Safety issue

Safety issue description

Paint application to the main rotor gearbox, gear carrier did not effectively protect the part from corrosion resulting from gearbox water ingress.
Issue number AO-2011-088-SI-01
Issue owner Robinson Helicopter Co
Transport function Aviation: Other
Issue status Closed – Adequately addressed
Date issue released 27/08/2012
Issue status justification

The action taken by Robinson in redesigning the affected part will reduce the likelihood of corrosion-related failure, once fully implemented across the fleet. Until that time, there are practical maintenance actions that can alert owners and operators to the presence of moisture in the gearbox and, hence the possibility of corrosion, allowing further action to be taken as-necessary.

Safety action

Action type Proactive action
Action number AO-2011-088-NSA-019
Organisation Robinson Helicopter Co
Action date 05/07/2012
Action description

The helicopter manufacturer has modified the gear carrier design to improve the corrosion resistance by cadmium plating the part.
Action status Monitor

Organisation response

Date received 23/03/2012
Organisation Robinson Helicopter Co
Response status Closed
Response text
Cadmium plating of gearbox components

Robinson have redesigned the at risk gearbox components with improved corrosion prevention measures.

While this will improve the corrosion resistance of the part, it will take time for the redesigned parts to be installed on helicopters currently in operation. Robinson's advice to owners and operators was to manage their risk by considering the potential for gearbox moisture ingress during helicopter operation and storage.

Additionally, while there is no practical method for determining the presence of corrosion damage to gearbox components, examination of gearbox oil during scheduled maintenance could provide an indication of moisture ingress, in the form of visible liquid water, or if the gearbox oil has become noticeably emulsified or ‘cloudy’.

Concerned operators should contact their maintenance provider or the aircraft manufacturer for further advice.