Cat. 2 investigation report: simplified-format report, adapted to the circumstances of the occurrence and the investigation stakes.
In descent to Nice airport, the crew tried to avoid storm cells by using the aeroplane’s weather radar. They encountered icing conditions and moderate turbulence. Shortly before coming out of the clouds and when the flight conditions were becoming calmer, the aeroplane was struck by lightning. Given the distribution of the lightning recorded in the same period, it is probable that the presence of the aeroplane participated in triggering the electric discharge phenomenon. The strength of the discharge current was very high and caused damage to the propeller that the manufacturer had never seen previously in operating conditions. Its structure was not compromised however.
A few days later, during the aircraft inspection, other structural damage not related to the lightning strike was found on the left wing. The wing had to be replaced.
The investigation showed that this structural damage had occurred between 16 November 2019, date at which the aircraft was released from the last maintenance operation and 30 March 2020, the lightning strike flight. This damage was probably caused by an in-flight overload of the wing even if a hard landing cannot be totally excluded. It was not possible to precisely determine or date the occurrence which caused it. The conditions of the last flight were favourable to high loads being applied to the structure. However, the load factors, speeds and bank values recorded do not show any situation which could have resulted in a structural overload of the wing during these last six flights.