An Airbus Industrie A320 incident in which the rudder pedal operation remained stiff after autopilot disconnect has led the US National Transportation Safety Board (NTSB) to call for an April 1997 Airbus service bulletin (SB) to be made compulsory. The NTSB cites a pilot report on a November 1996 Northwest Airlines landing during which runway alignment adjustments had to be made with roll controls only. Airbus tests found that, at autopilot disconnect, the rudder artificial feel and trim unit could remain connected to the autopilot, making rudder pedal operation heavy. The SB ensures unit disconnect.
Source: Flight International
