What happened
On April 30, 2016, at approximately 05:05 UTC, a training flight involving a flight instructor and a student pilot ended in an accident at Innsbruck Airport, Austria. The flight, which was the student's second training session of the day, was proceeding normally through several turns until the approach for runway 26.
During the crosswind leg of the approach, the instructor noted that the student had failed to extend the airbrakes. To manage the approach altitude, the instructor decided to perform a side-slip maneuver (left slip) to assist the student in descending. During the execution of this maneuver, the aircraft drifted to the right of the approach centerline. The instructor, focused on maintaining the correct altitude and monitoring the landing site, did not immediately realize the deviation from the centerline.
Approximately 50 to 60 meters above the ground, the instructor recognized the deviation and ceased the side-slip. As the maneuver was terminated, the nose of the AS-K 13 pitched up, causing a significant loss of airspeed and a subsequent stall. To avoid a collision with a hangar building located directly ahead, the instructor intentionally dipped the left wing. This maneuver induced a leftward rotation around the vertical axis, leading the tail of the aircraft to strike an airport fence. The impact caused the tail section to break away and resulted in heavy damage to the wings.
The investigation
The Austrian Federal Safety Investigation Board (SUB) examined the aircraft, the flight conditions, and the pilot's actions. The investigation confirmed that the aircraft's maintenance was up to date and that all necessary certifications and medical requirements for the crew were valid. The investigation also verified that the aircraft's weight and center of gravity were within permissible limits for the flight.
Findings
- The pilot's concentration on maintaining altitude and monitoring the landing site led to a failure to notice the aircraft drifting right of the approach centerline during the side-slip.
- The termination of the side-slip maneuver caused the aircraft nose to rise, leading to a loss of airspeed and a subsequent stall.
- The instructor's decision to dip the left wing was a deliberate action taken to prevent a collision with a hangar building.
- The resulting rotation caused the rear fuselage to collide with the airport perimeter fence, leading to the total loss of the aircraft.
- There were no pre-existing technical defects found in the aircraft's control surfaces or structural components.