North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Sq., 1950

[Dizzyfugu]

Had this on the project list for some time, and with the "Following in the footsteps of the P.R.19" gaining momentum these days I finally built it: the North American Mustang FR.6.


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) by dizzyfugu, on Flickr


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) by dizzyfugu, on Flickr


Some background
The North American Aviation P-51 Mustang was an American long-range, single-seat fighter and fighter-bomber used during World War II, the Korean War and other conflicts. The Mustang was conceived, designed and built by North American Aviation (NAA) in response to a specification issued directly to NAA by the British Purchasing Commission. The prototype NA-73X airframe was rolled out on 9 September 1940, 102 days after the contract was signed and, with an engine installed, first flew on 26 October.


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) by dizzyfugu, on Flickr


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) by dizzyfugu, on Flickr


The Mustang was originally designed to use the Allison V-1710 engine, which had limited high-altitude performance. It was first flown operationally by the Royal Air Force (RAF) as a tactical-reconnaissance aircraft and fighter-bomber (Mustang Mk I). The addition of the Rolls-Royce Merlin to the P-51B/C (Mustang Mk III) model transformed the Mustang's performance at altitudes above 15,000 ft, giving it a much better performance that matched or bettered almost all of the Luftwaffe's fighters at altitude. The definitive version, the P-51D (Mustang Mk IV), was powered by the Packard V-1650-7, a license-built version of the Rolls-Royce Merlin 60 series two-stage two-speed supercharged engine, and armed with six .50 caliber (12.7 mm) M2 Browning machine guns.

The Mustang VI (later re-designated FR.6; the Mustang V was a lightweight fighter of which only one prototype reached England) was an indigenous, British project that was based on the P-51D. It was to meet Air Ministry Specification F.4 of 1940 for a high altitude fighter, designed to fight at extremely high altitudes, in the stratosphere.

Background was that Great Britain feared, with an ever increasing air superiority over the British Isles, that German bomber raids might come in at very high altitudes in the near future, staying out of reach from conventional defense measures. Earlier reconnaissance flights of Ju 86P aircraft had already shown that this was a realistic scenario. Additionally, the domestic development progress of pressurized cockpits for high altitude fighters convinced authorities that Germany would easily be on the same technical level, so that a high altitude interceptor was indeed needed.

While Westland and Vickers responded with twin-engined designs, North American was also requested to modify the relatively new Mustang (which was designed for medium to high altitudes) for extreme altitudes, as F.4/40 specification was revised into F.7/41 in early 1941. British pressurized cabin technology was to be incorporated, but the engine could be based on US technology.
North American was quick to respond and modified a P-51D airframe. This prototype was internally coded NA-73HK and ready for inspection in mid-late 1942.

The NA-73HK's most obvious feature was the enormous high aspect ratio wing, achieved by extended wing tips, together with a fortified internal wing structure and weight saving measures (which had already been designed for the lightweight Mustang V). This new wing necessitated enlarged tail surfaces and a slightly elongated fuselage to provide a longer moment arm.

The aircraft was powered by a Packard V-1650-20 engine that delivered 1.233 hp (920 kW) at 35,000 ft (10,668 m). It was based on the Rolls Royce Merlin 76 (RM 16SM), but instead of the standard two-speed, two-stage supercharger it was coupled with a General Electric C-23 turbo-supercharger. The system was fitted with A.D.I and a General Electric ignition system with a tubular ignition harness developed by the Scinitilla company. A water injection system was added for short-term power boosting, too. The original Bendix-Stromberg carburetor was retained, even though optimized for lower air density use and a higher air mass flow. It drove a new, four-bladed propeller with increased diameter and enlarged single blade area.


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) by dizzyfugu, on Flickr


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) by dizzyfugu, on Flickr


Since the slender P-51 airframe did not allow the placement of the turbo-supercharger in front of the cockpit it was re-located into a large ventral fairing which replaced the original radiator tunnel – the basic layout resembled that of the P-47 Thunderbolt. But due to lack of internal space the system had to be connected through external exhaust pipes running along the fuselage flanks. This was a draggy arrangement, but it would not matter much anymore once the aircraft was at its intended operating altitude of 40.000 ft (~12.000m) and beyond.

The cockpit retained an aft-sliding bubble canopy, even though it had to be reinforced and was quickly recognizable through its stiffener bars. The cockpit pressurization system was driven by a separate Rotol supercharger attached to the engine, providing a constant pressure of 3.5 psi (24 kPa) over the exterior pressure. This resulted in an apparent cabin altitude of 24,000 feet (7,300 m) when the aircraft was operating at its design altitude of 45,000 ft (14,000 m).
This cabin altitude was still too high for normal breathing, so the pilot had to wear an oxygen mask during flight. A rubber gasket filled with the pressurized air sealed the canopy when the system was turned on, and a valve ensured the pressure was controlled automatically. Moreover, the pilot also had to wear a high altitude suit as he might have been required to bail out at altitude.

Detail work turned into time-consuming process, though. For instance, the Mustang VI, how the type was called by the RAF, and "The White Horse" by its pilots and service drews, required a new, sophisticated electrical system. This was necessary in order to minimize the number of seals and points of entry into the cockpit for the controls and instrumentation. It worked, but it was complicated: it took an electrician experienced in the features of the Mustang VI almost four hours to undertake a pre-flight check of this system!

The armament was modified, too. The original six 0.5" machine guns were to be replaced by four long-barreled Hispano 20 mm cannon in the wings. These offered greater range and ensured more damage against the expected, big targets.


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) by dizzyfugu, on Flickr


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) by dizzyfugu, on Flickr


Five prototypes were used in the development process in early 1943. Despite its complexity the White Horse proved to be successful, as it easily reached 50.000 ft. (15.000 m) altitude and handled well. But production was delayed as the standard P-51D had priority and no immediate high altitude threat from Germany materialized.
Serial production eventually started in mid-1944, but at a much smaller scale than initially planned:  the original production plan from late 1942 demanded no less than 500 specimen, but towards late 1943 this drastically reduced to 100, and eventually only a mere 50 of these aircraft actually reached its exclusive user, the Royal Air Force, until early 1945.

When the Mustang VI arrived at the frontline in January 1944, there was virtually no sign of high altitude aircraft to be intercepted – and there was hardly any other use for this specialized aircraft. As a consequence most of the almost new airframes were modified to carry cameras for high altitude reconnaissance missions. These machines were converted by the Forward Repair Unit (FRU) to have two camera compartments fitted: one behind the cockpit cabin, facing to port or starboard, with respective windows added behind the cockpit and above the turbocharger compartment, and another in the extension segment in front of the tail wheel, where up to two vertical cameras could be mounted (even though the location proved to be rather unsuitable, as hot air from the radiator and oil leaking from the turbocharger frequently obscured clear vision). These modified aircraft were re-designated Mustang PR.VI, which turned into FR.6 from late 1944 on.

After WWII hostilities ended, a small number of Mustang FR.6 was kept in RAF service and allocated to squadrons in Germany and in the Far East, where the aircraft were exclusively used for reconnaissance duties.


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) by dizzyfugu, on Flickr


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) by dizzyfugu, on Flickr


One of the type's last missions took place in 1951, when Hainan Island (People's Republic of China) was targeted at the behest of U.S. Naval Intelligence for RAF overflights. RAF Mustang FR.6 of 80 Squadron, based at Kai Tak Airport in Hong Kong, were deployed, together with Spitfire PR.19 from 81 Squadron.



General characteristics
Crew: 1
Length: 34 ft (10,37 m)
Wingspan: 48 ft 9½ in (14.90 m)
Height: 14 ft 7½ in (4.46 m) w. tail wheel on ground & vertical propeller blade
Empty weight: 4,870 kg (10,737 lb)
Loaded weight: 5,100 kg (11,244 lb)
Max. take-off weight: 6,020 kg (13,272 lb)
Fuel capacity: 1,200 l (264 imp gal)

Powerplant
1 × Packard V-1650-20 liquid-cooled piston engine, rated at 1.233 hp (920 kW) at 35,000 ft (10,668 m)

Performance
Maximum speed: 420 km/h (261 mph; 227 kn) at sea level, 660 km/h (409 mph) at 15.000 m (49.130 ft)
Cruise speed: 362 mph (315 kn, 580 km/h)
Range: 460 km (286 mi; 248 nmi) at maximum continuous power with 595 l (131 imp gal) of fuel at sea level; 1,440 km (895 mi) with 1,200 l (264 imp gal) of fuel at 15.000 m (49.130 ft)
Service ceiling: 50.500 ft (15.420 m)
Maximum ceiling: 55,610 ft (16,950 m)
Rate of climb: 11.5 m/s (2,260 ft/min) at sea level, 3.92 m/s (13 ft/s) at 15.000 m (49.130 ft)

Armament
4× 0.787 caliber (20mm) Hispano cannons with 200 RPG in the outer wings; some aircraft only carried a pair or these or were completely unarmed to save weight
2× hardpoints for up to 2.000 lb (907 kg) of external ordnance under the wings, typically only two drop tanks were carried.



The kit and its assembly
I've always been a big fan of the Westland Welkin and its elegant high altitude livery in PRU Blue and Medium Sea Grey, but lacking a suitable kit this had always been just a plan - until you build a suitable aircraft on your own! The plan for a high altitude Mustang had also been lingering for some time, as I found good donation parts in the stash (see below).

So... why not combine these into a whif model? Specification F.4/40 was a good real world background, and maybe a single-engined aircraft in the style of the Bv 155 would have been a better answer than the twin-engined Welkin or its competitor, the Vickers 432?

The basis is the Hasegawa P-51D. It's a decent kit with good detail but only of average fit. It's an old casting, but for this conversion it was a very good basis.

Many things were changed in order to create the FR.6, though:
● Wing tips extended with parts from a HUMA Me 309 (leading and training edge sweep match perfectly!)
● Extended rear fuselage, with a 2C putty plug (about 1 cm) inserted
● Elongated fin, the upper half comes from a Special Hobby He 100D
● New stabilizers, taken OOB from an ART Model Bv 155
● New ventral fairing; it's a seriously trimmed radiator from the aforementioned ART Model Bv 155 with scratch parts
● New/larger carburetor air intake, from a Matchbox Martin Marauder
● Camera windows on the real fuselage - simply drilled holes, filled with black glass paint and Humbrol Clearfix
● New propeller; the spinner is OOB, the blades come from the ART Model Bv 155, too
● New canopy; it's a vacu piece, also leftover from the ART Model Bv 155 (it fits almost perfectly!)
● Long-barreled Hispano cannons from a late Spitfire kit from Special Hobby

Fortunately I had everything at hand, true spare-parts recycling. Building the thing was pretty straighforward, the biggest issue were the fuselage with its extension and the bulbous, dorsal fairing, and the extended fin.


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) - WiP by dizzyfugu, on Flickr


The exhaust system was completely scratched from styrene profiles. I used the Bv155 and a P-47 explosion sketch as design benchmarks – but I give NO guarantee for realism! Some small details were added with white glue, which was also handy as a kind of fluid putty that would bridge some gaps in the piping.


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) - WiP by dizzyfugu, on Flickr


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) - WiP by dizzyfugu, on Flickr


Painting and markings
I had a clear benchmark, to my Mustang FR.6 ended up with upper sides in uniform Medium Sea Grey (Humbrol 165) and lower sides in PRU Blue (Humbrol 230). Since the Mustang has a similar layout as the Spitfire, I went for a high waterline - I think that this makes the aircraft more interesting than an all-grey upper side?


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) - WiP by dizzyfugu, on Flickr


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) - WiP by dizzyfugu, on Flickr


The basic tones were later highlighted through dry-brushing with lighter shades (Humbrol 145 and 167) and a thin black ink wash.


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) by dizzyfugu, on Flickr


The interior incl. the landing gear was painted in Interior Green (Humbrol 78). The complex exhaust system received special attention with some graphite, as I wanted to present the pipes as painted, yet totally scorched and worn from the hot gases inside, so that they stand out in front of the all-blue background.

The markings come from a Special Hobby Spitfire F.23 which contains markings for several RAF 80 Squadron machines based in Hong Kong. I kept the aircraft rather sober, with minimal markings and just the 80 Squadron 'Bell' badge as individual highlight.

After some additional dry-brushing with medium grey overall, the kit was sealed with a coat of matt acrylic varnish.


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) by dizzyfugu, on Flickr


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) by dizzyfugu, on Flickr


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) by dizzyfugu, on Flickr


1:72 North American Mustang FR.6, aircraft "W2-Q/TV416" of RAF 80 Squadron, Tengah Air Base, detached to Kai-Tak Airport, Hong Kong; 1950 (whif/Hasegawa kit conversion) by dizzyfugu, on Flickr



A quick one (a bit more than one week's work) and everything was kept very simple and straightforward, even though it might appear different. In the end the modified Mustang looks very nice and elegant, despite the extra plumbing and slightly distorted proportions. It actually looks like the illegitimate offspring between a P-51D and a Bv 155 in a dark night over the Channel...?

[The Big Gimper]

Once again you are taken WHIFing to new "heights" Dizzy.  The tall tail is a wonderful touch.

I can now remove the P-51 as a potential target of my Bv 155 upgrades. 

[Tophe]

Nice transformation!

[The Rat]

The word 'BEAST' is jumping to the front of my mind. Well done! 

[Dizzyfugu]

Yup, that thing looks pretty utilarian. But there's potential for more: check this overnight USAF version profile a fellow model builder at FlickR from Canada (FrancLab) made last night, after I posted the pics:


North American-Lockheed P-51XH by Franclab, on Flickr

[CSMO]

Ho;ly Cow!!!! You "steam-punked" a Mustang. That is just uber-cool, to the max.

I nominate this little beast for a Whiffie. It deserves one.

Adios, Larry.

[PR19_Kit]

Now why does this seem familiar somehow? 

LOVE it Thomas! 

[sandiego89]

Well done, like all the duct work! 

[Dizzyfugu]

Ho;ly Cow!!!! You "steam-punked" a Mustang. That is just uber-cool, to the max.

I nominate this little beast for a Whiffie. It deserves one.

Adios, Larry.

Uh, wow, thanks a lot - not only for the nomination (highly appreciated! ), but to everyone for the feedback!

I remember that I saw that stretched-wing, silver Mustang some time ago, but was not aware of it when I built mine. It came to be when I played with spare parts from the pile and found that the Me 309 wings were perfect for a P-51 wing extension, and the rest was a inspired by many leftover parts from a Bv 155 conversion (the French Navy "Requin" I did two years ago). Good or plausible ideas seem to linger in many minds, so there must be sometjing to them... 

[Captain Canada]

Nice work ! Sure changes the look, but still recognizable. I like the look of the duct work too.....nice touch of interest !

[Dizzyfugu]

Nice work ! Sure changes the look, but still recognizable. I like the look of the duct work too.....nice touch of interest !

Thank you. The ducting layout was more or less copied from the Bv 155 - I just made sure that it was not buried half way in the fuselage, but rather be mounted externally, and with free space to the fuselage (instead of fixing the parts directly). I think that adds much to the overall, "technical" impression?

[Hobbes]

Well done, it certainly looks the part of a bodged-together-at-short-notice project