About: The National Transportation Safety Board determines that the probable cause of this accident was the descent below Minimum Descent Altitude during a nonprecision approach under adverse operating conditions, without visual contact with the runway environment. The Board has been unable to determine the reason for this descent, although the two most likely explanations are (a) improper use of cockpit instrumentation data, or (b) an altimetry system error.       Sponge   NotDistinct   Permalink