wuzak
Captain
I noticed you said the RAF (working with NAA RR) were looking for high altitude capability, not long range capability.
Did the RAF have designs for a long range escort fighter?
- Thread starter MikeGazdik
- Start date
I noticed you said the RAF (working with NAA RR) were looking for high altitude capability, not long range capability.
drgondog
Major
True Wuzak - but long range was an understood existing capability whereas the Allison suffered above 15000 feet.
Indeed, Drgondog. My idea was hypothetical - although it was considered, as I posted earlier. The initial idea behind fitting two-speed-two-stage Merlins to Mustangs came from the British and involved both the shipping of incomplete Mustangs to the UK for fitting the Merlin and production of the Mustang in the UK, these ideas came prior to Packard building the V-1650-3.
drgondog
Major
True - with caveats. The primary facts were that NAA was being denied priorities from Packard and NAA entered into speculative production in UK for a RR Merlin modeled P-51 in late 1941. It was only when the combination of RAF initiative, the USAAF waking up to long range fighter need, Col Tommy Hitchcock reporting enthusiastically that the Brits were going to mate the RR Merlin with high expectations - that NAA was given the go-ahead by Arnold's direction to proceed with a Packard Merlin powered 1650-3. This particular project was one example of the best of US/Britain co-operation but most was between Packard/NAA/RR and RAF - not US, until the results came in..Then Arnold was able to exert enormous influence to get the P-51B production into high gear.
Don't you mean 1942? It was Rolls-Royce who suggested fitting a Merlin to the Mustang first that year after their liaison test pilot Ronnie Harker suggested it in his Mustang flight report in April '42. Aside from the Merlin 61 suggested by Harker, it was also considered that the Merlin XX be fitted; the V-1650-1, but its performance was calculated to be less than a Merlin 61 engined Mustang, and as you hinted at, Packard didn't seem to be in too much of a hurry. Philip Legarra, NAA's field rep in the UK was very keen on the Merlin XX going into the Mustang and shared this view with Freeman.
Very much agree. By the amount of correspondence that shuttled between the various individuals involved, it had to be worth it.
drgondog
Major
No - with respect to RR Merlin XX the conversations began in very late 1941 as deliveries of the first RAF Mustangs were being run through Acceptance testing. The first ships arrived at Speke in October 1941.. the interim and final reports recommended converting to the Merlin 61 in the Spit IX.. It was the RAF that jumped on the advise and began actual work in April, 1942.
Tommy Hitchcock was paying close attention to the Mustang X team and his recommendations circumvented the 2nd Merlin 1650-3 from the Curtis XP-60 project and move it to NAA sometime between January 29 and February 16th, 1942. In April Ronnie Harker RR flew and raved about the potential with a Merlin -61, as Hitchcock's reports hit the Pentagon.
By the time the approvals from Pentagon to NAA to proceed with the P-51B, the RR team was already doing the Installation drawings. As you know the Mustang X flew in Oct 1942. The P-51B was ready save for numerous problems with the Engine and did not make its first flight until November, 1942 when the first XP-51B flew for first time with Packard Merlin 1650-3.
While production tooling was being prepared, the NAA team worked out the coolant and cooling system problems that plagued the XP-51B project in Sep-Oct timeframe.
Tommy Hitchcock was paying close attention to the Mustang X team and his recommendations circumvented the 2nd Merlin 1650-3 from the Curtis XP-60 project and move it to NAA sometime between January 29 and February 16th, 1942. In April Ronnie Harker RR flew and raved about the potential with a Merlin -61, as Hitchcock's reports hit the Pentagon.
By the time the approvals from Pentagon to NAA to proceed with the P-51B, the RR team was already doing the Installation drawings. As you know the Mustang X flew in Oct 1942. The P-51B was ready save for numerous problems with the Engine and did not make its first flight until November, 1942 when the first XP-51B flew for first time with Packard Merlin 1650-3.
While production tooling was being prepared, the NAA team worked out the coolant and cooling system problems that plagued the XP-51B project in Sep-Oct timeframe.
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Between whom? Rolls-Royce didn't evaluate a Mustang until April 1942 and although the RAF's Mustang Is arrived in October '41, acceptance trials commenced in November 1941 and they got them in service until May 42. Although RAF pilots had flown their first example, AG345 completed in the USA in April 1941, Fighter Command settled on the Spitfire as the RAF's premier interceptor because of the Mustang's poor performance at altitude, this is despite the Mustang I being 35 mph faster than the Spit V at 15,000 ft. The first mention of Merlins in Mustangs was Ronnie Harker's test-flight. Prior to this, there was no consideration of it in Britain since the aeroplane hadn't entered service at that point.
Surely you are making this up. I've never seen any evidence that the Americans were talking of putting a Merlin into a Mustang that early. The Mustang X did not exist at this time and nor did talk about it; it was an apple in RR's eye. After Harker's test flight on 30 April 1942 in a Mustang I at Duxford, he spoke to Ray Dorey, manager at Hucknall, who wrote a letter to Freeman about the idea and this is how it all kicked off. In late 1941, although the idea was put forward by the Air Staff on Verney's recommendation in November, only one Spitfire had been modified with the Merlin 61, Mk.III N3297, on Hives's request in spring 1941. The next was Mk.I R6700, which did not fly until 6 January 1942. It was Rolls who first suggested the Merlin XX in May 42, in case not enough 61s were available for the Spit IX and the Mustang against fears the Air Staff had. Packard hadn't built their first V-1650-3 in late 41 - your timeline is seriously at variance with reality, or is this your hypothetical reality? Must be.
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drgondog
Major
Carefully read Mustang by Ray Wagner and Rolls-Royce and the Mustang and draw your own conclusions - the competing and independent accounts dovetail very well and work well with my conversations with Horkey as I best remember from memory. If you don't like the recounts - make up your own story.
I have this book and the first mention of Merlins in Mustangs is Harker's test flight report prepared the day after his test flight of 30 April 1942, as you well know. I haven't read Mustang by Ray Wagner, but I'm assuming you have a copy and will provide evidence of Merlin in Mustang activity in the USA that you claim, prior to Harker's test flight, if I ask nicely.
drgondog
Major
I will direct you to page 103 and 104 of Mustang Designer in which the XP-60 was flown with the Packard Merlin 1650-1 on September 18, 1941. This is the timestamp Ed Horkey referred me to as the time NAA Mustang team actively petitioned the USAAF for the funding to try the 1650 in the P-51.
On page 104, Ray Wagner details the background of the availability of the 1650-1 used in that test vehicle when the XP-60 project was dropped. This termination coincided with the proposed installation of the new 1650-3 (Merlin 61) on January 29, 1942
for the XP-60D. NAA, according to Horkey asked for the engine in February, 1942 when the reports from RAF trials noted the strong suggestion that the Mustang be fitted with the P-51.
I do not have any documents from NAA to the USAAF for this request - just Horkey's recollection - and he and Schmeud were in direct and persistent contact with the British Acceptance trials team in the October through Feruary, 1942 timeframe.
The final push came from Tommy Hitchcock after April 30, 1942 when Harker flew the Mustang I -- and his urging directly to Arnold, according to Horkey, was the stimulus for the specification release to NAA on June 12 and contract issued to NAA on July 24, 1942.
In Hitchcock's summary Memorandum dated 8 October states that "The Air Ministry instructed the Rolls people to install five Merlin engines in Mustang airplanes. Simultaneously with this develeopment it was arranged to have North American company to install the Merlin 61 in their Mustang airframe".
Now turn the question back to you.
Why do you think that Merlin/Mustang conversations and activity did Not take place at NAA before Harker's first flight?
NAA had a superior airframe to all US fighters before Brits received their first Mustang I.
NAA was struggling to get a contract for the P-51A as the XP-51 languished at Wright Pat, receiving no attention from USAAF
NAA had not yet secured the contract for the A-36
NAA did know that the Packard Merlin XX offered far superior performance than the V-1710, and knew of the results for Merlin 61
NAA did not have the funds to fund the P-51B, but knew that the performance of a P-51/1650-3 would be far superior to P-51A
NAA did know that the 1650-3 had 'come available" on the February 2, 1942 cancellation of the XP-60D tests.
Why do You think that the concept of Merlin/P-51 was an epiphony at NAA after Ronnie Harker's test flight and subsequent 'official' recommendation that a Merlin-61 be installed? You think that an incredibly talented design team was satisfied with the dog performance of the 1710 versus the Merlin?
Why do you think that recollections of Ed Horkey were flawed relative to timing of interest at NAA for a Merlin powered Mustang?
On page 104, Ray Wagner details the background of the availability of the 1650-1 used in that test vehicle when the XP-60 project was dropped. This termination coincided with the proposed installation of the new 1650-3 (Merlin 61) on January 29, 1942
for the XP-60D. NAA, according to Horkey asked for the engine in February, 1942 when the reports from RAF trials noted the strong suggestion that the Mustang be fitted with the P-51.
I do not have any documents from NAA to the USAAF for this request - just Horkey's recollection - and he and Schmeud were in direct and persistent contact with the British Acceptance trials team in the October through Feruary, 1942 timeframe.
The final push came from Tommy Hitchcock after April 30, 1942 when Harker flew the Mustang I -- and his urging directly to Arnold, according to Horkey, was the stimulus for the specification release to NAA on June 12 and contract issued to NAA on July 24, 1942.
In Hitchcock's summary Memorandum dated 8 October states that "The Air Ministry instructed the Rolls people to install five Merlin engines in Mustang airplanes. Simultaneously with this develeopment it was arranged to have North American company to install the Merlin 61 in their Mustang airframe".
Now turn the question back to you.
Why do you think that Merlin/Mustang conversations and activity did Not take place at NAA before Harker's first flight?
NAA had a superior airframe to all US fighters before Brits received their first Mustang I.
NAA was struggling to get a contract for the P-51A as the XP-51 languished at Wright Pat, receiving no attention from USAAF
NAA had not yet secured the contract for the A-36
NAA did know that the Packard Merlin XX offered far superior performance than the V-1710, and knew of the results for Merlin 61
NAA did not have the funds to fund the P-51B, but knew that the performance of a P-51/1650-3 would be far superior to P-51A
NAA did know that the 1650-3 had 'come available" on the February 2, 1942 cancellation of the XP-60D tests.
Why do You think that the concept of Merlin/P-51 was an epiphony at NAA after Ronnie Harker's test flight and subsequent 'official' recommendation that a Merlin-61 be installed? You think that an incredibly talented design team was satisfied with the dog performance of the 1710 versus the Merlin?
Why do you think that recollections of Ed Horkey were flawed relative to timing of interest at NAA for a Merlin powered Mustang?
Interesting information and conclusions, but the tie-in with the Curtiss XP-60 doesn't in any way imply any reference to the Mustang at all, except for your man Horkey's recollections. It's a bit tenuous, unless you can provide anything other than his word.
Now, I knew you were going to say that - Unfortunately without a document or evidence in print at least, it's a bit difficult to prove or justify; having worked in professional research establishments, I know the value of personal recollections, but also how they can not necessarily be relied on for historical accuracy. Now, I can see that its quite likely that NAA could have enquired about putting a Merlin 28 in the Mustang with the USAAF, but clearly nothing was immediately done within the USAAF until the British forwarded interest through the US Ambassador to Britain, John G Winant, who went directly to Arnold in June 1942.
The question is - and this might help answer some of yours - why has nothing to this effect come out sooner? It's been over 70 years since the Mustang first flew, why has no other researcher cottoned on to it?
I can accept that NAA reps might have spoken with the USAAF, but not with RAF personnel, simply because there's no evidence of such correspondence that has come to light. You mentioned Rolls-Royce and the Mustang by David Birch; he's done a huge amount of research to produce what is an excellent recollection, using official sources, both from the UK and USA to complete his volume. Wouldn't you think he would have uncovered such correspondence with regards to the RAF side of things? The history of the Mustang is very well covered by a large number of authors and such correspondence would/should have been discovered by now. Any discussions that were held between the RAF acceptance trials people and NAA surely would have pricked up both the Air Staff's and Rolls-Royce's ears at the time, producing a flurry of correspondence, as you'd naturally assume so and as what actually happened when the proposal was put forward by RR. Therefore any written evidence would be kept in the National Archive or perhaps the Air Historic Branch or the Rolls-Royce Heritage Trust, for which Birch produced his book.
I could go on, but I don't see the point. Documentary proof is what's required and until it is produced, the status quo of the last 70 or more years remains, I'm afraid. That's how history works; you should know that.
Now, I knew you were going to say that - Unfortunately without a document or evidence in print at least, it's a bit difficult to prove or justify; having worked in professional research establishments, I know the value of personal recollections, but also how they can not necessarily be relied on for historical accuracy. Now, I can see that its quite likely that NAA could have enquired about putting a Merlin 28 in the Mustang with the USAAF, but clearly nothing was immediately done within the USAAF until the British forwarded interest through the US Ambassador to Britain, John G Winant, who went directly to Arnold in June 1942.
The question is - and this might help answer some of yours - why has nothing to this effect come out sooner? It's been over 70 years since the Mustang first flew, why has no other researcher cottoned on to it?
I can accept that NAA reps might have spoken with the USAAF, but not with RAF personnel, simply because there's no evidence of such correspondence that has come to light. You mentioned Rolls-Royce and the Mustang by David Birch; he's done a huge amount of research to produce what is an excellent recollection, using official sources, both from the UK and USA to complete his volume. Wouldn't you think he would have uncovered such correspondence with regards to the RAF side of things? The history of the Mustang is very well covered by a large number of authors and such correspondence would/should have been discovered by now. Any discussions that were held between the RAF acceptance trials people and NAA surely would have pricked up both the Air Staff's and Rolls-Royce's ears at the time, producing a flurry of correspondence, as you'd naturally assume so and as what actually happened when the proposal was put forward by RR. Therefore any written evidence would be kept in the National Archive or perhaps the Air Historic Branch or the Rolls-Royce Heritage Trust, for which Birch produced his book.
I could go on, but I don't see the point. Documentary proof is what's required and until it is produced, the status quo of the last 70 or more years remains, I'm afraid. That's how history works; you should know that.
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Just a few points more, Drgondog.
Those statements are circumstantial and offer nothing to to add to NAA going to the USAAF about Packard Merlins in Mustangs.
Of course they were, there was nothing to suggest the Allison was a dog and had bad performance; the Mustang I could out perform the current British and American fighters in speed and range - as you know, in fact, the only concern, which was raised by the British, not the Americans, was that it couldn't reach the altitudes of combat in Europe, which in 1941 the USAAF did not have any experience with, so I don't agree with this. NAA had very good reason to be happy with their fighter and they were.
Those statements are circumstantial and offer nothing to to add to NAA going to the USAAF about Packard Merlins in Mustangs.
Of course they were, there was nothing to suggest the Allison was a dog and had bad performance; the Mustang I could out perform the current British and American fighters in speed and range - as you know, in fact, the only concern, which was raised by the British, not the Americans, was that it couldn't reach the altitudes of combat in Europe, which in 1941 the USAAF did not have any experience with, so I don't agree with this. NAA had very good reason to be happy with their fighter and they were.
It might (note, I say "might") now be impossible to determine exactly the point at which the Merlin was considered for the Mustang by various people at NAA. I have no doubt, however, that some of the design engineers were thinking about it during the design phase or shortly after the original design was completed. I say this because one of the defining traits of engineers involved in R&D is that they can never leave well enough alone. They are always trying to improve whatever they are working on. They would not be good at R&D if they said "good enough" and never thought about improvement. The plane was being produced for the British, so I find it highly improbable that nobody would ask: "What engines are the British using, how do they perform, and can we fit any of them onto our new fighter?" Remember that no Allison engine was available when the first airframe was completed, so it would be logical to be thinking about a "just in case we can't get enough Allisons" option.
Please remember that there was certainly a big difference between the knowledge and abilities of the leading-edge designers and that of the pertinent officials of the USAAF. Just because the USAAF wasn't yet asking for long-distance, high-altitude fighters, that does not mean that knowledge base for just such a plane was not developing. Work had already been done on the P-38, for example.
Furthermore, even if the USAAF believed that the B-17's were not vulnerable to fighters, the fighter designers knew that this was hogwash. At the first sight of of a B-17, an American fighter designer would immediately ask the question: "How can we shoot these suckers down, since our enemies will likely have something similar soon."
On the other hand, it would not surprise me that some of the "Higher Ups" and production managers of NAA were as nuuumannn stated, "happy with their fighter." Continual changes are typically opposed by those tasked with getting finished products to the client. There is always a battle between the "good enough" camp and the "but it can be better" camp.
In short, there should be a delay between the initial design concepts and the written requests made through official channels. The precise timeline may now be lost to history since those who did the work are now gone.
Oh, and can you tell that I have experience with project development and improvement in industry?
drgondog
Major
I do know that and I take no offense at the question you pose. One can not prove a negative
It might be of interest to know that, according to Bert Kinzey, when the army ordered 150 P-51s (the 4 cannon version) on 7 July 1941, two - the 93rd and 102nd - were to be set aside for eventual conversion to and testing with the Merlin; this is why the first XP-51B was unarmed and the second had 4 20mm cannon.
(P-51 Mustang in Detail Scale Part 1, 1996, pages 17-18.)
One possible gripe is that Kinzey refers to turbocharger, not supercharger...but there's no reason to doubt his conclusions because he did go to NAA.
Good to see this is developing beyond our original discussion. Firstly Nincompoop; I think you are taking my "happy with the fighter" quote out of context; the reason I said it was to counter Drgondog's assertion that the Allison engine performance was a dog. Considering the Mustang was faster and had a greater range than any British or American fighter then in service at that time, NAA were happy with it as a fighter and of course they would look at continuing development; goes without saying. Of course the Americans were investigating higher altitude performance in their fighters, XP-60 and P-38 development and also we all know that Allison were working on improving the altitude performance of the V-1710 to reinforce this, but it was the RAF evaluation team that examined the first production examples in the States (the first AG345 flew for the first time on 1 May 1941) that realised its altitude performance was below what was required over Europe, but this still did not seem to deter from the USAAF putting the order in in July '41. And no, I can't tell you have experience with project development and improvement in industry, not that it's relevant or anything.
Drgondog, sounds like you've had some fascinating discussions with people about these things, would have been real interesting to sit in and listen. You're in an enviable position to be able to get access to these guys and the resources you can. I live in the middle of nowhere in a small country on the other side of the world from you! If I was in your position I'd be divorced for neglecting my family, by now! As for conversations between RAF and American personnel about better altitude, you can guarantee they happened; yep, chit-chat makes the world go round, but when you get to something as important and as urgent - remember, at that time (late '41 early 42) the British were struggling to cope with the Fw 190 - and as pertinent as a fighter with exceptional performance it was bound to get tongues wagging and pens writing. These RAF guys with 26 Sqn that received the Mustang in January '42 had encountered the Fw 190, so discussions regarding offering better performance than their foe led to quite a bit of discussion and evidence shows they were real pleased with the performance of the Mustang - altitude performance aside. As it was, the Mustang I could match the Fw 190 on even terms. Regarding Atwood and Schmued, it seems that Legarra and Bouchelle of NAA did much of the leg work from the British side of things; these two guys seemed to have spent some time in the UK, with visits to Hucknall to view progress on the Mustangs being converted there.
Aozora, interesting information and although I hadn't seen that book and it would be interesting to see the rest of that chapter, I was aware that two Mustangs from the original USAAF order were to be kept aside for evaluation, because this was a condition of the approval that a US company was to build aircraft for the British who were at war, since the USA was not at that stage. The decision to evaluate them fitted with Merlins didn't come until later, not when the contract to build was signed. At Wright field there was discussion of fitting these aircraft with the V-1650-1 (Merlin 28 ) supplied by Packard for trials, (this is the crux of the matter) and conventional wisdom states this was in conjunction with the suggestion by Rolls Royce of fitting such an engine, as an interim to allay fears by the Air Staff that there wouldn't be enough Merlin 61s for the Spitfire and the Mustang, in May 1942. British reps from A&AAE Boscombe Down had been to the States (when - sometime earlier than mid May 42?) to discuss the fitting of a Merlin 28 to the Mustang, but their response was not encouraging, correspondence states that "...it did not get any further". By June the Americans had promised that by July they would have a Merlin 28 Mustang in the air, which affirms initial consideration and investigation, but the conversion didn't happen. By August 1942, Kindleberger had contacted the USAAF about the unfeasibility of the Merlin 28 and preference for the 61 instead.
If anyone can supply it, I'd like to see further reference to Wright Field's investigation of the V-1650-1 for the two XP-51s they had; it'll make interesting reading. Would the USAF Museum be a good source for this?
Drgondog, sounds like you've had some fascinating discussions with people about these things, would have been real interesting to sit in and listen. You're in an enviable position to be able to get access to these guys and the resources you can. I live in the middle of nowhere in a small country on the other side of the world from you! If I was in your position I'd be divorced for neglecting my family, by now! As for conversations between RAF and American personnel about better altitude, you can guarantee they happened; yep, chit-chat makes the world go round, but when you get to something as important and as urgent - remember, at that time (late '41 early 42) the British were struggling to cope with the Fw 190 - and as pertinent as a fighter with exceptional performance it was bound to get tongues wagging and pens writing. These RAF guys with 26 Sqn that received the Mustang in January '42 had encountered the Fw 190, so discussions regarding offering better performance than their foe led to quite a bit of discussion and evidence shows they were real pleased with the performance of the Mustang - altitude performance aside. As it was, the Mustang I could match the Fw 190 on even terms. Regarding Atwood and Schmued, it seems that Legarra and Bouchelle of NAA did much of the leg work from the British side of things; these two guys seemed to have spent some time in the UK, with visits to Hucknall to view progress on the Mustangs being converted there.
Aozora, interesting information and although I hadn't seen that book and it would be interesting to see the rest of that chapter, I was aware that two Mustangs from the original USAAF order were to be kept aside for evaluation, because this was a condition of the approval that a US company was to build aircraft for the British who were at war, since the USA was not at that stage. The decision to evaluate them fitted with Merlins didn't come until later, not when the contract to build was signed. At Wright field there was discussion of fitting these aircraft with the V-1650-1 (Merlin 28 ) supplied by Packard for trials, (this is the crux of the matter) and conventional wisdom states this was in conjunction with the suggestion by Rolls Royce of fitting such an engine, as an interim to allay fears by the Air Staff that there wouldn't be enough Merlin 61s for the Spitfire and the Mustang, in May 1942. British reps from A&AAE Boscombe Down had been to the States (when - sometime earlier than mid May 42?) to discuss the fitting of a Merlin 28 to the Mustang, but their response was not encouraging, correspondence states that "...it did not get any further". By June the Americans had promised that by July they would have a Merlin 28 Mustang in the air, which affirms initial consideration and investigation, but the conversion didn't happen. By August 1942, Kindleberger had contacted the USAAF about the unfeasibility of the Merlin 28 and preference for the 61 instead.
If anyone can supply it, I'd like to see further reference to Wright Field's investigation of the V-1650-1 for the two XP-51s they had; it'll make interesting reading. Would the USAF Museum be a good source for this?
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OK. I was a bit confused by the "happy with the fighter" comment. Thanks. Overall, I think that we basically agree. The official timeline comes down to finding documents.
I thought that maybe my comments about the way that R&D engineers tend to view the world (always tinkering and never leaving well enough alone) might have given me away. I am very familiar with the constant battle between the production group's "stop tinkering and let's build it" versus the R&D group's "but we can improve it more." Some of us simply cannot help wanting to tinker with a design to make improvements.
I would be surprised if the NAA R&D folks had not thought about using a Merlin engine and made informal inquiries, at least to gather data. On the other hand, it does not surprise me that it took the RAF's request to actually get something done about it. At this point, the RAF certainly knew more about what was needed in their theater than did the USAAF.
My point was primarily that it is very difficult to pin down the exact time when a new idea is considered, especially if there are informal discussions going on among various groups. Determining the date of a formal, documented request is much easier. In the grand scheme of things, however, our quibbling about the exact timing of events that happened long ago is probably not that big a deal. It is fun to do, though.
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Yeah, we have a similar situation where I work; I'm an aircraft engineer who works line maintenance on airliners and some guys get caught in the trap of not knowing what is required of line maintenance and when to down tools and leave work for the next maintenance opportunity.
I guess you're right regarding precise timing and it would be very interesting to find documents or anything else pertaining to investigating the V-1650-1 in American fighters. The XP-60 example that Drgondog raised is a pertinent point and it would seem logical for Packard to put forward the engine to the USAAF for the Mustang, but one thing that is not often taken into account is that in late (until, that is, December 7) 1941, the USA was not at war; things just didn't happen very quickly in a peacetime environment within the military, but as soon as war clouds gather the US military showed it could pick up the pace. Their interest in the Merlin Mustang in 1942 is a case in point.
wuzak
Captain
When did the USAAC/F first take notice of the P-51 and start to order production aircraft?
When NAA were investigating the Merlin 20-series/V-1650-1 for the P-51/Mustang I, was it intended for the USAAC/F or the RAF?
When NAA were investigating the Merlin 20-series/V-1650-1 for the P-51/Mustang I, was it intended for the USAAC/F or the RAF?
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