The HRH was designed to comply with the US experimental – amateur-built rules. It features a single main rotor, a single-seat enclosed cockpit with a windshield, skid-type landing gear and a four-cylinder, air-cooled, four-stroke, 165hp (123kW)Subaru EJ25 automotive engine. It is the high power to weight ratio that gives the aircraft its name.[1][2]
The aircraft fuselage is made from a mix of welded 4130 steel tube and bolted-together aluminum tubing, with a composite cabin shell. Its 25ft (7.6m) diameter two-bladed Waitman composite rotor has a chord of 8in (20cm). The tail rotor has a 46in (117cm) diameter. The aircraft has an empty weight of 1,000lb (454kg) and a gross weight of 1,350lb (612kg), giving a useful load of 350lb (159kg). With full fuel of 18.5 U.S. gallons (70L; 15.4impgal) the payload is 239kg (527lb). The HRH can hover in ground effect at 7,000ft (2,134m) and out of ground effect at 5,000ft (1,524m)[1][2]