Following up on an earlier, Airworthiness Directive Transport Canada has issued a Civil Aviation Safety Alert (CASA) to address transmission issues with Bell 206, 206L and 407 helicopters. The purpose of this CASA is to inform operators of “the vulnerability of the main transmission freewheel lubrication system to contamination, to emphasize how critical it is to ensure a conforming filter is installed and to follow the manufacturer's recommended procedures for aircraft storage and reactivation.”
According to Transport Canada, there have been two accidents involving Bell 206s where a malfunction of the main transmission freewheel system led to a failure of the main rotor mast. In both occurrences, the failure occurred after landing and led to separation of the main rotor blades, rotor hub and a portion of the mast from the helicopter. The investigations of these two accidents revealed that “contamination of the freewheel lubrication system was the root cause.”
Bell Helicopter released Alert Service Bulletins for each affected helicopter model and Transport Canada issued AD CF-2016-13 to mandate compliance with the bulletins. Compliance is required within 100 hours time in service after the May 16 effective date.
Meanwhile, the FAA recently issued Information for Operators 16012 to alert operators and repair facilities of potential failure of the engine-mount assemblies on Bell 206L1s and 206L3s due to corrosion.