Incident
On 7 April 2018 at 14:10 local time, a serious incident involving a near collision occurred approximately 2 km northwest of Buttwil Airfield (LSZU) at an altitude of 3100 ft AMSL. The two aircraft involved were a Reims Aviation F152 (registration HB-CCN) and an Archaeopteryx hang glider with an electric motor.
The F152, operated by Flugschule Eichenberger AG, was conducting a training flight with a flight instructor and a student pilot. After a navigation flight, the instructor and student performed an additional traffic pattern for training. They took off from runway 34 shortly after 14:00. While turning into the left downwind leg along the visual approach chart route, the student pilot noticed the Archaeopteryx crossing its flight path from left to right at the same altitude. The hang glider pilot had also departed from Buttwil and was on a local thermal flight.
The instructor immediately took over control and initiated a full left circle to avoid the hang glider. The two aircraft passed within less than 200 meters of each other, both at the same altitude. Both aircraft subsequently landed at Buttwil without further incident.
Aircraft and Operations
Reims Aviation F152 (HB-CCN)
- Type: Reims Aviation F152, identical to Cessna 152, built under license in France.
- Owner: Flugschule Eichenberger AG, Buttwil.
- Operation: Training flight under Visual Flight Rules (VFR); flight phase: approach.
- Flight Crew:
- Flight instructor: Swiss citizen, born 1959. Held a Commercial Pilot Licence (CPL(A)) issued by the Federal Office of Civil Aviation (BAZL). Total flight hours: 6260; 90 in the last 90 days; 5100 on type; 65 on type in the last 90 days.
- Student pilot: Swiss citizen, born 1984. Total flight hours: 45; all on type; 6 in the last 90 days.
- Both departure and destination were Buttwil Airfield.
Archaeopteryx Hang Glider
- Type: Archaeopteryx with electric motor, three-axis controlled.
- Owner: Private.
- Operation: Private flight under VFR; flight phase: cruise.
- Pilot: Swiss citizen, born 1960.
- Both departure and destination were Buttwil Airfield.
Airspace and Regulations
The incident occurred in Class G airspace. According to Swiss regulations, operation of hang gliders within a distance of less than 5 km from the runways of a civil or military airfield, or 2.5 km from the reference point of a heliport, below 2000 ft above aerodrome elevation (AAE), is prohibited. Exceptions for Buttwil may only be granted by the airfield manager.
The Archaeopteryx was one of three motorized hang gliders of this type stationed at Buttwil. The pilots of these hang gliders were members of the local gliding group, and regular operation was carried out in consultation with the Buttwil airfield operator.
Safety Equipment
Both aircraft were equipped with Flarm collision warning devices. However, it could not be determined whether a warning was issued on either device.
Reporting
The Swiss Transportation Safety Investigation Board (STSB) learned of the incident on 9 April 2018 after the F152 instructor filed a report via the EU occurrence reporting portal, classifying the approach as dangerous. An immediate report to the STSB reporting office, as required by Article 17 of the Swiss Ordinance on the Safety Investigation of Transport Incidents (VSZV), was not made. According to the Swiss Aeronautical Information Publication (AIP), accidents and serious incidents must be reported immediately to the REGA alarm center (telephone 1414).