CEN09LA023

During an aerial application flight, the airplane, piloted by a commercial pilot, contacted a transmission wire during an undetermined phase of flight. The vertical stabilizer separated from the airplane and was not recovered. Aircraft control was not possible and the airplane subsequently impacted terrain. The pilot was seriously injured. Examination of the wreckage revealed damage to the anti-snag deflector cable and vertical stabilizer consistent with a wire strike. Displaying signs of wear, the pilot's restraint system failed in two locations resulting in additional injury to the pilot.

On October 18, 2008, approximately 1406 central daylight time, a single-engine Piper PA-36-285 was substantially damaged upon impact with terrain near Silverton, Texas during an undetermined phase of flight. The commercial pilot, the sole occupant of the airplane, was seriously injured. Visual meteorological conditions prevailed and no flight plan was filed for the Title 14 Code of Federal Regulations Part 137 aerial application flight. There were no reported eyewitnesses to this accident. However, a resident near the accident scene heard the airplane's engine operating followed by the sound of a crash. The resident called emergency services and rushed to the scene to provide medical attention. A majority of the airplane was recovered and examined by the National Transportation Safety Board (NTSB), inspectors from the Federal Aviation Administration (FAA), and a technical representative from Piper Aircraft Company. Of note, the vertical fin was not recovered. The airplane was equipped with a wire deflector which was mounted on the cockpit windshield. The wire deflector had a bend towards the left side of the airplane, with a more pronounced bend near the midspan of the deflector. An anti-snag deflector cable was installed which would have ran from the cockpit to the vertical fin. The cable was torn immediately forward of the vertical fin, with "broomstrawing" noted on the end of the cable. The spar caps, on either side of the vertical spar, displayed compression damage with shear lips bent towards the aft of the airplane. The spar web also displayed "tearing," with shear lips bent towards the aft of the airplane. No pre-existing defects were noted in the area of the vertical spar where the vertical fin would have been attached. The rudder displayed compression wrinkling on the lower portion of the control surface. Propellers on the engine displayed leading edge gouging and chord-wise scratches consistent with engine power at the time of the accident. No anomalies with the airplane flight control surfaces or engine were detected during the examination. All of the pilot's restraints were faded and appeared worn. The pilot's left lap belt had failed inboard of the adjustment buckle, with the failure area displaying signs of wear and stretching. The cable securing the shoulder harness to the inertial reel had failed just below the connection to the shoulder harness. The failed area was consistent with where the cable ran over the retraction pulley. No identification tags were located on the belt to record date of manufacturer. A review of the airframe logbook revealed that all of the restraint cables were replaced on March 14, 1997 and the center shoulder harness cable was subsequently replaced on April 28, 2000. There was no entry found for the replacement of the restraint webbing material. There is no replacement schedule for seat restraints under Federal Aviation Regulations (FAR) Part 23. The Piper service manual for the airplane states "...safety belts should be replaced if cut, frayed, or broken stitching is evident...." In addition, Advisory Circular (AC) 43.13-1B CH 1 "Acceptable Methods, Techniques, and Practices - Aircraft Inspection and Repair" states "[s]afety belts eligible for installation in aircraft must be identified by the proper Technical Standard Order (TSO) markings on the belt." Furthermore, the AC states "[t]he webbing of safety belts, even when mildew-proofed, is subject to deterioration due to constant use, cleaning, and the effects of aging. Fraying of belts is an indication of wear, and such belts are likely to be unairworthy because they can no longer hold the minimum required tensile load." The pilot was incapacitated for several weeks after the accident. His injuries prevented the completion of an NTSB Form 6120. On July 18, 2008, the pilot was involved in a accident involving substantial damage to a Grumman G-164A during a forced landing due to a loss of engine power for undetermined reasons (DFW08CA192). During that investigation, the pilot reported accumulating 1,850 total hours. The local power companies did not report any downed wires in the vicinity of the accident.