B777-200
Flight Crew Air Transport Pilot (ATP)
Troubleshooting
Aircraft Equipment Problem Less Severe
Flight Crew Overcame Equipment Problem
Aircraft
On VNAV/LNAV approach 22L when 25 flaps selected autothrottles (A/T) commanded full power and repeatedly re-engaged when disconnected. Attempted to continue approach overriding A/T but did a missed approach. TOGA appeared to function normally. Same thing reoccurred on second approach ILS 22R. Turned off A/T arm switches and landed using manual throttles. On both approaches Flight Director & autopilot correctly followed VNAV & ILS commands.
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B777 flight reported autothrottles drove thrust to full power on approach after flaps 25 were selected. Autothrottles would re-engage even when disconnected until autothrottle arm switches were turned off.