Mi-8 crash in Karachai-Cherkessia in summer 2011: no human factor revealed

On the 29th of August, 2011 in Karachai-Cherkess Republic, 2 km away from Arkhyz there was an aircraft occurrence with PANH Helicopters Mi-8MTV-1 RA-25560. The aircraft had a hard landing in mountainous area. Two crew members and three passengers were injured, the aircraft sustained damages.

On the 20th of June 2013 Interstate Aviation Committee officially reported about completion of aircraft occurrence investigation. The official report states the following:

“The reason for the accident occurrence involving Mi-8MTV-1 RA-25560 was insufficient aircraft performance necessary for a safety flight (landing or go-around maneuver) in actual flight conditions (altitude, speed, OAT, aircraft flight weight, landing pad peculiarities), which met established limitations described in the AFM; there was a self-induced right engine power reduction after it was switched to take-off mode before hovering over the landing pad, which resulted in an abrupt descend, collision with the ground and major damages to the aircraft.

Right engine power decrease led to abnormal performance of engine electronic regulator ЭРД-3ВМ series 2 No. 06882074 due to the failure of integrated microcircuit 580ВВ55 on microcomputer 8Т5.103.093 No. 082.08.04.

The failure of microcircuit 580ВВ55 series 0711 occurred due to welding seal damage of electrical conductor No. 22 that was connected to the transversal contact plate. Damage occurred due to defective ultrasonic welding.

The reason for this type of manufacturing fault is most likely lies in poor quality control of microcircuit manufacturing. Investigation results brought recommendations for flight safety improvement”.