2.2.4. Human Factors

The goal of system safety assessments is to enhance a system's reliability, performance and safety by considering the persons (e.g., flight crew, ground crew and engineers) that will interact with the system. Reducing the e ffects of possible human errors must be a proactive and systematic activity considered during the design phase of a system [15]. Therefore, every system analysis must encompass human factors, particularly during the MMEL development and justification process. For instance, the application of sound ergonomic principles in the design of cockpit instrumentation, displays and controls can alert flight crews of any technical failures and provide timely and effective information (e.g., appropriately sized and readable figures) [15].

Consequently, as part of justifying the inclusion of an item in the MMEL, human factor analysis is conducted to anticipate the operation of cockpit systems/computers in varying operational conditions. However, it must be noted that the managemen<sup>t</sup> of human factors is equally important throughout the lifetime of the aircraft during which MEL applies. Hence, it is imperative to understand the impact of an inoperative MEL item on crew performance when developing the lists [3]. For instance, Job Task Analysis [25] is a technique that can be conducted before carrying out any MEL-related task to identify the required resources (e.g., knowledge, certifications, and experience) for the successful execution and completion of the task.

Furthermore, worksheets and logbooks should be used to communicate any component failure during post-flight or pre-flight inspections. Logbook entries are the starting point for assessing defects of components included in a MEL [8] and help the ground crew understand the causes of failures. This practice facilitates communication between pilots and engineers and ensures that they are aware of MEL tasks that have been completed or are pending. Moreover, the consistent use of logbooks encourages teamwork and improves coordination, especially between work shifts.
