Associated links (A19Q0109)
Isabelle Langevin, Manager of Investigations (Air)
31 March 2021
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Hi, my name is Isabelle Langevin. I’m the Manager of Air Investigations for the Transportation Safety Board of Canada’s Quebec Region. Today, the TSB is releasing its investigation report into a fatal collision with terrain that occurred near Lac Valtrie in the Rouge-Matawin Wildlife Reserve in Quebec. The TSB determined that a failure of one of the main rotor blades was the cause of the accident.
I would like to begin with a reminder that the purpose of a safety investigation is not to assign fault or determine civil or criminal liability, but rather to advance transportation safety by conducting independent investigations into selected transportation occurrences. We find out what happened and we determine how we can prevent a similar event from happening in the future.
On 10 July 2019, a privately registered Robinson R44 helicopter was conducting a day visual flight rules flight from Lac de la Bidière to Sainte-Sophie, Quebec, with 1 pilot and 1 passenger on board. The aircraft never arrived at its destination and no signal was detected from an emergency locator transmitter, commonly referred to as an ELT. The following day, the aircraft and its occupants were reported missing to the Joint Rescue Coordination Centre in Trenton, and search operations began.
The aircraft was found in a remote wooded area 14 days after it was reported missing, thanks to historical data retrieved from the occupants’ cell phones, which helped to perform triangulation calculations. The aircraft was destroyed and the occupants were found dead.
The aircraft was taken to the TSB Engineering Laboratory for further examination. During the examination, one of the blades revealed multiple adhesive failures that reportedly led to the separation of some sections of the skin at the bond joint. This separation allowed humidity to infiltrate below the skin and weaken adhesion to the bonding joint over time. The investigation determined that during the flight, a sudden increase in adhesive failures likely contributed to reducing the stiffness of the blade. This affected the blade’s performance, causing an imbalance between the two blades, which generated severe vibrations. This was followed by a significant drop in the rotational speed of the main rotor, preventing the aircraft from remaining airborne, which led to the collision with terrain.
The investigation showed that it is likely that when the last inspection was performed in April 2019, there were already adhesive failures that did not get detected by the tap test; this is an inspection that consists of gently tapping the skin with a small hammer designed for this purpose, or a specific coin, and listening to the sound produced by the tapping. A change in sound may indicate an adhesive failure. In addition, exposed metal surfaces at the skin-to-spar bonding joint on one of the blades were present and likely visible to the naked eye before the flight.
Finally, the investigation also determined that no flight plan or flight itinerary had been filed before departure. In such a situation, there is a risk that search operations will not be initiated within a reasonable timeframe, particularly when no ELT signal is detected, as was the case in this occurrence. The occupants’ chances of survival are then reduced and the search and rescue teams are missing important information that can help them establish the search area. In this occurrence, the absence of a signal from the ELT, whose switch was in the OFF position as a result of a malfunction of the locking system, as well as the size of the search area to be covered, combined with the density of the canopy cover, were factors that had an impact on the time needed to find the aircraft.