B737-800 flight crew reported a temporary loss of directional control during the takeoff roll which prompted the flight crew to reject the takeoff. After an aircraft inspection with no indications of a mechanical issue the flight crew conducted a safe departure with no issues.
Synopsis
B737-800 flight crew reported a temporary loss of directional control during the takeoff roll which prompted the flight crew to reject the takeoff. After an aircraft inspection with no indications of a mechanical issue the flight crew conducted a safe departure with no issues.
Narrative
Normal pre-flight; taxi procedures. No mechanical deficiencies reported or noted for aircraft. Scattered convective weather activity in the vicinity of the airport with no reports of wind shear. After having been cleared for take-off on Runway XXR; both throttles advanced to approximately 40% N1. With power stabilized on both engines; TOGA engaged and brakes (manually engaged) released. Throttles appeared to advance symmetrically as observed by Captain; First Officer and jumpseat observer. Very shortly after aircraft began take-off roll; prior to any airspeed indications; a sharp left trajectory ensued. Rapid application of right rudder followed by a reduction of thrust on both engines was accomplished in order to correct the leftward deviation and return the aircraft to a centered position on the runway. Cancellation of take-off clearance was requested and subsequent taxi to a safe exit from the active runway. All system response to thrust application; braking and steering functioned normally while exiting the active runway and taxiing to a holding location clear of other traffic. After a crew assessment of the scenario which included atmospheric conditions and possible anomalies; observed throttle/thrust; braking and steering operation before; during and after the incident; a determination was made that no mechanical anomaly could be attributed as a causal factor.
Second reporter narrative
Normal push; taxi out to Runway XXR in ZZZ. No mechanical discrepancies noted; so everything up until take-off was normal. When we were cleared for take-off; I saw the Captain advance both thrust levers evenly and slowly until they stabilized together at 39-40% N1. At this point; the TOGA buttons were pressed and the thrust lever advanced to the take-off setting. The aircraft began to yaw to the left and the opposite rudder was engaged to counter. The aircraft continued left so we elected to reject the take-off. We were at a very low speed when the rejection was accomplished. I told Tower of the reject and asked to pull off of the runway to assess the situation. The steering was fine and there were no cockpit indications of a mechanical issue. Captain (CA) and I decided that everything was safe to opt for another take-off attempt. Second take-off was a non-event and continued safely to ZZZ1. Plausible cause was the left engine possibly spooled up slower than the right after the TOGA buttons were pressed.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.