B747-200 RECEIVES GPWS ALERT WHILE COMPLYING WITH THE PUBLISHED ATTOL 1A DEP FROM VHHH.

Narrative

IN HKG WE RECEIVED THE ATTOL 1A CLRNC. WE DEPARTED RWY 7R TRACKING 073 DEGS TO PORPA. ONCE REACHING PORPA (7 DME ISR) WE BEGAN THE R TURN TO BREAM. (THE INS ALSO VERIFIED THAT WE WERE AT PORPA.) ENRTE TO BREAM (IN VFR DAY CONDITIONS) THE GPWS SOUNDED AND I; AS THE PF; ADDED PWR; STOPPED THE TURN AND STARTED ADDITIONAL CLB TO COMPLY WITH THE GPWS. AFTER PASSING ALL TERRAIN; ATC THEN TURNED US TO 090 DEG HDG. LATER I HAD THE FO ASK ATC. THEY INFORMED US THAT WE STARTED THE TURN EARLY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE ACFT WAS A B747-200 WITH NO AUTOFLT SYS; FMC; OR GPS. RPTR SAID THAT HE WAS HAND-FLYING THE DEP. RPTR ADVISED THAT THE ACFT'S ACTUAL POS ON THE CARGO RAMP WAS USED TO ALIGN THE INS PRIOR TO DEP AND THAT THERE WAS NO SIGNIFICANT DISPARITY BTWN THE DME AND INS ON ANY SUBSEQUENT FIXES. RPTR STATED THAT HE DID NOT TURN EARLY; BUT RATHER WAITED UNTIL XING THE PORPA FIX; AS INDICATED BY THE DME; INS; AND LKC VOR RADIAL. RPTR STATED THAT WHILE ATTENDING RECURRENT TRAINING; HE HEARD ABOUT TWO OTHER FLT CREWS HAVING THE SAME EXPERIENCE. RPTR ADVISED THAT HE COULD HAVE BEEN INSIDE THE TURN RADIUS PRESCRIBED IF THE PUBLISHED PROC IS BASED ON A STANDARD RATE TURN.