R.Mikesh, A.Shorzoe Japanese Aircraft, 1910-1941 (Putnam)

Nakajima Type 4 Biplane

   The design of the Type 4 biplane was made very cautiously, relying heavily on the experience gained with the Type 3. The company's intention was to gain Army acceptance of the aeroplane and to eliminate the reputation for failure that lingered after the Type 1 mishap.
   For this new and better streamlined aeroplane, the fuselage had minor modifications from that of the Type 3, and the area of the wings and horizontal tail surfaces was reduced. In planform, the shape of the new wing was reminiscent of the German Albatros reconnaissance aeroplanes. Jiro Sakuma was the chief designer under the close supervision of managing director Chikuhei Nakajima. Design calculations and experiment and test phases of the project were checked by Eiji Sekiguchi and Tatsuo Miyazaki respectively. Jingo Kurihara oversaw the general management of manufacture and final assembly. Like the earlier aeroplanes, this too used a Hall-Scott A-5 engine, but this was later replaced by a Hall-Scott A-5a rated at 150hp.
   The new aeroplane was completed in February 1919 and Army evaluation gave genuine approval of its excellent performance and inflight stability. The Army agreed immediately to order a large number. Following the issuance of its letter of intent, the Army requirement was changed to twenty prototypes and production models with minor changes to that of the Type 4. The aeroplanes built to this order became the Nakajima Type 5, the first civilian-built military standard aeroplane made in Japan. Following the Army's evaluation of the Type 4 it was used by Nakajima for test purposes.
   Fame for the Type 4 had not ended. Participating in the First Tokyo Osaka Airmail Flying Contest in October 1919, sponsored by the Imperial Flying Association, the Type 4, flown by Yozo Sato, took first prize after making the round-trip flight in 6hr 58min (to Osaka in 3hr 40min, to Tokyo in 3hr 18min). Second prize was won by an American-built Graham biplane flown by Toyotaro Yamagata, requiring 8hr 28min to make the trip. This decided advantage by the Japanese-built aeroplane firmly established Nakajima in the aviation market.

   Single-engine two-bay biplane. Wooden structure with fabric covering. Crew of two in open cockpits.
   150-165hp Hall-Scott A-5a six-cylinder water-cooled inline engine, driving a two-bladed wooden propeller.
   Span 13m (42ft 8in); length 7.50m (24ft 7 1/4in); height 2.90m (9ft 6in); wing area 35sq m (376.749sq ft).
   Empty weight 700kg (1,543Ib); loaded weight 1,200kg (2,645Ib); wing loading 34.3kg/sq m 7lb/sq ft); power loading 8kg/hp (17.6Ib/hp).
   Maximum speed 70kt (80.6mph) at sea level; minimum speed 32.5kt (37.5mph); service ceiling 3,500m
(11,482ft); endurance 5hr.
   One built in February 1919.


Nakajima Type 5 Biplane

   The success of the Type 5 was almost assured because of the successful demonstrations made its the forerunner, the Type 4, and the new aeroplane went into immediate production. Approximately one hundred were manufactured for the Army, one for the Government House in Taiwan, and a small number was built to fill civilian orders. After a time, several of the aeroplanes manufactured for the Army were released because of design shortcomings, but with modifications they served well in a civil capacity. Total production was 118.
   In original production aeroplanes and those modified into civil aircraft, there were numerous differences that were made at the request of the purchasers. Paint schemes and markings also varied widely. The most widely-known user of the Type 5 was the Mizuta Flying School.
   In one aviation event after another the Type 5 performed remarkably well. In May 1921 student pilot Toshio Hino displayed remarkable aerobatic proficiency in a Type 5, taking second prize in the Second Prize-winning Flight Competition held at Susaki Airfield in Tokyo, giving the Type 5 an even greater reputation. At the Second Airmail Flying Contest, this time between Osaka and Kurume, Kyushu, in November 1920, Mizuta entered with a Type 5 powered by a 220hp Sturdevant engine, but dropped out of the race because of radiator problems. He entered the third of these competitions with a Type 5; this time the route was between Tokyo and Morioka, in northern Honshu, but without awards. When the course was once again between Tokyo and Osaka, five of the fourteen entries were the 150hp Hall-Scott Nakajima Type 5s and there was one that had a 160hp Daimler engine.
   The Type 5s remained very popular in these events. In the Tozai Teiki Kokukai (East-West Regular Air Transport Association) event sponsored by the Asahi Shimbun in January 1923, six of the eight entries were Type 5s. At the Fourth Flight Competition in June 1923, Army-released Type 5s were the majority of the entries. In December 1924 at the Ise Bay Flight Competition, four Type 5s participated and achieved high scores.

   Single-engine two-bay biplane. Wooden construction with fabric covering. Crew of two in open cockpits.
   150-165hp Hall-Scott A-5a six-cylinder water-cooled inline engine, driving a two-bladed wooden propeller.
   Span 12.606m (41 ft 4 1/4in); length 7.046m (23ft 1 1/2in); height 2.882m (9ft 5 1/2in); wing area 34sq m (365. 984sq ft)
   Empty weight 780kg (1,719Ib); loaded weight 1,130kg (2,491Ib); wing loading 33.2kg/sq m 7lb/sq ft); power loading 7.53kg/hp (16.6Ib/hp).
   Maximum speed 70kt (80.6mph) at sea level; minimum speed 32.5kt (37.5mph); service ceiling 3,400m (11,155ft); endurance 4hr.
   118 built including civil production of seventeen from April 1919 to May 1921.


Nakajima Type 5 Trainer

   In May 1919, while the Nakajima company was still in its infancy and known as the Nihon Hikoki Seisakusho, it was informed by the Army of the acceptance of its newly designed and built Type 4 trainer. After failures of previous designs, it was the Type 4 that achieved the success Nakajima needed in attaining Army recognition of its aeroplanes. With minor changes to this aeroplane, the Army requested another prototype which became the Type 5 and this was followed by an order for twenty aircraft, a figure that was later increased to one hundred. This was an astonishingly large order, as well as the first order of this type placed with a civil company. Up to that time, almost all aeroplanes used by the Army were imported or licence-manufactured. Japanese-designed aeroplanes were looked upon as only experimental and not to be considered for acceptance as standard military equipment. For these experimental aircraft and small production runs, the Army had relied upon its own Tokorozawa Branch of Army Supply Dept.
   The design of the earlier Type 4 was based largely on the successful designs of the United States Standard H-3 and the German Albatros C II. The engine for the new aeroplane was to be the imported 125hp Hall-Scott from the USA. Under the direction of the company founder, Chikuhei Nakajima, engineers adapted these design concepts into a Nakajima product. The drawings were by Jiro Sakuma and structural analysis was undertaken by Eiji Sekiguchi. Tatsuo Miyazaki and Jingo Kurihara supervised production tool making and product manufacturing respectively.
   When the first aeroplane was completed, it was delivered to the Army by surface transport to Tokorozawa Airfield where it was closely examined and assembled, making its first flight towards the end of April 1920. It showed excellent performance. The pilot was Katota Mizuta, a former Army cavalry lieutenant, and flying instructor at the Tokorozawa Army Flying School. Production aircraft were equipped with the 150hp Hall-Scott engine of greater power than the prototype. Variations included one that was tested with a 130hp Benz and a modified engine cowling.
   As the Type 5 Trainers were delivered to the Army, they were assigned to various flight regiments and fIying schools. In service, a number of defects were encountered which resulted in serious accidents. Stalls were prematurely induced because of wing ribs having been manufactured to incorrect drawings. Inflight fires were not uncommon, caused by a build-up of engine oil in the bottom of the engine cowling. On 14 October, 1920, the 60th aircraft of this type, flown by Capt Saburo Iniwa, caught fire in flight and the ensuing crash killed the pilot and the mechanic. These and other defects brought an end to the Army's use of the Type 5 as standard equipment in favour of the Type Ko 1, Type Ko 2, and Type Otsu 1.
   After 1921 and approximately a year of service, many of the Type 5s were released by the military and used as civil aircraft. As a consequence the aircraft was better known as a civil aeroplane than a military trainer. It was this initial military order, however, that placed the Nakajima company on a sound financial footing, as well as instigating the disagreements that brought about the separation of Seibei Kawanishi from the company.

   Single-engine two-bay biplane. Wooden construction with fabric covering. Crew of two in open cockpits.
   150-165hp Hall-Scott A-5a six-cylinder water-cooled inline engine, driving a two-bladed wooden propeller.
   Span 12.606m (41ft 4 1/4in); length 7.046m (23ft 1 1/2in); height 2.882m (9ft 5 1/2in); wing area 34sq m (365.984 sq ft).
   Empty weight 780kg (1,719Ib); loaded weight 1,130kg (2,491Ib); wing loading 33.2kg/sq m 7lb/sq ft); power loading 7.53kg/hp (16.6Ib/hp).
   Maximum speed 70kt (80.6mph) at sea level; minimum speed 32.5kr (37.4 mph); climb to 1,000m (3,280ft) in 7min; service ceiling 3,400m (11,155ft); endurance 4hr.
   101 built from April 1919 to May 1921 (military purchase only).


Nakajima Type 6 Biplane

   As was to be expected the Type 6 Biplane was a version of the Type 5 with improved performance. It was built in August 1919 during the production run of the first twenty Type 5s for the Army. The major difference in the Type 6 was that the airframe was designed to take the heavier and more powerful 200hp Liberty Hall-Scott L-6 engine. The L-6 was a faster-running engine, and required a smaller diameter fighter-type propeller. It could be compared with first-line military aircraft of other major countries at that time.
   The Type 6 was in existence by the time Nakajima entered the first Tokyo to Osaka Prize-Winning Flight Competition on 22 and 23 October, 1919. The Type 4 piloted by Yozo Sato was the winner. The Type 6 piloted by Katota Mizuta had been expected to win because of its greater power but Mizuta became disoriented on his way from Tokyo to Osaka and made an emergency landing near the Kinokawa River in Wakayama City, south of his destination, and was disqualified. On his return from Osaka to Tokyo, Mizuta took off from the Joto Military Parade Grounds in Osaka, with engineer Kurihara in the rear seat, and flew to Susaki Airfield in Tokyo in 2hr 10min, taking advantage of a strong tailwind. This established a new speed record between the two Cities.

   Single-engine biplane. Wooden structure with fabric covering. Crew of two in open cockpits.
   200-244hp Liberty Hall-Scott L-6 six-cylinder water-cooled inline engine, driving a two-bladed wooden propeller.
   Span 12m (39ft 4 1/2in); length 7m (22ft 11 1/2in); height 2.80m (9ft 2 1/4in); wing area 32sq m (344.456sq ft).
   Empty weight 850kg (1,873Ib); loaded weight 1,300kg (2,866Ib); wing loading 40.6kg/sq m (8.3lb/sq ft); power loading 6.5kg/hp (14.3lb/hp).
   Maximum speed 76kt (87.5mph) at sea level; minimum speed 35kt (40mph); service ceiling 3,500m (11,482ft); endurance 5hr.
   One built in August 1919.