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Air transportation safety investigation A17O0264

The TSB has completed this investigation. The report was published on 30 October 2019.

Table of contents

Collision with terrain

Hydro One Networks Inc.
Airbus Helicopters AS 350 B2 (helicopter), C-GOHS
Tweed, Ontario, 8 NM NNE

View final report

The occurrence

On 14 December 2017, a Hydro One Networks Inc. Airbus Helicopters AS 350 B2 helicopter (registration C-GOHS, serial number 3240) equipped with an external platform, was transporting crews of power line technicians between a staging area and transmission towers in an area located 8 nautical miles north-northeast of Tweed, Ontario.

At 1144 Eastern Standard Time, the pilot picked up a crew of 3 power line technicians near the bottom of a tower for a return flight to the staging area. It had become common practice for power line technicians to attach tool bags and other small items to the external platform for flights to and from work sites. In line with this practice, the technicians attached a few items to the platform while boarding the helicopter, and then took their seats in the aft cabin.

The practice of carrying external loads attached to the platform was not a formalized procedure at the company and, as a result, adequate controls were not in place to ensure that these objects were properly stored or secured. Consequently, an empty canvas supply bag with an attached carabiner that was being carried on the platform was not adequately secured before the helicopter departed for the return flight to the staging area.

When the helicopter was 0.26 nautical miles from the staging area, the canvas bag separated from the platform and struck the helicopter's tail rotor, causing significant damage, severe imbalance, and intense vibration.

Shortly after, while the pilot was attempting to land, the helicopter's tail rotor, tail rotor gearbox, and vertical fin separated from the helicopter. The helicopter became uncontrollable and collided with terrain. The 3 power line technicians were unrestrained and became separated from the helicopter, either slightly before or during the impact, and received fatal injuries from contact with the helicopter or the surrounding terrain. The pilot was fatally injured on impact. The helicopter was destroyed.

Safety communications

Safety advisories


Aviation Safety Advisory A17O0264-D1-A1: Unsecured Cargo and Unrestrained Passengers in Helicopters
Read the Aviation Safety Advisory

Media materials

News release


Report on 2017 helicopter accident near Tweed, Ontario, highlights risks with external cargo and unrestrained passengers, and calls for clarification of safety belt regulations
Read the news release




A17O0264 (Tweed): Opening remarks
Kathy Fox, TSB Chair
Ewan Tasker, Manager, Air Investigations Ontario Region

Media advisories


TSB will hold a news conference to release its investigation report on the December 2017 fatal helicopter accident near Tweed, Ontario
Read the media advisory


TSB will provide a news briefing on its investigation into the helicopter accident near Tweed, Ontario
Read the media advisory


TSB will provide a news briefing on its investigation into the helicopter crash that occurred near Tweed, Ontario
Read the media advisory

Deployment notice


TSB deploys a team of investigators to a helicopter accident near Tweed, Ontario

Richmond Hill, Ontario, 14 December 2017 - The Transportation Safety Board is deploying a team of investigators to a helicopter accident near Tweed, Ontario. The TSB will gather information and assess the occurrence.

Investigation information

Map showing the location of the occurrence


Photo of Ken Webster

Ken Webster joined the TSB team in 2005, and works as Manager, Regional Operations out of the Ontario office. Mr. Webster has been investigator-in-charge in numerous TSB investigations, and assisted in several others, involving airplane, helicopter and air traffic control. Prior to the TSB he worked in civil aviation for 20 years, in several different capacities. As a pilot, Mr. Webster has flown numerous aircraft types throughout Canada and the US.


  Download high-resolution photos from the TSB Flickr page.

Class of investigation

This is a class 2 investigation. These investigations are complex and involve several safety issues requiring in-depth analysis. Class 2 investigations, which frequently result in recommendations, are generally completed within 600 days. For more information, see the Policy on Occurrence Classification.

TSB investigation process

There are 3 phases to a TSB investigation

  1. Field phase: a team of investigators examines the occurrence site and wreckage, interviews witnesses and collects pertinent information.
  2. Examination and analysis phase: the TSB reviews pertinent records, tests components of the wreckage in the lab, determines the sequence of events and identifies safety deficiencies. When safety deficiencies are suspected or confirmed, the TSB advises the appropriate authority without waiting until publication of the final report.
  3. Report phase: a confidential draft report is approved by the Board and sent to persons and corporations who are directly concerned by the report. They then have the opportunity to dispute or correct information they believe to be incorrect. The Board considers all representations before approving the final report, which is subsequently released to the public.

For more information, see our Investigation process page.

The TSB is an independent agency that investigates air, marine, pipeline, and rail transportation occurrences. Its sole aim is the advancement of transportation safety. It is not the function of the Board to assign fault or determine civil or criminal liability.