Posterior probabilities of causal factors leading to unairworthy dispatch after maintenance

ASRS maintenance reports from 1996 through 2000 (n = 937) were subjected to posterior probability analysis to determine the probability of causal factors leading to a specific maintenance-related event. Unintentional release of an unairworthy aircraft into revenue service was found to be the most frequent maintenance-related event (40 per cent). The top three maintenance errors leading to such an event were improper documentation (33 per cent), improper installation (27 per cent), and sign-off of work not performed (13 per cent). The probabilities of certain causal factors responsible for each of the maintenance errors were as follows: (a) For documentation errors ‐ lack of awareness (22 per cent), poor procedures (15 per cent), and lack of training (4 per cent); (b) For improper installation ‐ complacency (21 per cent), lack of awareness (21 per cent), and poor procedures (15 per cent); and (c) For sign-off of work not performed ‐ maintenance management (27 per cent), complacency (21 per cent), and poor procedures (14 per cent).