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This attractive little aeroplane was the first tandem-rotor helicopter to be certificated by the U.S. Civil Aeronautics Administration for commercial use, and is also one of the smallest helicopters to be built with a tandem layout. Its development began in 1946 with the Helicopter Engineering and Research Corporation headed by D.K. Jovanovich and F. Kozloski, where a small 2-seat prototype (N9000H) was built with the designation JOV-3. This aircraft, powered by a 125hp Lycoming O-290, was flown successfully in 1948. It had 3-blade rotors of 5.64m diameter, a gross weight of 618kg, a maximum speed of 161km/h and a range of 221km.

Jovanovich and Kozloski transferred in 1949 to the newly-formed helicopter division of the McCulloch Motors Corporation, where an enlarged development of the JOV-3 was built as the MC-4 with 6.71m rotors and a 165hp Franklin 6V4-165-832 engine. This prototype (N4070K) flew for the first time on so March 1951, and soon afterwards McCulloch began the construction of a prototype MC-4C (N4071K) and three generally similar YH-30's (52-5837 to '39) for evaluation by the U.S. Army. These were slightly larger than the MC-4, having 200hp Franklins and egg-shaped tail fins mounted on outriggers below the rear rotor head. The YH-30's trials programme yielded no military orders, and no civilian customers were immediately forthcoming for the MC-4C, which was certificated by the CAA on 17 February 1953. Jovanovich persevered with the design, however, and after forming his own Jovair Corporation some years later produced N4071K in developed form as the prototype for a new 4-seat private or executive helicopter known as the Sedan 4E . The Franklin 6A-335 of 210hp was now installed and the fuselage offered comfortable accommodation and easy 4-door access to 3 passengers in addition to the pilot. A supercharged version, the Sedan 4ES, was offered with a 225hp Franklin 6AS-335. The Sedan 4E received type approval from the FAA in March 1963, and some two years later small-scale production of this version was begun; the current version, with a 235hp 6A-350 engine, is slightly heavier. In mid-1963 Jovair offered the stripped-fuselage Sedan 4A as an agricultural, training or utility cargo version, with provision for some 450kg of cargo or crop spraying equipment in place of the rear passenger compartment.

The Model MC-4 tandem-rotor light helicopter was the first aircraft to be developed by McCulloch Motors' Aircraft Division, and made its first flight in March 1951. The Army acquired three examples of the slightly modified Model MC-4C in 1952 for engineering test and evaluation, designating the machines YH-30 and allocating them the serials 52-5837 through -5839.

The YH-30 was a craft of relatively simple construction, consisting of a steel tube framework to which was attached a light metal skin. The helicopter's single 200hp Franklin engine was mounted horizontally amidships and drove the two inter-meshing tandem rotors through a single horizontal drive shaft and two right-angled reduction units. Two small endplate rudders were fixed to the rear fuselage to provide additional lateral stability, and the aircraft was equipped with wheeled tricycle landing gear. The craft's two crew members enjoyed better than average visibility to the front and sides, though the view upward was blocked by the overhanging front rotor housing.

The Army's evaluation of the YH-30 showed the helicopter to be somewhat underpowered and its drive system to be overly complex. The type was therefore not procured in quantity, and the three evaluation machines were declared surplus in mid-1953 and disposed of.

 

 

 

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