On November 16, 2019, about 1510 Pacific standard time, a Piper PA-18 airplane, N8589D, sustained substantial damage when it was involved in an accident near Livermore Municipal Airport (LVK), Livermore, California. The pilot was the sole occupant on board and was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 banner tow flight. The pilot reported that he completed a preflight of the airplane, including the movement and "stability" of the flight controls, to set up a banner for pickup on the approach end of runway 07. The pilot departed runway 07 and completed one circuit in the left traffic pattern to return for the banner pickup. The tower controller then cleared the pilot for the banner pickup. The pilot approached the runway and made successful contact with the banner. As the pilot pulled the flight control stick back to gain altitude, the control stick separated from the stick stub assembly at the floor. The airplane made an uncontrolled descent and impacted the ground shortly thereafter. The airplane came to rest in a grass field about 150 ft from its first impact with the ground. Examination of the airplane by a Federal Aviation Administration inspector revealed that the hardware that secured the control stick to the stick hub assembly was secured on the control stick but was not attached through the mounting holes on the stick hub assembly. The stick hub showed signatures of rubbing and wear at the area near the bolt holes. Flight control stick and stick hub assembly The airplane’s maintenance logbooks revealed that the last inspection was performed on March 17, 2019, after which the airplane was returned to service. There were no maintenance entries that indicated the removal and installation of the control stick.