On June 2, 2006, approximately 1420 mountain daylight time, a Piper PA-28-160 airplane, N1123W, sustained substantial damage after impacting terrain following a loss of control near Laurel, Montana. The airplane was registered to and operated by a private individual. The certificated private pilot, the airplane's sole occupant, sustained serious injuries. Visual meteorological conditions prevailed for the personal flight, which was operated in accordance with 14 CFR Part 91, and a flight plan was not filed. The local flight was originating at the time of the accident, with its destination being the Billings Logan International Airport (BIL), Billings, Montana. In telephone conversations with the NTSB investigator-in-charge (IIC), and according to the Pilot/Operator Aircraft Accident/Incident Report (NTSB Form 6120.1), the pilot reported that after picking the airplane up from a local maintenance facility following an annual inspection, he taxied to Runway 04, did his runup, and announced his intention to exit the pattern south for BIL. The pilot stated that shortly after taking off and commencing a turn to the left at approximately 300 feet above ground level (agl), he experienced no aileron control. The pilot stated that the last thing he remembered was cutting the power and observing two fields in front of him. The airplane subsequently impacted terrain about one-half mile north of the airport boundary and came to rest in an upright position. There was no post-crash fire. In statements submitted to the IIC, two pilot-rated witnesses reported observing the airplane in a nose high climb after taking off, then assume a bank attitude of about 30 degrees to the left between 300 and 500 feet agl. The witnesses stated that the airplane continued in a 180-degree turn, leveled off, then pitched down and impacted the ground at a near 30-degree angle. In a statement submitted to the IIC dated June 6, 2006, the Director of Maintenance (DO) for the facility which completed the airplane's annual inspection reported that during the inspection process the left-hand yoke was removed per a Federal Aviation Administration (FAA) Airworthiness Directive #69-22-02. The DO stated that after completing the inspection he had another mechanic reinstall the control yoke. The DO reported that he subsequently checked the installation and inserted the cotter pin into the [clevis] pin for the left-hand yoke, then installed the covers for both yokes. The DO revealed that he also checked the controls, however, he did not check the controls all the way to their stops. In a statement submitted to the IIC dated June 6, 2006, the mechanic who was delegated by the DO to reinstall the pilot's control yoke reported, "I slid the control yoke over the column and tried to put the pin in, but it would not go. Thinking that it must not be on far enough, I rotated it right and left while applying forward pressure. Using my right hand, I held the copilot's yoke and adjusted the pilot's yoke to line up parallel to it. Using a flashlight, I looked underneath to see if the holes were lined up. I saw a small piece of silver on one of the corners, so I knew I must be close, so I put the pin in and tested the controls. Both elevators worked as required with the elevator. I told the DO that it was in but still needed to be cotter pinned." In a follow-up telephone conversation with the IIC, the DO revealed that after the airplane had been recovered to his employer's facility, the same facility where the annual inspection had been performed, a subsequent examination by the DO and other company maintenance personnel revealed that the left-hand control yoke had not been attached and secured properly to the left-hand control column. This resulted in the control yoke moving freely around the control column, and therefore providing no input to either of the airplane's aileron controls. The DO subsequently notified an FAA aviation safety inspector of his findings. In a report submitted to the IIC, a Lycoming Textron engine representative reported no anomalies with the engine which would have precluded normal operation. The representative also reported that he observed the pilot control yoke separated from the shaft, with the clevis pin still in place on the yoke. He also observed a crack in the control column shaft's upper hole, and that the clevis pin was not engaged on the shaft.