A B747-400 DEPARTING SYD IS ADVISED AFTER THE FACT THAT DURING A XBLEED START ENOUGH DEBRIS WAS MOVED TO CLOSE TXWY A; EVEN THOUGH PWR WAS REDUCED AS SOON AS A COMPLAINT WAS HEARD ON THE RADIO.

Narrative

#4 HIGH PRESSURE BLEED VALVE CLOSED; DEFERRED. NORMAL DEP FROM GATE AT 520000 LBS. PLANNED 2 ENG TAXI; NORMAL FOR THIS LEG; WITH LONG TAXI TO RWY 34L. APU TURNED OFF. AWAY FROM THE RAMP AREA AND CLR OF ACFT BEHIND; ON TXWY A PAST A2 TO RWY 34L; ACCOMPLISHED XBLEED START OF OTHER ENGS. RAN UP #1 OUTBOARD TO INCREASE DUCT PRESSURE. HEARD CALLER TO GND/TWR COMPLAIN ABOUT JET BLAST FROM OUTBOARD ENG. REDUCED THRUST IMMEDIATELY. LATER SYD OPS RECEIVED AN INCIDENT RPT. CLOSED TXWY A FOR (2 HRS?) GRASS/DIRT/DEBRIS ON TXWY AND REROUTED ACFT WITH ALTERNATE TAXI INSTRUCTIONS. AWAY FROM THE RAMP AND IN THE OPEN WITH NO ACFT BEHIND; I FELT I WAS EXERCISING CAUTION WITH MINIMUM THRUST ON #1 OUTBOARD. DID NOT ADVISE TWR OF RUN-UP. IN A REVIEW OF THE CHARTS; THERE IS NO REQUIREMENT TO ADVISE GND/TWR OF RUN-UP OR ENG START. THERE IS NO NOTICE OF UNSTABLE OFF TXWY GND CONDITIONS AND THE AVOIDANCE OF HIGH THRUST AWAY FROM THE APRON. ALSO; THERE IS NO ADVICE IN HANDBOOK FOR TAXI OUT; APU ON OR OFF. MEL ITEM (BLEED) PLACARD HAS NO ADVICE FOR ENG START 'COMPLICATIONS.' IN RETROSPECT; AN APU LEFT 'ON' IS A BETTER OPTION.