+++ DISCLAIMER +++
Nothing you see here is real, even though the conversion or the presented background story might be based historical facts. BEWARE!
Some background:
The APS-4 was a light-weight, pod-mounted airborne search Radar which was suitable for either Airborne Interception (AI) or Air-to-Surface-Vessel (ASV) applications. It was a member of a series of early air-borne radar equipment and was initially designated as AS-H (“Air-to Surface, version H”). This very advanced equipment for its time was first used by the US Navy on board of carrier-borne night fighter aircraft like respective F6F Hellcat and F4U-2 Corsair variants. The Royal Air Force was impressed enough with the system's performance that it was adopted in 1943 for domestic airframes, too, as an alternative to the British AI radars used on board of early Mosquito, Beaufighter and Defiant night fighters.
One very successful carrier of the APS-4, in RAF service known as the AI Mk XV, was the De Havilland Mosquito in its NF Mk.XIX and NF Mk.30 night fighter incarnations. Aware of the performance and effectiveness of the American single engine aircraft, though, the RAF decided to test similar domestic airframes towards the end of WWII as well. The shorter range of a single engine night fighter would, compared with the bigger but also more sluggish two engine types, be compensated by higher speed, agility and rate of climb. These lighter aircraft were intended as a second defense for homeland defense, esp. around large cities or industrial sites.
One of these projects concerned the Supermarine Spitfire, more specifically the new types powered by a Rolly Royce Griffon engine. The Griffon provided a substantial performance increase over the Merlin-powered Spitfire Mk IX, but initially suffered from poor high altitude performance due to having only a single stage supercharged engine. By 1943, Rolls-Royce engineers had developed a new Griffon engine, the 61 series, with a two-stage supercharger, leading to a slightly modified engine, the 65 series, which was eventually mounted in the Spitfire Mk XIV.
With this performance surplus, a night fighter, despite carrying the AI Mk XV equipment plus a second crew member, was still expected to offer a superior performance over German two-engine bombers that intruded British airspace and the heavy night fighters that lurked over the Channel and attacked grouping RAF night bomber formations before they entered Continental airspace.
From this idea, the Spitfire NF.XX was born, as an alternative to a Hawker Typhoon night fighter with a British radar and only a single crew member. In summer 1944 an initial prototype was built, converted from an early series production Mk. XIV airframe. Since the AI Mk XV came with a rather complicated and voluminous display, a second crew member was deemed necessary for effective operations, esp. at night and under poor visibility conditions. The radio operator would check the radar readings and verbally guide the pilot towards the target, who could concentrate on the flying job and keep the eyes on the surroundings.
In order to fit the equipment and the second crew member into the tight Spitfire airframe, and a separate compartment behind the pilot's cockpit and the real bulkhead was added. This second seat received a separate sliding canopy, resulting in a distinctive camel hump silhouette, which earned the Spitfire NF.XX quickly the nickname 'Camelback'. Supermarine had proposed a new service name for this aircraft, 'Nightfire', but it was not officially accepted, since the machine did not differ enough from the basic Spitfire day fighter to justify a completely new designation.
The AI Mk XV equipment and its antenna were carried in a bullet-shaped pod under the port wing, similar to the US Navy night fighters’ arrangement. The radar dish was designed to scan from side to side for AI applications, but it could also be commanded to look up and down by a few degrees. This enabled the aircraft to attack targets from above, and it could also search for surface vessels below, so that the aircraft could also act in ASV or pathfinder duties in a secondary role (much like the Mosquito night fighters, which frequently guided bomber formations to their targets).
In order to mount the pod to the outer wing and compensate for the gain of weight, the standard 0.303" Browning machine guns normally located there were deleted. Instead, the NF.XX was initially armed with two 20 mm Hispano cannon plus a pair of 0.5" machine guns, mounted in a fashion similar to the Spitfire's standard E wing.
The NF.XX was powered, like the Spitfire Mk. XIV, by the two-stage supercharged Griffon 65, producing 2,050 hp (1,528 kW). A five bladed Rotol propeller of 10 ft 5 in (3.18 m) in diameter was used, and for the night fighter role the standard single exhaust stubs gave way to a collector fairing on each side, which dampened flames and improved the crew's view in the darkness.
To help balance the heavy Griffon engine, the radio equipment was moved further back in the rear fuselage. Improved VHF radio equipment allowed for the aerial mast to be removed and replaced by a "whip" aerial further aft on the fuselage spine. Because of the longer nose and the increased slipstream of the big five-bladed propeller, a new tail unit, with a taller, broader fin and a rudder of increased area was introduced.
One problem that hampered all early Griffon-powered Spitfire variants also plagued the NF.XX, though: short legs. The NF.XX carried a total of 109.5 gal of fuel, consisting of 84 gal in two main tanks and a 12.5 imp gal fuel tank in each leading edge wing tank. With this internal capacity, the fighter's maximum range was just a little over 460 miles (740 km) since the new Griffon engine consumed much more fuel per hour than the Merlin engine of earlier variants, and the extra drag and weight through the radar equipment did not make things better.
As a simple remedy, a conformal, fixed belly tank between the radiators was devised. This carried an extra 90 gal, of fuel, extending the fighter's range to about 850 miles (1,370 km) – still not much for aerial patrol and extended loiter time for interceptions, but enough for short-notice home defense duties. Alternatively, a more conventional but jettisonable 100 gal. drop tank could be carried, but it produced considerably more drag and affected overall performance so dramatically that it was never used in service.
The first tests of the new aircraft were conducted in January 1945 and three pre-production machines (all converted Mk. XIV airframes) were allocated to night fighter units for field trials and direct comparison with two engine types. Despite its innate aerodynamic and weight penalties the Spitfire NF.XX still attained an impressive top speed of 400 mph (350 kn; 640 km/h) at 29,500 ft (9.000 m), even though in clean condition only. But it was still more than enough to take on much heavier German bombers and night fighters. The second crewman was another winning factor, since the pilot alone would be overloaded in the face of heavily armed enemy aircraft in the European theatre of operations and the local weather conditions.
Further initial experience with the type resulted in several ad hoc modifications: the wing span was increased in order to improve handling and climb performance, using standard wing tip extensions from Spitfire high altitude variants. Furthermore, a deeper rudder was added to the fin because the second cockpit created significant directional instability.
Armament was changed, too - more firepower and a longer range was deemed necessary to attack the German heavy night fighters, which themselves frequently carried defensive armament in the form of heavy machine guns. Consequently, the initial pair of 0.5" machine guns was deleted and replaced by an additional pair of 20 mm Hispano cannon, and all four guns received extended barrels for a higher weapon range.
In this form, the Spitfire NF.XX quickly entered RAF service in March 1945, but, in the meantime, the German night fighter threat had declined, so that only 50 machines were completed and delivered to RAF units in the UK until the end of hostilities.
The operational use of the machines was hampered by localized skin wrinkling on the wings and fuselage at load attachment points, a problem the type shared with the Mk. XIV day fighter. Even though Supermarine advised that the machines had not been seriously weakened, nor were they on the point of failure, the RAF nevertheless issued instructions in early 1945 that all F and FR Mk XIVs were to be retrospectively fitted with clipped wings to counter the threat. The NF.XX kept their elongated wing tips, however, and were simply limited to a top speed of 370 mph (600 km/h) and not allowed to dive anymore.
General characteristics:
Crew: 2 (pilot, radar operator)
Length: 32 ft 8 in (9.96 m)
Wingspan: 40 ft 2 in (12.2 m)
Height: 10 ft 0 in (3.05 m)
Wing area: 249.7 sq.ft (23.2 m²)
Airfoil: NACA 2213 (root), NACA 2209.4 (tip)
Empty weight: 8,680 lb (3,937 kg)
Gross weight: 10,700 lb (4,853 kg)
Max takeoff weight: 12,530 lb (5,683 kg)
Powerplant:
1× Rolls-Royce Griffon 65 supercharged V12, 2,050 hp (1,530 kW) at 8,000 ft (2,438 m),
driving a 5-bladed Jablo-Rotol propeller
Performance:
Maximum speed: 400 mph (640 km/h; 353 kn) in FS supercharger gear at 29,500 ft.
Combat range: 460 mi (741 km/400 nmi) with internal fuel only
850 mi (1,370 km/757 nmi)
Ferry range: 1,093 mi (1,759 km/950 nmi)
Service ceiling: 43,500 ft (13,259 m)
Rate of climb: 4,300 ft/min (21.8 m/s) in MS supercharger gear at 2,100 ft.
3,100 ft/min (15.8 m/s) in FS supercharger gear at 22,100 ft.
Time to altitude: 8 mins to 22,000 ft (at max weight)
Wing loading: 32.72 lb/sq ft (159.8 kg/m²)
Power/mass: 0.24
Armament:
4× 20 mm (0.787-in) Hispano Mk II cannon with 120 RPG in the wings
Provision for an auxiliary underfuselage tank, either a fixed conformal 90 gal tank or a
100 gal drop tank.
The kit and its assembly:
Well, Spitfire fans might call it crude to create a whiffy variant that incorporates so many ugly details. But this fever creation came into being through the simple thought: "What would a dedicated Spitfire night fighter with a radar look like?" From this initial creative spark I tried to build this fictional NF.XX variant with available late WWII technology from a Griffon-powered Spitfire.
The basis is the Airfix Spitfire PR.XIX kit, a nice and clean offering, even though the use of this photo recce variant meant some additional work. The radar pod comes wholesale from an F4U night fighter (Fujimi), since the wing installation appeared to me to be the only plausible (and proven) option.
The second cockpit and the "double bubble" canopy come from an RS Models Spitfire Mk.IX UTI trainer, which is/was a domestic conversion made in the Soviet Union. The kit comes with an extra two seater fuselage, so that, despite body donors, almost a complete Spitfire remains (just the cockpit missing, but this can be taken from the Airfix kit).
I also considered the Spitfire TR.IX arrangement, with a stepped bubble canopy, but found that the risen rear cockpit for the instructor would not make sense in a night fighter, so the UTI arrangement with separate canopies on the same level appeared to me to be the most suitable solution for this aircraft and its task.
Surgery was not easy, though: The whole cockpit area was dissected from the RS Models trainer and – together with the internal parts like the bulkheads, dashboards and seats – transplanted into an appropriate gap, cut into the Airfix kit fuselage. The windscreen position on both airframes was used as orientation benchmark.
Basically a simple idea, but, even though you have two Spitfire kits at hand, both models differ slightly from each other in many ways. Material thickness is different, as well as panel lines, which are all there on both models but simply do not fall in line. Internal width and available space is also different, esp. the rear bulkhead was not easy to integrate into the Airfix fuselage. It worked, somehow, but it consequently took some PSR effort and rescribing (at least, both donor kits have engraved details) in order to create this Griffon-powered two-seater.
The extended wings were created through the simple implantation of high altitude wing tips from an AZ Model Spitfire I/II/V/VI kit. They match very well with the Airfix PR.XIX wings, which were simply clipped at the correct position outside of the ailerons. Since the recce Spitfire comes without any weapons I added four brass barrels (Pavla) to the wings, plus respective bulges for the magazines (scratched from sprue) and casing ejector fairings under the wings.
I also changed the vertical rudder. Instead of the separate OOB part from the Spitfire PR.XIX I used a deeper and higher rudder from a late Seafire mark (left over from a Special Hobby kit, IIRC). The part lost its hook and the notch for its deployment mechanism, replaced by a piece of styrene that was PSRed into the rest of the rudder. It’s not an obvious change, but the bigger fin area is a good counterpart to the enlarged wings and the bulkier rear fuselage.
The conformal belly tank was scratched from the upper half of a Matchbox A-10 inner wing. There are aftermarket solutions available, but I simply did not want to spend as much money on a single resin part that no one will clearly see and that’s just as expensive as the whole Airfix basis kit. Some things are just ridiculous.
Painting and markings:
Very simple: classic late war RAF night fighter colors, with Medium Sea Grey and Dark Green (Humbrol 165 and 163, respectively) on the uppers surfaces, plus Night (I used Revell Acrylics 06, Tar Black, which is actually a very dark grey tone) underneath, with a high waterline and a black fin. Looks weird on a Spitfire, but also somewhat cool!? The model received a light black ink wash and some panel post-shading, using a blue-ish hue for the Night undersurfaces.
The interior is classic RAF Cockpit Green (Humbrol 78), the only catchy marking is the red propeller spinner – originally I just wanted to keep the spinner black, too, but found that to be too dull overall.
The markings come from different sources; the codes were created with single Dull Red letters from Xtradecal, roundels and other markings come from various other sheets. The added “G” to the serial number is, BTW, an indication that the aircraft had to be guarded all the time. A nice and appropriate detail for this high tech aircraft of its time. The roundels/fin flashes were taken from another Xtradecal sheet, IIRC they belong to an FAA SB2C Helldiver.
Finally, some wear marks were added with dry-brushed light grey and silver. Exhaust stains were added with dry-brushed dark and light grey, as well as some grinded graphite. A coat of matt acrylic varnish (Italeri) sealed the kit.
I feel a bit guilty of creating the probably ugliest Spitfire possible, with all the add-ons and the weird proportions through the second cockpit and the belly tank. Very massive, at least for this sleek aircraft. The night fighter paint scheme suits the Spitfire surprisingly well, though. Anyway, it’s whifworld, after all, and I tried to go through with the night fighter idea as good and consequential as possible – the fictional NF.XX is just my personal interpretation of the theme.
