The Helicopter Engineering Research Corporation was established by D. K. Jovanovich in Philadelphia immediately after the war. His initial design concept was for a coaxial rotor helicopter which had a large three-blade primary rotor and a secondary two-blade unit - but also had a small tail rotor. This design did not get further than the drawing board, but Jovanovich was influenced by his design team, who had largely come from Piasecki, to create the JOV-3 tandem rotor machine powered by a 100hp Franklin engine. It had a neat fuselage of steel tube covered with aluminium and fabric, with a tricycle undercarriage and a forward cockpit for two occupants seated in tandem. The rear pylon allowed the rear rotor to turn on a higher plane than the forward rotor so that the arcs could overlap safely.
The JOV-3 prototype (N9000H) was built and flown in 1948. It was subsequently fitted with a 125hp Lycoming O-290. Jovanovich transferred the design to the McCulloch Motors Corporation and a new prototype, the McCulloch MC-4 (N4070K) was constructed - this time with a 165hp Franklin 6V4-165-B32 powerplant.
McCulloch gained the interest of the U.S. Army and built three examples of the MC-4C, which were designated XH-30 (serials 52-5837 to 52-5839). These were substantially similar to the earlier variants, but had a further power increase to a 200hp Franklin 6A4-200-C6 engine. The U.S. Navy also received two similar XHUM-1 (Bu. 133817 and 133818). Unfortunately, neither the Army nor the Navy could find a role for the MC-4 and McCulloch subsequently lost interest, with three of the five evaluation aircraft being returned to Jovanovich. One example of the HUM-1 exists at the Pima County Museum in Arizona, and an XH-30 is held at the Fort Rucker U.S. Army Museum.
Jovanovich formed Jovair Corporation and modified the first production MC-4C (N4071K) into the four-seat Jovair Sedan 4E. Another engine upgrade took place with fitment of the Franklin 6A-350, and the Sedan was given a type certificate in 1962. One further Sedan 4E was built (N6570C). Jovair also built one example of the Jovair 4A (N4091K), which was a stripped-down open-frame version of the Sedan for training and general utility tasks. They intended to produce the Model 4ES with a supercharged 225hp Franklin 6AS-335, and a Model 4U crop spraying variant, but plans for these were eventually abandoned.
Jovair lost heart over the Sedan and the design rights were sold to Hughes, but they designed a small two-seat autogyro, the J-2, which was flown in June 1962. This prototype (N4068K) was an all-metal machine with side-by-side seating, tricycle undercarriage and a stub wing mounting twin booms with a conventional tailplane and tailfins. The autogyro rotor was mounted above the cabin and the J-2 was powered by a 180hp Lycoming O-360 engine which drove a propeller mounted behind the cabin.
At this stage, McCulloch returned to take charge of the Jovanovich helicopters and went on to certificate the J-2 in May, 1970. The J-2 then went into production with the first delivery to Colley Equipment in April 1971. The production target was an output of two aircraft per day but just 96 examples had been completed when production ceased. The design was then taken over by Aero Resources of Gardena, California (believed to be a reconstitution of McCulloch), but it appears that they produced no further examples of the J-2.
R.Simpson "Airlife's Helicopter and Rotorcraft", 1998