aviation accident: American Eurocopter AS350-BA near Oxnard (2004-11-09)
Probable cause: The inadvertent in-flight engagement of the collective down lock, which resulted in an uncontrolled descent and ground impact. The collective down lock engagement was likely due to a combination of the reduced clearance between the lock plate and the collective with this avionics panel design, the collective down lock alignment/adjustment, and the tendency of the flexible lock plate to vibrate with the natural harmonic rhythmus of the helicopter.