EASA AD CF-2025-35
Levelling and Weighing — Aft Moveable Ballast Box Assembly Door Hinge Failure
Summary
Canadian Airworthiness Directive CF-2025-35 addresses a safety issue on Bell Textron Canada Limited model 505 helicopters, serial number 65011 and subsequent, equipped with ballast kit Part Number SLS-706-201-001. The directive concerns failure of the aft movable ballast box assembly door hinge, which could lead to ballast weights escaping and damaging the tail rotor. This AD mandates removal and modification of the affected ballast box assembly to ensure continued safe operation.
What Changed
CF-2025-35 supersedes AD CF-2025-17 by introducing a mandatory modification of the aft movable ballast box door assembly as a terminating action. It corrects a previous part number error and allows the use of ballast weights again after modification, whereas the earlier AD prohibited their use entirely. The directive incorporates Bell Alert Service Bulletin 505-25-44 Revision A for the required modification procedures.
Why It Matters
This directive is critical for aviation professionals to prevent potential loss of tail rotor control caused by ballast weights escaping the aft ballast box. Operators and maintenance teams must comply to avoid severe vibrations and possible loss of helicopter control. Ensuring compliance maintains aircraft airworthiness and operational safety, reducing risk of accidents related to this component failure.
What To Do
Operators must remove ballast weights from the aft movable ballast box before further flight and prohibit their use until the modification is completed. The ballast box door assembly must be modified within 100 flight hours or 90 days, whichever occurs first, following the instructions in Bell ASB 505-25-44 Revision A. Completing this modification terminates the initial restrictions on ballast weight use.