Major parts of the helicopter have a shelf life (life cycle). At the end of this time period, these parts are either replaced or overhauled (inspected). For example, the main rotor gearboxes on our helicopters must undergo a complete overhaul after 3500 flight hours or 24 years of operation.
This was now due on the MKT, one of our two helicopters in Madagascar. As the maintenance team, we got ready to replace the gearbox. This involved disconnecting various hoses and cables from the gearbox and its connection to the engine. The connecting struts that link the gearbox to the helicopter could then be removed. We then used the hangar crane to lift the gearbox out of the helicopter. The next step was to separate the gearbox from the main rotor mast so that we could install the newly overhauled gearbox. Special care had to be taken not to damage the individual gears of the gearbox and the main rotor mast. After reassembly, the entire unit of the newly overhauled main rotor gearbox and mast were reinstalled in the machine. Once all the hoses and cables were reinstalled and reconnected, a number of tests had to be carried out to verify that everything was working properly. This included a flight with a full load as well as a performance check to ensure that all values were within the limits specified by the manufacturer. Once the results were satisfactory, the machine was released for flight operations again under supervision.
Nick, Pilot
