Background
The flight was a repositioning operation from Thompson to Island Lake, Manitoba. The crew initiated an instrument approach to Runway 12 at Island Lake.
Sequence of Events
On the final approach segment, the aircraft descended below the minimum descent altitude (MDA), prompting the crew to execute a missed approach. During the missed approach, the aircraft struck trees. Despite the impact, the crew managed to return to Island Lake and land on Runway 12 without further incident. The accident occurred during hours of darkness at approximately 2110 Central Standard Time. The two crew members were not injured, but the aircraft sustained damage to its right wing and landing gear doors.
Probable Cause
The official investigation identified contributing factors: the crew conducted an Area Navigation (RNAV) approach for which they were not trained, with an aircraft not properly equipped or approved for such use. The aircraft descended 300 feet below the MDA due to a combination of lapses, errors, and adaptations leading to a mismanaged approach. The aural warning on the altitude alerter had been silenced prior to the approach, preventing it from alerting the crew when descending below the MDA. Additionally, SkyNorth standard operating procedures for non-precision approaches were not followed, resulting in the descent below the MDA. During the ensuing missed approach, the aircraft struck trees.
Risk Factors
The investigation noted that the lack of a more-structured training environment and the type of supervisory flying provided increased the risk that deviations from standard operating procedures (SOPs) would not be identified. It was also noted that several instrument approach procedures in Canada contain step-down fixes not displayed on GPS units, which may increase the risk of collision with obstacles during step-downs on approaches.