B737-800
Flight Crew Air Transport Pilot (ATP)
Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Loss Of Aircraft Control
Flight Crew Returned To Gate; Flight Crew Regained Aircraft Control
Aircraft; Human Factors
During takeoff; after engaging TOGA; the right engine accelerated more rapidly than the left; causing the aircraft to drift left. I attempted to correct the nose steering with rudder pedal input; but the aircraft began veering hard to the left. I discontinued the takeoff and attempted to correct the aircraft back to the centerline with differential braking and tiller input. Initially; the nose gear was not responding to the tiller and a crew holding short of the runway reported that the nose gear appeared to be turned completely to the left and was smoking as the aircraft skidded on the runway. Suddenly; the nose gear moved rapidly to the right and steering control via the tiller was regained. We advised the Tower of our situation and cleared at the next taxiway. After clearing the runway; I stopped on the parallel taxiway and requested a tow back to the gate. Initially; Operations requested we taxi back to the gate and said they could not send a crew out on the taxiway to tow us back. Although I had apparently regained control of the nose wheel steering; I did not feel comfortable continuing to taxi because I did not know the cause of the failure and could not be sure it would not happen again while taxiing. I reiterated the need for a tow and they finally agreed to send a tug and crew.  I do not know why they did not want to send a tug; but when I tell them I need one; I expect it to be sent. After block-in; a Mechanic met us at the aircraft and told us it appeared the nose wheel steering momentarily went into bypass mode; rendering the steering inoperative.
The pilot of a B737-800 experienced a loss of control during takeoff roll. He observed a differential acceleration of the engines that caused a drift that he could not control with rudder pedal input; differential braking or tiller command. Once the takeoff was rejected; he regained control but was hesitant to taxi since he did not know the cause.