What happened
On February 23, 1999, at 10:20 local time, an Eurocopter AS 355 F2 (registration F-GGRS) was conducting an aerial work mission over the sea, approximately 4 nautical miles northwest of Calais. The mission involved transferring a port pilot from a vessel to the deck of a ship via a hoisting operation.
During the maneuver, the crew was engaged in hoisting the pilot using the aircraft's winch. As the cable was being tensioned, the cabin door was suddenly torn from the aircraft and fell into the sea.
The investigation
The investigation focused on the positioning of the hoisting cable and the sequence of events leading to the structural failure of the door attachment. Investigators established that at the start of the hoisting procedure, the cable was improperly positioned. Specifically, the cable was passing underneath the lower corner of the door. This misalignment went undetected by the crew during the initial stages of the operation.
Findings
- The primary cause of the accident was incomplete checks prior to the hoisting operation, which allowed the cable to be incorrectly positioned.
- The tension applied to the cable while it was caught under the door corner created enough force to lift and detach the door from the airframe.