AO-1991-015

The pilot flew a party of five tourists to land on the airstrip near the summit of Mt Tarawera. The approach and touchdown, in tail and crosswind conditions, was routine and an initial application of left brake gave no cause for concern. On the second application there was no response from the left brake and the aircraft began to drift to the right. The aircraft over ran the airstrip, went through some soft ground, and came to rest substantially damaged in a boulder strewn area of alpine scrub. The left mainwheel brake unit disc assembly had been weakened by corrosion and had failed. No injuries were sustained by the occupants. Recommendations were made concerning operations to the airstrip, and the susceptibility of the disc brake assembly type to corrosion and failure.