Landing gears and their tires represent parts that have no back-up and are flight critical. Maintainability T housands of man hours are expended in maintaining a fleet of airplanes. The airplane s structure, all of the mechanical parts, and many of the electrical parts are maintained on a scheduled basis. This is called scheduled maintenance or routine maintenance. When parts fail and must be replaced on an as-required basis, this is called corrective maintenance.
Much effort is expended during an airplane s design to simplify maintenance.
Pp Probability that the required number and skills of personnel are available. Figure 1 illustrates a logic model for simulating the considerations for Operational Availability. Figure 2 shows a plot of frequency distribution for maintenance times, assuming that the times are log-normally distributed. This might correspond to the historical data for 100 remove and replace tasks for a single part or for a random 100 tasks for the total airplane. This probability can be read directly if the maintenance data are plotted on log-probability paper, Figure 3.