The US Federal Aviation Administration (FAA) has issued an emergency airworthiness directive to airlines operating Boeing 737 MAX 8s and 9s.
The directive, which must be implemented within three days, says that there is a potential problem where incorrect angle of attack sensor input can cause the flight control system to send commands to the horizontal stabiliser to push the nose down. If the condition is not addressed, it could cause the flight crew to have difficulty controlling the aircraft, possibly with significant loss of altitude. The directive requires operators of the MAX 8 and MAX 9 to revise the aircraft’s flight manual to provide the crew with horizontal stabiliser trim procedures to follow under certain conditions. The announcement follows preliminary investigations into the crash of Lion Air 737 MAX 8.