What happened
On April 6, 1992, at approximately 19:37 local time, a Piper Warrior II PA-28-161 with registration HB-PGD departed from Basel-EuroAirport. The aircraft was piloted by a female private pilot who had not flown solo in exactly one year and had never previously conducted an unaccompanied flight without the supervision of a flight instructor. She filed a verbal flight plan rather than a written one, and no specific route was established other than a general area over the Laufon valley.
Radar data and witness accounts indicate that the aircraft performed several circles and 180-degree turns at altitudes around 3,000 feet QNH. After passing the waypoint "SW," she climbed to 3,200 feet and was instructed to switch to the "Basel Information" frequency, but no contact was ever made on that channel. The last radio communication with the control tower occurred at 19:43:33.
Witnesses observed the aircraft flying clean maneuvers in the Dittingen and Röschenz area near the Forstberg. In its final phase, the aircraft flew north of the Blauen mountain, executed a tight turn, and then descended over the Forstberg ridge toward the southwest before turning west. At approximately 20:06, the Piper crashed at high speed into the wooded southern slope of the Forstberg. The impact was catastrophic, destroying the airframe entirely. There were no survivors.
The investigation
The Swiss Transportation Safety Investigation Board (then EFUK) examined the flight history, medical records, and wreckage. The pilot had a total of 251 hours of experience, all accumulated since October 1976. Crucially, her logbook showed that every previous flight was either accompanied by an instructor or logged as a supervised solo flight; she had no record of independent navigation or decision-making.
Medical investigations revealed a critical gap in care coordination. The pilot had been hospitalized in February 1992 for benzodiazepine and barbiturate ingestion following a diagnosis of acute psychosis by her family doctor on October 1, 1991. Although she was discharged from psychiatric care in early March, her family doctor noted in April that she remained "psychotically" unstable. However, the Federal Office of Civil Aviation's medical advisor was never informed of this condition.
Technical inspections of the wreckage confirmed the engine was producing full power at impact, and there were no mechanical failures. The pilot’s last medical exam in May 1990 had cleared her as fit without restrictions. Alcohol and other drugs were not detected in her system, but the presence of prescribed psychotropic medications was noted.
Findings
The investigation concluded that the pilot flew in a mentally unfit state caused by psychosis. The primary causal factors included:
- The pilot’s acute psychological condition, which rendered her incapable of safe flight operations.
- A failure in the medical reporting system: her treating physicians did not inform the aviation medical authority of her diagnosis and ongoing treatment.
- The pilot’s lack of recent solo experience and absence of a flight instructor for this unaccompanied flight, despite her history of always flying under supervision.
Safety action
The investigation commission issued a recommendation to examine how treating physicians can effectively communicate with the medical advisor of the Federal Office of Civil Aviation. The goal was to establish a cooperation framework to ensure that pilots undergoing psychiatric treatment are properly monitored regarding their fitness to fly.