What happened
On January 10, 2000, a Saab 340B, registration HB-AKK, operated by Crossair as flight CRX 498, crashed near Nassenwil, Switzerland. The aircraft was performing a standard departure from Zurich. During the initial climb, the flight crew was engaged in various cockpit procedures, including managing engine power, flight director settings, and navigation programming. As the aircraft climbed, it began to deviate from its intended flight path. The flight crew attempted to correct the deviation, but the aircraft entered an uncontrolled state characterized by increasingly rugged aileron and steering inputs. The aircraft's attitude became unstable, leading to a loss of control and a subsequent impact.
The investigation
The investigation examined the flight data recorder (FDR) and cockpit voice recorder (CVR) to reconstruct the final moments of the flight. Investigators analyzed the aircraft's systems, including the Electronic Flight Instrument System (EFIS), the Flight Management System (FMS), and the yaw damper. The inquiry also reviewed the flight crew's training backgrounds, noting that the crew had been trained in flight schools in the former USSR. Additionally, the investigation looked into the differences between Eastern-style gyroscopic compasses and Western-style instruments, specifically how the rotation of the compass rose affects a pilot's ability to recognize unusual attitudes. The investigation also noted the presence of Phenazepam in the commander's luggage.
Findings
- The aircraft experienced an uncontrolled deviation from its flight path that could not be recovered.
- There was a significant deviation from Standard Operating Procedures (SOPs), including interrupted communication loops and incomplete climb power settings.
- The flight crew's ability to recognize unusual attitudes was potentially compromised by the use of Western-style instrumentation, which differs fundamentally from the Eastern-style instruments used in their prior training.
- The commander became increasingly confused regarding the aircraft's attitude, while the copilot became increasingly aware of the dangerous attitude.