CEN11LA209

The pilot took off to practice aerobatic maneuvers for an upcoming air show. After completing a hammerhead turn, he felt a slight vibration and the pitch control felt unusual. Returning to the airport, the vibration increased. The pilot landed but was unable to maintain directional control and the airplane ground-looped. The right horizontal stabilizer and elevator had separated from the airplane, striking the rudder and causing substantial damage. A postaccident examination revealed evidence of a pre-existing crack in the front spar near a riveted fitting. The spar moved outward and disengaged from the fitting. The inboard section rotated downward and separated from the airplane. The remaining portion of the stabilizer pivoted aft, separated from the airplane, and struck and damaged the rudder. A service alert from the airplane’s manufacturer outlined a similar previous occurrence. Another emphasized the importance of properly rigged tail wires, noting that if the tail wires were improperly rigged excessive torque loads could be applied to the horizontal stabilizer front spar, causing the attach fitting to fail. Examination of the last annual inspection entry disclosed no reference to the horizontal stabilizer spar being inspected, nor did it indicate that either service bulletin had been complied with.

On March 2, 2011, approximately 1635 central standard time, a Great Lakes 2T-1A-2, N6196L, registered to and operated by the pilot, was substantially damaged when the right horizontal stabilizer failed as the airplane completed some aerobatic maneuvers and separated from the airplane while it was on final approach for landing at Kleberg County Airport (IKG), Kingsville, Texas. Visual meteorological conditions (VMC) prevailed at the time of the accident. The personal flight was being conducted under the provisions of 14 Code of Federal Regulations (CFR) Part 91 without a flight plan. The pilot, the sole occupant on board, was not injured. The local flight had originated at IKG approximately 1630. According to the pilot's written statement, he took off at 1630 to practice aerobatic maneuvers for an upcoming air show. After completing a hammerhead turn, he felt a slight vibration and the pitch control felt "unusual." Returning to the airport, the vibration increased for a few seconds and then dissipated. A lineman at the FBO (fixed base operator) called the pilot on the radio and advised him something had fallen off the airplane. The pilot landed on runway 31 but was unable to maintain directional control, and the airplane ground looped to the right. Examination of the airplane revealed the right horizontal stabilizer and elevator had separated from the airplane, striking the rudder and causing extensive damage. The pilot sent the right horizontal stabilizer and elevator to Phoenix Aircraft Company in El Dorado, Kansas, for examination. According to the company's report, there was evidence of a pre-existing crack in the front spar of the right stabilizer near a riveted fitting. The spar moved outward and disengaged from the fitting. The inboard section rotated downward and separated from the airplane. The remaining portion of the stabilizer separated from the airplane in a pivotal aft motion and struck and damaged the rudder. The company also enclosed Great Lakes Service Alert 12-24-88, that outlined a similar previous occurrence, and Service Bulletin #15, that emphasized the importance of properly rigged tail wires. The bulletin noted that if the tail wires were improperly rigged, excessive torque loads could be applied to the horizontal stabilizer front spar, causing the attach fitting to fail. Examination of the last annual inspection entry disclosed no reference to the horizontal stabilizer spar being inspected, nor did it indicate that Service Alert 12-24-88 or Service Bulletin #15 had been complied with.