Date: 202005
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Dawn
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower ZZZ
Aircraft component: Rudder
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Private; Flight Crew Instrument; Flight Crew Multiengine
Human factors: Workload; Troubleshooting; Confusion; Situational Awareness
Second reporter function: Captain; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Less Severe; Ground Event / Encounter Loss Of Aircraft Control
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Returned To Gate; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Rejected Takeoff; Flight Crew Regained Aircraft Control
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: At the gate; Captain and I had a thorough rejected takeoff brief. We also discussed the gusty crosswind threat and decided to conduct a Flaps 5; max thrust with reduced V speeds and rotation at Vr max; along with a rolling takeoff. We were cleared for takeoff while turning onto [the taxiway] for XXL. The Captain gave me control of the throttles upon entering the runway after we confirmed we would be doing a rolling takeoff. After the Captain aligned the aircraft on the centerline; he gave me the controls to continue the takeoff. I increased the throttles to 40% for stabilization and the aircraft began yawing to the right. I was unable to correct the yawing using left rudder and advised the captain that I had no directional control. He stated that he had the aircraft and was rejecting. He closed the throttles; disconnected the autothrottles and also put in the reversers as the aircraft yawed back to the left. Once we had the aircraft stabilized; I advised tower that we were rejected the takeoff and advised the passengers to remain seated. The tower asked if we needed any assistance and after determining we didn't have any serious engine indications; we said no. They advised us we could take any taxiway off the runway. We took the reverse highspeed and proceeded to the run up pad for XXL to assess the situation. Once there; the Captain spoke with the flight attendants; passengers and maintenance. It was decided that we would return to the gate and change aircraft. We returned to the gate; briefed maintenance personnel and then debriefed the rejected takeoff.


Second narrative: Cleared for takeoff while approaching XXL hold short. As per briefing; we had Flaps 5; max thrust; with reduced numbers and with a plan to rotate at Vr max for wind shear precautions with a rolling takeoff. We executed a transfer of throttle controls to FO (First Officer) for right seat takeoff; as I lined up aircraft; stating we would do a rolling takeoff and I would lineup aircraft on runway. FO pushed throttles towards 12 O'clock position. I finished lining up aircraft on centerline and verbally transferred controls to FO. FO acknowledged aircraft control and we began a normal takeoff roll. I visually verified throttles in 12 Oclock position; as we transferred controls. As the thrust on #1 engine reached approximately 40% N1 the #2 engine seemed to lag behind somewhat to 30%-35%; the aircraft began drifting right of centerline. The aircraft continued to drift further right and the FO stated that rudder was ineffective to correct the steering. There were no indications of engine difficulties other than the right side engine seemed unresponsive to the throttle commanded position. The throttle position never went past the 12 Oclock position and the approximately 40%N1 range. As the aircraft turned to approximately 30 degrees right of centerline; the FO said she had no directional control. I then stated 'I have the aircraft; rejecting' and closed the throttles; disconnected the auto throttles and used the tiller to regain directional control and engine reversers to slow the aircraft down. The FO called the tower stating we were rejecting takeoff on XXL and then made a PA to keep flight attendants seated. Tower directed us to make any left turn and we complied stating we did not require any assistance. We insured checklists were completed and agreed to taxi to a holding pad to continue our discussion as to what happened. The rejected speed was approximately 25 to 30KTs. We taxied to the XXL holding pad and then contacted FAs (Flight Attendants) and then I made a PA to passengers. We then conferred with each other and to maintenance and all agreed that a return to the gate was our best course of action.


Synopsis: B737 flight crew reported a rejected takeoff after experiencing uneven thrust and loss of directional control.