Accident to the Cessna 401 registered N517HC on 30/10/2020 near Toussus-le-Noble

N517HC had remained unused in a hangar for around 14 years without any particular storage precautions being taken. The engine calendar time to overhaul limit recommended by the manufacturer had been exceeded by eight years and the aeroplane was sold for a reduced price by the maintenance workshop who owned it. For probably economic reasons and in accordance with the possibilities offered by the American regulations, the engine overhaul was not carried out.

It is very probable that the left engine had internal corrosion, the small amount of operating time over a long period being conducive to this damage, without this being detected during the inspections prior to the sale.

During the return to service process, various operations and inspections were carried out in parallel on the aeroplane by the maintenance workshop, the owner and the inspector awarding the Inspection Authorization. The latter then approved the aeroplane’s return to service.

During the flight, abnormal parameters were detected on the left engine and a warning was activated. The pilot-in-command initially continued the flight, the mechanic-passenger having indicated to him that it was probably a false alarm. 

During the return leg, the warning was activated again and a fire broke out in the left engine. The pilot-in-command, believing that he would not be able to reach the runway, decided to carry out an emergency landing in a field.

The investigation was not able to determine the cause of the fire. However, it is probable that the fire broke out level with cylinder No. 4 of the left engine.