Narrative:

Departed vhhh on SID ocean 2B runway 25L (commercial chart plate 10-3v6). As we approached flyover point drawn; I mistook linear distance (5 NM from end of runway 25L to prawn) as DME distance for fop and moved heading bug to command first officer to turn. When in the turn I realized the error and stated so to the first officer. After reaching cruise; we reflected on the event. At approximately 500 ft the GPWS alerted us with a terrain warning. WX at the time was VFR with haze and takeoff was into the sun. The alert prompted us to rechk altimeters and outside as well. I feel that the GPWS alerts might have played a part in distracting us during that phase of flight. Other factors include: GPS leg change in automatic switches to next track 2-4 mi early giving a false prompt. A mix of triple GPS and 1 universal FMS with taws forces a lot of xchking between each and raw data. It makes for a busy time in a busy environment. Conclusion: better coordination xcockpit will result in higher awareness at critical times. Supplemental information from acn 704756: departing hong kong; taws system repeatedly gave 'terrain; pull up' warnings. It was very distracting. Captain called a turn too early and turned the heading bug. I followed the heading bug. I should have disregarded the turn and continued to the fly-over waypoint; another 1.9 mi before turning. Minimum crew rest contributed to this incident.

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Original NASA ASRS Text

Title: A B747 FLT CREW DEPARTING HKG ON OCEAN 2B SID TURNED TOO SOON; IN PART BECAUSE OF GPWS DISTRS.

Narrative: DEPARTED VHHH ON SID OCEAN 2B RWY 25L (COMMERCIAL CHART PLATE 10-3V6). AS WE APCHED FLYOVER POINT DRAWN; I MISTOOK LINEAR DISTANCE (5 NM FROM END OF RWY 25L TO PRAWN) AS DME DISTANCE FOR FOP AND MOVED HDG BUG TO COMMAND FO TO TURN. WHEN IN THE TURN I REALIZED THE ERROR AND STATED SO TO THE FO. AFTER REACHING CRUISE; WE REFLECTED ON THE EVENT. AT APPROX 500 FT THE GPWS ALERTED US WITH A TERRAIN WARNING. WX AT THE TIME WAS VFR WITH HAZE AND TKOF WAS INTO THE SUN. THE ALERT PROMPTED US TO RECHK ALTIMETERS AND OUTSIDE AS WELL. I FEEL THAT THE GPWS ALERTS MIGHT HAVE PLAYED A PART IN DISTRACTING US DURING THAT PHASE OF FLT. OTHER FACTORS INCLUDE: GPS LEG CHANGE IN AUTO SWITCHES TO NEXT TRACK 2-4 MI EARLY GIVING A FALSE PROMPT. A MIX OF TRIPLE GPS AND 1 UNIVERSAL FMS WITH TAWS FORCES A LOT OF XCHKING BTWN EACH AND RAW DATA. IT MAKES FOR A BUSY TIME IN A BUSY ENVIRONMENT. CONCLUSION: BETTER COORD XCOCKPIT WILL RESULT IN HIGHER AWARENESS AT CRITICAL TIMES. SUPPLEMENTAL INFO FROM ACN 704756: DEPARTING HONG KONG; TAWS SYS REPEATEDLY GAVE 'TERRAIN; PULL UP' WARNINGS. IT WAS VERY DISTRACTING. CAPT CALLED A TURN TOO EARLY AND TURNED THE HDG BUG. I FOLLOWED THE HDG BUG. I SHOULD HAVE DISREGARDED THE TURN AND CONTINUED TO THE FLY-OVER WAYPOINT; ANOTHER 1.9 MI BEFORE TURNING. MINIMUM CREW REST CONTRIBUTED TO THIS INCIDENT.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.