ACR WDB DEVIATION FROM CLRNC ROUTE FOLLOWING WX AVOIDANCE.

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FL390; A1 ARWY; WBOUND. JUST PRIOR TO CAVOI-X A SERIES OF ISOLATED CB'S APPEARED ON RADAR REQUIRING DIVERSION S OF COURSE. IT APPEARED AT FIRST THAT WE COULD AVOID CB'S AND STAY WITHIN THE CONFINES OF THE ARWY. THE AUTOPLT WAS PLACED IN HDG MODE DURING THE SERIES OF DIVERSIONS. COM WAS DIFFICULT DUE TO MULTIPLE AGENCIES; MULTIPLE FREQS; LANGUAGE; POOR GND EQUIP IN THAT AREA; AND AN INOP T/R ON THE ACFT; ETC. DAN VOR WAS NOTAMED UNRELIABLE. REQUIRED POS RPTS WERE MADE. WE CROSSED CAVOI-X ON COURSE; STILL IN HEAD MODE OF AUTOPLT; BUT STILL DIVERTING FOR WX. DUE TO HUMAN FACTORS AND COCKPIT ENVIRONMENT HDG MODE WAS FORGOTTEN; WITH A CORRECTION TO COURSE; FOR A SHORT TIME; CAUSING A DIVERSION N OF COURSE. AT DAN BY APPROX 24 MI; AT APPROX ABEAM DAN; MISTAKES NOTICED AND IMMEDIATE TURN TO REGAIN COURSE TO PAPRA-X. 'ABEAM DAN; DIVERTING' RPTED TO BKK RADIO. NON RADAR ENVIRONMENT. HUMAN FACTORS CONTRIBUTING WERE PRIMARILY ASSOCIATED WITH THE BODY WISHING TO BE ASLEEP WHILE FORCED TO BE AWAKE AND THE ACCOMPANYING FATIGUE. UNDER THESE BODY CONDITIONS; THE CRITICAL SHORT DURATION STAGES OF FLT SUCH AS THE APCH AND LNDG; OR EMERS; CAN BE SUCCESSFULLY ACCOMPLISHED DUE TO 'GETTING UP' WITH ADRENALINE FOR THE SHORT DURATION EVENT. UNFORTUNATELY THE MUNDANE; ORDINARY FLT DUTIES TEND TO BE UNINTENTIONALLY HANDLED WITH LESSER INTENSITY; ACCURACY AND PRECISION; LEAVING ONE SUSCEPTIBLE TO THE ABOVE TYPE OF SITUATIONS. CONSCIOUS EFFORT TO AVOID SUCH INCIDENTS AND THESE CONDITIONS WORK SUCCESSFULLY MOST TIMES. WE WERE FAILED AND CAN ONLY INCREASE OUR EFFORTS AT PRECISION IN THE FUTURE. THIS PLT WILL USE HDG MODE VERY JUDICIOUSLY IN THE FUTURE AND WILL MAKE ENRTE DIVERSIONS USING THE TURN KNOB OF THE AUTOPLT AS SOP.