![]() ![]() The acronym represents software, usually documents governing operations hardware, the physical resources available liveware, consisting of the human operators composing the crew and environment, the external context in which the system operates. In Europe, Elwyn Edwards (1972) drew on the record of accident investigation and developed his SHEL model of human factors in system design and operations. A number of specific problem areas were identified, including workload management and task delegation, situation awareness, leadership, use of available resources including other crewmembers, manuals, air traffic control, interpersonal communications (including unwillingness of junior crewmembers to speak up in critical situations), and the process of building and maintaining an effective team relationship on the flightdeck. The conclusion drawn from these investigations was that “pilot error” in documented accidents and incidents was more likely to reflect failures in team communication and coordination than deficiencies in “stick-and-rudder” proficiency. ![]() At the same time, George Cooper and Maurice White analyzed the causes of jet transport accidents occurring between 19 ( Cooper, White, & Lauber, 1980), while Miles Murphy performed a similar analysis of incidents reported to NASA’s confidential Aviation Safety Reporting System ( Murphy, 1980). Charles Billings, John Lauber, and George Cooper developed a structured interview protocol and used it to gather firsthand information from airline pilots regarding human factors in crew operations and “pilot error” accidents. In the United States, a team of investigators at NASA–Ames Research Center began to explore broader human factors issues in flight operations. This type of investigation did not seem to address many of the factors identified as causal in jet transport accidents, and researchers began to broaden the scope of their inquiry. However, research efforts tended to focus on traditional human factors issues surrounding the interface of the individual operator with equipment. By the time these accidents occurred, the formal study of human error in aviation had a long tradition (e.g., Fitts & Jones, 1947 Davis, 1948). The theme in each of these cases is human error resulting from failures in interpersonal communications. In the same accident the failure of a flight attendant to communicate credible concerns about the need for de-icing expressed by pilot passengers. ▪Ī crew crashing on take-off because of icing on the wings after having inquired about de-icing facilities. ▪Ī breakdown in communication between a captain, co-pilot, and Air Traffic Control regarding fuel state and a crash following complete fuel exhaustion. ▪Ī crew distracted by nonoperational communication failing to complete checklists and crashing on take-off because the flaps were not extended. ▪Ī crew failing to review instrument landing charts and their navigational position with respect to the airport and further disregarding repeated Ground Proximity Warning System alerts before crashing into a mountain below the minimum descent altitude. ![]() ▪Ī co-pilot, concerned that take-off thrust was not properly set during a departure in a snowstorm, failing to get the attention of the captain with the aircraft stalling and crashing into the Potomac River. ▪Ī crew, distracted by the failure of a landing gear indicator light, failing to notice that the automatic pilot was disengaged and allowing the aircraft to descent into a swamp. The formal record of investigations into aircraft accidents, such as those conducted by the NTSB, provides chilling documentation of instances where crew coordination has failed at critical moments. Market penetration (number of Maintenance, Repair, and Overhaul (MRO) facilities supporting the gear) Operational environment and maintenance practices According to Ackert (2012), the primary cost drivers are as follows: The cost of either the loan or an exchange fee is added to the maintenance cost. Under an exchange agreement, upon completion of the overhaul the landing gear becomes part of the exchange pool for future customers of the maintenance facility. Thus, most overhaul facilities loan out replacement landing gear or offer to exchange the current set. ![]() This is a particularly lengthy maintenance event. Depending on the aircraft model, overhauls typically occur every 8 to 12 years, but the exact interval is based on the need to inspect and/or treat corrosion. Each gear assembly includes the strut assembly (inner and outer cylinders), drag braces/side struts, and hydraulic actuators to extend and retract the gears. An aircraft’s landing gear comprises nose gear and two to four main gear assemblies. ![]()
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