Emergency Airworthiness Directive (AD) 2024-02-55: Prompted By Reports Of Cracked Vertical Stabilizer Top End Cap Assemblies

Emergency Airworthiness Directive (AD) 2024-02-55 has been sent to owners and operators of Bell Textron Canada Limited Model 505 helicopters. 

This emergency AD was prompted by reports of cracked vertical stabilizer top end cap assemblies. Transport Canada, which is the aviation authority for Canada, has issued Transport Canada Emergency AD CF-2024-03, dated January 25, 2024 (Transport Canada AD CF-2024-03), to correct an unsafe condition for Bell Textron Canada Limited Model 505 helicopters, serial numbers 65011 and subsequent. 

Transport Canada AD CF-2024-03 states that there have been multiple occurrences of the vertical stabilizer top end cap assembly being found cracked, with some cases including the departure of the navigation/very high frequency omni-directional range (VOR)/glide slope antenna and tuning weight from the helicopter during flight. Detailed investigation has identified that the stabilizer top end cap assembly was not designed for the full fatigue spectrum. Transport Canada 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. 

Accordingly, Transport Canada AD CF-2024-03 mandates an initial and recurring inspections of the vertical stabilizer top end cap assembly, and corrective action if a crack is found. Transport Canada AD CF-2024-03 states that the corrective actions are interim actions until a permanent solution can be made available for the fleet. This emergency AD is intended to detect cracking in the vertical stabilizer top end cap assembly. This condition, if not addressed, could result in the antenna or tuning weight departing from the helicopter and impacting and damaging the tail rotor, resulting in the loss of directional control of the helicopter. 

The FAA reviewed Transport Canada AD CF-2024-03, which requires, within 10 hours air time, accomplishing a one-time detailed visual inspection of the vertical stabilizer top end cap assembly for cracking and accomplishing corrective action if cracking is found. Thereafter at intervals not greater than 25 hours air time following the accomplishment of the 10-hour air time inspection or the corrective action, Transport Canada AD CF-2024-03 requires performing recurring detailed visual inspections of the vertical stabilizer top end cap assembly for cracking.  

The FAA also reviewed Bell Alert Service Bulletin 505-24-38, dated January 24, 2024, which 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 2 instructions for a performing a recurring detailed inspection of the top end cap assembly.

FMI: www.regulations.gov