What happened
On a night-time repositioning flight from Thompson to Island Lake, Manitoba, the crew of a Sky North Air Ltd. Beech 100, registration C-GNAA, attempted an instrument approach to Runway 12. During the final approach segment, the aircraft descended 300 feet below the minimum descent altitude (MDA).
As the crew initiated a missed approach to climb away from the terrain, the aircraft's right wing and landing gear doors struck trees at an elevation of approximately 840 feet. Following the impact, the crew managed to climb to 2000 feet and return to Runway 12 to land without further incident. There were no injuries to the two crew members.
The investigation
The investigation examined the flight crew's actions, the aircraft's equipment, and the operator's training protocols. It was established that the crew was performing an RNAV approach for which the operator, Sky North Air Ltd., was not authorized and for which the pilots had not received specific training.
Several technical and procedural factors were identified:
- The aircraft's GPS unit was installed for en route use but was not approved for conducting RNAV approaches, and its data was not integrated with primary flight instruments.
- The altitude alerter's aural warning had been silenced by the crew prior to the approach, preventing an audible alert when the aircraft descended below the MDA.
- A series of rapid configuration changes—including landing gear extension, propeller RPM adjustment, and flap setting—occurred in a short window, destabilizing the approach.
- The first officer's altimeter, a three-pointer analog type, was noted to be more difficult to read at a glance.
Findings
- The crew conducted an unauthorized RNAV approach using an aircraft that was not properly equipped or approved for such procedures.
- The aircraft descended below the MDA due to a combination of errors and lapses in managing the approach.
- The silencing of the altitude alerter's aural warning precluded the crew from being alerted to the altitude deviation.
- The lack of a structured training environment and simulator-based instruction contributed to a lack of adherence to standard operating procedures.
- The rapid sequence of configuration changes near the MDA caused the aircraft to depart from a stabilized descent, leading to the descent below minimums.