Ground time
Accounting for planned ground time when forecasting due dates allows Fleet Planner to calculate optimal schedule dates for all maintenance tasks, minimizing ground time for each aircraft.
Fleet Planner forecasts the due date for maintenance tasks based on the forecast model (average daily hours and average daily cycles) and the latest aircraft usage (date, current hours, and current cycles) for each aircraft. The forecast takes into account ground time for each aircraft; in other words, hours and cycles do not accumulate on days that an aircraft is undergoing maintenance, and therefore not flying. Note that ground time does not affect the due dates of days-based intervals.
Ideally, the due dates calculated when forecasting a plan are the same as those calculated when a new plan is created or an existing plan is rescheduled; however, there are scenarios where there can be differences:
Scenario 1: Double-booked visits
An aircraft scheduled for two visits at the same time is not a valid scenario and should be fixed; however, Fleet Planner does allow this scenario to exist in the plan. The scheduling engine will create a scenario when a visit is placed on OVERFLOW. You may choose to create this scenario when manually moving a visit.
The scheduling engine cannot reliably calculate ground time for an aircraft that is scheduled for two visits at the same time. You must manually resolve the double-booking, and forecast.
Scenario 2: Visits in the past do not yet have a last done record
The scheduling engine might not correctly calculate ground time for visits in the past that do not have a last done record, when there is a more recent aircraft usage.
If a task is completed, enter the last done record. If the task is not complete, manually schedule it for a later date.
If you run a full reforecast, you will receive a warning for each task in a visit occurring in the past that is missing a last done record. Retirement visits occurring in the past will not receive this warning.
Scenario 3: Visits scheduled between the aircraft in-service date and manufacture date
A task scheduled from the manufacture date might not have the correct due date when the manufacture date is set years in the past but the in-service date is in the future.
You must ensure that you have entered the most recent aircraft usage record after the task is completed. It is also recommended to enter a usage record for the planned in-service date, with estimated hours and cycles.
Scenario 4: Missing aircraft usage record for the effective date
The scheduling engine might not correctly calculate the ground time when an aircraft has an effective date set in the past, and there is no aircraft usage record at the effective date. Note that when you create a plan you will see a warning indicating a missing aircraft usage record.
You must ensure that you have entered the aircraft usage record for the effective date.
Scenario 5: Missing last done 'usage when due' information for completed fixed interval scheduling (FIS) tasks.
For FIS tasks, the forecasting engine cannot reliably calculate the due date for a future instance if the last done 'due date', 'hours when due', and 'usage when due' information' is not provided.
You must ensure you have entered the last done record, for a FIS task set in the past, and include the due date, hours when due, and cycles when due.