What happened
On the morning of September 14, 1998, a Cessna 177B aircraft, registered as ZK-DKL, was conducting a scenic air transport flight through the Mount Cook area. At approximately 11:52 hours, the aircraft struck a mountain face covered in snow, located roughly 11 km northeast of Mount Cook. The impact resulted in the deaths of the pilot and two passengers.
The investigation
Investigators examined the flight path and environmental conditions leading up to the collision. The inquiry established that the aircraft likely encountered a powerful laminar downdraught shortly before hitting a thin layer of cloud. While the pilot had sufficient opportunities to maneuver the aircraft away from the ascending terrain and the approaching cloud, a timely corrective turn was not executed.
Several factors were considered regarding the pilot's actions. It was noted that the pilot may have continued on the existing course in anticipation of an updraught, or perhaps experienced a distraction that hindered the monitoring of the aircraft's descent. There was also the possibility that the pilot misjudged the strength of the downdraught or was unaware of its severity. Additionally, the pilot might have operated under the mistaken belief that the aircraft had already crossed the Main Divide to the west, potentially leading to a decision to maintain course in hopes of breaking out of the cloud into clearer conditions.