Just days after a Bell 212 was lost in the Northwest Territories in Canada, resulting in the loss of the pilot, the U.S. Forest Service issued a memo on June 2, temporarily grounding contract aircraft, detailed as "212 type aircraft", until more is learned about the cause of the accident.
A voluntary grounding of those aircraft types has also occurred in Canada in addition to the USFS grounding. The USFS has described the temporary measure as a "tactical pause" according to the memo that reads in part:
"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. There is a balance in sharing quickly and as accurate information as possible without jumping to incorrect conclusions.
As we are all aware, no causal factor is determined in any investigation for typically a year or more. Sharing of the information below is just that, sharing information so that our contractors have it as soon as we do so decisions can be made with all the data available. As more information is available, we will continue to share it.
The following information was shared with the Forest Service from Canadian Provincial Fire Managers and the Helicopter Association of Canada:
"HAC, Helicopter Association of Canada, has been provided information directly from the TSB as it relates to a recent accident involving a Bell 212 type aircraft. In the interest of aviation safety, and providing factual information to industry the following has been shared by the Transportation Safety Board and has been cleared for release. Initial reporting from the TSB is such that the aircraft experienced a torque tension strap failure.
The following text is direct from the TSB: The failure end is on the outboard blade retention pin position. There are no issues with the pin itself. It is the strap that has failed. Bell and Transport Canada have been made aware."
Tension torsion straps, or TT straps, as they are commonly referred to, are the part at the center of the current accident investigation. TT straps are typically unseen from an external view of a helicopter and are essential parts that fasten rotor blades to the rotor hub. TT straps allow the blades of the helicopter types in question to have rigidity and allow the blades to pitch with pilot input.
Learn more about TT straps in the video below.
