Boeing Company today published an update to the flight crew operations manual for its 737 Max 8, warning of a possible fault in the aircraft's angle of attack system that could cause the aircraft to violently pitch nose down, according to the FAA. The AOA measures the angular difference between the direction the aircraft is moving and the pitch of the aircraft's wing. The agency followed the ops manual update with an emergency airworthiness directive against the aircraft, warning operators the pitch-over threat exists even when the aircraft is being hand flown by pilots. The agency said operators have less than 30 days to comply with the AD.