What happened
On April 17, 1969, a Lear Jet 25, registration N-515 VW, departed Geneva for Basel-Mulhouse as a private flight under IFR conditions. The flight was intended for routine maintenance purposes. During the descent toward Basel, the aircraft encountered unstable weather characterized by maritime air masses, heavy snow, and moderate to heavy icing conditions.
As the aircraft approached the Basel-Mulhouse area, the crew communicated their positions via several radio beacons, including Hochwald and Sierentz. While attempting to establish the ILS approach, the crew experienced significant navigation difficulties. After a period of radio silence, the crew informed air traffic control that they were experiencing problems and intended to return to the Homburg beacon, requesting to climb to 3/500 feet. However, due to other traffic in the area, controllers instructed the aircraft to maintain 2,500 feet. Shortly thereafter, radio contact was lost.
On April 20, 1969, the wreckage and the two fatalities (the pilot and co-pilot) were discovered by a farmer on a wooded slope near Corban, in the Bernese Jura, approximately 13.5 nautical miles south of Basel-Mulhouse.
The investigation
The investigation examined the wreckage, which was found in a heavily burned state on a 35-degree slope. Investigators analyzed the flight's radio communications and the aircraft's navigation equipment. The investigation also reviewed the meteorological conditions, which included heavy precipitation and potential interference with radio compasses due to static electricity.
Findings
- The aircraft likely failed to intercept the ILS localizer beam, possibly due to a turn made at excessive speed.
- The crew reported a loss of RMI (Radio Magnetic Indicator) functionality, which may have been caused by atmospheric disturbances affecting the ADF signals.
- The crew did not explicitly declare a missed approach procedure, leading controllers to believe they were entering a holding pattern.
- The collision with terrain occurred while the aircraft was attempting to maneuver back toward the Homburg beacon after the interrupted approach.
- The instruction to maintain 2,500 feet prevented the crew from climbing to a safer altitude to clear the Jura ridges.