Incident Overview
On March 2, 2011, at approximately 1635 central standard time, a Great Lakes 2T-1A-2 aircraft, registration N6196L, was substantially damaged when its right horizontal stabilizer failed and separated from the airplane during final approach to Kleberg County Airport (IKG) in Kingsville, Texas. The pilot, who was the sole occupant, was not injured. The flight was conducted under 14 Code of Federal Regulations Part 91 as a personal flight without a flight plan, and visual meteorological conditions were present.
Sequence of Events
The pilot departed IKG around 1630 to practice aerobatic maneuvers for an upcoming air show. After completing a hammerhead turn, he felt a slight vibration and noted that the pitch control felt "unusual." He returned to the airport; the vibration increased for several seconds and then ceased. A lineman at the fixed base operator (FBO) radioed the pilot to alert him that something had fallen from the aircraft. The pilot landed on runway 31 but lost directional control, causing the airplane to ground loop to the right.
Damage and Examination
Post-accident examination revealed that the right horizontal stabilizer and elevator had detached from the airplane. The separated components struck the rudder, causing extensive damage. The pilot sent the right horizontal stabilizer and elevator to Phoenix Aircraft Company in El Dorado, Kansas, for analysis. The company's report indicated 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, causing the inboard section to rotate downward and separate. The remaining portion then pivoted aft and struck the rudder.
Service Information
Phoenix Aircraft Company provided Great Lakes Service Alert 12-24-88, which described a similar previous occurrence, and Service Bulletin #15. The bulletin emphasized proper rigging of tail wires, noting that improper rigging could result in excessive torque loads on the horizontal stabilizer front spar, potentially causing the attach fitting to fail. Examination of the aircraft's last annual inspection records found no reference to inspection of the horizontal stabilizer spar or compliance with Service Alert 12-24-88 or Service Bulletin #15.