P-51 Mustang (A-36 Apache), time it took to design?

[Todd Secrest]

When NAA (North American Aviation) told the British that the A-36 Mustang/Apache prototype (NA-73X) could be built in only 120 days, but it took only 102, which is cool.
But was the NA-73X already being designed, by NAA, before the British approached them (when the British had first asked NAA to build the P-40)?
If so, how long was the Mustang/Apache in design phase, before the British showed up?

 

[ColFord]

Two books............

First by Gruenhagen will give you a good overall grounding of the basics of the type and development (first published 1970s, revised edition 1980). Second by Marshall & Ford (published in 2020 so is up to date in terms of research and sources) will give you the "deep dive" into the development of the type from the first through to the P-51B and timeline up until D-Day in 1944 - it includes background on NAA's thinking about 'pursuit' types before the British came along with their requirement.

A-36 was the fourth variant to be developed:
1+2. NA73 & NA83 - Mustang Mk.I for RAF.
3. NA-91 - P-51 (no suffix) - Mustang Mk.IA for RAF produced under Lend Lease. It was this variant that was proposed to be called 'Apache' for the USAAF to differentiate it from 'Mustang' name which had been given to the type by the RAF. NAA rejected the name change, all aircraft of type and variants to be called 'Mustang'.
4. NA-97 - A-36A Mustang.
5. NA-99 - P-51A - Mustang - Mustang Mk.II in RAF service, 50 provided to RAF.

 

[pbehn]

I would recommend the above "P-51B", its a great read.

 

[drgondog]

Thanks Colin - We devoted much more detail to the development of the A-36 than Bob, but his book is THE seminal Mustang book. I am humbled by the positive response we have had, but one of the objectives was to 'fill in the blanks' and still a lot of work to do.

Thanks to you much RAF 'mystery' was swept away.

 

[drgondog]

When NAA (North American Aviation) told the British that the A-36 Mustang/Apache prototype (NA-73X) could be built in only 120 days, but it took only 102, which is cool.
But was the NA-73X already being designed, by NAA, before the British approached them (when the British had first asked NAA to build the P-40)?
If so, how long was the Mustang/Apache in design phase, before the British showed up?

Todd , by the comments you may have a fair amount of confusion regarding the development of the NAA Mustang.
No, NA-73X was the extension of the P-509 which Edgar Schmued had invested personal time in pursuit of a concept layout of the Allison High Speed Pursuit that NAA contracted Dr Clark Milliken, Dept Head Aero at CalTech, to prepare a Performance Study for Arnold.

While it was the pre-cursor for te March 1940 discusions with AFPC in lieu of P-40, it did have the imbedded radiator/oil cooler system under and aft of the cockpit and both cowl and wing armament with the weights and balances of the the Allison engine and general look that we associate with the Mustang.

NA-73X was the prototype developed in dialogue between NAA Engineering (including Atwood, Rice, Schmued and Horkey) and BAM/RAF technical staff in NYC between mid March and April 20. The NAA NA-1592 Specification (P-509) morphed into NA 1620 (NA-73). The Schmued Engineering team selection was just about done at this time and 7x24 effort was in high gear. Design drawings were often in parallel with design pkg release to Experimental Dept. The final engineering package was delivered in early August to Experimental Department. NAA Project Engineer Ken Bowen was tasked to move the NA-73 into production in parallel with the construction of X-73. April 24 to August 1 is as close to the start and end date of Schmued's design team elapsed time as I could nail down.

If there is an 'official' end date for X-73 it is contained in Atwood telex to Burdette Wright (President Curtiss) in which he cites 'finished experimental airplane complete Sept 9". It awaited the committed Allison V-1710 which did not arrive until Ocober to finish instrumentation and electrical and powerplant installation and prepare for flight test on October 26. Perhaps interesting is that Rolls-Royce and Packard signed license agreement to build Merlin XX - and NAA was very interested in progress as there was considerable displeasure with Allison.

The actual preliminary (internally funded by GMC) work on the (NA-97) A-36 as Low Level Pursuit began Approx 12 months later (Oct-Nov 1941) as NAA understood Attack funds for FY42 were still available. The airframe base design was the NA-83 production vesion of Mustang I. Apache had a brief 'marketing name' life with Army Public Relations, but it was for the 58 Mustang IA (NA-91) that US Army took from RAF total of 150.

The action took place at same time the actual production design of the A-36 began and had three purposes. First, (NA-101) XP-51B was begun with two airframes tasked to incorporate changes of cooling system and engine change from Allison V-1710 to Merlin 61. Second purpose was to modify and deploy Recon version of P-51-NA. Third purpose was to develop maintenance and training procedure and documents for the production A-36 as well as the newer P-51A which was under contract in early summer 1942.

Hope this helps.

 

[Thumpalumpacus]

Todd , by the comments you may have a fair amount of confusion regarding the development of the NAA Mustang.
No, NA-73X was the extension of the P-509 which Edgar Schmued had invested personal time in pursuit of a concept layout of the Allison High Speed Pursuit that NAA contracted Dr Clark Milliken, Dept Head Aero at CalTech, to prepare a Performance Study for Arnold.

While it was the pre-cursor for te March 1940 discusions with AFPC in lieu of P-40, it did have the imbedded radiator/oil cooler system under and aft of the cockpit and both cowl and wing armament with the weights and balances of the the Allison engine and general look that we associate with the Mustang.

NA-73X was the prototype developed in dialogue between NAA Engineering (including Atwood, Rice, Schmued and Horkey) and BAM/RAF technical staff in NYC between mid March and April 20. The NAA NA-1592 Specification (P-509) morphed into NA 1620 (NA-73). The Schmued Engineering team selection was just about done at this time and 7x24 effort was in high gear. Design drawings were often in parallel with design pkg release to Experimental Dept. The final engineering package was delivered in early August to Experimental Department. NAA Project Engineer Ken Bowen was tasked to move the NA-73 into production in parallel with the construction of X-73. April 24 to August 1 is as close to the start and end date of Schmued's design team elapsed time as I could nail down.

If there is an 'official' end date for X-73 it is contained in Atwood telex to Burdette Wright (President Curtiss) in which he cites 'finished experimental airplane complete Sept 9". It awaited the committed Allison V-1710 which did not arrive until Ocober to finish instrumentation and electrical and powerplant installation and prepare for flight test on October 26. Perhaps interesting is that Rolls-Royce and Packard signed license agreement to build Merlin XX - and NAA was very interested in progress as there was considerable displeasure with Allison.

The actual preliminary (internally funded by GMC) work on the (NA-97) A-36 as Low Level Pursuit began Approx 12 months later (Oct-Nov 1941) as NAA understood Attack funds for FY42 were still available. The airframe base design was the NA-83 production vesion of Mustang I. Apache had a brief 'marketing name' life with Army Public Relations, but it was for the 58 Mustang IA (NA-91) that US Army took from RAF total of 150.

The action took place at same time the actual production design of the A-36 began and had three purposes. First, (NA-101) XP-51B was begun with two airframes tasked to incorporate changes of cooling system and engine change from Allison V-1710 to Merlin 61. Second purpose was to modify and deploy Recon version of P-51-NA. Third purpose was to develop maintenance and training procedure and documents for the production A-36 as well as the newer P-51A which was under contract in early summer 1942.

Hope this helps.

I cat wait to get to y'all's book on the subject. I have a bit of reading lined up in front of that but info like this only whets my appetite.

 

[Mustangtmg]

When NAA (North American Aviation) told the British that the A-36 Mustang/Apache prototype (NA-73X) could be built in only 120 days, but it took only 102, which is cool.
But was the NA-73X already being designed, by NAA, before the British approached them (when the British had first asked NAA to build the P-40)?
If so, how long was the Mustang/Apache in design phase, before the British showed up?

I hope you've seen by now (not sure when you posted this originally), that your Mustang history needed a little "tweaking." That's alright. Colin Ford (whose post appears below this - well, it does on www2aircraft.net - pretty well tells the story.

It's too bad that because someone in the 1970s got confused by a September, 1941 ad for North American and thought that the plane diving in the artist's conception drawing was an A-36. The A-36A (the only model ever of A-36) contract was not signed until almost a year later (in August, 1942) so the ad of which I speak...see this link...page 174...

Flying Magazine

books.google.com

THIS ad and a couple other NAA ads of the day are part of what caused the confusion over 20 yrs after WWII ended, and as a result, the A-36A mistakenly became called "Apache" in books, magazines and videos.

If you have questions, Colin or I or others would, I'm sure, be glad to provide answers.

Cheers.

Tom

 

[Mustangtmg]

When NAA (North American Aviation) told the British that the A-36 Mustang/Apache prototype (NA-73X) could be built in only 120 days, but it took only 102, which is cool.
But was the NA-73X already being designed, by NAA, before the British approached them (when the British had first asked NAA to build the P-40)?
If so, how long was the Mustang/Apache in design phase, before the British showed up?

In my reply, I forgot to mention the two books above that Colin Ford recommended and put up photos of the covers.

They are not "perfect" - no book on ANY aircraft that was produced in so many models with so many variations within models can cover everything, so Gruenhagen and Marshall/Ford (their names are shorter than the books' titles! ), while they're not 100% correct, I'd put them something over 99.99% correct. Like that great old song by "Alabama" ... "Close Enough to Perfect."

There are other excellent books out there, and I'm blessed to have them in addition to the two above, but I can tell you, the above two are my primary "go-to" books when it comes to Mustangology.

 

[emu27]

the A-36A mistakenly became called "Apache" in books

The August 2014 "Aeroplane" magazine has an interview with a number of WWII A-36 pilots and to a man they call it the "Apache", has a photo of one of their aircraft with the name "The Invader" painted on the nose, now I wonder where they got that name from. Aircraft are often known by a name that has no official backing, F-16 Viper and A-10 Warthog being just two, from the evidence of the interview I'd say "Apache" falls into much the same category.

Thought I was across the P-51 but never heard of the P-509 before, thanks for the heads up, seems like a post Xmas treat is in order for a couple of books.

 

[GrauGeist]

The August 2014 "Aeroplane" magazine has an interview with a number of WWII A-36 pilots and to a man they call it the "Apache", has a photo of one of their aircraft with the name "The Invader" painted on the nose, now I wonder where they got that name from. Aircraft are often known by a name that has no official backing, F-16 Viper and A-10 Warthog being just two, from the evidence of the interview I'd say "Apache" falls into much the same category.

Thought I was across the P-51 but never heard of the P-509 before, thanks for the heads up, seems like a post Xmas treat is in order for a couple of books.

The Douglas A-26 Invader already had the name, officially.
The pilots could call it what they wanted, but that does not make it official.

My Uncle called his P-38 the "fork tail devil" (along with his cohorts), but that didn't change it's designated name.

 

[drgondog]

I July 1942, before the A-36 first flew Kindelberger formally requested that Army use only Mustang as name for P-51 and variants. Only the NA-91 P-51-NA/Mustang IA briefly held the name Apache assigned by Army Public Relations (or Materiel Cmd)

 

[SaparotRob]

I July 1942, before the A-36 first flew Kindelberger formally requested that Army use only Mustang as name for P-51 and variants. Only the NA-91 P-51-NA/Mustang IA briefly held the name Apache assigned by Army Public Relations (or Materiel Cmd)

Are you sure?

 

[SaparotRob]

I have to go now anyway.

 

[drgondog]

I have to go now anyway.

Yes, with respect to Kindleberger Telex requesting Mustang in July 1942, yes to Army including A-36 as Mustang in 1944.

 

[Thumpalumpacus]

Hey, drgondog , I ran across this on Youtube tonight. I'd be interested in your opinions if you might find the time to watch it. Do you know and have you talked with Mr Willis? Of course all other opinions are welcomed too. It's about 1 1/2 hrs, so no rush for answers.


View: https://www.youtube.com/watch?v=s8TAag3EQhg

 

[SaparotRob]

Bookmarked it. Thanks, bro'.

 

[Thumpalumpacus]

Bookmarked it. Thanks, bro'.

It was a good watch. I don't know how accurate Willis is, hence my question, but I deffo enjoyed it. Looking forward to Bill's opinion if he has time to watch and offer his view.

 

[drgondog]

Hey, drgondog , I ran across this on Youtube tonight. I'd be interested in your opinions if you might find the time to watch it. Do you know and have you talked with Mr Willis? Of course all other opinions are welcomed too. It's about 1 1/2 hrs, so no rush for answers.


View: https://www.youtube.com/watch?v=s8TAag3EQhg

I have seen the AAF Video but wil look at this one. I do 'know' Willis via Facebook.

 

[drgondog]

Hey, drgondog , I ran across this on Youtube tonight. I'd be interested in your opinions if you might find the time to watch it. Do you know and have you talked with Mr Willis? Of course all other opinions are welcomed too. It's about 1 1/2 hrs, so no rush for answers.


View: https://www.youtube.com/watch?v=s8TAag3EQhg

OK = Matt did a good job, factually and presentation - I have some differences regarding technical details and AAC/AAF doctrine evolution - as well as the moving parts of RAF Mustang order wind down, NAA/AAF marketing discussions in October/Decembr 1941 trying to get Dive Bomber funding, and big swinging dick battle between AAF-HQ Planning & Requiremets Chief vs AAF-Materiel Commnd Chief at Wright Field in Q1/1942 etc

I specifically orchestrated my stlye (and Co-author Ford) to base the book on a chronolgy that intertwined NAA with AAF with RAF, and ultimately LW to illustrate the behind the scenes moving parts of the Mustang development and evolution. A key note - Arnold was Very aware of the subordinate position of the AAC/AAF to to US Army as a 'customer'.

But here are the points of divergence.

First AAC/AAF Ground Support doctrine' to the 'mother ship' US Army evolved from battlefield recon (O-47) and artilliary/troop movement spotters - to 1.) fast attack bomber, dive bomber (LW Stuka influence imposed by Sec'y War as 'suggestion' to Arnold circa 1940) and artilliary/troop spotters; 2.) to fast attack bomber (A-20), battlefield air superiority Pursuit capable of CAS and recon, and artilliary troop spotters. The fast AttacK Pursuit evolved from P-39/P-40 to A-36 to P-51A/B and P-47.

The 'bridge'both in procurement and doctrine was the A-36

I was surprised that Matt Willis didn't understand why the design of dive brake per se, wasn't that big of a cruise drag issue on the A-36. If you look at the plan view of the A-36 wing, you will see the mechanism is aft of 40% Chord where the BL separates anyway. When dive brakes are open there is a huge form drag contribution but also incremental parasite drag of the 'gaps and holes' when in deployed position.

As to Mustang armament, the RAFwanted the 20mm guns in the NA-73 and all subsequent Mustangs but neither Army nor USN were willing to part with a % of the Olsmobile Hispano deliveries in 1940/1941.

Because of several fatal accidents the AAF-MC issued directive to wire dive brakes shut and limit wing rack load to 500 pounds. Te 27th, 86thand 311th in CBI ignored both as the A-36 wing was stressed for 1000 pound load. You recall the anecdote of the flight leader intentionally retaining his bombs (presumably 500# GP) in order to go back to the corvette? The dive pullout with full wing load was included in AoA stress analysis for loads on the wing structure.

The prototype A-36 was NA-83 AM 118. The preliminary spec for Low level attack pursuit dated 11-1941 was founded on NA-73 and originally included 4x20mm as primary wing armament.

Matt made a comment that the 'P-51H' had a 4x50 cal battery. He meant (I think) XP-51F/G/J.

Anecdotally, Howard 'Pete' Decker was my father's neighbor growing up in Greenvile TX and best friends. Pete Decker flew combat in the 27th FBG, flew the A-36, P-40 and finally the replacement P-47. For CAS, he placed the A-36 above the P-40 and P-47 - primarily becuse he could outrun anthing on the deck and the A-36 was Far superior for taking out any target they were sent to destroy as a precision dive bomber.

He is referenced in Straight Down.

 

[Thumpalumpacus]

Hey, thanks, Dog.