B747-400 PLT RPTS THAT HE WAS FATIGUED.

Narrative

I HAVE FLOWN THE BEIJING TRIP FROM ZZZ MANY; MANY TIMES PRIOR TO THE TRIP BEING REDUCED FROM 4 DAYS TO 3. I NEVER FELT UNDUE FATIGUE DURING THE FLT; AT LEAST NOT DUE TO INADEQUATE REST DURING THE LAYOVER. HOWEVER; WHILE FLYING THIS NEW 3 DAY SCHEDULE IT WASN'T LONG AFTER TKOF FROM BEIJING THAT I FELT FATIGUED; AND THIS FATIGUE WORSENED AS THE FLT WENT ON. I WAS THE FLYING FO AND HAD THE FIRST WORKING SHIFT. NOT LONG AFTER LEVELOFF I FELT THE CONSTANT NEED FOR A NAP AND HAD TO FIGHT CONTINUOUSLY TO STAY AWAKE. THIS IS PROBABLY BECAUSE AS USUAL; I AWOKE AT XA00 AM IN THE MORNING OF THE FLT AND WAS UNABLE TO GET BACK TO SLEEP. NORMALLY THIS WOULD NOT BE A PROB BECAUSE I WOULD HAVE THE ENTIRE DAY TO FIND ADDITIONAL TIME TO SLEEP. USUALLY THE 2ND NIGHT I SLEEP STRAIGHT THROUGH AND AM REFRESHED ENOUGH TO FEEL OK FOR THE FLT BACK TO ZZZ. WITH THE NEW 3 DAY TRIP; I DIDN'T HAVE THAT OPPORTUNITY AND IT COULD HAVE CAUSED AN UNSAFE SITUATION. ALTHOUGH ALL THE FLT CREW COMMENTED ON THE SHORT LAYOVER AND ASSOCIATED LACK OF SLEEP; NONE OF US THOUGHT WE WOULD FEEL SO WHIPPED SO EARLY INTO THE FLT. EVEN AFTER SPENDING 4 1/2 HRS IN THE BUNK I FELT VERY TIRED DURING THE DSCNT AND APCH. THE BOTTOM LINE IS: NEXT TIME I FEEL FATIGUED PRIOR TO DEP TIME; AND I'M THE FLYING FO; I WILL DECLINE TO FLY. I KNOW THIS WILL ADVERSELY AFFECT THE COMPANY'S PERFORMANCE; BUT THE COMPANY OBVIOUSLY DOESN'T FEEL CONCERNED ABOUT FATIGUED CREWS AND THE EFFECT ON THE SAFE CONDUCT OF THE FLT.