EASA 2024-0100

Supersedes but retains requirements of EASA AD 2018-0142R1, which mandates measurement of in-flight vibration levels and, depending on findings, removal of the dual hoist installation or removal of the deicing system. Updated AD extends the applicability. Prompted by a test flight of an AS332L helicopter after a retrofit reinstalling the deicing system where vibrations around the 12-Hz frequency were observed. Subsequent flight tests determined that this vibration was due to the specific helicopter configuration, involving riveted main frames and additional weight of the rotor deicing system on the main rotor head, as well as the hoist arm and hoists. If not corrected, this condition could generate divergent aeromechanic coupling between the helicopter structure and the rotor, possibly resulting in mechanical failure of structural parts and/or loss of control of the helicopter.