Narrative:

We had an unscheduled aircraft swap and the arriving aircraft was about 35 minutes late; which is why our departing flight was delayed. All preflight items were accomplished normally including the before taxi flight control checks. We accomplished the before takeoff checklist with all items completed satisfactorily and the captain turned to line up the aircraft with the runway centerline. The captain seemed to delay aircraft transfer a little longer than usual and after slightly advancing the thrust levers and told me to feel the stiffness in the controls because they did not feel correct. Also at this time I noticed that the captain's flight director was slaved as the master flight director when I knew that I had selected my flight director as the master. I felt the very stiff controls and when I attempted to pull back on the elevator; the autopilot disconnect horn went off even though I did not see an autopilot a or B selected. We elected to reject the takeoff; as we had just started to roll and had very little if any indicated airspeed. We advised tower; taxied clear; and after a short discussion about who; if anyone; had selected an autopilot on; elected to return to the gate to have maintenance check out the control panel/autopilot. The only thing that I can think that happened was that at some time after the before taxi checklist was completed with satisfactorily results and beginning the takeoff roll an autopilot (and probably the a as the captain's flight director was designated as the master) was commanded on; even though I do not remember seeing any on; nor do I or the captain remember or think that we selected it to on. Possibly a review of the control panel just before takeoff roll; but I honestly believe that we do enough checks currently.

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Original NASA ASRS Text

Title: B737 flight crew experiences stiff flight controls as the takeoff roll is initiated and the takeoff is rejected at low speed. Upon performing a second flight control check the autopilot disconnect horn sounds and the crew returns to the gate for maintenance.

Narrative: We had an unscheduled aircraft swap and the arriving aircraft was about 35 minutes late; which is why our departing flight was delayed. All preflight items were accomplished normally including the Before Taxi flight control checks. We accomplished the Before Takeoff Checklist with all items completed satisfactorily and the Captain turned to line up the aircraft with the runway centerline. The Captain seemed to delay aircraft transfer a little longer than usual and after slightly advancing the thrust levers and told me to feel the stiffness in the controls because they did not feel correct. Also at this time I noticed that the Captain's flight director was slaved as the master flight director when I knew that I had selected my flight director as the master. I felt the very stiff controls and when I attempted to pull back on the elevator; the autopilot disconnect horn went off even though I did not see an autopilot A or B selected. We elected to reject the takeoff; as we had just started to roll and had very little if any indicated airspeed. We advised Tower; taxied clear; and after a short discussion about who; if anyone; had selected an autopilot on; elected to return to the gate to have Maintenance check out the control panel/autopilot. The only thing that I can think that happened was that at some time after the Before Taxi Checklist was completed with satisfactorily results and beginning the takeoff roll an autopilot (and probably the A as the Captain's flight director was designated as the master) was commanded on; even though I do not remember seeing any on; nor do I or the Captain remember or think that we selected it to on. Possibly a review of the control panel just before takeoff roll; but I honestly believe that we do enough checks currently.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.