N528JCAir Tractor AT-602

The pilot reported that the tailwheel became unlocked on landing. The airplane drifted to the left, exited the runway, and ground looped which resulted in substantial damage to the right wing.

A post-accident examination revealed that the tailwheel lock pin was not engaged, although the cockpit handle was in the locked position. The cable was continuous from the cockpit handle to the locking mechanism, however, multiple attempts to move the tailwheel locking pin by manipulating the handle were unsuccessful. The pin became unstuck when it was assisted into position using a striking tool. Subsequent attempts to lock the tailwheel from the cockpit were successful and the mechanism functioned normally.