A "What If" Mustang......

[Artie]

Well, I'm not a "what if" modeller at all, but after a good friend of mine brainwashed me with his own fantasy planes, I decided to spend some time building a thing like that.

I have loads of ICM Mustangs spare parts (I think they're good donor kits to enhance the loads of Otaki/Airfix P51s you can find in my stash), so it was a matter of time to build this beauty.....

I thought that an Allison engined, bubble canopy Mustang would be a very good looking aircraft. I mated the nose and four gunnned wings from a P51A with a P51D fuselage (removed tail fillet). I painted it resembling a prototype, RAF tested example, andhere you are the resulting composite Mustang....Please, forgive me for this heresy, but I've enjoyed a lot building it..

Criticism, comments and shots into the air will be welcome :)

Edited February 21, 2012 by Artie

[Nigel Bunker]

No apology needed - an interesting concept and a great build. Welcome to the dark side, my boy.

[Don McIntyre]

A very nice build. You did a very nice job of blending the bits from different kits together. You don't happen to have a profile photo, do you? I'm curious to see how it looks from the side.

[ColFord]

Not as much "what if" as you might think. There were proposals for engining later model Mustangs with Allisons as a safeguard against shortages in R-R and Packard Merlin availability and to produce variants more suited to operational use at lower altitudes eg. in the Tac/R and Army support or fighter bomber roles where operations would have been below 15,000ft. This would have left the R-R or Packard Merlin engined versions for the 'pure' fighter and long range bomber escort roles.

Compared back to back at low altitude, the earlier Allison engined Mustang with a de-rated supercharger suited for operations below 10,000ft would outperform the R-R Merlin engined variants which were optimised for medium to high altitude performance. The earlier Allison engined variants were also a lot lighter and therefore handled better at low altitudes than the R-R Merlin engined version.

I've had a similar mash up of ICM and AM bits to do a RAF Tac/R Squadron 1945 'what if' for an Allison engined Mk.IV(FR), but also with the earlier 4 x 20mm Hispano armament and rear fuselage recce cameras as per a F-6D. That matches the operational requirements document developed in late 1944 for a replacement for the then aging and dwindling stocks of the Allison engined Mustang Mk.I, Mk.IA and Mk.II for the Tac/R squadrons in 2TAF.

Nice build.

This was one of my takes on the concept, but using a de-rated Merlin variant.

[Work In Progress]

Indeed, the Allison Mustang is usually sneered at as a useless aeroplane until RR dragged it from mediocrity, but it is all a qustion of the mission for which you use it, and it is actually a superior aeroplane to the Merlin Mustang at non oxygen levels. Not for nothing did the RAF keep its Allison Mustangs in service right to the end of the war, making them some of the most extensively used machines of the whole war.

Were I in a position to commission a complete Mustang restoration for my own use, on the airshow circuit, it would be an Allison variant, stripped of unnecessary military equipment and dressed up as an RAF Mustang II with a Malcolm hood.

[stevehnz]

A couple of good whifs here, they both have a look that says they could have been. I suspect Cols might be a little closer to the would have been than Arties but I like them both & that Artie is a super bit of modelling. Like Don I'd be keen to see a side profile. The Alison engined birds should have a slightly shallower fuselage than the Merlin engined ones but some Alison kits don't seem to reflect this. It'd be good to see how you brought it together. Did you go with an Alison radiator fairing or stay with the Merlin one?

Steve.

[ColFord]

W.I.P.

Having spoken to a number of RAF, RAAF, RNZAF and RCAF pilots who flew the Allison engined variants of the Mustang from 1942 until 1945, including a number of them who also flew the later Merlin engined variants in trials and in the fighter role, they all, universally spoke highly of their Allison Mustangs and its suitability for its role as a low level Tac/R aircraft. When in 1944 and 1945 various replacement aircraft were proposed (Typhoon FR.1b - fail, Spitfire FR.IX - too short range, Spitfire FR.XIVE - too short range, heavy) all they asked for were more Allison engined Mustangs. The Allison ran more smoothly at lower revs than the Merlin, in its derated form as modified for low level Tac/R work, it gave heaps of boost and accelerated rapidly and if low down and in a level sprint, there was not much could catch up to it until the jets came along. It was responsive on the controls and its wide undercarriage made it easier to land on rough airfields or in cross winds. There were instances where strong crosswinds on ALGs grounded the FR Spitfire units, so that the Tac/R Mustangs had to pick up all the operational demands. The Mk.IA with its 4 x 20mm Hispano cannon was well liked, the Mk.II with its 4 x 0.50 Browning HMGs was also well liked, especially when fitted with the Malcolm Hood which improved visibility, but more importantly for many of the pilots increased head room and ease of departure in an emergency compared to the coupe top hood.

It was a case of different aircraft for different roles. They all loved strapping on a Spitfire to fly as a pure fighter, and to practice aerobatics. A Merlin engined Mustang kept on climbing where a Allison engined version would run out of puff with its single stage supercharger and performed well up high, but was heavier on the controls and more tiring to fly for long periods at altitude.

It was with the greatest of sadness the Tac/R pilots saw the last of their Allison Mustangs retired in August 1945.

Kermit Weeks in the USA currently has a P51A being restored to flight, which will be modified to represent a cannon armed P-51/F-6A (Mustang Mk.IA equivalent), but with the standard hood, not the Malcolm Hood.

[stevehnz]

Thanks for that bit of info Col, I'm a bit keen on the Alison powered Mustangs, maybe its a bit of a soft spot for the underdog as I perceive they're often seen as a bit lacking compared to the Merlin powered ones but I guess horses for courses. Do you have any references for Malcolm hooded Mustang Mk Is & Ias? I'd like to put something like this together from a couple of Academy kits I have.

Steve.

[ColFord]

Steve,

Malcolm Hood on Mustang Mk.I, not aware of any. May have been one associated with trials of the installation, but evidence so far suggests Mk.IA was used to develop and trial the installation.

Malcolm Hood on Mustang Mk.IA, one definite, being the aircraft used to develop the installation and then used for service acceptance trials by A&AEE. I have a couple of Mk.IAs that may, very much a possibility, may have been fitted with the Malcolm Hood later in 1944, but have not had anything to confirm their details.

Malcolm Hood on Mustang Mk.II, a few when the Mk.IIs were first entering service in May 1944, then progressively more so that by November 1944 most, if not all in service were so fitted.

Regards,

[Andrew Jones]

Nice What-ifs chaps, some great modelling in both cases, If nobody minds me posting, here's a photo of my RR Griffon engined RAF Mustang VI.

Edited February 22, 2012 by Andrew Jones

[Prop Duster]

Artie, very clever and has the look of a real possible air craft, well done.

Colin are you sure that wasn't a real air craft you modeled?

All very creditable and well thought out.........

{mumbling to self}.....geesh I can't ever ge a regular P-51 built right and these guys go off and CREATE new ones

[General Jumbo]

Very interesting indeed! Now, who is hiding away a Sabre II or radial engined spam can?

[Ed Russell]

Now, who is hiding away a Sabre II or radial engined spam can?

Or even better (worse?) one of these........

Now, who would take a model of this (real aircraft) as the basis for a What-if?

Enough demand and a limited run can be made...........

PS - Artie and Andrew - great thinking to make great models! Not really into What-ifs myself but have had my arm twisted to make a few.

Edited February 22, 2012 by Ed Russell

[ColFord]

Ed,

If that is the one I think it is that used to haunt Canberra Airport for a few years, the phrase from an old tv commercial comes to mind "that would be the Dart!!". Used to see it there but at the time never had a good enough camera to take any reasonable photos.

Limited run, what scale???

Andrew,

I like your idea for a Griffon engined Mustang, looks much better than some of the concepts that were bandied around in late 1944-early 1945.

Maybe time for a Mustang Whif Group Build?

Now see folks, we have found a good use for all those ICM Mustang clones and spare parts left over from all those other kit builds. Thinks - I do have a Griffon Spitfire XIV nose left over from an Academy kit..............maybe 4 x 20mm like a Spitfire 21?

Regards,

[Test Graham]

The idea of re-engining later P-51s with Allisons (historically not modelling) would seem to be a non-starter, partly because of the excess weight involved. The range benefit came less from the engine than the fuel capacity: if better low-level performance was required then the Merlin 55M would be a more straightforward choice. Of course, this would be fairly boring as a model because it would look little different - perhaps a three-blade prop, perhaps not. However, the RAF never received as many Merlin P-51s as it would have liked, priorities being elsewhere, so the thought of diverting away from Fighter Command some of those it did get would not be well received.

A Griffon Mustang would also require a larger radiator (which might reduce interrnal fuel tank size) and thus a larger/deeper duct - the MB5 could perhaps be a guide.

Edited February 23, 2012 by Graham Boak

[gingerbob]

There were proposals for engining later model Mustangs with Allisons as a safeguard against shortages in R-R and Packard Merlin availability and to produce variants more suited to operational use at lower altitudes...

Col, I'd be interested in the information you have concerning this. The only references I've seen I interpret to be that a proportion of Mustang production continue to be Allison (presumably with the existing airframe) rather than switching entirely to the developed Merlin Mustang. But NAA shot that suggestion down immediately, as I'm sure the USAAF would have.

Graham, the Allison Mustang was more efficient than the Merlin Mustang (B/Mk.III) at low altitude, and so for the same tankage did have a better range for the TacR role. (forgive the US term) I think that some of that at least is due to the specific fuel consumption of the respective engines at the altitude in question.

bob

Edited February 23, 2012 by gingerbob

[ColFord]

Historically, and documented in AIR, AVIA and CAB files, is documented the back and forth about many options and issues with the British requirements for Mustang production. Continued production of the Allison engined variants was requested. Supply of airframes and knocked down kits without engines, to be assembled in the UK was requested. Exploration for arrangements for different engine variants, including later Allison engines rated for low altitude performance was requested. And more often than not after exploration and request and clarification and sometimes some very modest expenditure of time and effort to explore the requested options, NAA or the USAAF rejected the request, largely on the grounds of the quantities required to meet the demand already on hand from the USAAF and RAF for the type then in production and not wanting to divert effort from the main product. With regard to excess weight, the dry weight of the Allison V-1710-F30R was some 250 lbs (111 kgs) less than that of the Packard V-1650-7 or equivalent R-R Merlin.

At low altitude in its derated form the Allison, ran at lower revs with significantly lesser vibration for a fuel flow that gave it good range and good performance. Gery Beck, who built the 'new build' P-51A a few years back, commented on the low level performance of the type and how he was able to pull away from Merlin engined Mustangs. When starting at the same airspeed and a 'cruise' throttle setting, when both opened up to full throttle and boost at the same time, the Allison Mustang would accelerate away from the Merlin Mustang.

The issues around diverting Mustang supplies for roles other than those of fighter or fighter bomber, given the demand exceeding supply, was to cause much angst in trying to find a suitable replacement for the RAF's Allison Mustangs for the Tac/R role. Experienced RAF Tac/R pilots who were called upon to trial various types as potential replacements for the Allison Mustangs found most of them wanting in some way, be it low level performance, low level handling, lack of low level range, poor ground handling, poor camera installations or limitations on the numbers and types of cameras that could be fitted and the like. When offered a shiny new P-51D by a USAAF unit commander for his Allison Mustang in 1945, the OC of a RAF unit declined the offer and kept his Mustang. Not the least because of the possible view of KRs and higher brass on such a swap, but he knew his Allison Mustang gave him better performance down low and was better suited for the low level role required of it.

[Test Graham]

"The earlier Allison engined variants were also a lot lighter and therefore handled better at low altitudes than the R-R Merlin engined version."

That was said earlier: my comment about the increased weight of a hybrid was not directed at the engines alone - the V1650-7 will be heavier if only because of the second supercharger and the intercooler - but at the heavier airframe with a deeper fuselage and larger radiator.

The advantages of a low rating as opposed to a high one are clear, on any type. The RAF's fastest climbing, and thus best accelerating, fighter at very low level was not the comparatively heavy Mustang but the Spitfire LF Mk.V, with the possible exception of Mk.XIIs fitted with the later Griffon variant. The LF Mk.V would not have the range of the Allison Mustang, was out of production (although the equivalent Seafires were not), and both factors would be even more true of the few Mk.XIIs. No Mustang was ever fitted with a low-rated Merlin, for a true one-on-one comparison. Understandably enough: the problem, after all, was not the supply of engines but of airframes. An interesting What-If in itself, perhaps, would be a P-51A with the highset Spitfire or Hurricane-type nose. This would permit a larger and hence more efficient propellor.

It could be argued that the P-40 was better with the Merlin than the Allison, but although both had single-stage stage superchargers the Merlin had two gears, permitting better performance at higher altitudes, so it does not make for a true comparison. I mention it to exclude it.

Given the widepread use of the Spitfire in low-level FR roles, it clearly wasn't totally unsuitable for the job. After allowing for all the pilot preferences based on "we like what we've got", what the various alternatives to the Mustang lacked was range. The exception being the later P-51B/D with their extra tanks, which had longer legs than any Allison Mustang. Somewhere in here was the low priority given to the Spitfire's aft tank and larger tailplane. It was possible to double the Mk.V's internal capacity - the Mk.VIII was up 50% without any aft tank - or even more but not with the necessary camera behind the pilot. Whether Supermarine could have spared the necessary design effort is another matter. It is clear why any attempt to extend what was basically Mk.V development would not gain much support, it being seen as three generations behind the mainstream effort. Perhaps a job for Westlands?

In the end, the Mustang was a better airframe, with less drag. This is what allowed the Allison to run at lower revs in the cruise, not some magical alleviation of the laws of thermodynamics. No sensible Spitfire development was ever going to match that.

Edited February 23, 2012 by Graham Boak

[gingerbob]

In the end, the Mustang was a better airframe, with less drag. This is what allowed the Allison to run at lower revs in the cruise, not some magical alleviation of the laws of thermodynamics.

Not sure I agree- Granted we're comparing Allison to Merlin 61 (series), but Frank Tallman said he liked the P-40 better (as a civilian, not fighting!) because he could throttle it right back and run smoothly with low fuel consumption, which he could not do (as well) with the Merlin. Different engines do have different specific consumption, so it isn't just down to airframes. For example, the Griffon was a trifle thirstier for the same power (I think) compared to the Merlin, which was counted against it for PR Spits, but they went with it anyway.

One other point: the fighter-recon folks preferred to have internal fuel, rather than the vulnerable drop tanks. So getting the same range with some external tanks would not be considered "the same" to them.

bob

Edited February 23, 2012 by gingerbob

[Work In Progress]

There's no "typical" Allison V-1710 any more than there is a "typical" Merlin - both are in effect families of many different engines, some variants of both families more successful than others. But some Allison V-1710s are extremely good engines, and most of those fitted to types like the P-39, P-63, later P-40 and Mustangs, are among the good Allisons. The Allison like the Merlin also benefited from significant post-war development, and it is in the post-war environment that all the surviving big piston engine families were finally polished to be as good as they could be: Merlin, Griffon, V-1710, Wright 1820, Wright 3350, P&W 2800. Most of today's operational piston warbirds benefit substantially from the lessons learned in developing those engines for longer service lives than were deemed relevant during wartime.

In support of Graham, the P-51D has very good straightline cruising speed for its size, weight and power, and/ or very good range on a given fuel load (two sides of the same coin) in particular because its very advanced cooling arrangements which greatly reduced the net installed cooling drag in comparison to the earlier generation of airframes like the Spitfire and P-40. An Allison Mustang at low level is an inherently more efficient flying machine than a Spitfire V, and a two-stage Merlin Mustang at high level is inherently more efficient than a Spitfire IX or XVI.

An Allison Mustang with a turbocharger might well have been a devastatingly effective high level machine, possibly even better than one with a Merlin 60-series, but I don't think it was ever tried. the turbocharged V-1710 was a very effective engine in the later P-38s, and made the prototype P-39 a high performer.

[Prop Duster]

just to throw in a counter in for Ed's mystery ship, how about a ........

ROCKET Powered P-51!!(for REAL)

................................................................................

..............

CLICK HERE

NOTE: click through the pictures (#1-#8) then continue the text on pictures #9-27

Enjoy!

Edited February 24, 2012 by Prop Duster

[Work In Progress]

Oof. Just make sure your tailwheel has retracted properly before you hit the button!

[Artie]

Thank you very much for your comments, Sirs....To be honest, I expected some laughs and funny comments.......As I said before, I'm not specially interested about "what if" models..you see, too many kits to be built, so little time. The thing is that I've been lurking for some time with the idea of an Allison engined, bubble canopy "Mesteño" (the spanish word that later evolved to Mustang), and I had lots of spare parts from ICM P51s. The conversion was an easy and straight work. I needed somer filler at certain areas, but otherwise an easy task.

I painted the kit with RAF colours and yellow undersides to give it a credible appearance, despite being a completely fake aircraft. To make things even better, I didn't use the big fuel tank behind the pilot's seat, but the complete radio/batteries array you can find on early P51As. ...

Best regards from Tenerife

[Admiral Puff]

Or even better (worse?) one of these........

Now, who would take a model of this (real aircraft) as the basis for a What-if?

Enough demand and a limited run can be made...........

PS - Artie and Andrew - great thinking to make great models! Not really into What-ifs myself but have had my arm twisted to make a few.

The result of crossing a CAC Mustang (ex A68-187) with a Vickers Viscount - it appeared on the Australian Register as VH-UFO, although it never actually flew in that configuration. It was later sold in the US, converted back to a standard Mustang and is still flying as NL51FS.

[Procopius]

An Allison Mustang with a turbocharger might well have been a devastatingly effective high level machine, possibly even better than one with a Merlin 60-series, but I don't think it was ever tried. the turbocharged V-1710 was a very effective engine in the later P-38s, and made the prototype P-39 a high performer.

Didn't they try something like that on the F-82 Twin Mustang, only to discover that the Allison-engined types had noticeably inferior performance, or do I misremember?