MIA94LA171

The pilot was performing acrobatic maneuvers when he heard a 'pop' and noted that his right upper aileron was loose. He slowed down, and was able to return and land without further incident. Postflight inspection revealed a failure of the upper right inboard aileron welded bracket. Further metallurgical examination at the safety board laboratory revealed 3 distinct fatigue origins between the toe of the weld and the welded zones. The weld itself exhibited sharp and high weld crowns.

On July 4, 1994, about 1400 eastern daylight time, N61PS, a Pitts S2B, registered to the pilot David Swartz, experienced an in-flight control system failure while maneuvering on a 14 CFR Part 91 personal flight. Visual meteorological conditions prevailed at the time and no flight plan was filed for the local flight. The airplane was substantially damaged and the pilot was not injured. The flight originated about 1330 the same day.

The pilot stated that while performing aerobatics he heard a "pop". He then noticed partial loss of control of aileron travel. He returned to the airport and landed without further incident. Postflight inspection of the airplane revealed a failure of the upper, right, inboard aileron welded bracket. This same airplane experienced longeron failures at the welds on May 26, 1994, reference, NTSB accident case number MIA94LA154.

The failed aileron bracket was submitted to the NTSB laboratory for examination. The examination revealed three distinct fatigue origins between the toe of the weld and the welded zones. The weld itself exhibited sharp and high weld crowns.