The P-51 Mustang‘s good looks and hygienically clean aerodynamics were often callously mistreated at the hands of wayward engineers and assorted warmongers. We asked Matthew Willis, author of ‘Mustang, The Untold Story‘, to introduce us to the 10 weirdest Mustangs.

10. RAF ground attack variant

What do you do when you’re the RAF and you find yourself in receipt of “undoubtedly the best American fighter to have reached this country”? Why try to turn it into a mud-mover of course. The Mustang was an aircraft with a wing of unparalleled aerodynamic efficiency, which evidently so angered Their Airships that they tried to ruin it with a pair of 40mm cannon in ungainly pods or a battery of 3in rocket projectiles and associated ironmongery with more drag than Santa Pod. To be fair, the early Mustang had a superlative low-level performance which made it attractive as an attack aircraft, but the RAF’s test programme into a ‘universal wing’ plumbed for every kind of ordnance imaginable went further than most proposals.

9. US tank-obliterator

…Apart, that is, from North American Aviation themselves, who in their efforts to find a use for their new aircraft for a sceptical USAAF came up with numerous ideas involving plenty of pounds for air-to-ground. One of these became the A-36 dive-bomber (don’t call it an Apache unless you want a very disagreeable reaction from this author), but in amongst the slew of offers were a couple that included the same 37mm Oldsmobile cannon that was the primary weapon of the P-39 Airacobra. One version included a relatively sensible pair of 37mm guns. Another was to have four, two slung beneath each wing, for what would surely have made the most powerful gun armament of any single-engined aircraft during WW2. It would have made mincemeat of Axis tanks and nervous wrecks of the pilots, assuming they could have got the machine off the ground in the first place.

8. Jet

One of the most well-known features of the Mustang is its carefully designed radiator duct designed to recover pressure and add a small but significant amount of thrust from the air heated by the radiator. This was not enough for the boffins at the Royal Aircraft Establishment who proposed fitting a bundle of ramjets behind the radiator to give that much more oomph. Frank Whittle’s Power Jets company designed an installation that clustered twelve burner tubes within a cylindrical heat shield to fit into the Mustang’s radiator scoop exit, and carried out extensive static testing in 1944. The installation may have flown briefly towards the end of the war but by then it seemed more sensible for Whittle to focus on turbojet engines. The USAAF also liked the idea of a ramjet assisted Mustang, and fitted a P-51D with a ramjet on each wingtip. It briefly boosted top speed to 480mph before blowing up spectacularly – fortunately, the pilot escaped.

7. Beguine

The standard, very efficient Mustang radiator was also not good enough for J.D. Reed, who purchased surplus P-51C 42-103757 in 1947, and former test pilot Paul Penrose who encouraged Reed to have it extensively modified by NAA engineers for racing and record-setting. Gone was the belly scoop and instead, coolant and oil radiators were located in a large pod on each wingtip. The similarity to the ramjet pods mentioned above has often been noted. Sadly, the fate of this aircraft, named Beguine (after the dance) at the request of Reed’s wife, was also rather too similar. Penrose had complained of unpleasant roll characteristics but he and Reed fell out before they could be addressed, and Reed sold Beguine to Jaqueline Cochran. Bill Odom flew Beguine for Cochran, winning the Sohio Trophy at a canter, but during the Thompson Trophy race, Odom was having difficulty following the course, and while attempting to correct, rolled inverted and crashed into a house, killing a woman and child as well as Odom. The disaster led to a 13-year break in the National Air Races.

6. Twin Trouble

The Twin Mustang was an unusual concept at the time  – two complete Mustang-derived fuselages, each with their own full cockpit, attached to a single wing, the concept being an ultra-long range escort fighter with a pair of pilots to share the workload. There was much more that was weird about the Twin Mustang though. First of all, the complete inability of the prototype to leave the ground, until it was realised that the counter-rotating propellers were creating negative lift at the centre-section. The rotation of the engines was swapped and the problem solved. The next oddity was that the model used for training and development, the F-82B, had a somewhat better performance than the variant intended for service use, the F-82E. This was due to the end of wartime technology sharing agreements and the wide availability of licence-built Rolls-Royce Merlin engines. As a result, the small number of F-82Bs were the last to be powered by Merlins, and the service variants all had Allison V-1710 power. In many ways a fine engine, Allison never satisfactorily solved the problem of two-stage supercharging, and the model adopted for the F-82E had to be de-tuned for reliability. The Twin Mustang proved most useful as a night-fighter, never fulfilling its initial promise.

5. Mid-mounted mania

Rolls-Royce was impressed with the Mustang from the outset, thanks to test pilot Ronald Harker singing its praises after a flight at the Air Fighting Development Unit. For a while there was a plan for Rolls to re-engine existing RAF Mustangs with Merlin 61s in-house as it had done with the early Spitfire Mk IXs, but alongside that the company was developing far more ambitious ideas to get the best from Edgar Schmued’s creation. The company favoured a mid-mounted engine like the Bell P-39 and P-63, with a 2,000hp+ Griffon or the insane 4,000hp Crecy, a two-stroke monster combined with a jet turbine to recover energy from the fearsome exhaust flow. Neither the engine nor the aircraft flew, but it’s a truly intriguing what-if.

4. Wet feet

The British made a qualified success of turning the Supermarine Spitfire into a carrier fighter so why not try the same with the Mustang? On paper, the American fighter had a lot more going for it, with a much more heavily built airframe, a stable wide-track undercarriage and a better view. More to the point, it had peerless range, which was of great value in the Pacific war, especially when the B-29 came into play without a land-based fighter with the range to escort it.

The Mustang was completely against the typical form of USN fighters, which tended to be big, straightforward and powered by large air-cooled radial engines. The sleeker, subtler Mustang would have represented a big change in approach. Nevertheless, a P-51D was navalised and took part in deck-landing trials aboard USS Shangri-La in late 1944, proving that the fighter was easy to operate from a carrier. The US Navy was lukewarm about the Mustang, and even the test pilot on the programme was less than keen, citing the narrow margin between landing speed and stalling speed. NAA prepared designs for a naval Mustang, based on the P-51H, but the rapid US advance through the Pacific soon provided land bases for escort fighters – including Mustangs, and the USN stuck with big, bulky air-cooled fighters.

3. Turbo snoot

The Mustang’s many positive features kept it attractive as a military aircraft long after it was superseded in its primary role. F-51Ds were still popular in the ground attack role in the Korean War, and sought-after by smaller countries’ air arms. The US Department of Defense even showed interest in an updated Mustang for the export market and counter-insurgency work as late as 1967, approaching a company that had produced a popular civilian P-51 conversion, the Cavalier. These proved a modest success, and Cavalier considered truly modernising the type by fitting a more up-to-date turboprop powerplant. The result was certainly the oddest Mustang variant for looks, as the long, slim R-R Dart gave the Turbo Mustang a distinctly proboscis-like snout. Despite this monstrosity, a taller tail and the lack of a belly scoop, the aircraft was still recognisably a Mustang. It offered great close-air-support and counter-insurgency performance at a low operating cost, but Cavalier failed to gain any customers so sold the programme to a company that could put more resource behind it. Piper bought in and developed the Turbo Mustang into the PA-48 Enforcer, which was less inelegant but ultimately no more successful.

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2. Cowboy

Mustangs wielded a lot of different weapons over the years – machine-guns, cannon, bombs, rockets, even supply cannisters and napalm, but the oddest modification has to be for the weapon used by the First Air Commando in Burma from its P-51As – a lasso. Ironically, given the number of Mustang horses that found themselves on the receiving end of one. In the insurgent war fought by the Chindits and supported by the Air Commando, cutting enemy communications was a vital task. Someone had the bright idea to suspend a 450ft cable at each end from the Mustang’s bomb racks with a weight in the middle. The pilot, exercising great skill, had to drag the cable across telegraph lines in such a way that the weight wrapped around them…and as the aircraft flew on, the cables would break, or even uproot the telegraph poles. When enough telegraph wires had been cut, the pilot would jettison the cable. Simple, and quite mad.

1. Not A Mustang

When is a Mustang not a Mustang? And when is not-a-Mustang a Mustang. When Hollywood gets involved of course! The use of Mustangs to play enemy fighters started quite early, probably influenced by the old canard that they resembled a Messerschmitt Bf 109, which they do a bit if you squint and then keep squinting until your eyes are closed altogether and then imagine a Bf 109. Allison-engined Mustangs play the part Bf 109s in the 1943 pictures ‘Sahara’ and ‘A Guy Named Joe,’ while an RAF Mustang I (still in its RAF markings) does the same in the 1944 British film ‘For Those In Peril.’ Weirdly, a squadron of Air National Guard P-51Ds play the role of a squadron of Messerschmitts in the 1948 technicolour flick ‘Fighter Squadron.’ The practice of Luftwaffering up Mustangs was still going as late as 1992 when Planes of Fame’s P-51A once again donned Balkenkreutzes in ‘Iron Eagle III.’ The Messerschmitt got its own back, though, when a trio of Hispano Ha 1112 Búchons, relatively fresh from playing 109s and the occasional Hurricane in ‘Battle of Britain’ were recruited for the 1970 biopic ‘Patton.’ The preservation movement had barely started, and Mustangs weren’t available in Europe at the time. The Búchons were therefore dressed up with fibreglass belly scoops and USAAF markings to act as P-51Bs. They allegedly had some novel handling characteristics, and ultimately didn’t make the final cut of the film.

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