All MD 369 series helicopter operators and maintenance providers.
During the pre-flight inspection of a 369D, the pilot found a defect in the tail rotor gearbox housing, which was initially thought to be a paint crack.
The aircraft was grounded, and during an inspection by an engineer a significant crack was found.
CAA understands that paint was removed from the casing by the engineer to facilitate the inspection (See Figures 1 and 2 below).
CAA recommends that operators of 369 series helicopters pay particular attention to exposed gearbox and flight control casings during pre-flight inspections.
Paint defects, or evidence of oil leaks should be thoroughly investigated. If there is any doubt whether a component casing is cracked, or damaged, an engineer should be consulted.
Maintenance providers who are carrying out inspections of 369 tail rotor gearbox casings should consider paint removal if a preliminary inspection identifies a potential crack.
Paint removal and restoration should be carried out in accordance with the relevant aircraft, or component manufacturer instructions.
CAA requests that operators and maintenance providers report any cracks, or damage found, via the occurrence reporting process: https://occurrencereporting.services.aviation.govt.nz(external link)
Any questions can be directed to: warren.hadfield@caa.govt.nz
CAA will liaise with the manufacturer on this safety finding.
This CAN is considered to be an interim action and further CAN, or AD action may follow.
Figure 1 – Tail Rotor Gearbox crack found during the pre-flight inspection. Note the presence of oil residue.
Figure 2 – Crack with paint removed.
