What happened
On 30 March 2020, a Pilatus PC-12-47E, registration LX-JFD, was performing an owned-account transport flight from Paris-le-Bourget to Nice-Côte d'Azur. During the descent, the crew encountered icing and moderate turbulence while maneuvering to avoid storm cells using weather radar and a stormscope.
At approximately 15:23, as the aircraft was descending through FL 060 and entering calmer conditions, the crew witnessed a bright flash and heard a loud bang, indicating a lightning strike. While engine and propeller parameters initially appeared normal, the crew elected to land at Nice as quickly as possible. Upon landing, a post-flight inspection revealed damage to the propeller and the rear section of the fuselage.
The investigation
The BEA opened a safety investigation after the aircraft operator notified authorities of the strike. During subsequent maintenance inspections, personnel discovered additional structural deformations on the left wing skin and a deformed flap mechanism. This wing damage was unrelated to the lightning strike.
The investigation examined the engine, propeller, and airframe. Analysis of the engine revealed residual magnetism in several components, arcing, and melted material on various parts of the gearbox and compressor. The propeller manufacturer noted that the damage to the composite blade trailing edge was of a nature they had not previously observed in operational conditions, suggesting a very high-energy discharge. Meteorological data from Météo-France confirmed a massive lightning strike in the area with a discharge current of 147.7 kA, which is exceptionally high.
Findings
- The aircraft was struck by a high-energy lightning discharge that caused significant internal engine damage and damage to the propeller blade.
- The lightning strike may have been triggered by the presence of the aircraft itself within the electrical field.
- Structural damage to the left wing, including skin deformations and a deformed flap arm, was discovered after the lightning event but was determined to have occurred prior to the strike.
- The investigation could not definitively date the wing damage, though it likely resulted from an in-flight structural overload, as the aircraft's monitoring system did not record any recent hard landings or extreme maneuvers.
- The late detection of the wing damage was attributed to the difficulty of visually identifying such deformations during standard pre-flight inspections and the limitations of the aircraft's monitoring system in characterizing specific load events.