Incident Overview
On 24 June 2020, at approximately 10:56 local time, a serious airprox (dangerous approach) occurred near Innertkirchen, Canton Bern, Switzerland, at an altitude of about 7000 ft AMSL. The incident involved a Robin DR-400, registered HB-KFQ, and a Boeing F/A-18 Hornet fighter aircraft. Weather conditions were good and did not influence the event.
Sequence of Events
The pilot of the Robin DR-400 departed from Sion Airport (LSGS) around 10:15 LT with the intention to fly via the Grimsel Pass to the Hasli Valley, then cross the Terminal Control Area (TMA) and Control Zone (CTR) of Meiringen military airfield en route to Thun Airport (LSZW). The pilot, navigating terrestrially with a chart, attempted to obtain crossing clearance on frequency 135.475 MHz but was advised to contact Meiringen Tower on 130.150 MHz.
At 10:56:06 LT, the pilot contacted Meiringen Tower, stating "approaching Guttannen at 7600 ft, request crossing the CTR via north of the valley." At that moment, the aircraft was already north of Guttannen near Innertkirchen and within the TMA. The air traffic controller, unaware of the aircraft's actual position due to radar coverage gaps, instructed the pilot to hold over Guttannen and wait for clearance, as several F/A-18s had just departed from Runway 10 of Meiringen and were transiting the TMA towards the Susten Pass.
At 10:56:30 LT, a conflict occurred between the Robin DR-400 and one of the F/A-18s. The fighter pilot sighted the Robin about 5 seconds before closest approach and initiated an evasive descent, estimating the minimum distance at approximately 50 meters. The pilot of the Robin DR-400 did not perceive the dangerous approach or the evasive maneuver; he observed the fighters turning left after takeoff but considered it part of their normal departure route. After the encounter, he turned back toward Guttannen. He then re-established communication with the controller, who instructed him to continue holding. About two minutes later, the pilot received clearance to cross the CTR and later landed at Thun.
Analysis
The pilot of the Robin DR-400 was unaware of his exact location when he first called the tower; he believed he was south of Guttannen but was actually more than 5 km north, inside the TMA used by departing fighters. The controller also lacked accurate position information due to incomplete radar coverage of the DR-400's transponder, reasonably assuming the aircraft remained south of the TMA. The event highlights the importance of precise position determination, particularly to avoid airspace violations; terrestrial navigation with a chart can be challenging for accurately estimating distances to airspace boundaries.
Conclusion
The Swiss Transportation Safety Investigation Board (STSB) conducted a summary investigation under Article 45 of the Ordinance on Safety Investigation of Transport Incidents. No further investigative measures were pursued, as no additional findings beneficial for prevention were expected. The investigation was closed on 21 July 2022.