 The engine was Ivchyenko's AI-26 seven-cylinder radial, the version chosen being the 575hp AI-26GRFL designed to operate with crankshaft vertical. This drove via a cooling fan and centrifugal clutch to a main gearbox which turned the single main rotor at 232 (not 233) rpm, with a bevel drive to a shaft carried on external trunnions along the top of the long tail boom to a 2.6m three-blade tail rotor. The latter counteracted the main-rotor drive torque and provided yaw (directional) control, driven by pedals. Both rotors were again of fabric-skinned wood laminates, the main rotor having manual control via swash-plates, with spring-loaded automatic autorotative control following loss of drive torque. The fuselage was again based on a welded-tube truss, with unstressed D1 skin, but the tail boom was a D1 semi-monocoque. The main gearbox was housed in a large mast fairing above the engine compartment, with a front air inlet for the fan-assisted oil cooler. Again the undercarriage was a simple tricycle, with a castoring levered-suspension nosewheel and triangular-braced main units with oleo shock struts pinned to the upper longerons. Track was 3m and wheelbase 2.865m. The entire front of the fuselage was transparent, with sliding doors on the right for the pilot and on the left for the backseater (who had dual control in the first prototype). The transport version was to have a two-seat divan at the rear. Two prototypes built, first with VVS funds and bearing VVS insignia. The first prototype was tested from November 1948. Initially suffering from severe vibration and apparent blade flutter, the lades given ground-adjustable TE tabs and eventually modified with CG further aft, behind flexural axis. These blades first fitted to No.2 Yak-100, which began test July 1949. Gradually problems with vibration and flutter were solved, and a second prototype was built with modified blades with the cg behind the flexural axis which greatly improved behaviour without complicated damper systems. This dubler, first flown in July 1949, had a more-fully enclosed engine bay with grilled panels and an internally mounted tail-rotor drive shaft. NII-VVS testing took place in the second half of 1950. Factory test complete June 1950 and NII tests successfully accomplished later same year, but Mi-1 already adopted and Yak-100 project was lost dropped. Yak-100 Total length: 13.91m Main rotor diameter: 14.50m Tail rotor diameter: 2.60m Empty mass: 1805kg Max take-off weight: 2180kg Max. speed: 170km/h Static ceiling: 2720m Dynamic ceiling: 5250m Range: 325km Crew: 1-2  |
