What happened
On April 2, 2018, at approximately 15:00 local time, a DA 40 D aircraft, registered as HB-SDL, was preparing for a private flight from La Côte (LSGP) to Zurich (LSZH). The pilot had completed all necessary pre-departure checklists while at the parking position.
As the aircraft began taxiing southwest toward the holding point for runway 04, a helicopter located in a nearby field took off with its rotors running. While observing the departing helicopter, the pilot focused his attention primarily on the helicopter and briefly looked forward. During this period, the pilot failed to notice a sign marked "Run-up RWY 04" positioned to the left of the taxiway. Despite attempting to brake, the underside of the aircraft's left wing struck the sign.
Following the impact, the pilot stopped the aircraft to inspect the damage. Believing the scratches caused by the sign's mounting poles to be merely superficial, and after confirming that the ailerons remained functional, the pilot decided to continue the flight to Zurich. During the flight, the pilot chose a route near the Prealps to avoid turbulence, suggesting a potential awareness of structural concerns. Upon arrival in Zurich, a maintenance inspection revealed that the damage to the left wing was structural, necessitating the removal of the wing for repairs.
The investigation
The investigation focused on the pilot's actions during the taxi phase and the subsequent assessment of the aircraft's condition. Investigators examined the sequence of events leading to the collision and the pilot's decision-making process regarding the continuation of the flight despite the impact. The inspection of the aircraft confirmed that the damage was more significant than initially perceived by the pilot.
Findings
- The pilot was distracted by a departing helicopter during the taxi phase, which led to the oversight of the runway sign.
- The pilot performed an inaccurate visual assessment of the damage immediately following the collision.
- The decision to continue the flight to Zurich involved unquantifiable risks, as the pilot was unable to properly evaluate the extent of the structural damage.
- The pilot's flight path selection, aimed at minimizing turbulence, indicated an underlying awareness of possible structural instability.