What happened
During a scenic flight near the summit of Mt Tarawera, a pilot was transporting five passengers to a remote airstrip. The landing sequence, performed under tailwind and crosswind conditions, initially appeared normal. Upon touchdown, the pilot applied the left brake, which functioned as expected. However, a subsequent attempt to use the left brake resulted in no braking response, causing the aircraft to drift toward the right side of the runway.
As the aircraft lost directional control, it overran the end of the airstrip and traversed soft terrain before coming to a stop in an area of alpine scrub filled with boulders. While the aircraft sustained substantial damage, there were no injuries reported among the occupants.
The investigation
The investigation focused on the mechanical failure of the braking system during the landing roll. Investigators examined the components of the left mainwheel brake unit to determine why the braking force was lost during the second application. The examination of the hardware revealed that the brake unit disc assembly had been compromised by environmental factors.
Findings
Technical analysis established that the left mainwheel brake unit disc assembly had failed due to corrosion-related weakening. This structural degradation prevented the brake from functioning correctly during the landing roll, directly leading to the loss of directional control and the subsequent excursion into the scrubland.