Westland Wasp HAS1 crash near Marston Doles, Warwickshire, United Kingdom

An instructor and student pilot were carrying out pre-flight checks. One of the checks required the deselection of the hydraulic system to ensure mechanical flying control continuity and freedom of operation in the correct sense. As the instructor selected the hydraulic system off, the collective lever ‘jumped’ upwards and the aircraft lifted into the air. The instructor was unable to regain control and the helicopter struck the ground and rolled over. The cause of the abnormal collective movement could not be positively determined but a transient system malfunction could not be ruled out. Westland Wasp HAS1, G-CMBE 08-25