A319
Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface
Aircraft Equipment Problem Critical; Ground Event / Encounter Loss Of Aircraft Control
Flight Crew Regained Aircraft Control; Flight Crew Rejected Takeoff; Flight Crew Returned To Gate
Aircraft; Human Factors
After completing all checklists and following all SOP's and being cleared for takeoff; I entered the runway and set takeoff thrust at 50% N1. After moving the thrust levers to the flex detent the aircraft veered sharply to the left. Recognizing I had no directional control of the aircraft; I initiated a rejected takeoff at approximately 10 to 15 KTS. As I applied the brakes and steered the aircraft; the aircraft veered sharply to the right then back to center. After regaining complete directional control of the aircraft I taxied down the runway and exited. An announcement was made to the passengers regarding the rejected takeoff and I conferred with Dispatch and Maintenance Control to determine our course of action. I ran up the number one engine to check the parameters and check the brakes to deduce if perhaps a malfunction played a part. After conferring with the First Officer and the jumpseat rider; they said that the number one engine lagged considerably behind the number two engine once the thrust lever was placed in the flex detent. (Asymmetrical thrust)  I returned to the gate where approximately 9 passengers asked to get off the airplane. After accommodating our passengers and conferring with my flight attendants and refueling; we proceeded to destination. I am not completely certain of the cause for the rejected takeoff; though asymmetrical thrust may have played a part. Of note is that engine vibration was noticeable throughout the flight and particularly during climb. The N1 vibration indicators read between 1.8 and 2.6 which is well below any warnings; however vibration was felt and noticed.
A319 Captain experiences a loss of directional control when thrust is set for takeoff and the takeoff is rejected below 15 KTS. The left engine did not accelerate at the same rate as the right engine according to the First Officer and the jumpseat rider. A second attempt is successful although the number one engine vibrates noticeably during climb with N1 vibration indicating between 1.8 and 2.6.