What happened
On February 23, 1989, a Gulfstream Commander 690D, registration OE-FCS, was operating a scheduled charter flight from Vienna to Hohenems. Due to heavy fog at the intended destination, the crew diverted to Altenrhein. While the weather at Altenrhein initially appeared suitable for a visual approach, the aircraft encountered significantly worse conditions during its descent.
After navigating via the Altenrhein NDB, the crew transitioned from IFR to VFR flight rules. During the final approach to runway 10, the aircraft entered a dense fog layer. Witnesses observed the plane flying at a very low altitude near the shoreline before it struck the surface of Lake Constance, approximately 5,100 meters short of the runway threshold. The impact resulted in 11 fatalities, including the entire crew and nine passengers, and the total destruction of the aircraft.
The investigation
SUST examined the aircraft's maintenance records, flight logs, and the meteorological conditions at the time of the accident. The investigation established that the aircraft was overweight at departure, exceeding the maximum takeoff mass by 411 lbs. Additionally, the zero fuel weight was 61 lbs above the limit.
Investigators also analyzed the crew's performance and the use of onboard technology. The investigation found that the aircraft's altitude alert system was set to 1,60 and that the radar altimeter and weather radar were not utilized effectively during the approach. While there was a suspected issue with the flap extension cables due to fatigue, investigators ruled out asymmetric flap deployment as the primary cause of the crash, noting the aircraft was in a normal attitude just before impact.
Findings
- The primary cause of the accident was the crew continuing a visual approach under instrument meteorological conditions (IMC).
- The crew misjudged the actual weather conditions within the approach sector.
- There was a breakdown in crew coordination and task sharing during the final approach phase.
- The crew was subject to time pressure due to deteriorating weather and perceived pressure to complete the landing due to the presence of a VIP passenger on board.
- The altitude alert and radar altimeter systems were used inappropriately.