B777-200
Flight Crew Air Transport Pilot (ATP)
Workload; Confusion; Time Pressure
Aircraft Equipment Problem Less Severe; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Aircraft
Good weather; departing on 02R. After takeoff in the initial climb phase; the autopilot began in the LNAV mode to fly the published departure. Selected the autopilot between 500-1;000 FT; did normal flap schedule. During this process the EICAS displayed 'autopilot.' The First Officer was in the process of the after takeoff checklist and check in with ATC. We noticed the throttles had gone to the mechanical stops and speed began to exceed 250 KTS. The First Officer finally got to check in with the ATC departure and they requested us to slow to 250 KTS; which during this time; I selected speed intervention. The speed bug on the PFD was indicating 250 KTS. The speed window indicated 250 KTS when selected; but could not change the speed bug on the PFD in either direction. Continued to pull power back; but throttles kept going back to mechanical stop. Deselected autopilot; deselected autthrottles on the MCP; but also had to disconnect the autthrottles on the throttles before regaining control. Deselected F/D. Flew the departure manually for a short time and then reselected the F/D's on; autopilot on; autthrottles on and the aircraft seemed to be normal. EICAS advisory 'autopilot' went away. Autopilot automation failed to comply with airspeed. Next time I get an EICAS 'autopilot' advisory I will immediately disconnect all automation.
During these few seconds of trying to regain control of the automation; because we were in near-level flight and because the throttles were advancing to near full power; airspeed accelerated past the 250 KTS bug to 300 KTS in only 3-4 seconds. Captain turned off all automation very quickly; and slowed aircraft back to required 250 KTS speed. While we were above 250 KTS; approximately 15-20 seconds; ATC called to tell us he needed us to be at 250 KTS.
A B777 autothrottle system malfunctioned as the EICAS alerted AUTOPILOT with an audible warning. The aircraft accelerated beyond 250 KTS toward 300 KTS; which required disconnecting all autothrottle automation to regain control.