Mosquito NF XII HK117
The introduction of centimetric radar in the form of AI Mk.VII and Mk.VIII led to significant modifications to the Mosquito airframe to accommodate this advanced technology. One of the first aircraft to undergo these changes was the NF.II, with serial number DD715, which was taken off the Hatfield production line in July 1942. This aircraft was fitted with a perspex ‘thimble’ radome to house the scanning mechanism and equipment boxes of the AI Mk.VIII radar. The modified aircraft made its first flight in August 1942 and was then transferred to the Telecommunications Flying Unit (TFU) at Defford in September for flight trials. Following successful trials, a further ninety-seven NF.IIs were modified to the NF.Mk.XII standard at Marshall’s Flying School near Cambridge.
The first two of these aircraft, HJ945 and HJ946, arrived at Cambridge on 2 January 1943. HJ945, the production prototype, was delivered to Defford on 13 February 1943 for further trials. The NF.Mk.XII, powered by the same engines as the NF.II (Merlin 21 or 23s, each rated at 1,460 hp), was similar to its predecessor in most respects, except for the removal of the four Browning machine guns to make room for the radome. The all-up weight of both the prototype (DD715) and production aircraft was recorded as 18,441 lb (8,365 kg).
The first NF.Mk.XIIs were delivered to Fighter Command in March 1943, enabling the formation of ten night-fighter squadrons equipped with the new aircraft. The NF.Mk.XII served until the end of World War II, with the last UK-based squadrons phasing them out in January 1945. The NF.Mk.XII also served in a night-fighter training role with Operational Training Units (OTUs).
The production version of the Mk.XII, designated the NF.Mk.XIII, featured the stronger wing from the fighter-bomber Mk.VI variant, which included provisions for external drop tanks. The radome on later production aircraft was either the thimble type or the bull-nose type, the latter taken from the NF.Mk.XIX. Although the NF.Mk.XIII could carry a pair of bombs behind the cannon ammunition boxes, this capability was rarely utilized in the night-fighter role. The first NF.Mk.XIII, HK363, flew from the Leavesden factory in August 1942 and was subsequently sent to Boscombe Down for service trials. Late production models of the NF.Mk.XIII were equipped with more powerful Merlin 25-series engines, each rated at 1,635 hp.
Fighter Command began receiving the NF.Mk.XIII in October 1943, with further deliveries continuing into December. A total of eleven squadrons operated the NF.Mk.XIII both in the UK and abroad, with the final unit retiring the aircraft in September 1945. Like the NF.Mk.XII, the NF.Mk.XIII also saw service with OTUs.
Technical Data (Mk XII)
- Type: Twin-engined, night-fighter with a crew of two, of mixed wooden monocoque and stressed skin construction.
- Manufacturer: De Havilland Aircraft Company Ltd, Hatfield and Leavesden.
- Power Plant: Two 12-cylinder, supercharged Rolls-Royce Merlin 21 or 23 in-line engines, each rated at 1,460 hp.
- Dimensions:
- Span: 54 ft 2 ins (16.5 meters)
- Length: 40 ft 5 ins (12.32 meters)
- Height: 12 ft 6 ins (3.8 meters)
- Wing Area: 454 sq. ft (42.17 sq. meters)
- Weights:
- Tare: 13,696 lb (6,210 kg)
- Full Operational Load: 19,700 lb (8,935 kg)
- Fuel Capacity:
- Maximum: 547 gallons (2,485 liters)
- Operationally Loaded: 410 gallons (1,865 liters)
- Performance:
- Maximum Speed: 341 mph (545 km/h) at 20,000 ft (6,095 meters)
- Cruising Speed: 252 mph (405 km/h) at 20,000 ft
- Initial Rate of Climb: 3,000 ft/min (915 meters/min)
- Service Ceiling: 36,000 ft (10,970 meters)
- Maximum Range: 1,705 miles (2,730 km)
- Armament: Four 20-mm Hispano cannons in the forward lower fuselage, with 200 rounds per gun.
- Radar: AI Mk.VIII
Unit Allocation
- Operational Squadrons: Nos. 29, 85, 151, 256, 307, 406, 488, and 604 Squadrons.
- Night-Fighter Training: No. 54 OTU.