System Safety and System Safety Application

Exploring and Evaluating Airline System Safety:
Aircraft Maintenance-related Indicators
Abstract 
This paper explores how system safety concepts are being applied in aircraft or airline accident. The main objective of this paper is to demonstrate the relevance and usefulness of precursors in safety analysis, and not to develop exact and detailed predictive models. The paper discussed various causal factors of airline accidents and directed our attention to those related to aircraft maintenance. Firstly, the paper discussed a theoretical framework for modeling the possible escalation of small equipment problems into more severe incidents and, further on, into accidents. The Service Difficulty Reports (SDRs), with their different severity ratings, are analogous to the incidents described in the risk models presented in this paper. However, only the framework for such a model was discussed without attempting to develop an operational model. Finally, the paper concluded that our knowledge of and experience with small maintenance problems could be used to predict the occurrence of more serious problems in the future.
Introduction
Accident and fatality rates are the most widely accepted measures of overall airline system safety. These rates represent the risk associated with air travel in terms of the probability of an accident or fatality. However, accidents and fatalities are not necessarily the best indicators of the safety of airline operations. Equipment related factors are being considered as the leading indicators of accidents or incidents. Hence, the airline or aircraft may be positioned with a greater risk of accidents if it experiences a high incidence of equipment related difficulties during service.
A theoretical framework for relating equipment (maintenance) related problems to accidents are presented in this research that would seek to identify factors that possibly influence the safety posture of airlines and aircraft. Risk models are presented to demonstrate the possible linkages and to demonstrate the relevance and usefulness of precursors in safety analysis, and not to develop exact and detailed predictive models.
Airline System Safety and Its Evaluation
In recent years there has been great concern about the safety of the commercial aviation system. It has been observed that there are almost always insufficient maintenance personnel and inventory at most "spoke" airports and, therefore, necessary maintenance work must be deferred until the aircraft returns to one of the carrier hubs or maintenance bases. Another reason for the increased number of items on the deferred maintenance list is the inability of the airlines, once again due to the hub and spoke scheduling systems, to devote as much time during quick turnaround to fix items. Thus, deferral of maintenance is encouraged by the hub and spoke system. Pilots have voiced their concern over the pressures of deregulation leading to the Minimum Equipment List (MEL) abuse resulting from such extended deferred maintenance practices (Donoghue, 1987). The absolute minimum equipment required to be in working order is spelled out in the MEL for each aircraft.
Carrying a large number of deferred maintenance may not be a violation as such, but i...