P-51 Mustang & F-82 Twin Mustang Proposals and Variants

BarnOwlLover2 said:
Sorry for posting this so late, but the NAA-117 mock up (pre-production P-51H) did feature an armament of 4x20mm Hispano cannons. There's some speculation that this may've been driven by the British, who wanted a cannon armed Mustang for interception/escort fighter use. Any creedance to that, or was the USAAF indeed pursuing a cannon armed P-51?
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No evidence, but my money is on the British.

They quite rightly upgraded to cannons for fighters to take down bombers.
 
I've been told by a Mustang researcher that the XP-51F/G were looked at by the USAAF as cannon armed interceptors before the USAAF favored escort fighters (leading to the development of the P-51H). The pics of the mock up with 20mm cannons is from Michael O'Leary's Building the P-51 Mustang book in the section about the P-51H.
 
BarnOwlLover2 said:
I've been told by a Mustang researcher that the XP-51F/G were looked at by the USAAF as cannon armed interceptors before the USAAF favored escort fighters (leading to the development of the P-51H). The pics of the mock up with 20mm cannons is from Michael O'Leary's Building the P-51 Mustang book in the section about the P-51H.
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I don't think so. Both the F and G were lightweight experimental types that were more carefully designed to specific load factors and weight saving details. From those experiments, the H was developed as the production model. However, just about any Mustang model could have been fitted with 20mm cannon if the USAAF had wanted to.
Some A-36 did get fitted for ground attack with them.
 
The major weight savings in the lightweight mustangs was the gear, wing weight was very similar between them.

Even if it was designed for a much lower G the bending moment on the wing isn't like the recoil load from the guns.
 
sienar said:
The major weight savings in the lightweight mustangs was the gear, wing weight was very similar between them.

Even if it was designed for a much lower G the bending moment on the wing isn't like the recoil load from the guns.
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Actually, it went much further than that. NA weighed every part in the plane and applied British load standards, rather than the higher US ones to them. This and just reducing the weight of some part through careful design brought the P-51F down about 600 lbs. compared to the D. The new streamlined canopy, an small changes in profiles helped raise speed too. The H was very similar to the F model as the production plane.

P-51 Mustang Variants - P-51H - MustangsMustangs.com

The North American P-51 Mustang - P-51 Variants - P-51H. By Curtis Fowles, MustangsMustangs. P-51A, A-36, P-51B, P-51C, P-51D, P-51K, P-51H, F-6D, F-6K, F-51D, F-51H Mustangs
www.mustangsmustangs.com
 
T. A. Gardner said:
That's an A-36 Apache (the Allison engine P-51) used for ground support.
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That photo looks a lot (similar mountains) like this one... note that the aircraft is NOT an A-36, but a Mustang Mk 1A diverted to the USAAC and redesignated P-51-2.

41-37412/37420 (FD510/FD518) diverted to USAAF as P-51-2
41-37416
11-27-42 Ferry to Wayne Co. airport.
Dec 5, 1942 Newark port of embarkation.
Feb 1, 1943 8th AF-England.
3-43 12th AF-Oran, Algeria. 111th TRS.
Oct 8, 1944 Condemned, salvaged, 12th AF-Italy.
Click to expand...

P-51 Mustang 41-37416 California Oct 1942
P-51 Mustang 41-37416 California Oct 1942.jpg
 
T. A. Gardner said:
Actually, it went much further than that. NA weighed every part in the plane and applied British load standards, rather than the higher US ones to them. This and just reducing the weight of some part through careful design brought the P-51F down about 600 lbs. compared to the D. The new streamlined canopy, an small changes in profiles helped raise speed too. The H was very similar to the F model as the production plane.

P-51 Mustang Variants - P-51H - MustangsMustangs.com

The North American P-51 Mustang - P-51 Variants - P-51H. By Curtis Fowles, MustangsMustangs. P-51A, A-36, P-51B, P-51C, P-51D, P-51K, P-51H, F-6D, F-6K, F-51D, F-51H Mustangs
www.mustangsmustangs.com
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It's interesting that the H model canopy is actually bigger than the D model canopy, and better for 2-seater use.
 
T. A. Gardner said:
I don't think so. Both the F and G were lightweight experimental types that were more carefully designed to specific load factors and weight saving details. From those experiments, the H was developed as the production model. However, just about any Mustang model could have been fitted with 20mm cannon if the USAAF had wanted to.
Some A-36 did get fitted for ground attack with them.
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This info came from one of the authors of the book "P-51B Mustang: North American's Bastard Stepchild That Saved the 8th Air Force" He and he co-author is working on a follow up that'll talk about the P-51D, but will go into great detail/focus on the lightweights, P-51H and (hopefully per the author) the early F-82 Twin Mustangs. Per our discussions on the WW2Aircraft website, the USAAF looked at putting 20mm cannons on the F or G if it was adopted as an interceptor. But USAAF focus switched to longer ranged escort fighters during development and they wouldn't revisit the cannon situation until the P-51H apparently.
 
BarnOwlLover2 said:
This info came from one of the authors of the book "P-51B Mustang: North American's Bastard Stepchild That Saved the 8th Air Force" He and he co-author is working on a follow up that'll talk about the P-51D, but will go into great detail/focus on the lightweights, P-51H and (hopefully per the author) the early F-82 Twin Mustangs. Per our discussions on the WW2Aircraft website, the USAAF looked at putting 20mm cannons on the F or G if it was adopted as an interceptor. But USAAF focus switched to longer ranged escort fighters during development and they wouldn't revisit the cannon situation until the P-51H apparently.
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From what I remember, the lightweights were intended as interceptors.
 
T. A. Gardner said:
Actually, it went much further than that. NA weighed every part in the plane and applied British load standards, rather than the higher US ones to them. This and just reducing the weight of some part through careful design brought the P-51F down about 600 lbs. compared to the D. The new streamlined canopy, an small changes in profiles helped raise speed too. The H was very similar to the F model as the production plane.

P-51 Mustang Variants - P-51H - MustangsMustangs.com

The North American P-51 Mustang - P-51 Variants - P-51H. By Curtis Fowles, MustangsMustangs. P-51A, A-36, P-51B, P-51C, P-51D, P-51K, P-51H, F-6D, F-6K, F-51D, F-51H Mustangs
www.mustangsmustangs.com
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I've looked through the weight surveys of the P-51D and H.

Most of the savings was in the gear, something like 300lbs. The wing and fuselage were slightly lighter and the tail surfaces were slightly heavier in the H.

Mustang Designer gives more details on it. NAA realized that the US required much higher landing loads along with a 2g sideload on the engine mount. The airframe G loading wasn't that big of a difference, something like 7.33 vs 8.
BarnOwlLover2 said:
This info came from one of the authors of the book "P-51B Mustang: North American's Bastard Stepchild That Saved the 8th Air Force" He and he co-author is working on a follow up that'll talk about the P-51D, but will go into great detail/focus on the lightweights, P-51H and (hopefully per the author) the early F-82 Twin Mustangs. Per our discussions on the WW2Aircraft website, the USAAF looked at putting 20mm cannons on the F or G if it was adopted as an interceptor. But USAAF focus switched to longer ranged escort fighters during development and they wouldn't revisit the cannon situation until the P-51H apparently.
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One of the lightweight Mustangs had an engine that could handle a prop mounted cannon. I think it was the J.
 
Scott Kenny said:
From what I remember, the lightweights were intended as interceptors.
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F/G couldn't accept a fuselage tank, though they had longer range on the wing tanks than the P-51B/D (more fuel and better aero than the B/D). The H was designed to use a 50 gallon fuselage tank for longer ranged work, and was also engineered to suit USAAF desired for heavier armament (6x.50s instead of 4, 2000 lb bomb load, etc., re-stressing for 7.33g at 9600 lb combat weight).
 
sienar said:
I've looked through the weight surveys of the P-51D and H.

Most of the savings was in the gear, something like 300lbs. The wing and fuselage were slightly lighter and the tail surfaces were slightly heavier in the H.

Mustang Designer gives more details on it. NAA realized that the US required much higher landing loads along with a 2g sideload on the engine mount. The airframe G loading wasn't that big of a difference, something like 7.33 vs 8.

One of the lightweight Mustangs had an engine that could handle a prop mounted cannon. I think it was the J.
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That would require modifying the Allison engine to include either interrupter gear to fire the cannon between propeller blades or a new Propeller Speed Reduction Unit to fire the cannon through the prop hub. A new PSRU would also require revising the induction system to create space - for the cannon - between cylinder banks.
 
I remember footage of P-51s losing their drop tanks and peeling away.

One had a drop tank still stuck fast.

Any story behind that?
 
riggerrob said:
That would require modifying the Allison engine to include either interrupter gear to fire the cannon between propeller blades or a new Propeller Speed Reduction Unit to fire the cannon through the prop hub. A new PSRU would also require revising the induction system to create space - for the cannon - between cylinder banks.
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The Hispano-Suiza HS.404 cannon was delayed-blowback, so it could be set up to fire through a prop arc... Oerlikon 20mm was API so could not.
 
Hi,

BarnOwlLover2 said:
Sorry for posting this so late, but the NAA-117 mock up (pre-production P-51H) did feature an armament of 4x20mm Hispano cannons.
Click to expand...

Are you positive these were indeed 20 mm Hispano cannons? The USAAF was sort of committed to the 0.60" machine gun, which probably was of similar size and bulk as a 20 mm cannon ... of course, I haven't seen the pictures, might be a clear case if they show enough detail.

Regards,

Henning (HoHun)
 
HoHun said:
Hi,



Are you positive these were indeed 20 mm Hispano cannons? The USAAF was sort of committed to the 0.60" machine gun, which probably was of similar size and bulk as a 20 mm cannon ... of course, I haven't seen the pictures, might be a clear case if they show enough detail.

Regards,

Henning (HoHun)
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You're probably going to have to get a copy of Michael O'Leary's Building the P-51 Mustang for the photos, but the guns being fitted in the wing of the NA-117 mock up had gas cylinders on them. Most US aircraft MGs and cannons were recoil operated. The HS404 and derivatives were gas operated (or at least used a gas piston to unlock the breach). The .60 MG was based on the German 15mm/20mm MG151 cannons, which were also recoil operated.
 
BarnOwlLover2 said:
You're probably going to have to get a copy of Michael O'Leary's Building the P-51 Mustang for the photos, but the guns being fitted in the wing of the NA-117 mock up had gas cylinders on them. Most US aircraft MGs and cannons were recoil operated. The HS404 and derivatives were gas operated (or at least used a gas piston to unlock the breach). The .60 MG was based on the German 15mm/20mm MG151 cannons, which were also recoil operated.
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Browning or Fabrique Nationale also experimented with .60 caliber versions of the .50 caliber Browning Heavy Machinegun, but I am not clear if they entered production ... definitely not large-scale production.
 
Apophenia said:
Unlikely to have been the XP-51J. The V-1710-F32 had a big intercooler sitting right where your motor-cannon's breech would need to go.
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Merlin suffered a similar problem with the "V" between the cylinder banks being full of induction system. Rolls-Royce was the world-leader in super-charged induction systems during World War 2.
See Callum Douglas' book "The Horsepower Race."
 
Besides for the one based on the MG151 there was also a project for a Hispano converted to fire the .60 caliber cartridge. I do not know how far that effort went and if any were tested on actual aircraft.

I had not heard of the Browning design being upscaled to a .60 caliber version but it sounds like a good approach, I wonder why it didn't receive more focus.
 
BarnOwlLover2 said:
You're probably going to have to get a copy of Michael O'Leary's Building the P-51 Mustang for the photos, but the guns being fitted in the wing of the NA-117 mock up had gas cylinders on them. Most US aircraft MGs and cannons were recoil operated. The HS404 and derivatives were gas operated (or at least used a gas piston to unlock the breach). The .60 MG was based on the German 15mm/20mm MG151 cannons, which were also recoil operated.
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Some of the war-time .60 designs were HIspano-based.
 
Any info or such on the "RF-82" that had a camera pod? San Diego Air and Space Museum has HQ photos of it (they have low res versions of them on their Flickr page, you can buy the HQ versions in print or digital form). I asked about it at WW2Aircraft.com, and got some info, but aside from that and the photos, not much else. Or anything additional on the P-82C/D (P-82Bs used as R&D aircraft for F-82 night/AW fighters)?
 
Colonial-Marine said:
Besides for the one based on the MG151 there was also a project for a Hispano converted to fire the .60 caliber cartridge. I do not know how far that effort went and if any were tested on actual aircraft.

I had not heard of the Browning design being upscaled to a .60 caliber version but it sounds like a good approach, I wonder why it didn't receive more focus.
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I know that there was a P-38 that they did mount the .60 calibers in the nose and conducted firing trials with it, but I can't find the photo of that at the moment. If I recall correctly, the installation had 3 guns.

I'm pretty sure the US .60 was developed from this trials weapon of US design

The American Cal. .60 Anti-Tank Rifle, T1 & T1E1 - WeaponsMan

Germany, Poland, the UK, and the USSR all developed anti-tank rifles and used them with mixed results (the Germans, in World War I, then all of them, in the early years of World War II) Other nations including Czechoslovakia, Switzerland, Finland and Japan built anti-tank rifles, essentially...
weaponsman.com weaponsman.com

And more here, including the P-38 photo

 
Hi T.A.,

T. A. Gardner said:
I'm pretty sure the US .60 was developed from this trials weapon of US design
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The ammunition was US-developed, but the machine guns themselves were, after a brief attempt to adopt the 20mm Hispano to the new caliber, based on the German MG151 ... here is Chinn's take on the matter:

archive.org

The Machine Gun Volume 3 By George M Chinn : Free Download, Borrow, and Streaming : Internet Archive

693 pg
archive.org

It was quite the saga which directly lead to the later adoption of a MG213 based-design as well as the emergence of the Vulcan Gatling gun.

Regards,

Henning (HoHun)

L
 
For whatever reasons the US had a lot of trouble with small caliber autocannon development and manufacture during that time period. Only the 20mm Oerlikon was trouble-free but that wasn't very well suited to aircraft use. Though not technically a cannon the .60 caliber machine guns seem to have had the same problems because the guns were variants of 20mm autocannons.
 
.

Were there any P-51H proposals with a nose mounted Griffin engine ?

And if, why not ?

.
 
Hi,

Colonial-Marine said:
For whatever reasons the US had a lot of trouble with small caliber autocannon development and manufacture during that time period. Only the 20mm Oerlikon was trouble-free but that wasn't very well suited to aircraft use. Though not technically a cannon the .60 caliber machine guns seem to have had the same problems because the guns were variants of 20mm autocannons.
Click to expand...

The German MG151 they used as a basis for the 0.60" machine gun could be equipped either with a 15 mm or a 20 mm barrel and was a quite reliable and durable weapon. I guess the problem with the 0.60" machine gun specifically was not so much one of caliber as one of the desired kinetic energy ... the 15 mm MG151 had around 27kJ kinetic muzzle energy, the 20 mm MG151/20 around 30 kJ, but the 15.2 mm 0.60" machine gun generated 47kJ.

Of course, that would stress all parts of the gun a lot more, which is probably one reason the development was quite protracted.

The 0.60" round was developed into a quite powerful 20 mm service round in the end, so it's not like it was all for nought. It's just that the targets were way too ambitious to come to fruition in a WW2 time scale, and I would argue that the idea of a very high velocity heavy machine gun for air-to-air combat was in fact a bit of a fallacy.

Regards,

Henning (HoHun)
 
I was going to suggest fuel use versus weight/power but looking at it further and the diverse variants, not a lot in it over all. Might be the extra 300KG in weight or something related perhaps.
 
It's also worth noting that Curtiss applied the same process to their P-40 as the N and Q models--the latter having a bubble canopy. In Curtiss' case, they were unable to get the sort of speed increases NA did because they really didn't do any significant changes to the wing or fuselage profiles.
 
phil gollin said:
Were there any P-51H proposals with a nose mounted Griffin engine ?

And if, why not ?
Click to expand...

No P-51H derivative with a Griffon simply because that engine wasn't produced in the US.

Probably the closest match would be the unbuilt Rolls-Royce F.T.B. proposal of June 1943 - which would have installed a Griffon 65 amidships in a much-modified Mustang Mk.X airframe.
 
Apophenia said:
No P-51H derivative with a Griffon simply because that engine wasn't produced in the US.

Probably the closest match would be the unbuilt Rolls-Royce F.T.B. proposal of June 1943 - which would have installed a Griffon 65 amidships in a much-modified Mustang Mk.X airframe.
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Not that some of the old Reno Air Racers didn't stick a Griffon up front, but those were 1-off conversions not a serious combat design.
 
Any known photos of the XP-51F being readied for a test flight, and/or the XP-51F/G or P-51H and P-82 mock ups or wind tunnel models? I know that the XP-51F photos were published in the Building the P-51 Mustang book (images probably belong to Boeing now) as well as some photos of the P-51H mock up (same fate, no owned by Boeing). As well as there being wind tunnel model photos of the XP-82 (from NACA) and mock ups that were shown in the Schiffer Publish book on the F-82 and XP-82 restoration from the Gerald Balzer collection (as well as some good detail shots of the actual XP-82 or P-82B from the same source).

Anyone know a good place to try and locate some of these photos (SDASM has a lot of what I'm looking for, but not everything such as the mock up and XP/P-82 detail shots, or the rare XP-51F/G shots).
 
My understanding is that the weight difference between the Merlin and Griffon is such that it would be more involved than a straight swap. A lot of rebalancing of the airframe would be required to make the aircraft fit for combat.

Note the larger airframe of the later Spitfire marks.

Would have been a monster though.
 
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If you are interested in seeing the XP-82, it is available at the Valiant Air Command Museum in Titusville, Florida. I had pictures of it when its was undergoing restoration in Douglas, GA a few years ago and then a few pictures when it was repositioned to Titusville. I'll try to locate them. Here is a link to the XP-82 at the VAC. Checkout the left and right 360 cockpit views in the videos at the bottom of the page.
www.valiantaircommand.com

XP-82 Twin Mustang

The North American F-82 Twin Mustang is the last American piston-engine fighter ordered into production by the United States Air Force. Based on the North American P-51 Mustang, the F-82 was originally designed as a long-range escort fighter for the Boeing B-29 Superfortress in World War II. The...
www.valiantaircommand.com www.valiantaircommand.com
 

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