What was found
ON FINAL APPROACH A/P WOULD NOT DISCONNECT WITH THE YOKE DISCONNECT SWITCHES OR THE ON/OFF SWITCH ON THE AUTO FLIGHT CONTROL PANEL. IT WAS NECESSARY TO PULL C/BS TO DISCONNECT A/P. REPLACED MODE CONTROL PANEL OPERATION NORMAL. ANALYSIS REVEALED THAT THE FGCP FAILURE WAS CAUSED BY A DEFECTIVE AUTOPILOT ENGAGE TOGGLE SWITCH. MICROSWITCH, DIVISION OF HONEYWELL INC HAS IDENTIFIED AN INFERIOR SWITCH MANUFACTURING PROCESS FOR SWITCHES PROCUCED FROM MAR 1991 TO MAY 1993. DELTA ISSUED A SPECIAL INSPECTION TO FIND AND REMOVE FROM SERVICE ALL SUSPECT UNITS.