Air carrier flight crew reported rejecting the takeoff after hearing a loud bang; followed by the aircraft veering off centerline. Flight returned to gate for maintenance action.
Synopsis
Air carrier flight crew reported rejecting the takeoff after hearing a loud bang; followed by the aircraft veering off centerline. Flight returned to gate for maintenance action.
Narrative
Takeoff was planned for Runway XXL. Takeoff data was requested and returned for a Flaps 5; Bleeds On; Anti-Ice Off at an assumed weight of 153.0 and assumed temp of 41C with a reduced N1 of 94.6 and speeds of 154 (V1); 162 (VR) and 165 (V2). Weather was CAVU with gusty NNE winds 10-20 kts. No windshear advisories were in effect so I elected to accept the reduced thrust takeoff. Final weights were received with a TOG of 152.6. Takeoff clearance was received and I set takeoff power. Both engines accelerated symmetrically and normally to the reduced takeoff power N1. As PF (Pilot Flying); I then shifted my attention out the window to focus on the gusty crosswind takeoff. The aircraft accelerated normally and I heard the first officer announce 100 kts. Shortly thereafter I heard an audible bang and felt the airplane lurch. I believe the airplane swerved to the right but I cannot be sure of this memory. The noise and lurch we experienced was very similar to that of an engine failure in the simulator. Fearing an engine had failed or was degraded; I made a split-second decision to reject the takeoff in compliance with the company's takeoff safety policy and fleet guidance (engine failure above 100 kts. but less than V1). I announced 'reject' and performed the RTO procedure of closing the thrust levers; disconnecting the autothrottles; pulling the speedbrake; and selecting max reverse thrust. The First Officer had not advised the Tower and I prompted him to do so. As he began communicating with ATC; the airplane was decelerating rapidly. Worried we'd soon come to a stop and the Flight Attendants would command an evacuation; I overrode the autobrakes and picked up the p.a. microphone and made the announcement 'remain seated; remain seated; remain seated' as the First Officer was still communicating with the Tower. After we slowed but before we were stopped; the Tower asked if we could clear the runway. I felt I could safely comply with this request and exited the runway on the high-speed taxiway. After coming to a complete stop; I called for the Reject Takeoff memory items. The checklist was completed and the QRH was referenced for the remainder of the procedure. I did not have a good sense of our speed at the time of the reject. The First Officer's best recollection was between 120-130 KIAS. The brake cooling chart was referenced which put the airplane in the caution zone. The parking brake was not set. At this point I looked over the engine instruments and all appeared normal. After communicating with ATC; flight attendants and passengers; I elected to start the APU and shutdown the right engine. Calls were placed to Dispatch; Hub Maintenance and Operations. The decision was made to return to the gate. After a period of brake cooling and in consultation with Maintenance; a slow taxi to the gate was completed. The First Officer told Ramp Control to advise ramp personnel not to approach the main tires. Upon shutdown at the gate; an appropriate logbook write-up was made via ACARS. The First Officer and I debriefed in the cockpit while the passengers were disembarking. I then thoroughly briefed the gate Mechanic on what we experienced. After the passengers were off the aircraft; I conducted a debriefing with all of the Flight Attendants. They all agreed they heard a loud bang in the cabin and felt the aircraft swerve although they had differing opinions on where the noise came from. Maintenance was consulted and a determination was made that we were no longer fit-for-duty for the remainder of the day.
Second reporter narrative
Other than planning to depart Runway XY but being assigned Runway XXL; and the associated changes to the runway and takeoff information; everything had proceeded normally on the way to Runway XXL in ZZZ. The weather was clear skies with winds out of the north / north east at 10-20 kts. We planned for a flaps 5; reduced takeoff (94.6%) from Runway XXL. Flaps 5 was requested for the high-pressure altitude. V1 was 154 kts. We verified Runway XXL; Tower cleared us for takeoff and we began the takeoff roll. Everything proceeded as normal. Thrust was set at 94.6% and the appropriate callouts were made. The 100-kt. call was made. Not long after the 100-kt. call; at approximately 120 kts.; the aircraft briefly but somewhat aggressively jolted to the right. I had never felt anything similar to this on a normal takeoff roll; it felt as though someone sharply kicked the right rudder. The Captain called 'reject' and began the rejected takeoff procedure. The procedure went smoothly and per SOPs; and the RTO kicked in to stop the aircraft. Departing on a XX;000 ft. runway; the Captain applied the brakes to disarm RTO braking and relax the rate of deceleration. The Tower had cleared another aircraft for takeoff so the Captain asked me to let Tower know that we were rejecting immediately. As I was informing Tower; the Captain made the 'remain seated; remain seated' announcement. From here we rolled off one of the high-speed exits (I believe it was [Taxiway] XX) and stopped clear of the runway. There were no abnormal engine indications noted; although the power was already at idle. Also worth noting is that we did not receive any warning or caution annunciation on the takeoff roll. I ran the rejected takeoff memory items; and we decided not to set the parking brake; and that an evacuation was not required. We continued with the rejected takeoff QRH checklist and referenced the brake cooling charts. At about 120 kts. and 150-155k weight we were in the caution zone and noted we would need at least an hour before Maintenance could inspect the wheels/brakes. The Captain made a PA to the passengers letting them know what happened and that we were putting together a plan. Since we had no other indications; and could not identify the malfunction; we stopped the checklists here. Knowing that we would be returning to the gate; we started the APU and shut down the #2 engine. From here we took time to coordinate with various groups and allow the brakes to cool before taxiing. We called Maintenance to inform them of the issue and verify they were comfortable with us taxiing back to the gate with the elevated brake temperatures. We coordinated with Operations for a new gate; and the Captain contacted Flight Operations. I would estimate that after about 30 minutes we began the slow taxi; with as little brake application as possible; back to the gate. The after landing flow was also accomplished. The taxi in was uneventful. I believe we taxied XY; XY1; XZ; XA to the ramp/gate. Once on the ramp we asked Operations and/or the Ramp Controller (I can't recall if it was one or both of them) to inform the Ground Crew to stay away from the main wheels. We stopped at the gate and the Ground Crew chocked the nosewheel. Maintenance met us at the aircraft and we began to inform him of the situation. We both decided that we were unfit to continue for the rest of the day. Also worth noting is that many; if not all; of the flight attendants heard a bang and felt the same thing; and a number of passengers mentioned the same. Other than not knowing the cause of the jolt and swerve; I believe everything went about as well as it could have. The only thing the Captain and I discussed that we would change is that we would have rolled a firetruck.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.