The pilot of the vintage, tailwheel-equipped airplane was departing from a turf runway. The pilot described that as he initiated the takeoff toward the west, and into the setting sun, he looked inside the airplane to verify the engine instruments. It took his eyes several seconds to adjust to the shaded cockpit and when he next looked outside he was surprised to see that the airplane had drifted to the left and he was no longer able to see the runway edge markers. The airplane’s main landing gear then encountered a “dip” that ran alongside the runway and he was unable to apply corrective control inputs to bring the airplane back onto the runway. The airplane’s left wing subsequently struck a metal pole and trees, after which the airplane nosed over and caught fire. Bystanders extricated the pilot from the cockpit and the airplane’s wings, fuselage, and empennage were substantially damaged. A witness video of the takeoff showed that when the pilot began the takeoff roll, the airplane was not aligned with the runway and was oriented slightly left. As the engine power increased, the airplane veered further left. The airplane’s tailwheel was oscillating from side to side, and the rudder was visibly moving. Following the accident, the pilot could not recall whether he had locked the tailwheel prior to initiating the takeoff. Postaccident examination of the tailwheel assembly revealed that the tailwheel locking mechanism was locked, though it could not be determined whether this as-observed condition was consistent with the configuration during takeoff, had been engaged later during the accident sequence, or as the result of manipulation during the examination. Additionally, the tailwheel locking pin was broken into two pieces, with the upper half frozen into position in its guide while the lower half was worn. This condition would likely have resulted in the tailwheel lock operating unreliably, and with the tailwheel not properly locked, would have hampered any efforts the pilot would have made to realign the airplane with the runway after initiating the misaligned takeoff roll. Had the pilot confirmed the operation of the tailwheel locking mechanism prior to initiating the takeoff, it is possible that he could have recognized the deficiency and avoided the accident.