What happened
On 3 January 2021, a privately owned Mooney M20F departed from Airdrie Aerodrome (CEF4), Alberta, intended for a flight to Nelson Aerodrome (CZNL), British Columbia. The flight was being conducted under instrument flight rules (IFR) with a single pilot on board.
While flying through instrument meteorological conditions, the pilot experienced a failure of the aircraft's attitude indicator. Upon realizing the instrument was non-functional, the pilot declared an emergency with air traffic control (ATC). While following instructions from ATC to manage the situation, the aircraft entered an unintentional descent during a left turn. This maneuver caused the aircraft to enter a valley near Kananaskis Lake, Alberta.
During the descent, the aircraft lost direct radio communication with ATC. However, the pilot managed to maintain emergency communications by relaying messages through other aircraft operating in the same airspace. Following the incident, the aircraft successfully returned to Airdrie Aerodrome without further complications.
The investigation
The TSB conducted a Class 4 investigation into the event, focusing on the sequence of the instrument failure and the subsequent loss of control during the turn.