FAA directs Bell medium operators to remove, replace Airwolf TT straps

Written By Ben Forrest | Retrieved from Vertical Magazine  

In the wake of a fatal crash involving a failed tension torsion (TT) strap on a Bell 212 helicopter, the U.S. Federal Aviation Administration (FAA) has directed Bell medium operators to remove similar TT straps from service and to not install them in the future.

The requirement came via an airworthiness directive (AD) on Sept. 26, 2024, and it affects specific part numbers for multiple Bell types, plus several restricted-category helicopters.  

All the affected parts are manufactured by Ohio-based Airwolf Aerospace, which also made the TT strap that failed in the Bell 212 crash on June 28 near Fort Good Hope Airport in Canada’s Northwest Territories.

An initial investigation found the TT strap involved in the June 28 crash failed at 664 total hours time-in-service (TIS), causing the aircraft’s rotor blade to detach, the FAA said.  

Early indications from ongoing investigations suggest some wires may also have failed, per the FAA.

“This condition, if not addressed, could result in loss of a main rotor blade and subsequent loss of control of the helicopter,” the agency stated. “The FAA is issuing this AD to address the unsafe condition on these products.”  

The AD affects Bell 204B, 205A, 205A-1, 205B, and 210 helicopters carrying TT straps with the part numbers AA-204-310-101-101, AA-204-310-101-101C, AA-204-310-101-103, and AA-204-310-101-103C, installed by supplemental type certificate No. SR03408CH.  

“The FAA considers this AD to be an interim action,” the agency said. “If final action is later identified, the FAA might consider further rulemaking then.”  

Operators are being directed to remove TT straps that have accumulated 350 or more total hours TIS as of Oct. 11, 2024, and replace them with airworthy TT straps.

TT straps with less than 350 hours TIS as of Oct. 11 must also be removed and replaced before they accumulate 400 hours TIS since first installation.

In addition to the Bell civil helicopter types listed, the AD also applies to several former military aircraft. The full list is available here.

“Failure of an affected TT strap could occur at any time without any previous indications and result in a sudden and catastrophic condition,” the FAA said. “Thus, an urgent unsafe condition exists and the required actions must be done within 50 hours TIS.”  

The FAA notes 50 hours TIS can equal up to two months, based on average flight-hour utilization of these helicopters.  

“However, a significant portion of these helicopters in the U.S. fleet are high usage helicopters, which have an increased likelihood of occurrence of a failure and will reach the compliance time within a period of approximately one week based on the average flight-hour utilization rates of these helicopters,” the FAA said.

At the time of writing, it was unclear if Transport Canada would adopt the FAA’s AD.  

The Helicopter Association of Canada (HAC) received advance notice of the AD and said in a message to its members on Sept. 25 there had been “no indication that an AD is forthcoming from the FAA that will impact other TT straps made by this supplier.”  

In July, Transport Canada issued a re, asking operators of Bell mediums equipped with Airwolf TT straps to inspect them immediately.  

Several operators temporarily grounded their aircraft to comply.

The fatal crash at Fort Good Hope Airport, about 500 miles (700 kilometers) northwest of Yellowknife, claimed the life of pilot Tom Frith, the aircraft’s sole occupant.

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