CAPT OF B747-400 ON AN INTL FLT BECAME ILL AND HAD THE SENIOR FO TAKE OVER AND LAND ACFT AT DEST.

Narrative

TO MY THINKING; THERE IS REALLY NO PROB TO THE OP OF THE SPECIFIC FLT I SHALL DESCRIBE; BUT THE SIT DOES BEAR DOCUMENTATION AND CONSIDERATION IN THE GREATER SCHEME OF AIR SAFETY. THE FLT IN QUESTION WAS LONG RANGE INTL IN A B747-400 FROM NARITA TO CHICAGO. THE ACFT IS CERTIFIED FOR 2 PLTS BUT WAS OPERATED ON THIS TRIP WITH A DOUBLE AUGMENTED CREW BECAUSE OF COMPANY ASSOCIATION WORKING AGREEMENT. I WAS PLT IN CTL FOR TKOF IN NARITA AND WORKING THE FIRST SHIFT (ABOUT 5 1/2 HRS) WITH THE CAPT. ABOUT 1 HR BEFORE BEING RELIEVED BY THE RELIEF FO'S WHO WERE ASLEEP; THE CAPT ASKED ME TO TAKE OVER THE RADIO AND FLT PLAN MONITORING DUTIES BECAUSE HE DID NOT FEEL WELL. HE STATED THAT HE HAD GOTTEN A MIGRAINE HEADACHE AND FELT NAUSEOUS AS WELL. ON 1 OCCASION HE ATTEMPTED TO QUESTION WHETHER I HAD MADE A RPT OR NOT AND WAS NOT ABLE TO GET THE WORDS OUT. AT THIS POINT I COULD SEE HE WAS IN GREAT PAIN AND SUGGESTED THAT WE WAKE UP A RELIEF PLT EARLY WHICH I DID SHORTLY THEREAFTER. FOLLOWING MY BREAK; I RETURNED TO THE COPLT'S SEAT FOR APCH AND LNDG IN CHICAGO. THE CAPT; AT THE END OF HIS REST; WAS WORSE RATHER THAN BETTER AND ELECTED TO SIT IN THE SECOND JUMP SEAT FOR THE REMAINDER OF THE FLT. AS SENIOR COPLT I FLEW THE APCH; LANDED AND TAXIED TO THE GATE. THE OTHER COPLTS OCCUPIED THE CAPT'S SEAT AND CTR JUMPSEAT AND OPERATED AS WE NORMALLY WOULD. THE FLT WAS OPERATIONALLY UNEVENTFUL. ALTHOUGH THE CAPT WAS NOT UNCONSCIOUS HIS ABILITY WAS IMPAIRED. IT WOULD BE DIFFICULT TO SAY THAT HE WAS INCAPACITATED. HIS DECISION TO UTILIZE EXTRA CREW MEMBERS SHOWED GOOD JUDGEMENT IN THIS CASE. MANY PLTS WOULD HAVE BEEN TEMPTED TO 'TOUGH IT OUT' TO THE POSSIBLE DETRIMENT OF AIR SAFETY.