Flight Background
The flight was part of a group excursion by the Motorfluggruppe Birrfeld to Siena, Italy. The pilot and passenger, both group members, prepared for the trip on the morning of 28 May 2003. Weather conditions in the Bernese Alps and the Mittelland were challenging due to low cloud ceilings and a blocking situation, preventing the originally planned crossing of the Gemmi Pass. The pilot and passenger reviewed weather information and adjusted their route. The passenger, who held a private pilot license that had expired on 17 February 2003, assisted with preparations.
Flight Sequence
The pilot departed from Birrfeld airfield at 11:47 local time. The flight route, as recorded by radar and the aircraft's GPS, initially passed through Schinznach, Wildegg, and Hunzenschwil before reaching the VOR Willisau at approximately 12:03. After crossing the VOR, the aircraft flew on a course of about 206 degrees toward Huttwil at an altitude of 3,100 feet. The flight then turned slightly right over eastern Huttwil, then left over Wyssachen, and entered a climbing left turn near Mannshus. At approximately 12:08, while on a westerly heading near the crest of Bärhegechnübeli at 3,271 feet, the aircraft struck several trees and subsequently crashed into the slope behind the crest.
Investigation Findings
The Accident Investigation Bureau (BFU) opened an investigation on the same day. The aircraft was destroyed, and both occupants were killed. The investigation determined that the accident occurred because the pilot continued flight under visual flight rules into instrument meteorological conditions. The aircraft then collided with trees and terrain.