North American A-36

MIflyer · Dec 4, 2019

That old business about the Allison V-1710 engine not being supercharged has been making the rounds for a long time. And it is pure BS. The Allison in the P-39, P-40 and P-51 was supercharged to the same degree that the Merlin was in the Hurricanes and the Spitfires Mk I, IA, II and V.

But the Allison did not have a two speed supercharger, which limited it's performance in some respects. The A-36 had the Allison set up to maximize its performance at about 5,000 ft while the P-51A had it set up for max speed at 20,000 ft.

The P-38 had two stages of supercharging, the built in supercharger of the Allisons each being fed by a turbosupercharger.

In the case of the V-1710 in the P-39, P-40, and P-51, there was no supercharger "On/Off" switch, unlike some of the earlier Merlin installations and that may have led some pilots to conclude it did not have one. Also, the XP-39 initially had a turbosupercharger feeding the Allison's internal supercharger, but it was deleted when they found that the installation actually was slower than just the Allison by itself. Some writers later concluded that the USAAC had the turbo deleted due to a desire to emphasize low altitude performance but nothing could be further from the truth. The Army Air Corps emphasized high altitude performance.

The V-1710 in the P-63 had an additional stage of supercharging using an auxiliary supercharger run off the starter interface to substitute for the turbo; it used a hydromatic automatic transmission to vary supercharging.

Navalwarrior · Dec 4, 2019

MIflyer said:
That old business about the Allison V-1710 engine not being supercharged has been making the rounds for a long time. And it is pure BS. The Allison in the P-39, P-40 and P-51 was supercharged to the same degree that the Merlin was in the Hurricanes and the Spitfires Mk I, IA, II and V.

But the Allison did not have a two speed supercharger, which limited it's performance in some respects. The A-36 had the Allison set up to maximize its performance at about 5,000 ft while the P-51A had it set up for max speed at 20,000 ft.

The P-38 had two stages of supercharging, the built in supercharger of the Allisons each being fed by a turbosupercharger.

In the case of the V-1710 in the P-39, P-40, and P-51, there was no supercharger "On/Off" switch, unlike some of the earlier Merlin installations and that may have led some pilots to conclude it did not have one. Also, the XP-39 initially had a turbosupercharger feeding the Allison's internal supercharger, but it was deleted when they found that the installation actually was slower than just the Allison by itself. Some writers later concluded that the USAAC had the turbo deleted due to a desire to emphasize low altitude performance but nothing could be further from the truth. The Army Air Corps emphasized high altitude performance.

The V-1710 in the P-63 had an additional stage of supercharging using an auxiliary supercharger run off the starter interface to substitute for the turbo; it used a hydromatic automatic transmission to vary supercharging.

Resp:
Also, I think the British messed up the P-38 by insisting on several supposedly cost saving changes; one change was insisting on non-counter rotating Allisons . . . which ruined its performance and ease of handling. Lockheed tried to accommodate their requests, which brought criticism of the plane's ability.

MIflyer · Dec 5, 2019

Yes, and the Brits were buying Lightning I's, which were equipped with the C series Allisons, as was the Hawk 81's they were buying in large numbers, and they probably were thinking in terms of better logistics.

Navalwarrior · Dec 5, 2019

MIflyer said:
Yes, and the Brits were buying Lightning I's, which were equipped with the C series Allisons, as was the Hawk 81's they were buying in large numbers, and they probably were thinking in terms of better logistics.

Resp:
And every requested change lessened the P-38's attributes. It would have been interesting to see how it performed in RAF pilot's hands, if accepted as is.

Gnomey · Dec 8, 2019

Nice shots!

Mustangtmg · Dec 27, 2019

stug3 said:
That was the only part of it I saw, maybe the rest of it or the whole thing is floating around the net somewhere.

I'm not bragging ... well, maybe just a little ... but the Telegram, whose top part (it's from Dutch Kindelberger to Col Arthur Ennis) was emailed to me by the Historical Archivist at Boeing in April, 2019. Because I'd been corresponding with him on other Mustang-related subjects, he occasionally emailed me scans of anything and everything pertaining to the Mustang family. I received the Telegram along with a scan of the cover of the Parts Catalog for the A-36A. It says "A-36A Mustang," by the way.

He told me that I could post them online (they'd apparently been cataloged earlier, but he came across them, and as far as I know - and from what actual Mustang historians (both authors and just serious "regular folks") tell me, these two documents have NEVER been seen before. I actually wrote an article for The Hangar Deck that was posted right before these two documents were called to my attention by the email that I received.

I added that (you'd have thought that Boeing would've done that before emailing it to me) onto the images before posting them on the Facebook P-51 Mustang Group right after receiving them. The Archivist told me that I could post them online if I added that to the image. My image of the Telegram has my "stamp" on the bottom, and this one near the top, but that's neither here nor there.

I'll attach the scans of the whole Telegram and the Catalog cover. I thought that I'd already done that here, but maybe not...I've sent this info to a number of websites, so, they all tend to "run together."

Here goes!

Tom

Mustangtmg · Dec 27, 2019

johnbr said:
North American A-36A Mustang > National Museum of the United States Air Force™ > Display
https://www.boeingimagelicensing.co...ult&VBID=2JRSN2A4G8IMTX&SMLS=1&RW=1536&RH=780
WWII A-36 Apache/Invader Fighter Planes Photo Print for Sale View attachment 560505
View attachment 560502 View attachment 560503 View attachment 560504

Why do we have three different Mustang Models here???

The top on shows NA-91 Mustang Mk IAs (RAF) / P-51 Apache (before being modified to P-51-1-NA, P-51-2-NA, F-6A and XP-51B aircraft)

The 2nd photo is the A-36A Mustang at the National Museum of the US Air Force.

The 3rd photo is the A-36A Mustang owned and flown by the Collings Foundation.

The 4th photo is one of the XP-51 aircraft, pulled from the NA-73 batch intended for the RAF. This photo is from (I believe) the Summer of 1943 and is XP-51 SN 41-039.

I'm confused as to just why these are posted without an explanation that I can understand.

Maybe I'm just dense!

Navalwarrior · Dec 27, 2019

Mustangtmg said:
Why do we have three different Mustang Models here???

The top on shows NA-91 Mustang Mk IAs (RAF) / P-51 Apache (before being modified to P-51-1-NA, P-51-2-NA, F-6A and XP-51B aircraft)

The 2nd photo is the A-36A Mustang at the National Museum of the US Air Force.

The 3rd photo is the A-36A Mustang owned and flown by the Collings Foundation.

The 4th photo is one of the XP-51 aircraft, pulled from the NA-73 batch intended for the RAF. This photo is from (I believe) the Summer of 1943 and is XP-51 SN 41-039.

I'm confused as to just why these are posted without an explanation that I can understand. Maybe I'm just dense!

Resp:
To give aviation historians something to do. Just kidding. I'm sure others on this blog have answers, but as you pointed out the British ordered the fighter first . . . so they got the honor of naming it 'Mustang.' When the USAAC/USAAF held back the second British order (could legally do it since the US Govt paid for this second order), they used their traditional nomenclature of P for pursuit and the number 51 to designate this particular fighter. At some point, the AAF decided to use them as tactical photo recon aircraft by fitting cameras. Result, they were renamed F-6A; F for photo, 6 for model designation and A to denote 1st variant.
The first model built specifically for USAAF was the dive bomber variant; A-36A. A denotes 'attack', 36 denotes this particular model dive bomber built on the P-51 Mustang frame, and the letter A as the first variant. Again, the A-36A was the first variant on this airframe ordered (the P-51A soon joined the A-36A on the production line) directly for USAAF service. At this point all nomenclature is correct!
Confusion returns when Invader/Apache is added to the A-36A. However, 'Mustang' soon overshadows Invader/Apache as the war progresses. You will likely get many different explainations for this forum.
My belief for the return to the 'Mustang' name for P-51s, F-6A/Bs and A-36As: Since the RAF Mustang I and IA entered the war first, and the RAF preferred names versus numbers . . . the aircraft identification cards published were with 'Mustang' when ID by anti-aircraft crews, RAF pilots/air crews, ground and naval forces. So substituting different names for technical and non visual differences . . . causes confusion . . . when all you really needed to do was sound off quickly and clearly . . . Friend or Foe!

ColFord · Dec 27, 2019

May 29, 1940 - British Government places first order for the Allison Mustang, comprising 320 aircraft to the NAA designation NA-73, which were allocated the AG series serials in RAF service. Under the contract, first delivery to be by January 1941. Purchased and paid for by the British Government. Delivery under terms of contract is acceptance at factory and safe delivery to port of departure in the USA, when the crated aircraft then becomes the property of the British Government.

September 24, 1940, British Government places second order was for an additional 300 aircraft to the NAA designation NA-83, which were allocated AL, AM and AP series serials in RAF service. Purchased and paid for by the British Government. Production and delivery to follow on immediately to first order.

March 11, 1941, the Lend Lease Act came into force in the USA - this well pre-dates Pearl Harbor and the US entry into the war. This meant any additional orders that the RAF wanted to place was then required to be placed in accordance with the arrangements for Lend Lease. This meant the aircraft would be manufactured under an order from the US Government and as such it had to have a US Military designation for the aircraft.

So on September 25, 1941 the USAAF ordered 150 aircraft to meet a RAF specification, which would be the NAA designation NA-91 and which would be allocated serials in the FD serial range in RAF service. As the aircraft were ordered under USAAF arrangements they were also given US serial blocks and the USAAF designation P-51. In RAF service the NA-91 would be the Mustang Mk.IA. Of the 150 aircraft produced, 93 would be delivered to the RAF, the remainder being retained by the USAAF. Timing for this additional order is interesting as it is made around the same time the acceptance flight testing program of the NA-73/Mustang Mk.I was completed at NAA and the first aircraft was accepted by the RAF, crated and commenced its journey to the UK. So in light of the positive initial results, they wanted to order more.

Production of the NA-91 had not yet commenced at the time of the US entry into the war in December 1941, the production line was still manufacturing the last of the NA-73 production run and the start of the NA-83 production run for the RAF. Production of the NA-91 commenced immediately upon completion of the NA-83 order - actually with the last of the NA-83 going off the end of the line as the first of the NA-91 started coming down the start of the line.

The shortfall in the original order for the NA-91/Mustang Mk.IA aircraft to the RAF would be made up by the later delivery of 50 P-51A/Mustang Mk.II aircraft in late 1943 to early 1944.

A-36 in RAF service, if it had been accepted, had proposed designation of "Mustang Mk.I (Dive Bomber)".

That's the initial British ordering timeline and numbers.

Navalwarrior · Dec 28, 2019

ColFord said:
May 29, 1940 - British Government places first order for the Allison Mustang, comprising 320 aircraft to the NAA designation NA-73, which were allocated the AG series serials in RAF service. Under the contract, first delivery to be by January 1941. Purchased and paid for by the British Government. Delivery under terms of contract is acceptance at factory and safe delivery to port of departure in the USA, when the crated aircraft then becomes the property of the British Government.

September 24, 1940, British Government places second order was for an additional 300 aircraft to the NAA designation NA-83, which were allocated AL, AM and AP series serials in RAF service. Purchased and paid for by the British Government. Production and delivery to follow on immediately to first order.

March 11, 1941, the Lend Lease Act came into force in the USA - this well pre-dates Pearl Harbor and the US entry into the war. This meant any additional orders that the RAF wanted to place was then required to be placed in accordance with the arrangements for Lend Lease. This meant the aircraft would be manufactured under an order from the US Government and as such it had to have a US Military designation for the aircraft.

So on September 25, 1941 the USAAF ordered 150 aircraft to meet a RAF specification, which would be the NAA designation NA-91 and which would be allocated serials in the FD serial range in RAF service. As the aircraft were ordered under USAAF arrangements they were also given US serial blocks and the USAAF designation P-51. In RAF service the NA-91 would be the Mustang Mk.IA. Of the 150 aircraft produced, 93 would be delivered to the RAF, the remainder being retained by the USAAF. Timing for this additional order is interesting as it is made around the same time the acceptance flight testing program of the NA-73/Mustang Mk.I was completed at NAA and the first aircraft was accepted by the RAF, crated and commenced its journey to the UK. So in light of the positive initial results, they wanted to order more.

Production of the NA-91 had not yet commenced at the time of the US entry into the war in December 1941, the production line was still manufacturing the last of the NA-73 production run and the start of the NA-83 production run for the RAF. Production of the NA-91 commenced immediately upon completion of the NA-83 order - actually with the last of the NA-83 going off the end of the line as the first of the NA-91 started coming down the start of the line.

The shortfall in the original order for the NA-91/Mustang Mk.IA aircraft to the RAF would be made up by the later delivery of 50 P-51A/Mustang Mk.II aircraft in late 1943 to early 1944.

A-36 in RAF service, if it had been accepted, had proposed designation of "Mustang Mk.I (Dive Bomber)".

That's the initial British ordering timeline and numbers.

Resp:
ColFord, do you have a 'source' that states the second British order was paid for by the British? Initially I believed that a British order (any production order) was paid by them. However, recently an author (don't have it in front of me) stated that the US actually paid for their Mustang MkIs. I thought this strange, but it seemed to support the US decision to retain these Mustangs post Pearl Harbor attack. I am not doubting you, but would like to be able to cite the source. Thanks.

ColFord · Dec 28, 2019

I always go back to my primary source, Air Ministry and BPC files held in the UK Archives. The original two orders for the 620 Mustang Mk.I aircraft - NA73 and NA-83 - predates Lend Lease. It was a contract between NAA and the UK Government on a commercial basis, same as they had for the original Harvard Mk.I order from pre-War. So at that stage everything the British were contacting for and purchasing was purely on a "cash and carry" basis. It was why by the time that Lend Lease came in, the British had seriously depleted their foreign currency reserves and the various arrangements for trading 99 year leases on locations of interest to the US and other measures came into play including the sharing of UK developed technology.

It is the third order for the Mustang Mk.IA, the original P-51, NA-91 that the US paid for as a part of the Lend Lease arrangements and why after Pearl Harbor and the rapid expansion of US forces that the USAAF felt they could hold back for their own use some of those aircraft. I can tell you that in the UK files that the Air Ministry were less than impressed by that, especially as the senior command of the USAAF up to that point had done very little to support production of the Mustang for the RAF - issues with priority over materials, supply of engines, putting pressure on NAA management, etc.

I should note that I've also had access to some material from the US and NAA side of the process which backs up - sometimes with a different view of events - what is in the UK files as part of the process of reviewing the drafts of a book being written by two US authors/researchers on the origins, design and development of the Mustang which is due out first half of 2020. Very detailed, quotes lots of original source documents verbatim.

So I don't know where the other author has come up with the idea that either of the first two orders for the Mustang Mk.I were paid for by anyone other than the British. Maybe they have confused the purchasing arrangements for the P-51/Mustang Mk.IA/NA-91.

Navalwarrior · Dec 28, 2019

ColFord said:
I always go back to my primary source, Air Ministry and BPC files held in the UK Archives. The original two orders for the 620 Mustang Mk.I aircraft - NA73 and NA-83 - predates Lend Lease. It was a contract between NAA and the UK Government on a commercial basis, same as they had for the original Harvard Mk.I order from pre-War. So at that stage everything the British were contacting for and purchasing was purely on a "cash and carry" basis. It was why by the time that Lend Lease came in, the British had seriously depleted their foreign currency reserves and the various arrangements for trading 99 year leases on locations of interest to the US and other measures came into play including the sharing of UK developed technology.

It is the third order for the Mustang Mk.IA, the original P-51, NA-91 that the US paid for as a part of the Lend Lease arrangements and why after Pearl Harbor and the rapid expansion of US forces that the USAAF felt they could hold back for their own use some of those aircraft. I can tell you that in the UK files that the Air Ministry were less than impressed by that, especially as the senior command of the USAAF up to that point had done very little to support production of the Mustang for the RAF - issues with priority over materials, supply of engines, putting pressure on NAA management, etc.

I should note that I've also had access to some material from the US and NAA side of the process which backs up - sometimes with a different view of events - what is in the UK files as part of the process of reviewing the drafts of a book being written by two US authors/researchers on the origins, design and development of the Mustang which is due out first half of 2020. Very detailed, quotes lots of original source documents verbatim.

So I don't know where the other author has come up with the idea that either of the first two orders for the Mustang Mk.I were paid for by anyone other than the British. Maybe they have confused the purchasing arrangements for the P-51/Mustang Mk.IA/NA-91.

Resp:
Thanks much. I expect that the author assumed or extrapolated incorrectly . . . since the US held back the second order for British service. There is much misinformation in print/web inre to Allison engined Mustangs. I have found unit info from various US units that clearly lists incorrect info, particularly photo captions.

Navalwarrior · Dec 31, 2019

Navalwarrior said:
Resp:
Thanks much. I expect that the author assumed or extrapolated incorrectly . . . since the US held back the second order for British service. There is much misinformation in print/web inre to Allison engined Mustangs. I have found unit info from various US units that clearly lists incorrect info, particularly photo captions.

Con't:
The magazine 'Mustangs International,' Winter 2019 has some terrific photos/history of Allison engined Mustangs, plus a special on early mustang pilots . . . including Maj James Howard of Flying Tiger Fame and his record in the first Merlin Mustangs to operate in the ETO. On page 23 it mentions a Royal Air Force A-36A, Aircraft number 1437 Strategic Reconnaissance Flight, and page 25 two photos of aircraft HK 944 (large letter 'C' just aft of roundel). You can see the coverings in the lower nose where the two 50 cal MG were removed.