Glossary

Ad hoc Task

A task that is created without reference to the operational data.

Ad hoc Visit
A visit that is created by the user rather than the scheduling engine. Ad hoc visits are intended to be a solution for short-term planning needs.
Aircraft
An individual aircraft, specified by a unique tail number.
Blackout day

A day on a specific track during which no maintenance is completed and an aircraft may NOT sit on the track.

Blackout days appear in black on the Gantt chart and the scheduling engine will enforce them when scheduling. However, users can override them.

Calendar Days
The number of days the aircraft will be on the track. i.e. The number of Adjusted Work Days, plus the number of non-working days spanned by the visit.
Chained Task

A task that has a necessary order of completion with one or more other tasks.

Check
A high level description of work defined by the OEM's maintenance program or the engineering department.
Check Hierarchy Rules
Check hierarchy defines how smaller checks, (also known as lighter checks or inclusive task definitions) are included when larger checks, (also known as heavier checks or primary task definitions) are performed. Put another way, when a heavy check is performed it already includes all the work normally performed as part of a lighter check. Therefore, you automatically get credit for the lighter check.
Check Yield

The average of the yields of the Principle Task in all visits in the plan. (Note that ad hoc tasks are not included in this average.)

Driving Task
The task in the visit with the earliest due date.
Driving Task Due Date
The due date of the driving task.
Driving Task Spec
The task specification (days/hours/cycles) that will come due first.
Driving Task Spec Remaining
The number of days, hours, or cycles of the driving spec for the driving task that will be remaining on the visit start date. (Hours and cycles values are forecasts.)
Effective Due Date
Calculating due date using aircraft usage calculated from effective date. Effective due date is calculated as follows:

Usage_Date + [(AC_Cycles_On_Effective_Date + Task_Repeat_Cycles) - AC_Latest_Cycles] / Aircraft_Daily_Forecast_Cycles.

Note that the same calculation can be performed using flying hours. 

Extraction Rule
An allocation of aircraft that are allowed out of service over a given period.
FIS
Fixed Interval Scheduling. FIS allows up to 10% of task yield to be "recovered" when scheduling the next instance of a particular task. i.e. If an instance of a task is completed at 90% yield or less, the next instance can be completed at 110% yield.
Forecasted From
The date used to calculate the due date of this instance of the maintenance task, which is:
  • If applicable, the Completion Date in the Last Done operational data
  • For a repeating task or chained tasks, the visit end date from the previous task
  • For the first repeating or chained task or a one-time task, derived from the Calculation From value from the Task Definition operational data. i.e. one of:
    • the task's Effective Date
    • the aircraft's Manufacture Date
    • the aircraft's In Service Date
HC
Heavy check
KPI
Key Performance Indicator
LC
Light check
Non-working day (NWD)

A day on a specific track during which no maintenance is completed. An aircraft may sit on the track on a non-working day, but it cannot arrive or be released. Non-working days are sometimes called "plan across days." A holiday, such as Labor Day, is a typical example of a NWD.

Non-working days appear in gray on the Gantt chart and the scheduling engine accounts for them when scheduling. However, users can override them.

One-time Task

A task that occurs only once.

Plan Cost

The projected cost of the plan, calculated based on Daily Costs of the tracks.

Nonworking and blackout days are not included in this calculation.

Important:

If "Operational data has changed" appears in the the Plan Cost row, it means that location data for one or more tracks in the plan could not be found. This means that one or more of the yearly total costs is incorrect.

Plan Yield

The average yield for all tasks in the plan.

Principle Task
The task in the visit with the longest span, not including ad hoc tasks.
Priority Stream
A set of automerge rules that apply to the same source.
Repeating Task

A task that is repeated on a interval defined by one or more task specifications.

Retirement Visit
Fleet Planner creates a retirement visit when a planner adds a planned retirement date for the aircraft. Fleet Planner schedules the retirement visit to the retirement track, and the visit contains tasks due after the aircraft's retirement date.
Schedule Change Date
A significant date which planners should be aware of while scheduling maintenance.
Scheduling Start Date
The first date for which visits will be scheduled in a plan.
Scope
All the tasks except for the principle (longest span) task that are included in the visit.
Slack
The number of days between the Visit Start and Due Date of the first due task.
  • If slack is 1: The visit starts on the due date of the first due task, which will become overdue at midnight.

  • If slack is 0: The visit starts a day after the due date of the first due task. The aircraft should not be flown on this day.

Span
Total time aircraft is on ground, including non-working days.
Subfleet
A sub-group of aircraft in a fleet.
Task

A specific maintenance activity that must be performed on an industry-defined schedule or as a result of an aircraft fault. Tasks, sometimes called checks, must be assigned to a visit to be scheduled.

Terminating Task

A terminating task ends a repeating task. Suppose you have two tasks on the same aircraft: Task A and Task B. Task A is a repeating task that repeats indefinitely. When Task B is scheduled, it "terminates" Task A. Therefore, Task B is the terminating task.

Travel Days
The number of days the aircraft is in transit to or from the maintenance location.
TSC
Total Ship Cycles. Current number of cycles on the aircraft, taken from aircraft usage operational data.
TST
Total Ship Time. Current numbers of hours on the aircraft, taken from aircraft usage operational data.
Utilization

The average usage percentage of all tracks in the plan.

Nonworking days count as unused work periods, but blackout days do not.

Important:

If "No location data" appears in the Utilization row, it means that location data for one or more tracks in the plan could not be found. Utilization percentages will not be calculated.

Visit

A continuous period when an aircraft is parked at a specific track and is available for maintenance. A visit is assigned tasks that define the work that will be done and constrain the visit's span and start date.

Standard Work Days
The number of work days required for a visit, not adjusted by Track Proficiency.
Yield
Yield is calculated as follows: (Visit Start Date - Forecasted From Date) / (Due Date - Forecasted From Date).