Incident Overview
The serious incident, classified as ICAO Category A (high collision risk), involved a Piper PA-28-181 Archer II, registration HB-PPY, and two military parachutists from the Swiss Army's Parachute Reconnaissance Company 17. The incident occurred on June 26, 2016, at 13:14 UTC at Grenchen Airfield (LSZG). The closest proximity was approximately 40 m horizontally, with both aircraft at the same altitude.
Sequence of Events
On the afternoon of the incident, a group of five parachute reconnaissance soldiers planned a training jump over Grenchen Airfield, with a target landing on the threshold of grass runway 07L. At the same time, the Piper PA-28 was on an outer traffic pattern for runway 07. During the final approach, the aerodrome control officer (ADCO) instructed the Piper pilot to continue the approach to grass runway 07R and then perform a go-around. Shortly before the last two parachutists landed on the threshold of grass runway 07L, the ADCO observed that the Piper was also on final approach to runway 07L and ordered an immediate evasive turn.
Investigation Findings
The Swiss Transportation Safety Investigation Board (STSB) determined that the incident was caused by the pilot of the light aircraft aiming for the wrong runway due to confusion during the final approach. A contributing factor was that the aerodrome controller had altered his original separation concept without providing the pilot with information about the approaching parachutists. The investigation also noted that the concurrent presence of air traffic and parachutists without clearly defined spatial or temporal separation was not identified as causal or contributory, but represented a systemic risk.
Aircraft and Personnel
The Piper PA-28-181 was privately owned and operated by Segel- und Motorfluggruppe Grenchen. The pilot was flying under visual flight rules (VFR) on a private flight, departing and arriving at Grenchen. The military parachutists were operating under VFR as well, departing from Reichenbach Airfield (LSGR). The air traffic control was provided by Grenchen Aerodrome Control.
Meteorological Conditions
Weather conditions were consistent with visual flight, though specific details are not elaborated in the report beyond the general situation.
Aftermath
No injuries or damage were reported. The incident was reported to the STSB on June 27, 2016, and the investigation was opened on July 15, 2016. Since the event, the STSB issued safety recommendations and notices, and the relevant parties have taken measures to prevent recurrence.