Canada's TSB has released its final report on the Eurocopter AS 350 B2 helicopter accident of January 21, 2003 in Mekatina, Ontario.

The helicopter, after experiencing a hydraulic system failure, departed controlled flight and crashed while manoeuvring for landing at a logging site in Mekatina. Before the incident, the pilot and three passengers on board the helicopter were conducting a moose survey approximately 45 nautical miles northeast of Sault Ste. Marie, Ontario. The pilot and three passengers, all employees of the Ministry of Natural Resources of Ontario, were killed.

The TSB found that it is likely that the hydraulic pump belt failed in flight, causing the hydraulic failure. Examination of the failed belt and other similar unbroken belts from other helicopters revealed extensive cracking in the same location. Without proper control of the helicopter, the forces encountered by the pilot during the turn at low altitude may have been too extreme to overcome.

As safety deficiencies were uncovered by the TSB during its investigation, these were immediately made known to industry and regulators so they could be addressed as quickly as possible.

In response to the TSB findings in this investigation, many safety actions were taken by Transport Canada and by the Direction Generale de l'Aviation Civile:

• In early to mid-2003, Transport Canada issued two Airworthiness Directives to advise all AS 350 helicopter operators to complete a pre-flight check prior to every flight to ensure the proper functioning of the hydraulic pressure and helicopter controls. It was also specified that, in case of hydraulic failure, the aircraft is to be landed as soon as possible.
• On October 22, 2003 the TSB issued to Transport Canada an Aviation Safety Advisory to address the extensive cracking deficiency on the hydraulic pump drive belt. Although the belt manufacturer had produced a modification that incorporates a Poly-V design drive belt, numerous operators still continued to operate the helicopter with the belt used in this accident. On April 22, 2004 Transport Canada issued an Airworthiness Directive mandating the replacement, by September 30, 2004, of the old belt.

After extreme cold weather testing at Inuvik, Northwest Territories, the Direction Generale de l'Aviation Civile:

• made changes to the Rotorcraft Flight Manual concerning its emergency procedures, the hydraulic system description and training procedures;
• made the required modifications to the hydraulic bypass system to reduce residual pressure to an acceptable level; and
• issued in April 2004 an Airworthiness Directive to require hydraulic fluid to be replaced when exposed to temperatures below -15C.

No recommendations have been issued by the TSB because the industry and regulators have acted swiftly to address safety deficiencies when identified during the course of the investigation. This is considered a success, as the TSB's goal is to advance transportation safety and to ensure that similar accidents do not recur.

FMI: www.tsb.gc.ca