EASA SIB CASA-2017-02
Bell (BHTC) 206 Helicopters - Tail Rotor Drive Shaft Couplings - Loss of Hardware
Summary
The Transport Canada Civil Aviation Safety Alert CASA 2017-02 addresses the issue of missing hardware in the tail rotor drive shaft flexible couplings of Bell Helicopter models 206A, 206B, 206B-3, 206L-1, 206L-3, and 206L-4. This alert highlights several occurrences where bolts, washers, or nuts were found missing, potentially leading to tail rotor drive system failures. The document emphasizes adherence to Bell Helicopter maintenance practices to prevent such failures.
What Changed
CASA 2017-02 introduces awareness of the risk posed by missing hardware in the tail rotor drive shaft couplings of specified Bell Helicopter 206 models. It reinforces maintenance requirements including torque specifications, periodic torque checks after installation and every 100 hours, and the use of calibrated torque wrenches. The alert also recommends marking hardware with torque seal lacquer to detect loosening before failure.
Why It Matters
This alert is critical for aviation professionals as missing tail rotor drive shaft hardware can lead to loss of tail rotor authority and forced landings, posing serious safety risks. Operators, maintainers, and compliance teams must ensure proper installation and ongoing inspection to prevent in-flight failures. Following these recommendations helps maintain aircraft airworthiness and reduces the risk of accidents related to tail rotor drive system failures.
What To Do
Affected stakeholders should use calibrated torque wrenches when installing tail rotor drive shaft coupling hardware and avoid reusing hardware. They must verify that the tare/run-on torque meets specifications and perform torque checks after 10 to 25 hours of operation, then repeat every 100 hours as per Bell Helicopter maintenance manuals. Additionally, installed hardware should be marked with Bell Helicopter torque seal lacquer to allow visual detection of loosening.