Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.
Issue link: http://experimenter.epubxp.com/i/113663
S a f e t y W ir e card. The recovered file would not play using either the manufacturer's supplied software or any third-party playback software. It was suspected that the normal file closeout and shutdown process had not occurred consistent with an abrupt stoppage of the recorder. However, several third-party software file recovery programs were used to reconstruct the normal movie file structure. This reconstruction yielded a 51-minute 33-second video and audio file. Figure 12—SE micrograph of the right propeller shaf fracture surface, showing areas of overstress and post-fracture surface contamination. Figure 13—Cross-section of an intact section the right side propeller shaf af weld, showing the depth of the weld penetration relative to the joint (~25X, etched with 4% Nital). The reconstructed file revealed that during the accident flight none of the co-pilot's intercom conversations were audible on the recording. The co-pilot's voice was however heard when he was talking on the aircraft's radio. The pilot's voice appeared to be recorded normally during the flight. The video showed that the airplane yawed near the end of the recorded video. Both pilots were observed to manipulate the controls following the yaw. The video showed that the airplane was controllable after the yaw. The video ended in flight near the location of the accident site. The NTSB Vehicle Recorder Laboratory CVR Study is appended to the docket associated with this investigation. Propeller Shafts According to NTSB Materials Laboratory Factual Report Number 12-074, the left propeller shaft had completely separated at its aft weld. The majority of the contact areas of both mating separation surfaces had been obliterated by smearing, which was consistent with rotational rubbing of the fractured faces. The outer tube surface near the left tube's aft separation exhibited paint spalling and general discoloration. These features were not observed on the right propeller shaft tube. A magnified edge view of the tube separation revealed that approximately 25 to 35 percent of the through thickness of the propeller shaft tube had not been welded to the propeller shaft end. This incomplete weld penetration occurred in the inner areas of the joint. Visible defects, such as pores and voids, were observed in the welded areas. Other propeller shaft welds from the accident airplane were examined, and they exhibited incomplete weld penetrations. The Materials Laboratory Report is appended to the docket associated with this investigation. … Effective Investigation Techniques Figure 14—Cross-section of an cracked section the right side propeller shaf af weld, showing a crack emanating from a gap that had not been welded (~25X, etched with 4% Nital). 34 Vol.2 No.3 / March 201 3 Review of the cockpit video revealed that the airplane yawed near the end of the recorded video. This observation precipitated a follow-up examination of the propeller shafts, which revealed the weld failure. » The complete text of this report is available online here.