V-8 Single-Turbine Prototype
Since Plant No. 329 possessed only limited production facilities, construction of the fuselages and some other major parts of the first five V-8 prototypes took place at Moscow aircraft plant No. 23 situated in Fili (then a suburb of Moscow, now absorbed by the city). The finished elements of the airframe were delivered for final assembly to Plant No. 329. The first V-8 prototype powered with a single AI-24V engine was completed by the early summer of 1961. Unfortunately, not all of the proposed alterations could be effected at once.
The first prototype retained some elements of its Mi-4 predecessor: four-blade main rotor and three-blade tail rotor, swashplate and many other components of the flight control system; transmission, main landing gear units and tail bumper; the tailboom and the tail rotor pylon. As for the forward and center parts of the all-metal semi-monocoque fuselage of the V-8, they were completely new. For the first time large duralumin stampings and bonding were used in the fuselage construction. The forward fuselage was occupied by a comfortable and extensively glazed cockpit with excellent view for the pilots; the space under the flight deck floor housed DC batteries. The helicopter had a crew of three: captain, co-pilot/navigator and flight engineer. Their workstations were placed side-by-side: the pilots' seats were located to port and starboard of the passage from the cockpit into the passenger/cargo cabin, and the flight engineer's folding seat was placed between them. The flight instruments were conveniently arranged on the overhead electric switch panel and on instrument panels before the two pilots to port and starboard. The cockpit was accessed via lateral car-type doors.
The central fuselage was occupied by a cargo/passenger cabin measuring 5.34 by 2.34 by 1.8 m, the aft part of it ending in a full-section hatch with clamshell doors; it also comprised engine and main gearbox compartments and the service fuel tank. The cargo cabin of the V-8 was intended for transportation of cargoes and vehicles with a total weight of up to two tonnes. The rugged floor of the cabin incorporated a pulley and tie-down points for securing the cargo; a winch was located in the forward part of the cabin. Wheeled vehicles, various cargoes and stretchers with patients or casualties were loaded with the help of detachable ramps through a hatch with clamshell doors at the aft end of the cabin. Besides, small cargoes could be loaded through a side entry door on the port side of the cabin. Provision was made for a hoist of 150 kg capacity externally above the door for use in rescue operations. For the carriage of underslung bulky cargoes, the V-8 was equipped with a hinge-and-pendulum external sling system - a novel feature - capable of handling the loads of up to 2,500 kg . The prototypes had rectangular cabin windows. The engine and main gearbox access panels made it possible to service all the aggregates in the upper part of the helicopter without using step-ladders. Two external fuel tanks were attached to the sides of the fuselage by steel straps. The tail boom carried a horizontal stabilizer; its incidence could be adjusted on the ground.
Since it was the Civil Air Fleet authorities that had initially shown the greatest interest in the new helicopter, the first V-8 prototype was submitted for testing in passenger configuration. Its comfortable passenger cabin was provided with 18 seats. That was the number of passengers intended to be transported to a distance of 450 km. For shorter routes the Mil EDB developed a version with 23 passenger seats. The troop-carrier version developed for the military customer was to be equipped with seats for 14 troops. The helicopter could easily be adapted for ambulance duties, in which case it could carry 12 stretcher patients and a medical attendant. However, the transformation of the V-8 into other versions which had been planned initially did not materialize because of corrections introduced into the test programme by the development of the twin-engine version.
The single-engine V-8 took to the air for the first time on 24th June 1961 under the control of the test pilot Boris V. Zemskov. Manufacturer's tests proceeded smoothly. It was obvious from the outset that it was a good machine, but Mikhail L. Mil' was not in a rush to submit it for State acceptance tests. The V-8 was used primarily for demonstration purposes. On 9th July, just two weeks after the first flight, the helicopter took part in a new aircraft display and air fest in Tushino; later it was put on show at the Exhibition of National Economy Achievements (VDNKh) in Moscow.
Everywhere the new helicopter attracted considerable interest; once Nikita S. Khruschchov even held a meeting of the Politbureau of the Central Committee of the Communist Party in the passenger cabin of the V-8. All these events helped to enhance government support for the programme intended to provide for a successor to the Mi-4, the so called air workhorse. In December 1961 the first V-8 prototype was presented for joint State trials, but the period when it was regarded as a prototype for the future production version did not last long. From 1963 onwards it was used only as a flying test bench.
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