B777 flight crew reported asymmetric thrust and auto throttle failure on take off power application. The Captain rejected the take off and the flight crew returned to the gate for maintenance.
Synopsis
B777 flight crew reported asymmetric thrust and auto throttle failure on take off power application. The Captain rejected the take off and the flight crew returned to the gate for maintenance.
Narrative
I was the captain on this flight; ZZZ-ZZZ1. I was conducting OE for the First Officer (FO). This was to be the FO's first takeoff as PF (Pilot Flying). We were originally going to use runway XX; but at some point; the winds had shifted sufficiently; so we were advised by ATC that we would be departing on runway XY. Takeoff data was obtained for Runway XY; and do due to variability of winds; we decided to use max power for the takeoff. Engine start was normal; the after start checklist was completed normally; and we taxied out for departure. We were cleared for takeoff; and there was [an aircraft] on final. Apparently; it's a slight uphill gradient from taxiway onto the runway because I had to carry power to keep the aircraft moving; on the order of around 30% N1 rpm. Since we were already cleared for takeoff; I left that power in as I transferred control and told [the First Officer] it was his aircraft. The aircraft was aligned with the runway when I told the FO it was his aircraft. He continued to advance the throttles; engaged TOGA; and I split my attention between looking outside and monitoring the engine instruments. While checking how well the FO was tracking centerline; I noticed the aircraft drifting left of centerline. Not knowing if the FO was correcting; and seeing that I must take immediate corrective action; I applied right rudder. The aircraft continued to drift left. I added more rudder then looked down to see the right engine at max power; and the left engine's EPR needle indication at around the 8 o'clock position. Rejected the takeoff before RTO was armed (less than 85 knots). We returned to the gate. Maintenance met the aircraft. I spoke with the mechanics as they were diagnosing the problem. They informed me that the auto throttle system had failed a BITE test. We remained at the aircraft while [the company] and station ops determined what to do. The mechanics mentioned that they did not have anyone qualified to taxi the aircraft; or to do an engine run. Eventually; we left for the hotel. Prior to retiring for the evening; I checked in [the scheduling system]; and noted the asymmetrical thrust that we wrote up was still open; and the entry that the BITE test had failed. When I woke up; I checked the scheduling system again; and there was no mention of the BITE test failure; and only an entry that the engine passed all run up tests. In retrospect; I should have taken a screenshot of the previous night's log history.
Second reporter narrative
Normal engine indications up to clearance for take off. Aircraft was transferred to Pilot Flying (PF) (First Officer (FO)) with thrust levers slightly out of idle. FO applied thrust to advance to roughly 50%. Thrust levers and engine indications advanced normally. TOGA switches were pressed; and both Thrust Levers advanced. The aircraft yawed to the left; and the FO and Captain immediately applied full right rudder to prevent going off the runway. The Captain rejected the take-off; pulled both engines to idle. The Captain reported seeing asymmetric thrust with the left engine lagging behind the right engine which had accelerated to maximum thrust. The FO was focused on rudder and runway alignment at the time of reject and did not note engine N1 at the time of reject but both throttles had advanced simultaneously after TOGA was pressed. Rejected take off was accomplished at low speed without incident. Dispatch and Maintenance notified.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.