KUGISHO* 18 Shi FIELD RECONNAISSANCE AIRCRAFT "KEIUN"**
*Short for "Koku Gijutsu-sho" (Aviation Technical Arsenal). The "Yokosuka Kaigun Ko-sho" (Yokosuka Naval Arsenal) was known by various acronyms depending on the names the Arsenal received at various times of its history. "Yokosho" is one, but there were also "Kusho" (Kaigun Koku-sho), "Kugisho" (Kaigun Koku Gijutsu-sho) and "Ichi-Gisho" (Dai-Ichi Kaigun Gijutsu-sho). "Yokosuka" is the most "popular" name but early pre-WWII aircraft types are commonly referred to as "Yokosho" in Japanese literature. Later types like the "Suisei" or "Ginga" are usually referred as "Kugisho". In the Western literature (ex. Francillon) they are all called "Yokosuka".
** Not "Beautiful Cloud" as in Francillon. Japanese give names to clouds depending on their shape, from proverbs and other things. For example, the cloud known as "Cirrocumulus" in Japanese is called "Urokogumo" ("Cloud with the shape of a fish scale"; Uroko=fish scale, Kumo=cloud). Another example, "Cumulonimbus" in Japanese is "Nyudogumo" ("Cloud with the shape of a Buddhist monk's shaven head"). The rare and beautiful phenomenon called Cloud Iridescence was always seen by the Japanese as an exceptional event and the clouds were called by a variety of names like "SAIUN", "ZUIUN", "SHIUN", "KEIUN" and more (note that all are IJNAF aircraft type names). According to Buddhism, Amida Nyorai appears on the deathbed of a person on a 5-color cloud to take the deceased to heaven (see Japanese painting called Raigo). So the Cloud Iridescence phenomenon where the clouds seem to take various colors like a rainbow reminded the Japanese of the 5-color cloud and the paintings of Buddhist tradition and therefore gave the iridescent clouds such names as "Shiun" which was considered to be a sign of auspicious events or "Keiun" a chance to celebrate, a happy event.
Therefore, it is understandably extremely difficult to translate some aircraft names into English and Western aviation authors had to cut many corners.
P. 254 - PHOTO CAPTION:
"Keiun" was an aircraft with an eccentric outward appearance but the design was obviously a failure.
From the outbreak of war in the Pacific, the lack of a land-based reconnaissance aircraft with cutting-edge performance that could cover such a vast theater was keenly felt by the Navy. Since the prototype for the 13-Shi twin engine fighter (Made by Mitsubishi, mentioned in Francillon, page 547) requirement was rejected, this mission was diverted to the Type 2 field Reconnaissance aircraft or Nakajima J1N(Irving). But both their numbers and their performance were limited, and in order to augment their service, the JNAF made arrangements with the Army to "borrow" a few of their Type 100 Command Reconnaissance or Mitsubishi Ki-46 (Dinah) aircraft.
By 1943, a solution seemed near, as Kugisho started to test- produce the 18-Shi Field Reconnaissance Aircraft, purposely designed to JNAF requirements and assigned the name "Keiun".
Early in its design stages, a fateful decision was made for the in-line installation of two German DB601 liquid-cooled engines, produced domestically in Japan as "Atsuta" (Type 30), in what was termed a "twin-type" mounting, with the two powerplants buried front-and-back in the fuselage. The engines were connected, to each other and to the propeller, via a long extension shaft. It was a bold technique by which to meet a longstanding problem of insufficient horsepower; but with mediocre results.
By this stage of the war, severe attrition in air combat and Allied ground attacks meant an urgent need for the development of additional aircraft of all types, so in retrospect it's difficult to understand why such an eccentric design was allocated so much time and funding. But once both had been invested, apparently the Navy found it hard to admit defeat, though eventually few Navy insiders backed the project; objections to its further development mounted, and in June 1944, it was decided to halt the test-production of Keiun “temporarily.”
Plans had already been drawn up, however, to equip the type with jet engines and produce it as an attack bomber, that would be called "Keiun Kai". Thus the development of a "Keiun" to be used as a research plane for that program began, with one airplane being finished by the end of April, 1945.
But the reckless engine arrangement often caused problems and the test flights conducted until the end of the war, were not satisfactory. The plane was just a waste of valuable labor and materials during the war.
Artist’s impression of the proposed "Keiun Kai".
The "Keiun Kai" was to be based on the "Keiun", equipped with two "Ne-330" turbojet engines, installed side-by-side inside the rear section of the fuselage, with an air intake arrangement at the tip of the nose. But since the "Ne-330" never came to fruition as a viable aircraft engine, and the earlier model of "Keiun" was of unreliable and disappointing performance, it is doubtful that the "Keiun Kai" would have seen mass production even if the war had continued.
From Koku Fan Illustrated No.99
The text follows Francillon's (pages 472-475) more detailed history of the plane. Only differences or extras are the following: The test flights of the plane were conducted on May 27 and 29 (Note that Francillon mentions May 8 with pilot's name, not mentioned in Koku Fan). In the first test flight, it just took off and in the second, flew until altitude 600 m. but had engine overheating (fire occurred) problems. Flying time was about 10 min and although handling problems didn't occur, it had the same problems with the He119. (Nothing is mentioned about the changing of the engine or it's final fate as in Francillon).
In the "Keiun Kai", the twin jet engine's exhausts, would be positioned close to the tail, so the horizontal tail surfaces were to be positioned higher. (Note this detail in the design in the X-planes).
From "Nihon Riku-Kaigun Shisaku / Keikakuki":
Wing Span: 14.0m
Full Length: 13.05m
Full Height: 4.24m
Fully Equipped: 8,100kg
Engine: Aichi "HA 70" 01 Type water cooled (?) V type twin-type 24 cylinders 3,400hp X 1
Max. Speed: 783km/h (estimated)
Range: 1,269km (estimated)
From Koku Fan Illustrated No.99:
same as above plus:
Wing Area: 34.0 m2
Max. Weight: 9,400kg
Propeller: VDM constant speed 6 blade, diameter: 3.800m
Fuel: 1,556 l. + 1,764 l.
Max. Speed: 741km/h (at 10,000m)
Cruising Speed: 463km/h (at 4,000m)
Landing Speed: 166km/h
Min. to 10,000m: 21
Practical High Altitude: 11,700m
Flying Range: 3,6km
Data for "Keiun Kai":
Wing Span: 14.00m
Full Length: 9.250m
Wing Area: 34.00 sqm
Fully Equipped: 8,850kg
Fuel: 5,000 l.
Max. Speed: 783-796km/h (at 6,000m),
Landing Speed: 159km/h,
Climb to 10,000m: 7 min.
Practical Altitude: 10,500m
Armament: Torpedo (!!!!?????) or 800kg bomb.
Note the inconsistency between the weight/fuel capacity of "Keiun" and "Keiun Kai".