.

[RichTO90]

Stuart, Harker's idea, the initial five conversions tested by the RAF, and Hitchcock's involvement that led to the decision to use the Packard Merlin were in such close succession that it is difficult to describe it as an expection or even a plan. It was a series of fortuitous events.

[Stuart Galbraith]

Well you must make of this what you will.

https://www.defensemedianetwork.com/stories/p-51-mustangs-switch-to-merlin-engine-made-it-the-world-beater-of-world-war-ii/

'Lt. Col. Thomas “Tommy” Hitchcock, assistant air attache at the American embassy in London and a renowned polo player, submitted reports to Washington on the merits of the Merlin. Hitchcock quoted a Rolls-Royce finding that the engine change would give the Mustang a maximum speed of 432 miles per hour.

Hitchcock reported the success of early Merlin test flights to the Army Air Forces (AAF) brass and to North American Aviation, Inc., (NAA) officials. Meanwhile, NAA had been fully briefed by Rolls-Royce on the Mustang X project and had started planning their own Merlin-powered Mustang. The U.S. planemaker received authorization to install Merlin 65 engines imported from England into two P-51s that been built for the RAF but not yet delivered.'

 

Sounds to me like honours even between Harker and Hitchcock. Harker for the idea, Hitchcock for convincing North American and the USAAF that it was a good idea.

 

 

Edited March 21 by Stuart Galbraith

[RichTO90]

The extraordinary thing is that Harker raised his idea on 30 April 1942 and the Mustang X first flew on 12 October 1942, while the first XP-51B flew on 30 November 1942. Meanwhile, the USAAF already had ordered 400 of the Packard-engined planes in August, based upon expectations.

Edited March 21 by RichTO90

[Ol Paint]

The timeline is not so surprising when looked at in context.

The Packard Merlin was the shiny new kid on the block and represented a sudden source of engines that could be applied to production.  In negotiating the initial production, Gen. Arnold received a commitment that the USAAC would receive engines for an additional 3,000 aircraft above those included in existing production programs (18,000 authorized by Congress) in exchange for supporting the British Purchasing commission's order for 6,000 units. 

Quote

With the September 1940 contracts for the single-stage Packard Merlin, the Air Corps had nearly three times as many Merlins on order as it had V-1710s, and all of the Allisons were scheduled for delivery by January 1, 1941.  This situation evened out somewhat in December  when the US ordered and additional 3,691 V-1710s to be built in five different models.  Clearly any commitment to the Allison by the US was pending ording of the aircraft that were to use it.  The Merlin was ordered before identifying the US aircraft it was to power.  The first Packard built Merlin, a V-1650-1 was run in early 1941, with deliveries beginning that October, some 15 months after Packard began the project...

                    Table 15-1
    US Liquid-Cooled Engine Orders As Of October 1940
                                       For Britain/France    For Air Corps    Total
Allison V-1710                            4,315                1,050                5,365
Packard Built Merlin                  6,000               3,000               9,000

Above quote from "Vee's for Victory!" by Daniel D. Whitney.

With a supply of engines (initially single-stage supercharged) without airframes on order, the engines essentially got shopped around to various programs.  Ultimately, the V-1650-1s ended up going into the P-40s.  But that source of engines being shopped around by the USG and given North American's involvement in potential P-40 production, plus the prototype Merlin-powered P-40 starting flight testing in June 1941, followed by serial production deliveries starting in January 1942 (per America's Hundred Thousand), the mix of factors is there for North American to have at least done some studies on the Merlin Mustang before any official moves were made.

The Merlin isn't magic.  The P-40E was powered by the V-1710-39/F3R single-speed/single-stage engine rated at 1,150hp military power.  The P-40F running the two-speed/single-stage V-1650-1 rated at 1,240hp.  According to America's Hundred Thousand, the P-40E at 8,400lb was capable of 360mph at 15,000ft (best speed/altitude combo), which was 5mph slower than the P-40F (at a slightly higher weight of 8,500lb) at that model's best altitude of 20,000ft.  However, the Merlin P-40F was slower than the E at 15,000ft by about 10mph.  (I will note that the typically excellent Greg's Airplanes and Automobiles charts the P-40F performance as being faster at all altitudes, so pick your poison.*)  

The point is that similar displacement, similar weight, and similar boost levels will produce similar power output and similar performance.  The real improvement for the Mustang was Rolls-Royce's/Stanley Hooker's excellent supercharging setup in the two-speed/two-stage models coupled to the relatively sudden availability of the engines and the easier integration of the induction package into the airframe.  It was a confluence of factors that produced a good aircraft.  But there were a bunch of other equally good, or better, aircraft also flying. 

Speaking of which, the R-2800 fighters shot down far more aircraft for the USA than the third-place Merlin fighters... 

Doug

*  Then there's the documentation Greg provides on the Allison P-40E operations at higher than authorized manifold pressures to produce over 1,500hp, but that's a different can of worms.

[Markus Becker]

15 hours ago, Ol Paint said:

The Merlin isn't magic.  The P-40E was powered by the V-1710-39/F3R single-speed/single-stage engine rated at 1,150hp military power.  The P-40F running the two-speed/single-stage V-1650-1 rated at 1,240hp.  According to America's Hundred Thousand, the P-40E at 8,400lb was capable of 360mph at 15,000ft (best speed/altitude combo), which was 5mph slower than the P-40F (at a slightly higher weight of 8,500lb) at that model's best altitude of 20,000ft.  However, the Merlin P-40F was slower than the E at 15,000ft by about 10mph.  (I will note that the typically excellent Greg's Airplanes and Automobiles charts the P-40F performance as being faster at all altitudes, so pick your poison.*)  

The speed isn't the key point here, it's the altitude. The typical Allisons were restricted to the medium to high-ish altitudes because of their single stage, single speed superchargers. For heavy bomber escort an engine with a critical altitude of 25k feet was needed. 

I dare say a plane that could have made 390 mph at that altitude wouldn't have been a noticeably infernor escort than one making 440. 

[Stuart Galbraith]

Im thinking the speed is only really an issue as far as rate of climb is concerned. Which for a long range escort is probably distinctly secondary to the speed they can dive at without the wings coming off.