B777 flight crew reported communication issues with ground crew and a thrust lever not a full idle during pushback. After ground crew directed the flight crew to stop engines and set brakes"; they were able to start taxi."
Synopsis
B777 flight crew reported communication issues with ground crew and a thrust lever not a full idle during pushback. After ground crew directed the flight crew to stop engines and set brakes"; they were able to start taxi."
Narrative
At ZZZZ we were parked on the hard stand. We were pushed back on to the taxiway. Then the tug began to pull the aircraft forward. As we monitored the aircraft's forward progress; it became clear that we were being towed forward longer than usual. My initial thought was the tug driver was pulling our aircraft clear of any other aircraft that might be about to push as well. At that moment; our aircraft veered slightly left of the taxi line. I immediately looked left to make sure we were clear of any aircraft; ground equipment etc; which we were. The tug driver returned our aircraft to the taxi line almost immediately. Then a Ground crew member voice which sounded winded and flustered came on the intercom and said what sounded like 'stop engines.' We all three immediately turn towards the center console and notice the left thrust lever was slightly out of idle by maybe half of the control knob. I glanced at the engine instruments which appeared to be symmetrical; as the Captain immediately returned the left thrust lever to full idle. The aircraft was now at a complete stop. As a side note; everything during the push had seemed completely normal up to this point; with the exception of a slightly longer than normal push. The communication had been quiet. The Captain asked the ground crew if there was a problem and if they wanted him to park brakes. Ground crew member responded again 'stop engines' followed by 'yes set brake'. The aircraft was still stopped and the aircraft brakes were set. The Captain once again ask if there was a problem and if everything was OK. There was a slight pause and the voice said everything OK. The Captain asked what happened and no clear answer was given. The Captain asked if the aircraft was OK. The voice said aircraft was OK. By this time the tug was pulling away as we could see it out the right side window. The all clear was given and the ground crew left. All three crew agreed that the aircraft was OK from what the ground crew told us. We began our taxi for takeoff with no additional problems during the flight.Cause - Human factors played a role in this event. How the left thrust lever was not at full idle we are not sure. It was not physically forward enough to draw our attention. Nor were there any higher than normal engine indications or sounds. Aerodynamically the aircraft should have veered right if there was more thrust produced by the left engine. Not veer left like it did. I also believe there was some communication challenges with English to Foreign language and vice versa. More so when stress levels are elevated. Suggestions - In my opinion; communication played a big factor during this event. During pushback; communication needs to be timely; accurate; and clear. In that order. I think we all agree that this push was longer than usual. It was quiet for a long time. Was the headset used by the ground crew wireless? Did we lose communication for a while and no one realize it? We were talking to a middle person. And not directly to the tug driver. Therefore there was possibly a delay in communicating what was happening with the tug and aircraft. Hence the long push/pull and the veer off the taxi line. There needs to be direct hard wired instant communication between the Captain and the tug driver.
Second reporter narrative
During pushback in ZZZZ; the Captain noted that we seemed to being towed forward farther than usual. Soon after this the plane started a slight turn left off the centerline of the taxiway and the aircraft picked up speed slightly. All 3 pilots noticed this immediately and the Captain queried the ground handler. As he did this he noticed the left thrust lever was about half a knob forward and he returned it to idle. He also applied brakes after asking the ground handler if that was needed. The turn was corrected; we returned to centerline and the plane was brought to a stop. The Captain tried to query the ground handler if there were any problems with the tug but no sure answer was received. We were assured that all was well with the aircraft and the ground crew and we eventually proceeded for takeoff with no additional problems on our flight to ZZZ.Cause - Human factors contributed since the left thrust lever was slightly out of idle but when that happened we aren't sure. It also seems the plane exited the centerline (to the left) the opposite direction of what we would expect with the left lever out of idle. Some problems with English to Foreign language communication contributed to confusion in the moment.Suggestions - I think direct communication with the supertug driver would be better than with a separate handler on the headset.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.