FATIGUED FLT CREW OF B767 FAILED TO ENGAGE LNAV DIRECT TO HNL AND DEVIATED FROM COURSE. LOST COM WITH ZHN.

Narrative

THIS WAS THE FINAL HR OF FLT ON A TRIP THAT DEPARTED AT XA10 AND WAS A TURN FROM HONOLULU TO ZZZ AND BACK. THE CAPT AND I WERE DEADHEADING CREW FROM HONOLULU TO ZZZ AND WERE ONLY ABLE TO OBTAIN ABOUT 1 HR OF REST ON THE FIRST LEG. ONCE WE WERE IN RADAR CONTACT WITH ZHN; WE WERE CLRED DIRECT TO HNL AND PLT'S DISCRETION TO 10000 FT. I CHOSE THE HDG SELECT MODE TO GET THE ACFT POINTED IN THE GENERAL DIRECTION WHILE I PROGRAMMED HNL DIRECT INTO THE FMC. I ACTIVATED AND EXECUTED THE COMMAND BUT FAILED TO ENGAGE LNAV AND REMAINED IN HDG SELECT. AFTER A FEW MINS; I RECOGNIZED THAT WE WERE DRIFTING OFF COURSE AND RE-ENGAGED LNAV DIRECT. CTR DID NOT SAY ANYTHING AND WE WERE IN VMC; SO NOTHING WAS SAID. LEVELING AT 10000 FT; I RECOGNIZED THAT WE NEEDED A LOWER ALT AND ASKED THE CAPT TO REQUEST LOWER. THERE WAS NO RESPONSE. WE HAD NOT BEEN HANDED OFF TO APCH. WE TRIED CTR AGAIN WITH NO RESPONSE ON THAT FREQ. OTHER PLTS HAD WARNED US THAT NIGHT THAT THEY HAD SOME DIFFICULTY CONTACTING ZHN THE NIGHT BEFORE. WE CHANGED TO APCH. THEY CLRED US FOR THE VISUAL APCH AND ASKED; 'HOW DO YOU COPY?' I BEGAN TO WONDER IF CTR HAD BEEN TRYING TO REACH US AND HAD NOTICED OUR COURSE DEV. I'M UNAWARE OF WHETHER OR NOT THERE WAS ANY CONFLICT. WE DID NOT BELIEVE SO. I THINK SEVERAL THINGS CONTRIBUTED TO THIS SIT. NEITHER THE CAPT NOR I WERE ADEQUATELY RESTED. THE COMPANY HAS NOT BEEN HONORING OUR CONTRACT FOR OUR CREW REST SEATING ON THE ACFT. OUR DEADHEAD TIME WAS NOISY AND THE LIGHTS WERE ON. FATIGUE WAS THE MAJOR FACTOR IN OUR OVERSIGHT. IN ADDITION; THE CAPT ELECTED TO GIVE ME THE LEG FOR THE EXPERIENCE (I HAVE LESS THAN 100 HRS IN THE B767) IF I WOULD DO ALL THE RADIO AND PAPERWORK TOO. THROUGHOUT THE NIGHT; HE DOZED OFF. I FELT HE WAS TOO FATIGUED TO BE AS EFFECTIVE AS HE MIGHT HAVE BEEN. I ALSO THINK HE CHOSE TO HAND OFF ALL OF THE RESPONSIBILITY TO ME -- EFFECTIVELY MAKING IT A 1.2 PLT CREW INSTEAD OF A 2 PLT CREW. WE'RE ALL FORCED TO FLY AROUND HALF-ASLEEP. ALSO; THERE MAY BE SOME PROBS WITH ZHN'S RADIOS. BOTTOM LINE: IF I WERE 100%; I WOULD NOT HAVE MISSED ENGAGING LNAV.