What happened
On November 2, 1980, a DC-6A, registration HB-IBS, was conducting a commercial sightseeing flight over the Alps from Basel-Mulhouse. The flight, operated by Balair AG, included a crew of three, a steward, two flight attendants, and 6 and 68 passengers.
While flying near the Matterhorn at approximately 15,000 feet, the aircraft first encountered moderate turbulence. The captain subsequently increased the altitude to 16,500 feet. During a subsequent maneuver to provide passengers with a view of the Dent Blanche, the aircraft entered a second, much more violent period of turbulence southeast of the Matterhorn. Because several passengers were not secured in their seats, the sudden movement caused physical injuries, including a serious spinal fracture to one female passenger who was thrown into the aisle. A flight attendant was also injured when she was knocked down while attempting to check seatbelts.
The investigation
The investigation examined the flight conditions, crew communications, and passenger safety protocols. It was established that the crew was fully qualified and the weather conditions, while clear, featured significant winds from the northwest. The investigation also looked into the effectiveness of the cabin crew's warnings and the instructions provided to passengers prior to takeoff.
Findings
- The aircraft entered an area of strong turbulence caused by the prevailing wind conditions near the mountain peaks.
- Prior to departure, a tour leader had informed passengers that they could unbuckle their belts to swap seats so that everyone could enjoy a window view.
- Although the co-pilot issued multiple verbal warnings via the loudspeaker to fasten seatbelts, many passengers and some cabin crew members failed to hear or understand the announcements due to engine noise and distractions from the scenery.
- The decision to fly close to the Matterhorn's southeast side, despite known turbulence risks in northwest winds, contributed to the severity of the event.
Safety action
- The investigation noted that the tour leader's instruction to allow passengers to unbuckle during the flight was inappropriate for safety.
- The practice of turning off the seatbelt sign while flying through potentially turbulent mountain terrain was also deemed unwise.