Severe Pitch Oscillations Lead to Injuries on Falcon 900B

Casualties unknown • Bucharest FIR Area – ROMANIA, FR

A government flight involving a Falcon 900B experienced violent pitch oscillations during descent, resulting in seven fatalities due to unsecured passengers.

What happened

On September 14, 1999, a Falcon 900B, registration SX-ECH, operated by Olympic Airways, was performing a government flight from Athens to Bucharest. During the initial climb, after the retraction of flaps and slats, the flight crew observed the "PITCH FEEL" warning light illuminate. The crew disengaged the autopilot to check control forces before re-engulating it, but the warning light remained active throughout the cruise and descent phases.

As the aircraft descended through FL 150, the indicated airspeed increased significantly from 240 knots to 332 knots. During this phase, the autopilot disengaged, and the pilot in command began flying the aircraft manually. Between FL 150 and FL 140, the aircraft entered a period of intense instability, undergoing 10 pitch oscillations within approximately 24 seconds. These oscillations were severe, with vertical accelerations reaching as high as +4.7 g and -3.26 g.

Because passengers were not wearing seat belts during the descent, the violent vertical accelerations caused them to strike the cabin ceiling and furniture. The event resulted in 7 fatalities, one serious injury to a crew member, and several other injuries to passengers.

The investigation

The investigation, conducted by the Romanian Civil Aviation Inspectorate with support from the French BEA and the US NTSB, focused on the flight data recorder (DFDR) and cockpit voice recorder (CVR) analysis. Investigators examined the aircraft's flight guidance computers and the functionality of the "Arthur" unit (the artificial feel unit). Technical bench tests were performed on the autopilot servomotor and the horizontal stabilizer actuators to determine if mechanical or electronic failures contributed to the loss of control stability.

Findings

  • The crew failed to perform an adequate risk assessment regarding the ongoing "PITCH FEEL" malfunction.
  • The pilot in command overrode the autopilot on the pitch channel during a period of high airspeed.
  • Inappropriate control column inputs were made while the aircraft was at high speed and while the artificial feel unit was stuck in a "low-speed" configuration, which triggered Pilot Induced Oscillations.
  • Passengers were not secured with seat belts during the descent phase, directly leading to the fatal injuries during the vertical accelerations.

Probable cause

The accident was caused by pilot-induced oscillations resulting from inappropriate manual control inputs during high-speed flight, compounded by a malfunctioning artificial feel unit and an inadequate assessment of the existing pitch warning.

Frequently asked questions

What happened in the 1999-09-14 aircraft accident near Bucharest FIR Area – ROMANIA, FR?

A government flight involving a Falcon 900B experienced violent pitch oscillations during descent, resulting in seven fatalities due to unsecured passengers.

What aircraft was involved and where did it happen?

The accident on 1999-09-14 involved a aircraft, registration SX-ECH, at Bucharest FIR Area – ROMANIA, FR.

What was the probable cause of the accident?

The accident was caused by pilot-induced oscillations resulting from inappropriate manual control inputs during high-speed flight, compounded by a malfunctioning artificial feel unit and an inadequate assessment of the existing pitch warning.

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