Engineers at a Canadian Transportation Safety Board (TSB) lab in Ottawa will, on Monday, begin examining a failed tension torsion (TT) strap from a Bell 212 helicopter that crashed in the Northwest Territories, fatally injuring the pilot, Vertical has learned.
Investigators still don’t know what caused the TT strap to fail, but confirmed to Vertical the strap failed at the outboard pin position, prompting one of the rotor blades to detach from the aircraft.
“When that strap fails, you will lose the blade,” said Jon Lee, the TSB’s manager of regional operations for Western Canada. He emphasized any number of factors could have caused the part failure, and the intent of the investigation is to improve safety, not determine fault.
“The how and the why is unknown to us right now,” Lee said. “The process of starting to understand the type of failure, the failure mode, begins on Monday at our lab.”
Another strap from the same rotor system that didn’t fail will also be examined at the TSB lab, he said. The typical timeline for issuing a final investigation report is 450 days, but any urgent safety information will be communicated before the final report.
“If we find something that’s urgent for the industry, they’ll know right away,” Lee said.
The TSB communicated the TT strap failure to Transport Canada during a preliminary investigation that began after the incident on June 28, setting in motion a series of events that led several Canadian operators to temporarily stand down their Bell medium helicopters.
Acting on information from the TSB, the U.S. Forest Service also stood down 31 helicopters, but had returned the bulk of those aircraft to service by Wednesday, a spokesperson said.
The crash claimed the life of pilot Tom Frith, who was fighting wildfires on behalf of Great Slave Helicopters in the remote community of Fort Good Hope, about 500 miles (800 kilometers) northwest of Yellowknife.
TSB engineers will complete a detailed inspection of the parts, including electron microscope scanning, materials analysis, and other processes, to understand why the strap failed.
At the same time, investigators will collect data on the “entire maintenance history” of the aircraft, as well as the pilot’s background, pilot training, weather conditions at the time of the crash, and the operator’s organizational structure, Lee said.
“Through a process of deduction, we eliminate those issues that are not contributory to the occurrence,” he said.
“The way we approach an occurrence is [with the assumption that] everybody’s out there doing the best they can, and something terribly wrong happened. Now, we’re going to investigate what happened and why it happened. We’re trying to understand the underlying conditions that contributed to the occurrence happening without an emphasis on regulation, blame, finger pointing, liability.”
Because the Bell 212 is manufactured in the United States, the U.S. National Transportation Safety Board (NTSB) will act as an agent with the Federal Aviation Administration (FAA) to share information relevant to the investigation.
“If we identify safety deficiencies, we communicate those to the FAA through the NTSB, and then they can take action as required,” said Lee, noting he cannot commit to a timeframe for the investigation.
“It takes as long as it takes,” he said. “We have the responsibility of doing a thorough investigation, and to produce a product [the investigation report] that the industry can lean on — a product that’s defensible, is logical, is complete. In order to do that, it takes time. It’s a very methodical process.”
