Following a low oil pressure warning and smoke from the engine exhaust, the pilot diverted to a nearby airport. Following detailed inspection of the engine by the manufacturer, significant corrosion was identified which had formed holes, leading to a loss of oil from the reduction gearbox housing into the engine exhaust. The corrosion resulted from numerous unapproved engine compressor washes which had been carried out without the drain plug being removed. This was a known issue on the engine, and the manufacturer had added warnings to the Approved Maintenance Manual and issued a Service Information Letter. The operator and contracted maintenance provider confirmed that any future engine washes would only be conducted by approved maintenance personnel and in accordance with the Approved Maintenance Manual.
