The H-4 was designed to comply with the United States FAR 103 Ultralight Vehicles rules, including the category's maximum empty weight of 115 kg (254 lb). The aircraft has a standard empty weight of 70 kg (154 lb). It features two contra-rotating main rotors, a single-seat open cockpit without a windshield, four-wheeled landing gear and four twin-cylinder, air-cooled, two-stroke, 10 hp (7 kW) GEN 125-F engines to provide operational redundancy since the aircraft cannot autorotate in the event of a power failure.[1][2]
The aircraft fuselage is a simple open frame with a seat mounted on it. Its two coaxial, contra-rotating two-bladed rotors have diameters of 4 m (13.1 ft). The main rotors are both of fixed pitch design, with no articulation in any axis. Steering is accomplished by pivoting the rotor head on a gimbal using a control handle, in a similar manner to a weight shift hang glider. Climb and descent is controlled by increasing and decreasing the throttle. The aircraft lacks a tail rotor, as the coaxial, contra-rotating main rotors produce zero net torque. Yawing motion is produced and controlled by electronic gyroscopically-controlled differential electric braking of the main rotors. With its empty weight of 70 kg (154 lb) and a gross weight of 220 kg (485 lb) the H-4 has a useful load of 150 kg (331 lb). With full fuel of 19 litres (4.2 imp gal; 5.0 US gal) the payload is 136 kg (300 lb).[1][2]
The company indicated that it had suspended production plans by 2012 due to lack of dealers outside Japan and put the cost of a single H-4 at ¥7,500,000.00 (about US$80,887.59 in 2013). The company stated that it could build the aircraft economically only in lots of ten and at a discounted rate only in lots of one hundred. To facilitate future production, the company indicated that it was "looking for sponsors, investors and partners".[3]
On 29 June 2000, the prototype H-4, registered JX0076, was on a test flight at the company plant in Matsumoto-City, Nagano. The pilot was hovering, when the H-4 was hit by a wind gust and contacted the building, 40 m (131 ft) to the northwest and then impacted the ground. The pilot was injured and the airframe damaged.[4][5]
