Program Profile - Aircraft Introduction and Allocations

The Program Profile has had a major overhaul in the way that data is specified for aircraft introductions, allocation to environments and flying hours. There are also some new tools to speed up the process of configuring allocation to environments.

Aircraft introduction and retirement

The Start Year for the Program will set the initial year for the simulation run, as well as setting the start year for any time-based cost profile tables. This should be entered as fiscal year so that it aligns with the inflation tables that are used for changing the cost base year and calculating Then Year $ results.

Note that the first year an aircraft can be introduced is always 12-months after the Start Year for the Program. This allows for 12-months of costs to be specified before the introduction of an aircraft can be entered in annual profile tables in a number of the input sectors.

Program Profile input form - aircraft introduction

Program Profile form showing aircraft introduction tab

The number of aircraft introduced can be specified annually over a 30-year period, with the option to introduce all aircraft at the start of each year, or spread introductions evenly throughout the year. The number of aircraft in service throughout the life of the program is shown in the graph. The number of aircraft in service at the start of any particular year can be seen by moving the mouse cursor over a line marker.

The Service End Year input can be enabled by selecting the check box to its left. This input allows a year to be specified for the final service year of the program. At the end of the specified year all remaining aircraft will be retired, even if they have not reached their life expectancy or flying hours limits.

Allocating aircraft to Environments

The Environments sub-sector allows an annual requirements profile to be specified over a 70-year period for the Active, Reserve, FRS and Other environments. The absolute number of aircraft required is entered for each individual year. The number of excess aircraft is calculated automatically as the total supply of aircraft minus the number of aircraft allocated for each year.

Program Profile input form - Environments

Program Profile form showing Environments tab

Note that the calculation of aircraft Supply in the table only takes into account age-related retirement and not attrition, flying hours retirement or early retirement due to emergency repair. The supply figure shown is the number of aircraft scheduled to be in the fleet at the end of the year. Extra information on supply is shown in the Long Description panel at the bottom of the screen when the mouse cursor is hovered over a particular row in the Supply column. This gives information on the number and pattern of introductions and scheduled age-related retirements in the year.

The allocation that is specified in the tab should be the number of aircraft at the end of the specified year. In the simulation, during aircraft ramp-up periods (aircraft coming into service) and ramp-down periods (aircraft retiring) any changes in demand allocations may be profiled over the year to match patterns of introduction and retirement. During ramp-up, any demand increases that can be met by existing aircraft will be applied immediately; the remainder will be ramped up over the year as aircraft are introduced. During ramp-down, any demand decreases will occur as aircraft are scheduled to retire due to age. If total demand decreases are greater than the number of scheduled aircraft retirements, then the difference will be applied as a demand reduction at the start of the year.

Program Profile input form - Allocation to Environments table

Close up of allocation to Environments table

It is possible to have a negative value for excess aircraft if more aircraft are allocated than are available. Over allocation can be prevented using the "Prevent Over Allocation of Aircraft" check box. This will highlight any years with over allocation and prevent the simulation from running until the over allocation is resolved. Note that this only takes into account introductions and age-related retirements. Other forms of disposal (such as attrition or flying hours life) or downtime due to PDMs, emergency repairs or modernizations could still cause a shortfall of aircraft during a simulation run.

The number of aircraft per squadron can be specified for each environment. The number of squadrons at peak is calculated for each environment based on the requirements profile and the number of aircraft per squadron. If a zero value is specified when aircraft are allocated to the environment then the text will be displayed in red, and the simulation cannot be run until this is changed.

Aircraft Allocation tools

The allocation tools are provided as a convenient way of specifying allocation of aircraft to environments. They can be used in conjunction with, or instead of, the Allocation to Environments table.

The Aircraft Allocation Tool determines the number of aircraft allocated to each environment for each year based on the allocation of aircraft to environments at peak supply. The tool then calculates the percentage split between environments and uses this to allocate aircraft during the ramp-up and ramp-down periods.

Program Profile input form - Aircraft Allocation Tool

Aircraft Allocation Tool with values set for aircraft at peak

When allocating aircraft, the tool will ensure that only whole numbers of aircraft are allocated. Appropriate rounding of data will be applied to ensure that the correct numbers of aircraft are allocated. Where standard rounding approaches would result in too many or too few aircraft being allocated then the size of the fractional aircraft, followed by priority of environments, will be used to determine which environment(s) will get the extra aircraft.

For example, if there are 50 aircraft with a 25% split between the 4 environments (with 0 for Excess Inventory) then this would result in 12.5 aircraft per environment. Applying standard rounding would mean allocating 13 aircraft per environment but this would mean a total allocation of 52 aircraft. In this case, with all the decimal parts being equal, the two highest priority environments would be allocated 13 aircraft each, and the two lowest priority environments would be allocated 12 aircraft each.

The Graphical Allocation Tool represents the allocation of aircraft to environments as a stacked bar chart for each year. In the tool, two graphs are shown. The top graph allows users to adjust the number of aircraft in each environment by clicking the + or – buttons above or below the bars. As the top graph is adjusted, changes will be reflected in the bottom chart. The user can change the year of adjustment in one of two ways: using the left/right scroll buttons next to the top chart of by clicking on the corresponding bar in the bottom chart. The selected year is identified above the yellow arrow.

Program Profile input form - Graphical Allocation Tool

Graphical allocation tool showing annual allocation graph and allocation buttons for the selected year