Maintenance - Unscheduled and Scheduled

The Unscheduled and Scheduled maintenance sub-sectors both contain the same layout of inputs. Each can be represented at either a Simplified level or a Detailed level, and each is split between aircraft and engine parts.

Maintenance - Unscheduled tab with Simplified option selected

Unscheduled Maintenance tab with Simplified option selected

In Simplified mode, the DLR and O-Level consumables and I-Level consumables costs per flying hour can be specified. Cost Growth Factor curves can be specified for DLR costs and consumables costs that allow factors on the baseline costs to be specified for each year of the program.

Maintenance - Unscheduled tab with Detailed option selected

Unscheduled Maintenance tab with Detailed option selected

In Detailed mode, the rate of actions is defined using either mean flight hours between removals or actions per 1000 flying hours. An action requires O-Level labor to remove/replace the component. The percentages of parts that are Repaired at O-Level, Repaired at I-Level and Depot Repair/Replace can be specified. The percentage for False Removal is automatically calculated so that all four percentages add to 100%. If data is specified so that the percentages add to more than 100% then the text of the inputs will turn red, and it will not be possible to run the simulation until the problem is corrected. 

Consumables costs and labor hours are specified for any repairs that are carried out at O-Level or I-Level. Repair Parts cost and Repair/Replace cost are specified for I-Level Repair and Depot respectively. A False Removal cost is specified for any False Removals.

Maintenance - Cost Growth Factor using annual table

Cost Growth Factor graph defined using a table of annual values

Aging curves for action rates and DLR and consumables costs can be applied to Unscheduled and Scheduled maintenance, for aircraft and engine parts separately. These can be specified as table values or as quadratic functions.

When table values are used for aging, the aging actions factor is expressed as a percentage of aircraft life, with values at every 5% of life. The DLR and consumables cost growth factors are expressed over time for the program with a value representing each year, over a 70 year period. All factor values can be entered either in the table on the left hand side of the screen or by holding down the Shift button and moving the cursor across the screen in order to draw the aging curve.

When quadratic equations are used for aging, the action rates factor uses aircraft age as the X variable. The DLR and consumables growth factors use years since the first year that an aircraft can enter service is the X variable. The quadratic equation allows A, B and C parameters to be specified for an equation of the form: Ax^2 + Bx + C. There is also the option to specify the factor as a linear equation, where A is automatically set as 0, C is specified as 1 and B is editable. When the equation parameters are set, clicking on the Display button will show the function on the graph.

Maintenance - Cost Growth Factor using equation

Cost Growth Factor graph defined using a quadratic equation