Narrative:

Subject: yssy airport runway 34L. Remaining runway distance available from runway intersection-possible engineering miscalculation. During our preflight planning at yssy operations the captain and I (flying first officer) began discussing a notation in the 'dispatcher comments' section of the flight plan which indicated a planned intersection takeoff from runway 34L; labeled R34LD (11286 ft). This information initially captured our attention because our flight was also planned for takeoff at maximum gross weight. Cross-checking the flight plan message with other available data (ie weight manifest and NOTAMS) I identified the intersection as taxiway A5 and the data confirmed the same remaining runway length available from the A5 intersection as the dispatcher's note in the flight plan; 11286 feet. Both the captain and I; experienced and familiar with the yssy airport; instinctively sensed something did not feel right with the remaining available distance and became skeptical. The relief pilots; also very familiar with yssy; agreed. The captain pulled out his airport diagram page so we could visually examine runway 34L and the intersection in question. The runway is 12999 feet. Out of curiosity I marked off the distance from the end of runway 34L to the A5 intersection with a piece of paper and pen and calculated the distance using the scale at the bottom of the chart. My measurement revealed approximately 2400 feet! Subtracting this distance from the full length appeared to give us approximately. 10599 feet (12999-2400=10599) available runway for takeoff instead of 11286 feet. I re-measured the distance with the captain and relief pilots and we all agreed that the disparity in distance (approximately. 687 feet) was significant enough and represented a potentially dangerous situation if the calculation was anywhere close to correct. The captain immediately contacted the dispatcher by telephone making him aware of the problem and attempted to reconcile the apparent error. After their lengthy conversation; dispatch was as flabbergasted as we were and did not have an instant answer. The captain and one of the relief pilots stayed back to wait for more information from dispatch and tried to contact airport ground control to obtain current information for the runway and taxiway closure. The other relief pilot and I went to the airplane to set-up and prepare for departure. Once onboard; I contacted ground control to verify the status of the runway and the available length for takeoff. Ground control confirmed that the taxiway was open and the full length runway was available for takeoff. We departed and had an uneventful flight. Even though this particular problem became moot for our flight and the situation worked out this time; the distance discrepancy still needs to be investigated and reconciled. A distance error of this magnitude could be disastrous.

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Original NASA ASRS Text

Title: A B747-400 PILOT COMMENTS THAT YSSY ARPT OPS MADE A 2400 FT REPORTING ERROR WHEN DETERMINING RWY 34L TKOF DISTANCE FROM INTXN A5.

Narrative: SUBJECT: YSSY AIRPORT RUNWAY 34L. REMAINING RUNWAY DISTANCE AVAILABLE FROM RUNWAY INTERSECTION-POSSIBLE ENGINEERING MISCALCULATION. DURING OUR PREFLIGHT PLANNING AT YSSY OPERATIONS THE CAPTAIN AND I (FLYING FO) BEGAN DISCUSSING A NOTATION IN THE 'DISPATCHER COMMENTS' SECTION OF THE FLIGHT PLAN WHICH INDICATED A PLANNED INTERSECTION TAKEOFF FROM RUNWAY 34L; LABELED R34LD (11286 FT). THIS INFORMATION INITIALLY CAPTURED OUR ATTENTION BECAUSE OUR FLIGHT WAS ALSO PLANNED FOR TAKEOFF AT MAXIMUM GROSS WEIGHT. CROSS-CHECKING THE FLIGHT PLAN MESSAGE WITH OTHER AVAILABLE DATA (IE WEIGHT MANIFEST AND NOTAMS) I IDENTIFIED THE INTERSECTION AS TAXIWAY A5 AND THE DATA CONFIRMED THE SAME REMAINING RUNWAY LENGTH AVAILABLE FROM THE A5 INTERSECTION AS THE DISPATCHER'S NOTE IN THE FLIGHT PLAN; 11286 FEET. BOTH THE CAPTAIN AND I; EXPERIENCED AND FAMILIAR WITH THE YSSY AIRPORT; INSTINCTIVELY SENSED SOMETHING DID NOT FEEL RIGHT WITH THE REMAINING AVAILABLE DISTANCE AND BECAME SKEPTICAL. THE RELIEF PILOTS; ALSO VERY FAMILIAR WITH YSSY; AGREED. THE CAPTAIN PULLED OUT HIS AIRPORT DIAGRAM PAGE SO WE COULD VISUALLY EXAMINE RUNWAY 34L AND THE INTERSECTION IN QUESTION. THE RUNWAY IS 12999 FEET. OUT OF CURIOSITY I MARKED OFF THE DISTANCE FROM THE END OF RUNWAY 34L TO THE A5 INTERSECTION WITH A PIECE OF PAPER AND PEN AND CALCULATED THE DISTANCE USING THE SCALE AT THE BOTTOM OF THE CHART. MY MEASUREMENT REVEALED APPROXIMATELY 2400 FEET! SUBTRACTING THIS DISTANCE FROM THE FULL LENGTH APPEARED TO GIVE US APPROX. 10599 FEET (12999-2400=10599) AVAILABLE RUNWAY FOR TAKEOFF INSTEAD OF 11286 FEET. I RE-MEASURED THE DISTANCE WITH THE CAPTAIN AND RELIEF PILOTS AND WE ALL AGREED THAT THE DISPARITY IN DISTANCE (APPROX. 687 FEET) WAS SIGNIFICANT ENOUGH AND REPRESENTED A POTENTIALLY DANGEROUS SITUATION IF THE CALCULATION WAS ANYWHERE CLOSE TO CORRECT. THE CAPTAIN IMMEDIATELY CONTACTED THE DISPATCHER BY TELEPHONE MAKING HIM AWARE OF THE PROBLEM AND ATTEMPTED TO RECONCILE THE APPARENT ERROR. AFTER THEIR LENGTHY CONVERSATION; DISPATCH WAS AS FLABBERGASTED AS WE WERE AND DID NOT HAVE AN INSTANT ANSWER. THE CAPTAIN AND ONE OF THE RELIEF PILOTS STAYED BACK TO WAIT FOR MORE INFORMATION FROM DISPATCH AND TRIED TO CONTACT AIRPORT GROUND CONTROL TO OBTAIN CURRENT INFORMATION FOR THE RUNWAY AND TAXIWAY CLOSURE. THE OTHER RELIEF PILOT AND I WENT TO THE AIRPLANE TO SET-UP AND PREPARE FOR DEPARTURE. ONCE ONBOARD; I CONTACTED GROUND CONTROL TO VERIFY THE STATUS OF THE RUNWAY AND THE AVAILABLE LENGTH FOR TAKEOFF. GROUND CONTROL CONFIRMED THAT THE TAXIWAY WAS OPEN AND THE FULL LENGTH RUNWAY WAS AVAILABLE FOR TAKEOFF. WE DEPARTED AND HAD AN UNEVENTFUL FLIGHT. EVEN THOUGH THIS PARTICULAR PROBLEM BECAME MOOT FOR OUR FLIGHT AND THE SITUATION WORKED OUT THIS TIME; THE DISTANCE DISCREPANCY STILL NEEDS TO BE INVESTIGATED AND RECONCILED. A DISTANCE ERROR OF THIS MAGNITUDE COULD BE DISASTROUS.

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.