Investigation of the A-7 Hook Point Attachment Bolt Loosening Problem

摘要

Loosening of the hook point attachment bolt in the aircraft arresting hook assembly of the A-7 attack aircraft has caused a potentially dangerous situation and has demanded considerable maintenance effort. This report reviews the history of the loosening problem and attempted solutions to it. Research into a hitherto neglected possible causal mechanism, self loosening, is discussed. Experiments designed to evaluate the contribution of this new factor to the problem are reported. The conclusions drawn from these tests are: that loosening occurs as a result of plastic strain of the bolt, that the crushing of the washer also causes loss of torque, and that the existence or non-existence of a self loosening contribution could not be established.