Specifying schedules for dependent work units

This page enables you to specify scheduled for dependent work units in a maintenance program. Tell me more

Select the “Edit Dependent Schedule Information” link under the "Edit Dependent Work Units" page or “Edit Schedule Information” page.

The “Edit Dependent Schedule Information” page appears.

Note: This page can be invoked only if dependent work units are defined for the work unit selected in the previous page.

The system displays the following fields in the “Maintenance Program Information” group box:

Maintenance Program #	The maintenance program for which the schedule information must be specified.
Revision #	The revision number of the maintenance program.
Program Desc	The description of the maintenance program.
Status	The status of the maintenance program, which can be “Fresh”, ”Active”, “Inactive” or “Return”.

The system displays the following fields in the “Primary Work Unit Details” group box:

Work Unit #	The work unit for which schedules are defined for the dependent work units.
Work Unit Type	The type of the work unit, which can be “Task”, “Standard Procedure”, “Aircraft Work Package” or “Component Work Package”.
Execution Type	The execution type of the work unit, which can be “Minor” or “Major”.

Enter the following field in the “Dependent Work Unit Details” group box:

Work Unit #

Use the drop-down list box to select the dependent work unit for which the schedules must be specified. The system lists all the work units of the selected primary work unit.

Click the “Get Details” pushbutton.

The system displays the following details:

Work Unit Type

The type of the work unit, which can be “Task”, “Standard Procedure”, “Aircraft Work Package” or “Component work Package”.

Enter the following fields in the “Dependent Schedule Details” group box:

Schedule Type

Use the drop-down list box to specify the type of the schedule based on which the work unit must be carried out. The system provides the following options:

One Time – Select this option if the work unit must be carried out only once after the execution of the primary work unit.
Recurring – Select this option if the work unit must be carried out repeatedly at certain defined intervals after the execution of the primary work unit.

Ensure that the schedule type selected here is the same as the schedule type selected for the primary work unit.

Update Basis

Use the drop-down list box to select the mode by which the due dates for performing the work units must be calculated. The system provides the following options:

Schedule – If the option is selected as “Scheduled”, then NSD/NSV (Next Schedule Date/ Next Schedule Value) for executing the work units will be calculated based on a scheduled fixed interval.
Actual Completion – If the option is selected as “Actual Completion”, then NSD/ NSV will be calculated by adding the Repeat Fixed / Floating Interval value to the date or value at which the work unit is actually executed.
Time Window – This option is applicable for the following conditions:
1. Within the Tolerance limits: If the option is selected as “Time Window”, then NSD/NSV will be calculated based on a scheduled fixed interval
2. Beyond the Tolerance limits: If the option is selected as “Time Window”, then NSD/NSV will be calculated by adding the Repeat Fixed / Floating Interval value to the date or value at which the work unit is actually executed.

Example

Assume that the scheduled date for a work unit is 11-10-2003. If tolerance value is specified as +/-2 days, the Earliest schedule date for the work unit is 09.10.2003 and Latest schedule date for the work unit is 13.10.2003 (inclusive of 9.10.2003 and 13.10.2003) and the repeat interval is set as 20 days.

If the “Update Basis” is selected as “Schedule”, and if the work unit was executed on 10.10.2003 (within the specified limits) then the next schedule date of the work unit is 31.10.2003 (The NSD for the work unit is based on a fixed interval of 20 days irrespective of when the work was executed (11.10.2003+ 20 days (Repeat Interval)).
If the “Update Basis” is selected as “Actual Completion”, and if the work unit was executed on 09.10.2003 (within the specified limits) then the next schedule date of the work unit is 29.10.2003 (ie 09.10.2003+20 days (Repeat Interval)).
If the “Update Basis” is selected as “Time Window”,
1. If the work unit was executed on 10.10.2003 (within the specified limits) then the next schedule date of the work unit is 30.10.2003. (10.10.2003+20days).
2. If the work unit was executed on 05.10.2003 (beyond the specified limits) then the next schedule date of the work unit is 25.10.2003 (05.10.2003+20days).
3. If both date based and usage based schedules are defined for the work unit then the “Sch.Exe Rule” (Values “Earliest” and “Latest”) identified for the work unit in the maintenance program will be considered.

Enter the following fields in the “Dependent Date Based Schedule Details” group box:

Time Unit	Use the drop-down list box to specify the time unit for the date-based schedule. The system provides the options ”Days”, “Months”, “Month End” and “Years”. The system displays “Days” by default.
Threshold Interval	The period from the induction date or the operational date, the due dates for the work units must be calculated (Decimal).
Repeat Floating Interval	The interval after which the execution of the work unit must be repeated, from the period when the primary unit was last executed (Numeric).
Alert Interval	The period at which an alert message must be displayed about an impending due date for performing the work unit (Decimal).
Positive Tolerance	The maximum time period subsequent to the next schedule date, within which the work unit must be performed (Decimal).
Negative Tolerance	The maximum time period ahead of the next schedule date, within which the work unit could be performed (Decimal).
Terminating Interval	The period, reaching which the work on the work unit must be terminated (Decimal).

Enter the following fields in the “Dependent Usage Based Schedule Details” multiline:

Parameter

The parameter based on which the work unit must be performed (Alphanumeric, 30).

Help facility available

The system displays the following field:

UOM	The unit of measurement defined for the parameter.

Enter the following fields:

Threshold Value

The parameter value at which the first execution of the work unit is due (Numeric).

Repeat Floating Interval

The interval after which the execution of the work unit must be repeated, from the period when it was last executed (Numeric).

Alert Interval

The parameter value at which an alert message would be displayed about an impending work due on the work unit (Numeric).

Positive Tolerance

The upper limit of the parameter value greater than the next schedule value, within which the work unit must be performed (Numeric).

Negative Tolerance

The lower limit of the parameter value lesser than the next schedule value, within which the work unit (Numeric).

Terminating Value

The parameter value, reaching which the work on the work unit must be terminated (Numeric).

Terminating Value Type

Use the drop-down list box to select the terminating value type. The system lists the options “Interval” and “Absolute”. The system displays “Interval” by default.

The system displays the following field on clicking the “Edit Schedules” pushbutton.

Parameter Description

The description of the parameter.

Click the “Edit Dependent Schedules” pushbutton.

Note: The system saves the schedule details for the dependent work units of the selected work unit in the maintenance program.

Specifying schedules for dependent work units – An overview

Work packages, procedure and tasks that constitute a maintenance program may have an independent schedule or a dependent schedule. The entities in the maintenance program having dependent schedule occur at a periodic interval depending on the occurrence of another entity. After the completion of all entities, the entire cycle is repeated again. This kind of circular reference of dependency and interval is identified as PM cycle.

Click here for more explanation on PM cycle.

Refer to the topic, “Editing schedule information for maintenance program – An overview” for more details on the type of schedules that can be defined.

PM cycle

Work units, which have a dependency relationship, are performed one after the other at specific interval periods. Every dependent work unit is assigned a cycle number. For example,

Assume that the following work units in the form of checks have a dependency relationship among them,

A is dependent on C
B is dependent on A
2A is dependent on B
C is dependent on A

When these work units are performed for the first time, cycle numbers are assigned to the work units like,

A – 1
B – 1
2A – 1
C – 1

On completion of the first cycle, the system increments the cycle number for the next cycle of the work units.

If B check is not performed in the next cycle, its cycle number remains as 1.