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Some background:
The Nakajima J9N Kitsuka (中島 橘花, "Orange Blossom", pronounced Kikka in Kanji used traditionally by the Japanese) was Japan's first jet aircraft. In internal IJN documents it was also called Kōkoku Nigō Heiki (皇国二号兵器, "Imperial Weapon No.2"). After the Japanese military attaché in Germany witnessed trials of the Messerschmitt Me 262 in 1942, the Imperial Japanese Navy issued a request to Nakajima to develop a similar aircraft to be used as a fast attack bomber. Among the specifications for the design were the requirements that it should be able to be built largely by unskilled labor, and that the wings should be foldable. This latter feature was not intended for potential use on aircraft carriers, but rather to enable the aircraft to be hidden in caves and tunnels around Japan as the navy began to prepare for the defense of the home islands.
Nakajima designers Kazuo Ohno and Kenichi Matsumura laid out an aircraft that bore a strong but superficial resemblance to the Me 262. Compared to the Me 262, the J9N airframe was noticeably smaller and more conventional in design, with straight wings and tail surfaces, lacking the slight sweepback of the Me 262. The triangular fuselage cross section characteristic of the German design was less pronounced, due to smaller fuel tanks. The main landing gear of the Kikka was taken from the A6M Zero and the nose wheel from the tail of a Yokosuka P1Y bomber.
The Kikka was designed in preliminary form to use the Tsu-11, a rudimentary motorjet style jet engine that was essentially a ducted fan with an afterburner. Subsequent designs were planned around the Ne-10 (TR-10) centrifugal-flow turbojet, and the Ne-12, which added a four-stage axial compressor to the front of the Ne-10. Tests of this powerplant soon revealed that it would not produce anywhere near the power required to propel the aircraft, and the project was temporarily stalled. It was then decided to produce a new axial flow turbojet based on the German BMW 003.
Development of the engine was troubled, based on little more than photographs and a single cut-away drawing of the BMW 003. A suitable unit, the Ishikawa-jima Ne-20, was finally built in January 1945. By that time, the Kikka project was making progress and the first prototype made its maiden flight. Due to the worsening war situation, the Navy considered employing the Kikka as a kamikaze weapon, but this was quickly rejected due to the high cost and complexity associated with manufacturing contemporary turbojet engines. Other more economical projects designed specifically for kamikaze attacks, such as the simpler Nakajima Tōka (designed to absorb Japanese stock of obsolete engines), the pulsejet-powered Kawanishi Baika, and the infamous Yokosuka Ohka, were either underway or already in mass production.
The following month the prototype was dismantled and delivered to Kisarazu Naval Airfield where it was re-assembled and prepared for flight testing. The aircraft performed well during a 20-minute test flight, with the only concern being the length of the takeoff run – the Ne 20 only had a thrust of 4.66 kN (1,047 lbf), and the engine pair had barely sufficient power to get the aircraft off the ground. This lack of thrust also resulted in a maximum speed of just 623 km/h (387 mph, 336 kn) at sea level and 696 km/h (432 mph; 376 kn) at 10,000 m (32,808 ft).
For the second test flight, four days later, rocket assisted take off (RATO) units were fitted to the aircraft, which worked and gave the aircraft acceptable field performance. The tests went on, together with a second prototype, but despite this early test stage, the J9N was immediately rushed into production.
By May 1945 approximately forty airframes had been completed and handed over to IJN home defense frontline units for operational use and conversion training. These were structurally identical with the prototypes, but they were powered by more potent and reliable Ne-130 (with 8.826 kN/900 kgf) or Ne-230 (8.679 kN/885 kgf) engines, which finally gave the aircraft a competitive performance and also made the RATO boosters obsolete - unless an 800 kg bomb was carried in overload configuration. Most were J9N1 day fighter single seaters, armed with two 30 mm Type 5 cannons with 50 rounds per gun in the nose. Some operational Kitsukas had, due to the lack of equipment, the 30 mm guns replaced with lighter 20 mm Ho-5 cannon. A few were unarmed two-seaters (J9N2) with dual controls and a second seat instead of the fuselage fuel tank. This markedly limited the aircraft’s range but was accepted for a dedicated trainer, but a ventral 500 l drop tank could be carried to extend the two-seater’s range to an acceptable level.
A small number, both single- and two-seaters, were furthermore adapted to night fighter duties and equipped with an experimental ”FD-2” centimeter waveband radar in the nose with an “antler” antenna array, similar to German radar sets of the time. The FD-2 used four forward-facing Yagi style antennae with initially five and later with seven elements (the sideway facing rods) each. These consisted of two pairs, each with a sending (top and bot) and a receiving antenna (left and right). The set used horizontal lobe switching to find the target, an electrical shifter would continuously switch between the sets. The signal strengths would then be compared to determine the range and azimuth of the target, and the results would then be shown on a CRT display.
In order to fit the electronics (the FD-2 weighed around 70 kg/155 lb) the night fighters typically had one of the nose-mounted guns replaced by a fixed, obliquely firing Ho-5 gun ("Schräge Musik"-style), which was mounted in the aircraft’s flank behind the cockpit, and the 500l drop tank became a permanent installation to extend loiter time, at the expense of top speed, though. These machines received the suffix “-S” and flew, despite the FD-2’s weaknesses and limitations, a few quite effective missions against American B-29 bombers, but their impact was minimal due to the aircrafts’ small numbers and poor reliability of the still experimental radar system. However, the FD-2’s performance was rather underwhelming, though, with an insufficient range of only 3 km. Increased drag due to the antennae and countermeasures deployed by B-29 further decreased the effectiveness, and the J9N2-S’s successes could be rather attributed to experienced and motivated crews than the primitive radar.
Proposed follow-on J9N versions had included a reconnaissance aircraft and a fast attack aircraft that was supposed to carry a single bomb under the fuselage against ships. There was also a modified version of the design to be launched from a 200 m long catapult, the "Nakajima Kikka-kai Prototype Turbojet Special Attacker". All these proposed versions were expected to be powered by more advanced developments of the Ne-20, the Ne-330 with 13 kN (1.330 kg) thrust, but none of them reached the hardware stage.
The J9Ns’ overall war contribution was negligible, and after the war, several airframes (including partial airframes) were captured by Allied forces. Three airframes (including a two-seat night fighter with FD-2 radar) were brought to the U.S. for study. Today, two J9N examples survive in the National Air and Space Museum: The first is a Kikka that was taken to the Patuxent River Naval Air Base, Maryland for analysis. This aircraft is very incomplete and is believed to have been patched together from a variety of semi-completed airframes. It is currently still in storage at the Paul E. Garber Preservation, Restoration and Storage Facility in Silver Hill, MD. The second Kikka is on display at the NASM Udvar-Hazy Center in the Mary Baker Engen Restoration Hangar.
General characteristics:
Crew: 2
Length: 8.13 m (26 ft 8 in) fuselage only
10.30 m (33 ft 8¾ in) with FD-2 antenna array
Wingspan: 10 m (32 ft 10 in)
Height: 2.95 m (9 ft 8 in)
Wing area: 13.2 m² (142 sq ft)
Empty weight: 2,300 kg (5,071 lb)
Gross weight: 3,500 kg (7,716 lb)
Max takeoff weight: 4,080 kg (8,995 lb)
Powerplant:
2× Ishikawajima Ne-130 or Ne-230 axial-flow turbojet engines, each with 8.83 kN/900 kg or 8.68 kN/885 kg thrust
Performance:
Maximum speed: 785 km/h (487 mph, 426 kn)
Range: 925 km (574 mi, 502 nmi) with internal fuel
Service ceiling: 12,000 m (39,000 ft)
Rate of climb: 10.5 m/s (2,064 ft/min)
Wing loading: 265 kg/m² (54 lb/sq ft)
Thrust-to-weight ratio: 0.43
Armament:
1× 30 mm (1.181 in) Type 5 cannon with 50 rounds in the nose
1× 20 mm (0.787 in) Type Ho-2 cannon with 80 rounds, mounted obliquely behind the cockpit
1× ventral hardpoint for a 500 l drop tank or a single 500 kg (1,102 lb) bomb
The Nakajima J9N Kitsuka (中島 橘花, "Orange Blossom", pronounced Kikka in Kanji used traditionally by the Japanese) was Japan's first jet aircraft. In internal IJN documents it was also called Kōkoku Nigō Heiki (皇国二号兵器, "Imperial Weapon No.2"). After the Japanese military attaché in Germany witnessed trials of the Messerschmitt Me 262 in 1942, the Imperial Japanese Navy issued a request to Nakajima to develop a similar aircraft to be used as a fast attack bomber. Among the specifications for the design were the requirements that it should be able to be built largely by unskilled labor, and that the wings should be foldable. This latter feature was not intended for potential use on aircraft carriers, but rather to enable the aircraft to be hidden in caves and tunnels around Japan as the navy began to prepare for the defense of the home islands.
Nakajima designers Kazuo Ohno and Kenichi Matsumura laid out an aircraft that bore a strong but superficial resemblance to the Me 262. Compared to the Me 262, the J9N airframe was noticeably smaller and more conventional in design, with straight wings and tail surfaces, lacking the slight sweepback of the Me 262. The triangular fuselage cross section characteristic of the German design was less pronounced, due to smaller fuel tanks. The main landing gear of the Kikka was taken from the A6M Zero and the nose wheel from the tail of a Yokosuka P1Y bomber.
The Kikka was designed in preliminary form to use the Tsu-11, a rudimentary motorjet style jet engine that was essentially a ducted fan with an afterburner. Subsequent designs were planned around the Ne-10 (TR-10) centrifugal-flow turbojet, and the Ne-12, which added a four-stage axial compressor to the front of the Ne-10. Tests of this powerplant soon revealed that it would not produce anywhere near the power required to propel the aircraft, and the project was temporarily stalled. It was then decided to produce a new axial flow turbojet based on the German BMW 003.
Development of the engine was troubled, based on little more than photographs and a single cut-away drawing of the BMW 003. A suitable unit, the Ishikawa-jima Ne-20, was finally built in January 1945. By that time, the Kikka project was making progress and the first prototype made its maiden flight. Due to the worsening war situation, the Navy considered employing the Kikka as a kamikaze weapon, but this was quickly rejected due to the high cost and complexity associated with manufacturing contemporary turbojet engines. Other more economical projects designed specifically for kamikaze attacks, such as the simpler Nakajima Tōka (designed to absorb Japanese stock of obsolete engines), the pulsejet-powered Kawanishi Baika, and the infamous Yokosuka Ohka, were either underway or already in mass production.
The following month the prototype was dismantled and delivered to Kisarazu Naval Airfield where it was re-assembled and prepared for flight testing. The aircraft performed well during a 20-minute test flight, with the only concern being the length of the takeoff run – the Ne 20 only had a thrust of 4.66 kN (1,047 lbf), and the engine pair had barely sufficient power to get the aircraft off the ground. This lack of thrust also resulted in a maximum speed of just 623 km/h (387 mph, 336 kn) at sea level and 696 km/h (432 mph; 376 kn) at 10,000 m (32,808 ft).
For the second test flight, four days later, rocket assisted take off (RATO) units were fitted to the aircraft, which worked and gave the aircraft acceptable field performance. The tests went on, together with a second prototype, but despite this early test stage, the J9N was immediately rushed into production.
By May 1945 approximately forty airframes had been completed and handed over to IJN home defense frontline units for operational use and conversion training. These were structurally identical with the prototypes, but they were powered by more potent and reliable Ne-130 (with 8.826 kN/900 kgf) or Ne-230 (8.679 kN/885 kgf) engines, which finally gave the aircraft a competitive performance and also made the RATO boosters obsolete - unless an 800 kg bomb was carried in overload configuration. Most were J9N1 day fighter single seaters, armed with two 30 mm Type 5 cannons with 50 rounds per gun in the nose. Some operational Kitsukas had, due to the lack of equipment, the 30 mm guns replaced with lighter 20 mm Ho-5 cannon. A few were unarmed two-seaters (J9N2) with dual controls and a second seat instead of the fuselage fuel tank. This markedly limited the aircraft’s range but was accepted for a dedicated trainer, but a ventral 500 l drop tank could be carried to extend the two-seater’s range to an acceptable level.
A small number, both single- and two-seaters, were furthermore adapted to night fighter duties and equipped with an experimental ”FD-2” centimeter waveband radar in the nose with an “antler” antenna array, similar to German radar sets of the time. The FD-2 used four forward-facing Yagi style antennae with initially five and later with seven elements (the sideway facing rods) each. These consisted of two pairs, each with a sending (top and bot) and a receiving antenna (left and right). The set used horizontal lobe switching to find the target, an electrical shifter would continuously switch between the sets. The signal strengths would then be compared to determine the range and azimuth of the target, and the results would then be shown on a CRT display.
In order to fit the electronics (the FD-2 weighed around 70 kg/155 lb) the night fighters typically had one of the nose-mounted guns replaced by a fixed, obliquely firing Ho-5 gun ("Schräge Musik"-style), which was mounted in the aircraft’s flank behind the cockpit, and the 500l drop tank became a permanent installation to extend loiter time, at the expense of top speed, though. These machines received the suffix “-S” and flew, despite the FD-2’s weaknesses and limitations, a few quite effective missions against American B-29 bombers, but their impact was minimal due to the aircrafts’ small numbers and poor reliability of the still experimental radar system. However, the FD-2’s performance was rather underwhelming, though, with an insufficient range of only 3 km. Increased drag due to the antennae and countermeasures deployed by B-29 further decreased the effectiveness, and the J9N2-S’s successes could be rather attributed to experienced and motivated crews than the primitive radar.
Proposed follow-on J9N versions had included a reconnaissance aircraft and a fast attack aircraft that was supposed to carry a single bomb under the fuselage against ships. There was also a modified version of the design to be launched from a 200 m long catapult, the "Nakajima Kikka-kai Prototype Turbojet Special Attacker". All these proposed versions were expected to be powered by more advanced developments of the Ne-20, the Ne-330 with 13 kN (1.330 kg) thrust, but none of them reached the hardware stage.
The J9Ns’ overall war contribution was negligible, and after the war, several airframes (including partial airframes) were captured by Allied forces. Three airframes (including a two-seat night fighter with FD-2 radar) were brought to the U.S. for study. Today, two J9N examples survive in the National Air and Space Museum: The first is a Kikka that was taken to the Patuxent River Naval Air Base, Maryland for analysis. This aircraft is very incomplete and is believed to have been patched together from a variety of semi-completed airframes. It is currently still in storage at the Paul E. Garber Preservation, Restoration and Storage Facility in Silver Hill, MD. The second Kikka is on display at the NASM Udvar-Hazy Center in the Mary Baker Engen Restoration Hangar.
General characteristics:
Crew: 2
Length: 8.13 m (26 ft 8 in) fuselage only
10.30 m (33 ft 8¾ in) with FD-2 antenna array
Wingspan: 10 m (32 ft 10 in)
Height: 2.95 m (9 ft 8 in)
Wing area: 13.2 m² (142 sq ft)
Empty weight: 2,300 kg (5,071 lb)
Gross weight: 3,500 kg (7,716 lb)
Max takeoff weight: 4,080 kg (8,995 lb)
Powerplant:
2× Ishikawajima Ne-130 or Ne-230 axial-flow turbojet engines, each with 8.83 kN/900 kg or 8.68 kN/885 kg thrust
Performance:
Maximum speed: 785 km/h (487 mph, 426 kn)
Range: 925 km (574 mi, 502 nmi) with internal fuel
Service ceiling: 12,000 m (39,000 ft)
Rate of climb: 10.5 m/s (2,064 ft/min)
Wing loading: 265 kg/m² (54 lb/sq ft)
Thrust-to-weight ratio: 0.43
Armament:
1× 30 mm (1.181 in) Type 5 cannon with 50 rounds in the nose
1× 20 mm (0.787 in) Type Ho-2 cannon with 80 rounds, mounted obliquely behind the cockpit
1× ventral hardpoint for a 500 l drop tank or a single 500 kg (1,102 lb) bomb
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Comments2
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"A small number, both single- and two-seaters, were furthermore adapted to night fighter"
As far as I know, specialized night fighters of that time could not be single-seat - a separate crew member was required to operate the radar.