Multiple elements contributed to fatal Chinook helicopter crash in Ottawa River, investigation concludes

Capt. David Domagala and Capt. Marc Larouche died when the CH-147F Chinook helicopter crashed near Garrison Petawawa on June 20, 2023. (Cpl. Lindsay Jellicoe/Department of National Defence)

The investigation into a Chinook helicopter crash near Petawawa, Ont. that killed two military pilots concludes an "unperceived acceleration" and environmental conditions were "significant contributors" to the crash in the Ottawa River.

Capt. David Domagala and Capt. Marc Larouche died when the CH-147F Chinook helicopter crashed near Garrison Petawawa on June 20, 2023. Two flight engineers were able to escape the crash with minor injuries.

A Royal Canadian Air Force (RCAF) helicopter and Canadian Armed Forces (CAF) boat search the Ottawa River near Fort William in Pontiac Regional County Municipality, Que. on Tuesday, June 20, 2023. THE CANADIAN PRESS/Spencer Colby

The helicopter, known by its call-sign Hammer 31, was conducting a nighttime training flight over the Ottawa River at the time of the crash.

On Monday, the Royal Canadian Air Force's Directorate of Flight Safety announced the conclusion of its investigation.

"The Flight Safety Investigation determined that as the crew initiated a turning manoeuvre over the river, the aircraft entered a constant but imperceptible descent," the RCAF said in a statement.

"None of the crew realized the aircraft's altitude and/or rate of descent until impact, resulting in a Controlled Flight into Terrain accident. It concluded that unrecognized downward acceleration, along with environmental conditions that night, were significant contributors to the accident, causing spatial disorientation among the crew."

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The Department of National Defence had previously said the helicopter started to descend during the training exercise and was turning left when it struck the Ottawa River "with high energy."  The investigation was said to be focusing on human, technical and environmental factors.

"This accident was not caused by a single factor, instead, multiple elements contributed to the unrecognized spatial disorientation of all crew members of Hammer 31, leading to the continued descent until water impact," Col. Jean-Francois Gauvin, Director of Flight Safety, said in a statement.

"Over 16 months, we thoroughly analyzed a large amount of data and collaborated closely with partners to identify additional contributing factors. Several recommendations are provided to help prevent similar accidents in the future.”

The report makes several recommendations to amend the CH-147F publications, including a recommendation to mandate the use of automation Level-3 (Native Mode Digital Automatic Flight Control System) when operating below 200 feet above water at night. The report also makes recommendations to improve emergency response preparedness.

Canadian Armed Forces (CAF) conduct searches around a series of islands on the Ottawa River near Fort William in the Pontiac Regional County Municipality on Tuesday, June 20, 2023. Two RCAF 450 Tactical Helicopter Squadron members were missing following a CH-147F Chinook early morning crash near Garrison Petawawa. (Spencer Colby/THE CANADIAN PRESS)

Officials say, "preventative measures" are recommended at the base, squadron, wing, division and strategy levels to "enhance safety and mitigate the risks associated with over-water missions."

The Royal Canadian Air Force has a fleet of 14 CH-147F Chinooks, with the current fleet acquired starting in 2013.

The next-of-kin of the fallen pilots were briefed on the conclusions of the flight safety investigation report before it was released, according to the Department of National Defence.

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