What happened
On July 24, 2008, a Dassault Falcon 900EX, registration OH-FFC, was performing a repositioning flight from Nice to Helsinki. While descending through flight level 400 in the Tallinn FIR, the pilot attempted to reduce the aircraft's speed. Instead of selecting the airbrake, the pilot accidentally moved the slats/flaps lever to position one.
At the time of the error, the aircraft was traveling at approximately 260 knots, which was roughly 60 knots above the maximum allowable speed for the selected configuration. This mistake caused the leading-edge slats and flaps to extend at excessive speed, triggering severe aerodynamic oscillations. The aircraft experienced rapid vertical and speed fluctuations, with accelerations ranging between +2.0g and -0.3g.
During the approximately 10 seconds of intense turbulence, a flight attendant working in the cabin was thrown against the ceiling multiple times, sustaining minor injuries including bruises and abrasions. The flight crew managed to regain control of the aircraft within 20 seconds by disconnecting the autopilot and autothrottle. The remainder of the flight and the landing at Helsinki-Vantaa proceeded normally.
The investigation
The investigation examined the cockpit ergonomics, the pilot's training, and the airline's operational procedures. Investigators noted that the pilot acting as the pilot flying was on his third line training flight and had relatively limited experience with this specific aircraft type.
Analysis of the cockpit layout revealed that the airbrake and slats/flaps levers are positioned very close to each other on the center console. Although the levers have different shapes and operating mechanisms, the proximity makes accidental selection possible. The investigation also revealed that the airline had experienced two similar incidents earlier in 2008, which had been reported only internally.
Findings
- The primary cause of the incident was the accidental selection of the slats/flaps lever instead of the airbrake lever.
- Contributing factors included the pilot's limited experience with the aircraft type and potential fatigue due to the length of the duty day.
- The ergonomic placement of the controls on the center console was identified as a significant contributing factor to the error.
- The deployment of the flight surfaces at excessive speed resulted in structural damage to the inner right-side slat and required the replacement of six flap actuators, with repair costs totaling approximately 135,000 Euros.
Safety action
Following the incident, the airline updated its Standard Operating Procedures (SOP) to include a specific verification process for airbrake use, requiring the pilot flying to call for confirmation and the pilot monitoring to verify the lever position and light indications.
Additionally, the investigator recommended that Dassault Aviation redesign the control layout or the lever mechanism to ensure the airbrake and slats/flaps controls are clearly distinct. The manufacturer noted that for newer models, such as the Falcon 7X, the airbrake mechanism would be modified to require a lifting motion before being pulled back to prevent such errors.