What happened
On January 21, 2024, at approximately 16:45 local time, two light aircraft were engaged in a coordinated formation flight near Ballwil, Switzerland. The first aircraft, a Piper PA-28R-201T with registration HB-PQG, was flying with a pilot and two passengers. The second aircraft, a Gyroflug SC01 known as a Speed Canard with registration HB-UCT, carried a pilot and one passenger. Both aircraft were traveling from Raron toward Birrfeld.
The pilots, who were friends, had previously flown in similar loose formations to take photographs. During this flight, the aircraft approached each other at 10,000 ft AMSL and later descended to 5,000 ft AMSL. While flying near the Ägerisee, the pilot of the HB-PQG attempted a side-change maneuver to position the aircraft behind and above the HB-UCT to capture better sunset imagery. During this maneuver, the pilot of the HB-PQG increased the nose attitude, causing the aircraft to slow down and lose visual contact with the lead aircraft. This loss of contact was not communicated via radio.
As the pilot of the HB-PQG focused on searching for the lead aircraft, the two planes collided vertically. The upper forward fuselage and propeller of the HB-PQG struck the lower rear fuselage, main landing gear, and propeller of the HB and-UCT. The impact caused the engine of the HB-PQG to stop and damaged its windshield. The HB-UCT experienced a sudden pitch change of 20 to 30 degrees nose-down. Both aircraft performed emergency landings; the HB-PQG landed in a field near Emmen, while the HB-UCT successfully landed on the runway at Emmen airfield. There were no fatalities and no injuries to the crew or passengers, though both aircraft sustained heavy damage.
The investigation
SUST examined flight data, radar records, and GPS logs. The investigation focused on the briefing procedures, the specific flight maneuvers performed during the side-change, and the communication between the two crews. The investigators also reviewed the meteorological conditions, noting that while there were moderate turbulences due to an inversion, the weather and sun position did not contribute to the accident.
Findings
- The primary cause of the collision was the loss of visual contact during a side-change maneuver within the formation.
- The choice of maneuver—climbing to move behind and above the lead aircraft—was inappropriate for a side-change, as it increased the risk of losing sight of the leader.
- There was a lack of pre-established procedures or communication protocols to handle an unexpected loss of visual contact.
- The pilot of the HB-PQG did not communicate the loss of visual contact over the shared radio frequency.
- The pilots had not sufficiently discussed the risks associated with position changes in formation flight.