2 r 3 autopilots for cat III

Date:         29 Dec 98 03:12:37 
From:         piqueme1@hotmail.com (Peter)
Organization: MindSpring Enterprises
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Why do some catagory 3 airliners have two autopilots (Douglas), and
some have 3 autopilots (Boeing)?  Catagory 3 refers to airport weather
approaching zero visability.