What happened
On May 26, 2016, at Mollis Airport (LSMF), two aircraft were participating in a formation flight training session as part of an annual flight display course. The formation consisted of a Boeing Stearman E75, registered as HB-RBG, acting as the lead aircraft, and two Pilatus PC-7s acting as wingmen. The second aircraft involved in the collision was a Pilatus PC-7, registered as T7-FUN.
After performing several maneuvers, including a low-level pass and a full circle, the lead pilot issued the command "Grande" to initiate the separation of the formation. Following this command, the two PC-7 wingmen increased power to overtake the Stearman. While the wingmen were in the process of maneuvering, the pilot of the HB-RBG initiated a vertical flight maneuver. During this climb, the left upper wing of the Boeing Stearman E75 struck the right wingtip of the T7-FUN.
The collision caused the Stearman to roll sharply to the left. The pilot managed to regain control and performed a safe landing at Mollis. The T7-FUN also returned to the aerodrome without further incident. While there were no fatalities or injuries to the crews or passengers, both aircraft sustained heavy damage.
The investigation
SUST examined the flight planning, the briefing process, and the maneuvers executed by the pilots. The investigation looked into the roles of the three aircraft involved, including a third Pilatus PC-7 (T7-FMA) that was present but not involved in the impact. The investigators also reviewed the training backgrounds of the pilots and the specific procedures used during the formation separation.
Findings
- The primary cause of the collision was that the lead pilot initiated a vertical maneuver before ensuring the wingmen were at a safe distance.
- The flight plan involved crossing flight paths and maneuvers that created a high risk of collision.
- There was a lack of visual contact between the pilots during the critical phase of the separation.
- A misunderstanding existed between the participating pilots regarding their specific roles and responsibilities during the maneuver.
- The lead pilot's training regarding his specific functions within a formation flight was found to be insufficient.
Safety action
Following the investigation, SUST issued a safety recommendation to the Federal Office of Civil Aviation (BAZL) to ensure that pilots authorized for formation flight displays are adequately trained for their specific positions within a formation. Additionally, a safety notice was issued emphasizing the need for detailed flight planning and comprehensive briefings to manage the complexities of formation maneuvers and prevent similar occurrences.