Dehradun, July 20 -- The Aircraft Accident Investigation Bureau's (AAIB) preliminary report into the May 8 helicopter crash in Uttarkashi district of Uttarakhand revealed that the accident was caused by an overhead fibre cable that struck the helicopter's main rotor blade during emergency landing. The Bell 407 helicopter, operated by Aerotrans Services Pvt Ltd, was en route from Kharsaili in the Yamunotri Dham to Jhala helipad in Gangotri Dham when it plunged into a gorge about 200-250 metres deep in the Gangnani area of the district, killing six people and grievously injuring another onboard. As per the AAIB report, released on Saturday, the chopper was airborne for about 20 minutes before it began descending from its cruising altitude. Pilot Robin Singh (59), who had 6,160 hours of flying experience, attempted to make an emergency landing on the Uttarkashi-Gangotri road near Gangnani. However, during the landing, the chopper's main rotor blade hit an overhead fibre cable running parallel to the road, leading to the crash. "The aircraft failed to land and subsequently tumbled down the hillside, eventually coming to rest against a tree roughly 250 feet into a gorge," the report said. The report states that the US's National Transportation Safety Board (NTSB) and Canada's Transportation Safety Board (TSB), Canada have appointed official representatives and technical advisors to assist with the investigation of the crash. The AAIB also made public its interim report on another incident, involving a two-seater Cessna 152 that crashed in Mehsana's Ucharpi village on March 31 during a training sortie, leaving the trainee pilot seriously injured. According to the report, the Cessna 152, manufactured in 1984, had undergone a scheduled inspection just a day prior to the crash....