Nakajima Kikka

The , initially designated , was Japan's first turbojet-powered aircraft. It was developed late in World War II, and the single completed prototype flew only once, in August 1945, before the end of the conflict.

The early development of the Kikka was influenced by, but was not a direct copy of, the Messerschmitt Me 262, the world's first operational jet-powered fighter aircraft. A Japanese military attaché had reported back from Nazi Germany after witnessing trials of the Me 262 in 1942, and a subsequent technical mission to Germany set about transferring the technologies and associated engineering information for the BMW 003 axial-flow turbojet engine and other jet-related material to Japan, although these efforts were not straightforward. During September 1944, the Imperial Japanese Navy requested that Nakajima design an jet-powered combat aircraft capable of speeds of at least 430 miles per hour while carrying a 1,100-pound bomb and possessing an operational range of no less than 125 miles. In line with Imperial Japan's declining military position, it was also stipulated that the airframe should be largely suitable for production by unskilled labour and fitted with foldable wings to better permit its storage within tunnels and aircraft shelters across the home islands.

In contrast to the Me 262, the Kikka possessed a more compact airframe and featured a straight wing (instead of a swept wing), and was originally not intended to even have landing gear, although this choice was later reversed. To assist the early jet engines, it was also to be capable of using a pair of rocket-assisted take-off (RATO) boosters. The Kikka featured an all-metal airframe. It was intended to be deployed not only as a tactical bomber but also in the interceptor role. Early on, the designer had intended to power the aircraft using a pair of Tsu-11 motorjets, however, this was switched to a pair of Ishikawajima Ne-20 axial-flow turbojet engine (which were more closely based on the BMW 003 units that had powered the Me 262) instead. At one stage, there were ambitions to have nearly 500 Kikkas completed before the end of 1945.

The first aircraft performed its maiden flight on 7 August 1945; it was damaged four days later by a hard landing. Only a single Kikka was ever completed prior to the Surrender of Japan that ended the conflict. At least three airframes and various engines were transported to the U.S., where they underwent technical analysis. No nation ever made operational use of the type. Two examples are in the collection of the National Air and Space Museum in the U.S.

Design and development

The origins of the Kikka are closely associated with the development of the world's first jet-powered fighter aircraft, the Messerschmitt Me 262. Trials of the Me 262 conducted in 1942 had been witnessed by a Japanese military attaché in Nazi Germany and enthusiastically reported back to the Japanese government. Further requirements included the airframe being built largely with unskilled labor, and that it should have foldable wings. The latter feature would enable the aircraft to be hidden in tunnels and aircraft shelters around Japan as the nation was preparing for the defense of the home islands. Nakajima designers Kenichi Matsumura and Kazuo Ohno produced an aircraft that bore only a superficial resemblance to the Me 262. One early decision was to place the engines in pods that were slung underneath each wing, which made it easier to install and test a variety of powerplants.

Operational history

thumb|right|The Nakajima Kikka, equipped with [[JATO|RATO rockets for lift off]]

The first prototype commenced ground tests at the Nakajima factory on 30 June 1945. The following month, it was dismantled and delivered to Kisarazu Naval Airfield where it was re-assembled and prepared for flight testing. The maiden flight took place on 7 August 1945 (the day after Hiroshima was bombed by atomic bomb), with Lieutenant Commander Susumu Takaoka at the controls. The aircraft performed well during a 20-minute test flight, with the only concern being the length of the takeoff run. For the second test flight, four days later (four days prior to Japan's declaration of surrender), rocket-assisted take-off (RATO) units were fitted to the aircraft. The pilot had been uneasy about the angle at which the rocket tubes had been set, but, with no time to correct them, they decided to simply reduce the thrust of the rockets from 800 kg to only 400 kg. Four seconds into take off the RATO was actuated, immediately jolting the aircraft back onto its tail leaving the pilot with no effective tail control. After the nine-second burning time of the RATO ran out, the nose came down and the nose wheel contacted the runway, resulting in a sudden deceleration, however, both engines were still functioning normally. At this point, the pilot opted to abort the take off but fighting to brake the aircraft and perform a ground loop only put him in danger of running it into other installations. Eventually, the aircraft ran over a drainage ditch, which caught the tricycle landing gear, and the aircraft continued to skid forward and stopped short of the water's edge. Five of these were two-seat trainers.

Postwar

thumb|right|A Kikka stationed at the [[Naval Air Station Patuxent River|Patuxent River Naval Air Base, Maryland, 1946]]

thumb|Nakajima Kikka in the [[Steven F. Udvar-Hazy Center]]

After the conflict, airframes 3, 4, and 5 (and possibly other partial airframes) were brought to the U.S. for study. Today, two 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, Maryland. The second Kikka is on display at the NASM Udvar-Hazy Center in the Mary Baker Engen Restoration Hangar. Correspondence in 2001 with Japanese propulsion specialist Kazuhiko Ishizawa theorized that Nakajima constructed the Museum’s Kikka airframe for load testing, not for flight tests. This may explain why the engine nacelles previously fitted on the Museum’s Kikka airframe are too small to enclose the Ne-20 engines. Furthermore, Susumu Watanabe, who was in charge of engine outfitting for the Kikka, recalled that the engine nacelles of the strength tester were the same as the standard aircraft, and that the strength tester was stressed until failure. Based on this information, the mock nacelles were potentially added for display purposes after transit to the United States.

Two Ne-20 jet engines had been taken to the US and sent for analysis to the Chrysler Corporation in 1946. This was only revealed in 2005 by W. I. Chapman, who was in charge of the project at the time. A working engine was assembled with the parts of the two Ne-20s, and tested for 11 hours and 46 minutes. A report was issued on 7 April 1947, titled "Japanese NE-20 turbo jet engine. Construction and performance". The document is now on display at the Tokyo National Science Museum.

Variants

Nakajima Aircraft Company developed some variants of the aircraft:

Five of the planes under construction at the end of the conflict were to be completed as two-seat trainers.

Operators

;

Imperial Japanese Navy (planned)

Specifications (Kikka)

thumb|right|Ne-20 engine taken from the second Kikka prototype on display at the [[Steven F. Udvar-Hazy Center in Chantilly, Virginia]]