A series of experimental types appeared in the 1930s, including the Ki-19 mid-wing twin-engine bomber.
Era
Nakajima Ki-12
A series of experimental types appeared in the 1930s, including the Ki-12 low-wing monoplane with retractable landing gear.
Nakajima Type 1
In 1917, Chikuhei Nakajima set up the “Airplane Institute” at Ojima Town in Gunma Prefecture. In 1918 they built their first airplane; the “Nakajima Type 1” with a U.S.A. made engine.
In 1917, Chikuhei Nakajima (33 years old at that time), who retired as Engineering Captain of the Navy, contemplating developing a public aircraft industry, set up the “Airplane Institute” at Ojima Town close to Ota Town in Gunma Prefecture (currently Ota City). The building was a simply remodeled sericultural hut along the Tone River. In the beginning, there were only nine members, but in the following year they built their first airplane; the first “Nakajima Type 1” with a U.S.A. made engine. But the first Type 1 sadly crashed after take off. The second Type 1 also failed, and the third one finally did take off, but hit a ditch upon landing and also crashed. In that age, it was said that there was a pasquinade in Ota Town, “Too much paper money, too high a price for rice. Everything goes up, except Nakajima planes”.
Nagoya-Sento Ki-001 BEN

Confusion over pre-war Japanese fighters was so complex many fictional or misidentified types received code names.
After the Pearl Harbor attack military intelligence gathered every piece of downed Japanese aircraft they could find. From that operation they came up with this aircraft. They found a manufacturing plate with the words Nogoya Sento, they thought that was a manufacturer, it was a plant location. From the wings and tail group, it looks like they found parts of an Aichi type 99 Val.
Given the allied code name ‘BEN’ after one of the 5th Air Force Intelligence officers, the code was dropped in less than a year.
It was 1943 before the war department figured out there was no such a plane.
Naglo D II

The DII quadruplane built by the Naglo Werft of Pichelsdorf, near Berlin, was designed by Ing Gnädig (who was, at the time, still in the employ of the Albatros Werke) and participated in the second D-type contest at Adlershof in the summer of 1918 (the debriefing minutes of which indicating that it was to appear for further testing after modification). Powered by a 160 hp Mercedes six-cylinder water-cooled engine and inten¬ded to carry an armament of two LMG 08,15 machine guns, the Naglo DII appears to have been based on an Albatros DV type fuselage. The bottom wing, completely independent of the three main lifting surfaces, being attached to an extruded keel and braced with splayed struts. Official type testing was undertaken on 24 May 1918, and during the D-type contest, evaluation pilots praised the excellence of the construction and workmanship of the D II while calling for an improvement in the flight characteristics.
Engine: Mercedes 6 cyl, 160hp
Empty weight: 1,596 lb (724 kg).
Loaded weight: 2,015 lb (914 kg
Span: 29 ft 6 1/3 in (9,00 m).
Wing area: 241.12 sq ft (22.40 sq.m).
Nagler-Rolz NR 54

Development of the NR 55 concept continued in 1941 with the generally similar NR 54 V1, in which reductions were made in size and weight. The engine power was reduced to 24hp and the rotor diameter to 7.8m with the engines mounted 1.2m from the centerline driving the propellers, which were 1.8m further out along rotor blade. The carburetor was never perfected to work satisfactorily and due to this no test flights were ever made. Performance with empty and loaded weights of 80 and 175kg respectively, was estimated to have a 55 mph cruising speed.
The NR 54 V2 was produced in 1941. The single-seat helicopter flew on remarkably little power. The 6.9m rotor consisted of two single blades, each of which had an 8hp motor driving a small airscrew at 6000rpm to give a torqueless drive, and the pilot’s controls consisted of two levers, one to alter rotor blade pitch and the other to control the engines. The entire airframe broke down for transporting and could carried by a single man. The little ship was said to cruise at 80km/h and climb at 140m/min.

Four of the NR 54V2 machines were built before the war ended, but it is not known how close the NR 54 was to being ready for production at that point. At least one of them was brought to the USA for evaluation and is now in the collection of the National Air and Space Museum.

NR 54 V2
Engine: 2 x 8hp
Main rotor diameter: 7.92m
Max take-off weight: 140kg
Empty weight: 36.5kg
Cruising speed: 80km/h
Ceiling: 457m
Range: 48kg
Crew: 1
Nagler-Rolz NR 55
The Nagler-Rolz Flugzeugbau built a helicopter similar in configuration to the RI and RII. This ship had an empty weight of 700 pounds and though it was flown in hover, it could not be lifted out of ground effect. With the coming of World War II, the company received contacts from the German Government for the development of small single-seat helicopters.
In 1940 the first machine from the new company appeared as the NR 55, which had a single-blade rotor. This rotor blade was counterbalanced by a 40hp engine which applied to it a torqueless drive by means of two small airscrews which pulled it round at about 135rpm. Because of gyroscopic forces at the engine location, the carburetor was mounted on the centerline of the rotor hub and fuel-air mixture was piped out to the engine cylinders. The rotor diameter was 10.5m, and the machine weighed about 338kg loaded, but, although a cruising speed of 97km/h was thought feasible, only hovering and lift test were undertaken because the machine was built purely for testing the rotor system.
Development of the NR 55 concept continued in 1941 with the generally similar NR 54 V1.
Nagler-Rolz Flugzeugbau
With the outbreak of war, Nagler joined with Franz Rolz to form the Nagler-Rolz Flugzeugbau.
The new company built a helicopter similar in configuration to the RI and RII. This ship had an empty weight of 700 pounds and though it was flown in hover, it could not be lifted out of ground effect. With the coming of World War II, the company received contacts from the German Government for the development of small single-seat helicopters.
Nagler Honcho
The 1972 single-place Honcho 100 (N1750Z) was powered by an AiResearch 85-90 gas turbine feeding compressed air to the rotor.
The 1973 two-place Honcho 200 and Honcho 202 were was powered by a Solar-T-62-Titan gas turbine.
Honcho 100
Engine: AiResearch 85-90 gas turbine
Rotor: 28’7″
Length: 10’9″
Useful load: 275 lb
Honcho 200
Engine: Solar-T-62-Titan gas turbine
Honcho 202
Engine: Solar-T-62-Titan gas turbine
Nagler VG-1 Vertigyro
The 1963 VG-1 Vertigyro (N5395Z) comprised a Piper Colt aircraft fuselage, complete with engine and prop. Its Sud Djinn rotor system was driven by a turbine engine, enabling the craft to be flown as a gyroplane, a helicopter, or a combination of both. Only the one was built.
The vehicle could take off and fly as a helicopter at 75mph, powered by a Garret-AiResearch GTC-85-90 gas turbine to feed compressed air to nozzles in the two-blade rotor, then convert into an autogyro to do 85mph powered by the one 108hp Lycoming O-235.
Engines: 1 x Garret-AiResearch GTC-85-90 gas turbine / 1 x Lycoming O-235, 108hp
Rotor diameter: 36 ft 0 in
Minimum gyro speed: 45 mph
Seats: 2