Flight crew reported a rejected take off and returned to the gate for maintenance. It was discovered that there were numerous rejected take offs in the past 10 days so the crew refused the aircraft to give maintenance time to make appropriate repairs.
Synopsis
Flight crew reported a rejected take off and returned to the gate for maintenance. It was discovered that there were numerous rejected take offs in the past 10 days so the crew refused the aircraft to give maintenance time to make appropriate repairs.
Narrative
We were cleared for takeoff; I stood the throttles up to 1.1 EPR; commenced the takeoff roll at approximately 80/85 kts. an EICAS message 'UNSCHED STAB TRIM' in yellow appeared. Captain commanded control of the aircraft and aborted the takeoff. I followed him through on the abort procedures. I advised the Tower we were aborting the takeoff and announced we would taxi clear the runway. The Relief Pilot advised passengers and cabin crew to remain seated. We held on a taxiway while consulting with Maintenance and the BTMS (Brake Temperature Monitoring System) chart in the FM. We waited for the brakes to cool before setting the parking brake. We learned from Maintenance that this message had occurred three times in the past ten days in flight on this airplane. Based on discussions with Maintenance and our crew; we collectively decided a gate return would be prudent to allow Maintenance an opportunity to investigate further.Maintenance boarded the aircraft and initially suggested repeating the same procedure for the previous occurrences of this same problem. They did some more troubleshooting and decided to replace a module in the equipment bay. Based on further detailed discussions with Maintenance; we felt the replacement of the module did not improve their confidence nor ours that the root cause of the problem was addressed. The crew met and discussed our thoughts and the fact that this problem was now determined to be chronic because of the multiple occurrences within ten days; the possibility of another RTO due to the low confidence that the problem was understood; and out of an abundance of caution due to passengers fear we felt the right thing to do was to allow Maintenance adequate time to troubleshoot the problem; determine the root cause and; address it before the airplane would be allowed to fly again.
Second reporter narrative
On takeoff; Runway XXR/ZZZ; at approximately 90 kts. EICAS UNSCHED STAB TRIM illuminated. We RTOd at 95 kts. and uneventfully cleared the runway. We ran the QRC RTO and the QRH UNSCHED STAB TRIM checklists. While waiting for the brakes to cool; per the cooling chart; we contacted Dispatch and Maintenance. As a result of these communications it was decided that we would return to the gate for Maintenance.This was the 4th occurrence of this issue in 11 days; and all previous Maintenance intervention had failed to prevent repeat occurrences. There was a limited amount of time for Maintenance to address the issue since we were facing an arrival curfew at ZZZ1. ZZZ Maintenance tried their best to fix the issue but we were led to believe that they had little confidence that their actions would fix the problem and prevent a recurrence. As a result of this low confidence; the flight crew was uncomfortable continuing with this repeat Maintenance issue so we advised Dispatch that we were unable to operate the flight with this issue.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.