PanAm flight 812, a Boeing 707, suffered a runway excursion following an aborted takeoff at Sydney Airport, Australia. Flight 812 was departing on a nine-hour flight to Honolulu, Hawaii, USA with 125 passengers and a crew of 11. While taxiing to the threshold of runway 34 at Sydney-Kingsford Smith International Airport, the crew completed the taxiing checklist and, in communication with Sydney Tower, received and acknowledged an airways clearance. The aircraft was initially instructed to lineup on the runway and hold but, before it had entered the runway, this instruction was changed to a take-off clearance specifying that it would be a radar departure and that, after taking off, the aircraft was to turn right onto a heading of 050 degrees and to maintain 3,000 feet. This clearance was acknowledged and the pre-take off checks were conducted as the aircraft was turning onto the runway and lining up. These checks included a gyro compass comparison which was conducted as the aircraft heading passed through 010 degrees at which time the aircraft was 34 degrees from runway alignment. At 17:57 hours flight 812 commenced its take-off from a rolling start. The take-off was being carried out by the first officer from the right hand seat and, after the first officer had applied take-off thrust, the captain took control of the throttles while the flight engineer made fine adjustments to the throttle settings to balance the power. As the aircraft accelerated at an apparently normal rate the captain called progressively “80 knots your steering”, “one hundred” and “vee one”. Almost immediately after the “vee one” call the aircraft struck a flock of seagulls and there were two sharp reports from outside the aircraft. The captain observed a decay in number 2 engine EPR and aborted the take-off. The captain stated that he applied considerable braking simultaneously with the selection of speed brake and reverse thrust and full braking almost immediately afterwards. During the early stages of the deceleration, the flight engineer saw several flickers of the anti-skid lights on the brake panel, he noted that the hydraulic pressure was normal and saw that the four reverse lights were illuminated and that the N-values on all engines was about 110% with EPR indications “well up”. When the captain took control of the aircraft the first officer assisted by maintaining the nosewheel on the ground and keeping the wings level and, when reverse thrust was applied, he also placed his feet on the brakes and found that the pedals were fully depressed. The aircraft overran the runway and struck sections of the approach lighting installation which caused the nose landing gear assembly and then the port main landing gear assembly to be removed. Finally, the nose of the aircraft came to rest partially embedded In soft ground 560 feet beyond the end of the runway and the crew and passengers then evacuated the aircraft. There were no injuries. The probable cause of the accident was that, in the circumstances of an abandoned take-off, the aircraft could not be brought to a stop within the nominally adequate runway length because of an error in the calculation of load, a reduction in wind velocity from that forecast and the use of rolling start and braking techniques which would not ensure most effective use of the available runway length.