WPR12LA417

During cruise flight in the experimental amateur-built airplane, the pilot heard a "bang" sound, and the airplane immediately began to descend and roll to the left. He applied opposing aileron and right rudder control inputs and was able to regain partial control; however, as the descent progressed, the airplane's turn rate began to increase. The airplane struck the ground in a left-wing-low attitude, sustaining substantial damage. Examination of the airframe did not reveal any failures or anomalies that would have precluded normal operation. Although postaccident examination of the wreckage revealed two separated cables (a wing brace and an elevator trim tab cable), physical evidence indicated that the cable separations most likely occurred during the accident sequence. Additionally, if the elevator trim tab cable had separated in flight, the movement of the trim tab to the up position likely would not have resulted in the flight control difficulties experienced by the pilot. Thus, it was not possible to determine why the airplane departed controlled flight and why the pilot was unable to regain control.

The airplane was built by the pilot, and issued its experimental light-sport certificate in December 2006. Since that time it had accrued a total of 1,066 flight hours. The last conditional inspection was completed on January 13, 2012, 68 flight hours prior to the accident. On September 13, 2012, about 1320 Pacific daylight time, an experimental light-sport Seymour Skyranger, N936LS, experienced an in-flight loss of control near Perris, California. The pilot/builder was operating the airplane under the provisions of 14 Code of Federal Regulations Part 91. The sport pilot sustained minor injuries, and the airplane sustained substantial damage. The personal flight departed Corona Municipal Airport, Corona, California, about 1240, with a planned destination of Perris Valley Airport, Perris. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot reported that during cruise flight, he heard a "bang" sound, and the airplane immediately began to descend and roll to the left. He applied both right aileron and right rudder control inputs, and was able to regain partial control. He elected to land the airplane in a field rather than activate the ballistic recovery parachute; however, as the descent progressed, the airplane's turn rate began to increase. He became concerned that the airplane was too low to activate the parachute, and that it may become entangled in the rigging cords, so he braced for impact. The airplane struck the ground in a left-wing-low attitude, and the pilot was able to egress unaided. The airplane was recovered to a hangar by friends of the owner, and subsequently examined by the NTSB investigator-in-charge. Control continuity was established from the cockpit controls through to the respective control surfaces, with the exception of the elevator trim tab. The trim tab was positioned on the right elevator, and had been modified by the owner with the addition of a spring connecting the upper trim horn to the elevator spar. The trim control cable had pulled through its control fitting in the lower footwell, and as such, the spring had pulled the trim tab to the full-up position. The owner stated that he installed the spring to prevent the tab from fluttering in the event of a control cable failure. All major structural members were intact, with damage limited to bending and crush damage centered around the forward fuselage. The left wing internal brace cable, which connected the aft spar at the outboard trailing edge to the forward spar at the inboard leading edge, had separated where it entered its outboard crimp fitting. The cable was sent to the NTSB Office of Research and Engineering for analysis. Examination revealed that the cable was a 7 x 7 wire rope type, composed of seven strands and seven wires per strand. Each fractured wire, 49 in total, was examined using a stereomicroscope. The fractured wire surfaces had either a cup and cone morphology or a slanted morphology approximately 45 degreesto the wire longitudinal axis. Both morphologies were consistent with an overstress fracture, with no indications of wear or rubbing of the wires inside the sleeve. Examination by both the FAA inspector at the accident site, and NTSB investigator-in-charge at the follow up examination, did not reveal any mechanical anomalies with the airframe that would have precluded normal operation. The airplane came to rest in a corral adjacent to a residence. The airplane remained in a nose-down attitude, sustaining crush damage to the forward fuselage. The nosegear had been separated, and the engine, firewall, and left main landing gear had become displaced aft. The left wing was bent upwards about 10 degrees at the lift strut, and sustained crush damage to the leading edge tip. The remaining structure was largely intact and examined by an FAA inspector who responded to the accident site.