The FAA and Transport Canada have issued emergency airworthiness directives requiring operators of Bell 505 helicopters to conduct initial and recurring inspections of the aircraft’s vertical stabilizer top end cap assembly for cracking.

The FAA’s emergency airworthiness directive (AD 2024-02-55), dated Jan. 26, and that of Transport Canada (AD CF-2024-03), issued one day earlier, followed “multiple occurrences” of cracking found in the Bell 505 vertical top end cap assembly. In some cases, the helicopter’s VOR glideslope antenna and tuning weight were lost during flight.

“Detailed investigation has identified that the stabilizer top end cap assembly was not designed for the full fatigue spectrum,” the FAA states, referencing Transport Canada’s directive. “AD CF-2024-03 further states that an investigation determined that if no corrective actions are implemented, there is the potential for the antenna and tuning weight to depart, which could impact and damage the tail rotor, resulting in the loss of directional control of the helicopter.”

The directives specify Bell Textron Canada Model 505 helicopters, serial numbers 65011 and subsequent.

As required by Transport Canada, the Bell 505 design authority, the FAA also requires that operators conduct a one-time detailed visual inspection of the vertical stabilizer top end cap within 10 hours’ air time and take corrective action if cracking is found. They are thereafter to inspect for cracking at intervals of no greater than 25 hours’ air time.

Bell Alert Service Bulletin 505-24-38, dated Jan. 24, specifies procedures for performing a one-time detailed inspection of the top end cap assembly for cracking, provides instructions for replacing a cracked top end cap assembly, and provides instructions for performing a recurring detailed inspection of the top end cap assembly, the FAA said.