Mi-6 HOOK (MIL)

When first flown in 1957, the Mi-6 Hook was the world's largest rotary-wing aircraft. The Mil-6 was built for the Soviet Air forces and Aeroflot. The helicopter was designed to meet the needs for a machine able to transport heavy trucks, tracked vehicles, oil installations and other cumbersome loads, as well as of the teams of geologists working in Siberia. It was to raise heavy loads with high-altitudes in the mountainous regions.

Five prototypes were built, then a preproduction of thirty helicopters began in 1960. It is believed that five hundred would have been built by the end of 1969. The rate of manufacture would have been of eight per month in three different factories. It was delivered to export; its selling price would have been of 2 million dollars at the date of July 1965. A version of transport for 80 to 100 passengers was in the course of tests during the summer 1967. It differs from the preceding one by the port-holes from its fuselage and its interior installation. More than 800 of this heavy-lift helicopter were built before production ended in 1981.

The large, five-blade main rotor is centered over the fuselage midsection. The stabilizing wings are unequally tapered with blunt tips, mounted high on the fuselage, and tilted upward to the front. Two turboshafts are mounted on top of fuselage midsection with round air intakes above cockpit. Oval-shaped exhaust ports on sides. The fuselage is long and bus-like, with a round, stepped-up cockpit and round, glassed-in nose section and fixed landing gear. The upswept rear section has a tapered tail boom. The swept-back fin is tapered with a small rotor on right and unequally tapered flats forward of the fin.

The principal rotor has five blades and the anti-torque rotor is four-bladed. The blades of the principal rotor are made of tubular metal members, similar airfoils and a metal coating. In position of stop, their end is very low. They have one fixed at the edge of escape of their end. Their order is carried out hydraulically and their leading edge is de-iced electro-thermically. The axis of the principal rotor is tilted of 5° forwards. It turns at the speed of 120 rpm. The circumferential speed reaches 220 m/s. The blades of the rotor of tail are also de-iced thermically. The rotor is assembled on the right-sided of the higher end of beam of fuselage.

Two wings cantilever, high, are assembled laterally above the legs of the train. They have a variable incidence according to the cases of vol. Their optimal steering is obtained automatically in the event of setting in autorotation of the principal rotor. They can be deposited for certain uses, flying crane, for example. With cruising speed, they support 20% of the lift of the helicopter.

The fuselage is of monocoque semi steel construction. Of roughly square section, its height is not constantly regular. It has the many surfaces glazed with before its back part is in the shape of beam. The vertical surface, which supports the anti-torque rotor is used as vertical stabilizer. Two small side horizontal surfaces with variable incidence towards the back part of the beam are used as correct shutters. The cockpit has places for two pilots, a radio operator operator, a flight engineer and with before inferior a navigator. The cabin is capable to be arranged in several ways:

• mixed cargo & passenger liner: The passengers set in seats along side walls. Additional seats in the middle have the capacity to 65 passengers, the luggage being carried in the aerofoil. Seats in the center can be removed and side seats folded back, a broad surface provided with rings of mooring allows the carrying of freight. Loading is carried out by two doors in shells and ramp loading located at the back end of the fuselage and hydraulically ordered. A system of hoist and pulleys as well as an electric winch of capacity 800 kg allow the handling of the loads. The floor is planned for maximum masses of 2000 kg to m2
• transport: to 70 parachutists equipped;
• ambulance: Forty-one stretchers are taken along with two people of accompaniment. Oxygen equipment is planned for the casualties; flying crane: A trap door in the floor, plumb with the centre of gravity, allows the passage of a sling for carrying, up to 9000 kg , of external cumbersome loads;

Access to the fuselage is carried out by two doors on either side, right-hand side and left and a left front door. The crew can have in help particular doors of evacuation. Ten port-holes on each side light the principal cabin.

A triple hydraulic system, with separated pumps, pressure of 118 to 152 bars, feeds the flight control system, the jacks of the footbridges of access to the engines, the doors back and the loading ramp, the adjustment of the pilot seats, etc. The electric principal circuit, D.C. current 27 volts, is fed by two generators of 12 kw and batteries ensuring 30 minutes of autonomy in help. A circuit three-phase 360 V, 400 Hz, alternate, necessary to certain radio operator equipment and to de-icing, is fed by two alternators of 90 kVA. The electric de-icing is used on the leading edges of the blades of the two rotors, with the air intake of the turbomotors and the windshields. The intake guide vanes of driving compressors are de-iced by hot air. The standard equipment includes/understands the systems of radiocommunication HF and VHF of intercommunication, radio compass, radio altimeters, autopilot, radio beacon, directional gyroscope and all instruments allowing the flight by all times of day and night.

Two Soloviev D-25B (TB-2BM) turbomotors each one developing 4100 kw on takeoff and 3505 kw of nominal nominal output are mounted side by side above the cabin, in front of the hub rotor. Their shafts emerge laterally upstream of the auxiliary aerofoil, from which the coating, located in the breath, is protected by stainless sheet steels. Side hoodings, operated hydraulically, drop to form platforms necessary for the maintenance and the revision of the engines, box of gears and head of the rotor. These platforms are accessible by a scale and a trap door in the cockpit. An auxiliary group of power, including an AI-8 gas turbinedeveloping 74 kw and a generator of 24 kw, ensures the starting of the engines and the various constraints on the ground. The air intake placed immediately above the entries of the principal engines is the entry of a cooling blower.

Eleven inboard tanks containing 6315 kg of fuel feed the turbomotors. A cylindrical additional tank, capacity 1745 kg , can be carried laterally, outside on each side. Moreover, on mission of convoying, two additional reserves of 3490 kg full capacity can be gone up in the principal cabin. An automatic system guarantees that the center of gravity is maintained within the reasonable limits. The fuelling can be carried out the helicopter being in hovering.

The undercarriage is a nonretractable tricycle. The principal train is equipped with single wheels 1.325 X 480 mm with hydraulically-operated brakes. The nose gear is directional twin wheels of 720 X 310 MM with shock-absorbers under the back of the beam. The oil and air shock absorbers of the principal train are with double rooms, high and low pressure. The rooms high pressure are inter-connected, making it possible to quench the oscillations of the apparatus with full load and to remove resonance ground. Possible assembly of careenages to the wheels of the principal train.