Metallurgical Examination of a Failed AH-64D Pilot Cyclic Stick (Part Number 7-511512001-3)
Final rept. Jan 2003-Feb 2003
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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The U.S. Army Research Laboratory was requested by the U.S. Aviation and Missile Command AMCOM to examine a pilot cyclic stick part number PN 7-511512001-3 and a copilot cyclic stick PN 7-511515001-3 taken from an AH-64D Apache helicopter, which crashed at Ft. Rucker, AL. The pilot stick was received broken into two pieces while the copilot stick was cracked, but not completely separated. While this investigation focused on the pilot stick, findings from the copilot stick were included at times for comparative purposes. The objective of this failure analysis was to determine if any metallurgical evidence existed that suggested that the fractured pilot stick might have contributed to the cause of the crash or whether it occurred as a result of the mishap. The metallurgical findings suggested that the pilot stick fractured during a single event. There was no evidence of fatigue observed on the fracture surface of the pilot stick. The fracture morphology consisted primarily of ductile dimples, indicative of overload conditions. There existed some areas that were indicative of cleavage fracture, but nothing that would suggest a fatigue-induced failure.