When the B777's autothrottles failed to engage promptly on a mtogw takeoff with minimum stopping dis...

Narrative:

After being cleared for takeoff from being instructed to 'line up and wait' - I ran the power up to 55% N1 holding brakes due to an extremely heavyweight takeoff (T/O) at 764;000 with a stop margin of: 648 feet. I released the brakes at the same time I depressed the GA switches to engage the autothrottles but they did not engage until after I depressed the autothrottles disconnect switch and then recycled the switches from off to on. At which time I pulled the power to idle to 'reject' the T/O at low speed. The aircraft was moving from the initial start T/O position during this time and I did not want to invalidate the accelerate-stop distance calculation of 648 ft by applying power a takeoff power further down the runway than normal so I decided to taxi off the runway at the next exit and make another takeoff from the beginning of the runway. Aircraft speed was never greater than 30 to 40 knots during taxi down the runway to exit the runway as instructed by tower.

Original NASA ASRS Text

Title: When the B777's autothrottles failed to engage promptly on a MTOGW takeoff with minimum stopping distance; the Captain elected to reject the takeoff. A subsequent attempt proved successful with normal autothrottle response.

Narrative: After being cleared for Takeoff from being instructed to 'Line Up and Wait' - I ran the power up to 55% N1 holding brakes due to an extremely heavyweight Takeoff (T/O) at 764;000 with a Stop Margin of: 648 feet. I released the brakes at the same time I depressed the GA switches to engage the Autothrottles but they did not engage until After I depressed the Autothrottles Disconnect Switch and then recycled the switches from OFF to ON. At which time I pulled the power to idle to 'Reject' the T/O at low speed. The aircraft was moving from the initial start T/O position during this time and I did not want to invalidate the Accelerate-Stop distance calculation of 648 FT by applying power a Takeoff Power further down the runway than normal so I decided to taxi off the runway at the next exit and make another Takeoff from the beginning of the runway. Aircraft speed was never greater than 30 to 40 knots during taxi down the runway to exit the runway as instructed by Tower.

Data retrieved from NASA's ASRS site 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.

Attributes
ACN	1207957
Time
Date	201410
Local Time Of Day	1801-2400
Place
Locale Reference	VHHH.Airport
State Reference	FO
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B777-200
Operating Under FAR Part	Part 121
Flight Phase	Takeoff
Flight Plan	IFR
Component
Aircraft Component	Autothrottle/Speed Control
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 180 Flight Crew Total 31000 Flight Crew Type 1800
Events
Anomaly	Aircraft Equipment Problem Less Severe

When the B777's autothrottles failed to engage promptly on a mtogw takeoff with minimum stopping distance; the captain elected to reject the takeoff. A subsequent attempt proved successful with normal autothrottle response.