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Pilot v Autopilot

PUBLISHED: 11:40 23 June 2011 | UPDATED: 14:04 10 October 2012

In September 1999 a Dassault Falcon 900 suffered violent pitch oscillations, killing six of the passengers. The aircraft was being operated for the Greek government by Olympic Airways, and was in Romanian airspace.

In September 1999 a Dassault Falcon 900 suffered violent pitch oscillations, killing six of the passengers. The aircraft was being operated for the Greek government by Olympic Airways, and was in Romanian airspace.

The incident has been investigated by an international team, headed by

Romanian officials with French, Greek, German, UK and U.S. cooperation.

Initial theories about clearair turbulence have been replaced by suspected pilotinduced oscillations as the crew sought to override an autopilot on which the pitchfeel feedback failed. A similar, nonfatal incident has since

occurred to another Falcon 900, this time in the USA.

France's DGAC and the FAA have issued ADs requiring the aircraft’s speed to be limited when the 'pitchfeel' light is on, indicating that the feedback to the pilot is reduced by the absence of artificial feel.

The investigators compared information from the first aircraft's flight data recorder and the autopilot. The aircraft had been at about 14,000 feet, on autopilot, and descending at 2,400 fpm at 330 knots. The pilot pulled back on

the yoke, without disengaging the autopilot. The autopilot reacted by increasing

nosedown trim.

When the pilot then released the yoke, the nose pitched down further, the autopilot disconnected, and the pilotinduced oscillations reached +4.4/3.3 g. At one point, when the pilot's autopilot failed, control was automatically transferred to the copilot's autopilot.

The French investigators concluded that had the pilot simply let go of the yoke, the oscillations would have damped within two seconds. The flight controls and the autopilot system itself were intact, but the unit creating

artificial feel, or feedback, had failed when outside its 'normal' position.

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