Maintenance and inspection as risk factors in helicopter accidents: Analysis and recommendations

Abstract

In this work, we establish that maintenance and inspection are a risk factor in helicopter accidents. Between 2005 and 2015, flawed maintenance and inspection were causal factors in 14% to 21% of helicopter accidents in the U.S. civil fleet. For these maintenance-related accidents, we examined the incubation time from when the maintenance error was committed to the time when it resulted in an accident. We found a significant clustering of maintenance accidents within a short number of flight-hours after maintenance was performed. Of these accidents, 31% of these accidents occurred within the first 10 flight-hours. This is reminiscent of infant mortality in reliability engineering, and we characterized it as maintenance error infant mortality. The last quartile of maintenance-related accidents occurred after 60 flight-hours following maintenance and inspection. We then examined the “physics of failures” underlying maintenance-related accidents and analyzed the prevalence of different types of maintenance errors in helicopter accidents. We found, for instance, that the improper or incomplete (re)assembly or installation of a part category accounted for the majority of maintenance errors with 57% of such cases, and within this category, the incorrect torquing of the B-nut and incomplete assembly of critical linkages were the most prevalent maintenance errors. We also found that within the failure to perform a required preventive maintenance and inspection task category, the majority of the maintenance programs were not executed in compliance with federal regulations, nor with the manufacturer maintenance plan. Maintenance-related accidents are particularly hurtful for the rotorcraft community, and they can be eliminated. This is a reachable objective when technical competence meets organizational proficiency and the collective will of all the stakeholders in this community. We conclude with a set of recommendations based on our findings, which borrow from the ideas underlying the defense-in-depth safety principle to address this disquieting problem.

A Preliminary Investigation of Maintenance Contributions to Commercial Air Transport Accidents

“…Studies for analyzing maintenance related safety occurrences were carried out by Rashid et al [16] and Saleh et al [17]. The human factor analysis of both studies revealed that the most contributing factor towards maintenance incidents are associated with improper procedures being followed for inspections and installation of components, along with casual factors that are deeply rooted within the organizational and managerial levels.…”

“…Data was acquired from incidents reports obtained from the Australia Transport Safety Bureau, TSB of Canada, CAA of New Zealand, the UK's AAIB, and the USA's NTSB. Saleh, Tikayat Ray, Zhang, and Churchwell [17], presented risk factor-based research findings focused on maintenance and inspection of helicopter accidents tracing the time for when the error was committed to the actual time when the accident took place. The study showed that about 31% of maintenance related accidents occurred within the first 10 flight hours.…”

Statistical learning for turboshaft helicopter accidents using logistic regression

“…We only include in our analysis adverse events formally classified as accidents. The NTSB defines accident as an occurrence: (1) associated with the operation of an aircraft that takes place between the time any person boards the aircraft with the intention of flight and all such persons have disembarked; (2) in which any person suffers death or serious injury; (3) in which the aircraft receives substantial damage. Incidents, minor adverse events that affect or could affect the safety of operations and which result in light or no damage, are not considered in this analysis.…”

“…For context, the fatal accident rate of civilian helicopters in the U.S. has shown little or no progress over the last decade, and it is about 17 times higher than fatal accident rates of passenger cars. Over 120 helicopter accidents occur every year, with several hundred injuries and fatalities, and a few hundred million dollars in yearly losses (details in Churchwell et al [1], and Saleh et al [2]). These issues are cursorily noted to motivate the need for more research into helicopter accidents and for more vigorous safety intervention efforts by the regulators and other stakeholders in this industry.…”

“…Such findings, however, have to be interpreted cautiously because the lack of exposure data in these studies (the absence of denominator for calculating accident rates, such as total number of medical helicopters in operation or their total flight hours). A more extensive literature review can be found in the related articles by the authors [1,2].…”