Dynamic rollover contributed to 2015 Key Lake crash: TSB
June 3, 2016 By Transporation Safety Board of Canada
In its investigation report (A15C0005) releasedon Thursday, the Transportation Safety Board of Canada (TSB) found that an unanticipated increase in cable tension during stringing operations, along with other events, led the helicopter to a collision with terrain. The helicopter sustained substantial damage. The pilot, who was the sole occupant, sustained serious injuries but was able to evacuate without assistance.
On January 21, 2015, the pilot of a Eurocopter AS350 B2, operated by Airspan Helicopters Ltd., was conducting aerial work approximately 11 nautical miles southeast of Key Lake Airport, Sask. The work consisted of pulling feeder cable through a row of electrical transmission towers using a 37 foot–long tool called a needle. The pilot completed the first 10 towers of the centre phase without incident. As the pilot was continuing the stringing operation, the needle suddenly lunged and abruptly stopped. The helicopter then began an uncommanded roll and rotation to the left, descended, and collided with the terrain.
The investigation found that the needle’s abrupt stop was possibly caused by the needle contacting the tower or by the feeder cable catching on an obstacle on the ground. The consequent increase in cable tension, in conjuction with a slight drift of the aircraft and a crosswind, contributed to an effect called dynamic rollover, which led to the loss of control and subsequent collision with the ground.
The investigation also revealed a number of systemic safety risks. These included: training that does not adequately prepare pilots for abnormal flight conditions; not using available shoulder harnesses; not following normal checks and procedures; inadequate ground monitoring; and incomplete and unclear flight manual supplements.
Airspan did not have a fully implemented safety management system in place, but it was not required to by regulation. The TSB has identified safety management and oversight as a Watchlist issue. As this occurrence demonstrates, some transportation companies are not effectively managing their safety risks. The Board has been calling on Transport Canada (TC) to implement regulations requiring all operators in the aviation industry to have formal safety management processes and for TC to oversee these companies’ safety management processes.
Following the occurrence, Airspan suspended AS350 helicopter stringing operations until further notice. They reviewed and amended their standard operating procedures, including amendments to pre-flight checks, stringing operations, and feeder cable–pulling procedures. The operator also hired third-party consultants to audit the company’s safety management system.