Industry focuses on ‘critical’ part after fatal NWT helicopter crash

Operators across North America grounded a range of Bell helicopters as a vital piece of hardware became the focal point of the Fort Good Hope helicopter crash investigation.

Pilot Tom Frith, who was the only person on board a Bell 212 helicopter assigned to help fight a wildfire outside the community, lost his life in an accident at Fort Good Hope’s airport on Friday, June 28.

In the days since that incident, word about investigators’ initial conclusions spread rapidly in the aviation industry, leading many companies to ground similar helicopters for inspection.

According to the Helicopter Association of Canada, which cited information from the Transportation Safety Board, the part being scrutinized is a specific brand of tension torsion strap, commonly known as a TT strap.

TT straps are described as “flight-critical” by the manufacturers that sell them, a designation normally taken to mean that failure of such a part would have serious consequences for the aircraft.

Helicopters are lifted up by rotors. An engine drives a central rotor hub, making the rotor blades spin so quickly that they generate lift.

Each TT strap is part of the mechanism that holds the rotor blade onto the rotor head of the helicopter. It has to hold the blade in place but also allow the blade to twist in flight.

“If you think of an airplane wing pitching up when the airplane takes off, our blades do the same thing,” said Trevor Mitchell, president of the Helicopter Association of Canada, reached by phone on Tuesday.

“This is part of that entire mechanism that allows the blades the ability to move within the rotor head itself, and they also retain the blade to the rotor head. It doesn’t look like much from the outside, but it does provide a very critical flight-critical function.”

The straps are ordinarily constructed using thousands of tiny stainless steel wires.

If a strap were to fail, a likely consequence would be the separation of the blade from the helicopter.

This is why Mitchell says his association, having heard from the TSB, advised other operators of the concern.

“We provided that information to operators so that if they were operating that brand of strap, then they could determine for themselves, along with their customers, what would be the most appropriate course of action moving forward,” he said.

Several companies make TT straps. “We’re not saying that this manufacturer of TT straps is a bad manufacturer or anything like that,” Mitchell stressed. “It could be a one-off. We really don’t have any further information other than that.”

The association said it did not want to comment on the specific incident, and the TSB has not publicly commented on any initial conclusions reached by investigators.

Even so, the association’s guidance was swiftly picked up by operators across the continent.

The Hotshot Wake Up, a Substack that covers wildfires and firefighting technology, reported on Tuesday that the US Forest Service had issued what was described as a “tactical pause” on the use of Bell medium helicopters. A medium helicopter is an industry term for a type of helicopter that includes the Bell 212.

Quoting from the US Forest Service directive, The Hotshot Wake Up reported the service had been advised: “Initial reporting from the TSB is such that the aircraft experienced a torque tension strap failure.”

Pilots in Canada reported similar groundings, though many helicopters that don’t use the same manufacturer are understood to have since resumed operations.

“We heard the vast majority of Bell medium operators voluntarily grounded their fleet immediately after notification of the accident as an extra level of safety,” said Mitchell.

“Many of these operators, if they were using different manufacturers’ parts, worked with their clients and their stakeholders to get themselves back airborne.”

The forest service memo noted that the investigation is at its earliest stage and a full report from the TSB is likely many months away.

Importantly, there is so far no publicly available indication of why a strap may have failed in this instance, which will be important for investigators, the manufacturer and operators to determine.

“In every case of an aviation accident, there is an information gap that is appropriate due to the needed investigation but is unsettling due to continuing operations using the same aircraft while the investigation gets to the facts,” read the forest service memo quoted by The Hotshot Wake Up.

“There is a balance in sharing quickly and as accurate information as possible without jumping to incorrect conclusions.”

Mitchell said the helicopter industry will closely watch the investigation and praised both the TSB and Canadian helicopter operators for their handling of the incident to date.

“The industry as a whole did a voluntary shutdown prior to their customers saying they had to shut down,” he said.

“I think the Canadian industry really did put safety front of mind, and they did what was right by their people, their front-line people, their companies and their customers.

“The Helicopter Association of Canada, our board and our members provide our heartfelt condolences to the company and the family involved in this tragic accident.”