4.9 Maintenance Tasks

Maintenance tasks address failures in a maintainable item. This can be done by addressing hidden failures, changing the item's design to reduce failures and increase reliability, treating existing failures after they have occurred, or preventing a failure before it occurs by maintaining an item or constantly monitoring it based on its condition. These tasks estimate maintenance/inspection interval, downtime, cost, and technical feasibility.

There are six maintenance task types (MSG-3 / RCM II naming shown together): Inspection / Functional Check (On-Condition), Operational / Visual Check (Failure Finding), Lubrication / Servicing, Scheduled Restoration, Scheduled Discard, and Run-To-Failure.

Table 4: Sections present in each maintenance task type

Common sections are covered fully under Inspection / Functional Check (4.9.1) below, and referenced by name for the remaining task types since they share the same section design. Per the source table, the sections that appear (subject to task type) are: Failure Mode Metrics, Worksheet Summary, Feasibility Metrics, Symptoms of Failure / Protected Functions, Multiple Failure P(f), Failure-Finding Interval, Cost Metrics, P-to-F Interval, Maintenance Tasks & Personnel, Maintenance Equipment & Consumables, Inspection Tasks & Personnel, Inspection Equipment & Consumables, Summary of activities, and Technical Feasibility Assessment. Not all sections apply to all task types — see each task type's subsection below for which of the common sections apply, and the task-type-specific sections.

Note: Tasks shown in the source guide are illustrated using generic example information.

The process in the task tabs involves first entering failure metrics, followed by feasibility metrics (if present), then cost metrics, action details, and finally assessing task feasibility.

4.9.1 Inspection / Functional Check

Inspection / Functional check is a type of preventative maintenance that aims to track degradation and various failures of a maintainable item by monitoring symptoms to predict and fix failures immediately.

4.9.1.1 Failure Mode Metrics

This section contains Item MTTF, failure mode baseline P(f), task effectiveness factor, failure mode revised P(f), and allows for capturing narrative/justification for the Revised P(f).

The effectiveness factor is a fraction or factor by which the failure will be mitigated through the incorporation of the maintenance task. A factor of 1.0 signifies a "perfect" corrective action, while a factor of 0 denotes a completely ineffective corrective action.

Table 5: Properties in Failure Mode Metrics section

Parameter	Formula	Comment
Item MTTF	—	Referenced from FMEA source and not editable in RCM. Update the analysis to modify MTTF.
Baseline P(f) — Exponential distribution	P(f) = 1 − e^(−λ_fm × t), where failure mode failure rate λ_fm = NFMR × Item failure rate	Referenced from FMEA source and not editable in RCM.
Baseline P(f) — Weibull distribution	Assumption: failure mode follows the item's failure distribution and shape parameter (β). Failure mode characteristic life (η_fm) is calculated using equations derived from the item's reliability and failure mode FMRs. Then P(f) = 1 − e^(−(t/η_fm)^β)	Referenced from FMEA source and not editable in RCM.
Effectiveness Factor (ε)	ε = 1 − (Baseline P(f) / Revised P(f))	Allows users to enter values.
Revised P(f)	Revised P(f) = Baseline P(f) × (1 − Effectiveness factor)	Allows users to enter values.

(Note: the source PDF's mathematical notation for the exponential/Weibull formulas lost some symbol glyphs (e.g. lambda, eta, beta, exponent formatting) during text extraction. The formulas above have been reconstructed based on standard exponential/Weibull reliability formulas and the surrounding text, which explicitly states: "failure mode failure rate = NFMR * Item failure rate" and the Weibull assumption text. Treat exact notation as approximate; the relationship types (exponential CDF, Weibull CDF) are accurate per the source.)

To complete this section (Figure 65):

1. Review the Item MTTF and Baseline P(f)
2. Enter a decimal in the Effectiveness Factor field
3. Review the Revised P(f) — overwrite Revised P(f) if required
4. Enter a narrative for Revised P(f)

Note:

• If Item MTTF, Item duration of operation, or Failure Mode Ratio is modified in the FMEA source, then update the analysis (section 4.3.3) to reflect the changes.
• Effectiveness factor and Revised P(f) are calculated as mentioned in Table 5, however the tool allows user override.

4.9.1.2 Worksheet Summary

This section displays the system downtime, proposed interval, task cost, and technical feasibility for the maintenance task. System downtime, proposed interval, and task cost are calculated as illustrated in Table 6. All are read-only fields.

Table 6: Worksheet summary calculation formulas

For Inspection/Functional Check and Operational/Visual Check:

• System Downtime = Maintenance Downtime × No. of occurrences of Maintenance + Inspection Downtime × No. of occurrences of Inspection
• Proposed Interval = Inspection Interval
• Task Cost = (Maintenance Cost + Cost of Failure) × No. of occurrences of Maintenance + (Inspection Cost + Cost of Detection) × No. of occurrences of Inspection

For Lubrication/Servicing, Restoration (Scheduled Restoration), Discard (Scheduled Discard), and Run-To-Failure:

• System Downtime = Maintenance Downtime × No. of occurrences of Maintenance
• Proposed Interval = Maintenance Interval
• Task Cost = (Maintenance Cost + Cost of Failure) × No. of occurrences of Maintenance

(Figure 66: Worksheet Summary section in Maintenance Task)

4.9.1.3 Feasibility Metrics

This section includes the ability to capture P-to-F interval (as a fraction of Item MTTF) and its narrative, whether a symptom should be monitored for the failure mode, and the monitoring technique. Monitoring interval is the same as Inspection Interval (see 4.9.1.6).

To complete this section:

1. Enter P-to-F Factor
2. Review P-to-F Interval and modify if required
3. Enter a narrative for P-to-F Interval

(Figure 67: Feasibility Metrics for Inspection/Functional Check)

4.9.1.4 Symptoms

The Symptoms Editor (Figure 68) can be used to add symptoms associated with the failure mode and to define the corresponding monitoring technique.

To add a symptom:

1. Click the Add icon
2. Select / define a symptom
3. Define the monitoring technique for the symptom

Note (Model-Based FMEA workflow):

• Symptoms defined in the Failure diagram linked to the Functional failure item are displayed automatically (via an import/link icon)
• If a symptom is created in MBRCM, it can be linked/exported to the failure diagram (via an export/link icon)

4.9.1.5 Cost Metrics

This section includes the ability to capture additional costs incurred due to the failure mode, in addition to the maintenance cost, its detection, and narratives/justifications.

To complete this section:

1. Enter a numerical value in the Cost of Failure field
2. Enter a narrative describing the cost of failure
3. Enter a numerical value in the Cost of Detection field
4. Enter a narrative describing the detection cost

(Figure 69: Cost Metrics for Inspection/Functional Check)

4.9.1.6 Maintenance Action Details

This section allows for the planning and costing of a maintenance action. It consists of maintenance action details, a table for maintenance and inspection tasks and personnel, and a separate table for spares/equipment/consumables.

Note: To import maintenance data from an Excel file, first export the tasks to the Maintenance Actions Editor (see 4.8.3 Failure Effect Category Task), and then proceed with the data import into the RCM analysis. For detailed instructions on creating a mapping to import maintenance data from Excel, refer to the Import Configuration User Guide and the Maintenance Import document.

To complete this section, first complete maintenance action detail fields (Figure 70):

1. Enter a maintenance Action ID in the provided field
2. Enter a maintenance Action Name in the provided field
3. Enter a maintenance Description in the provided field
4. Select a Location of Maintenance from the drop-down menu, or click the Add icon to create new maintenance locations (see 4.14.3)
5. Enter a numerical value for Maintenance interval and select a time interval
6. If monitoring is done periodically, enter a numerical value for the Inspection interval and select a time interval. Otherwise, select the checkbox for Continuous Monitoring.
   • Note: By default, Inspection interval is set to Model-Based and is calculated as a factor of P-to-F interval. The interval factor can be set by navigating to Preferences > Application Preferences > RCM. To manually enter a value, toggle to Direct Entry by clicking on the drop-down menu.

Note: The entered maintenance action name is displayed in the task (horizontal) tab and FEC Task table (4.8.3).

To complete the maintenance/inspection tasks and personnel table (Figure 71, Figure 72):

• Click the Add New Maintenance Task icon to add a new maintenance task
• To add new personnel to a selected maintenance task: click Add (without skill code), or click Add with Skill Code to add personnel with a defined rate (refer to 4.14.4 for details on Maintenance Personnel)
• Click the Move Down icon to move maintenance tasks or personnel down by one row
• Click the Move Up icon to move maintenance tasks or personnel up by one row
• Click the Delete icon to delete a selected maintenance task or personnel
• Select a cell in the ID column to edit the maintenance task ID or personnel ID
• Select the arrow to expand/minimize maintenance personnel for selected maintenance tasks
• Select a cell in the Description column to edit the maintenance task name
• Select the check-box in the Downtime column if the action requires downtime
• Select a cell in the Duration column to enter a numerical value for the action duration
• Select a cell in the Rate column to edit the cost per person per hour for maintenance personnel
• Select a cell in the # Personnel column to edit the number of maintenance personnel required
• Select the Inspection tab, which contains a similar layout to the Maintenance tasks and personnel tab

Note: Inspection tabs are applicable for Inspection / Functional Check and Operational / Visual Check maintenance tasks only (Table 4).

To complete the Spare, Equipment and Consumables table for maintenance/inspection (Figure 73, Figure 74):

• Click the Add New Maintenance Item icon to add a new maintenance item
• Click the Move Down / Move Up icons to reorder
• Click the Delete icon to delete a selected maintenance item
• Select a cell in the ID column to edit the maintenance item ID
• Select a cell in the Item Name column to edit the maintenance item name
• Select a cell in the Cost column to edit the maintenance item cost
• Select a cell in the Quantity column to edit the maintenance item quantity
• Review the Total column, which displays total cost based on individual cost and quantity

Note: Inspection tabs are applicable for Inspection / Functional Check and Operational / Visual Check maintenance tasks only. Also note: the "Linked Failures" tab is in development (not yet functional at time of writing).

To view the key metrics for the maintainable item (Operational availability, MTBM, MPMT, MMT, MTTR, MALDT) and maintenance/inspection duration, downtime, and cost due to the maintenance action:

• Select the Summary tab (Figure 75)

Note: Item-level metrics are determined by evaluating all tasks assigned to all the failure modes. If task worksheets are not completed, then some metrics may appear as N/A.

Table 7: Formulas for maintenance/inspection duration, downtime, and cost calculation

Parameter	Maintenance	Inspection
Duration	= sum of duration in Maintenance Tasks and Personnel tab	= sum of duration in Inspection Tasks and Personnel tab
Downtime	= sum of Downtime duration in Maintenance Tasks and Personnel tab	= sum of Downtime duration in Inspection Tasks and Personnel tab
Cost	= Rate × Duration × #Personnel in Maintenance Tasks and Personnel tab	= Rate × Duration × #Personnel in Inspection Tasks and Personnel tab

4.9.1.7 Technical Feasibility Assessment

This section includes a series of questions from the chosen RCM configuration designed to evaluate the applicability and effectiveness of the task in reducing the likelihood of failure, and the ability to capture narrative/justifications. The outcome of this assessment appears in the Worksheet Summary section (4.9.1.2) and Failure Effect Category table (4.8.3).

Note: A task is considered applicable and effective if it meets all the criteria.

Table 8: Technical Feasibility Assessment criteria for MSG-3

Task	Applicability	Effectiveness
Inspection/Functional Check	Is reduced resistance to failure detectable, and does there exist a reasonably consistent interval between a deterioration condition and function failure?	Safety: Does the task reduce the risk of failure to assure safe operation? Operational: Does the task reduce the risk of failure to an acceptable level? Economic: Is the task cost-effective, i.e. the cost of the task must be less than the cost of the failure prevented?
Operational/Visual Check	Is identification of failure possible?	Safety: Does the task ensure adequate availability of the hidden function to reduce the risk of a multiple failure? Economic: Does the task ensure adequate availability of the hidden function in order to avoid economic effects of multiple failures and is it cost-effective?
Lubrication/Servicing	Does the replenishment of the consumable reduce the rate of functional deterioration?	Safety: Does the task reduce the risk of failure? Operational: Does the task reduce the risk of failure to an acceptable level?
Restoration	Does the item show functional degradation characteristics at an identifiable age and do a large proportion of units survive to that age? Is it possible to restore the item to a specific standard of failure resistance?	Economic: Is the task cost-effective? Safety: Does the task reduce the risk of failure to assure safe operation? Operational: Does the task reduce the risk of failure to an acceptable level?
Discard	Does the item show functional degradation characteristics at an identifiable age and do a large proportion of units survive to that age?	Economic: Is the task cost-effective, i.e. the cost of the task must be less than the cost of the failure prevented? Safety: Does the task reduce the risk of failure to assure safe operation? Operational: Does the task reduce the risk of failure to an acceptable level? Economic: Is the task cost-effective, i.e. the cost of the task must be less than the cost of the failure prevented?

(Note: the source table's Restoration/Discard rows appear to repeat overlapping applicability/effectiveness criteria text between the two task types in the PDF's layout — reproduced above as extracted; the repetition in the Discard row appears to be a genuine feature of the source document's table content, not a duplication error introduced here.)

4.9.2 Operational / Visual Check

Operational / Visual Check is centered on identifying hidden faults as they occur, to avoid these faults from having a larger adverse impact on the system. An example of a Failure-Finding task would be to detect a fuse burnt-out before an electrical surge criticality damages a component.

The following sections in this worksheet are the same as described above:

• Failure Mode Metrics (4.9.1.1)
• Worksheet Summary (4.9.1.2)
• Technical Feasibility Assessment (4.9.1.7)

4.9.2.1 Feasibility Metrics

This section includes the ability to capture protected functions, P(f)s, narratives/justifications, and to calculate the Failure Finding Interval. Refer to the Appendix (Failure Finding, section 5.1) for an example from RCM II that describes terminologies used in the Failure Finding worksheet and discusses all the formulae used in MADE to calculate the Failure Finding Interval (Figure 77).

To complete this section:

1. Select Protected Functions — click the Add icon
2. Select appropriate Protected Function(s) (Figure 78)
3. Enter function P(f)
4. Add narrative/justification in the Description field
5. Click Ok
6. Combined Protected Functions P(f) field is set by default to "Model-Based" value and is calculated as the lowest P(f) among all the assigned Protected Functions.
   • To enter a custom value: click the Model-Based drop-down, select Direct Entry, enter a value between 0 and 1
7. Multiple Failure P(f) field is set by default to "Model-Based" value and is calculated as the product of Revised P(f) and Combined Protected Functions P(f).
   • To enter a custom value: click the Model-Based drop-down, select Direct Entry, enter a value between 0 and 1
8. Enter a narrative for the Multiple Failure P(f)

Formula summary:

• Combined Protected Functions P(f) (Model-Based default) = min(P(f)) over all assigned Protected Functions
• Multiple Failure P(f) (Model-Based default) = Revised P(f) × Combined Protected Functions P(f)

To calculate Failure Finding Interval using various methods (see Appendix 5.1.3 for full formulas):

1. Click Failure Finding Interval Calculator
2. Select a calculation method from the drop-down (Figure 79)
3. Enter appropriate parameters for the selected method — MTBF (M) is Item MTTF and is set by default to Model-Based value.
   • To enter a custom value: click the Model-Based drop-down, select Direct Entry
4. Click Ok
5. Enter a narrative for the FFI

Note: The Failure Finding Interval field will display N/A if the required variables for its calculation are not defined, or if the interval is infinite.

4.9.2.2 Cost Metrics

Same as 4.9.1.5 Cost Metrics, except: ability to enter detection cost.

4.9.2.3 Maintenance Action Details

Same as 4.9.1.6 Maintenance Action Details, except:

• Ability to choose between continuous monitoring or not
• Ability to enter Maintenance Interval
• Maintenance tabs (Tasks and Personnel, Equipment and Consumables)

Note: Inspection interval is set by default to Model-Based value and equals the Failure Finding Interval.

• To enter a custom value: click the Model-Based drop-down, select Direct Entry, enter a value

4.9.3 Lubrication / Servicing

A lubricating or servicing task is designed for the purpose of maintaining inherent design capabilities.

The following sections in this worksheet are the same as described above:

• Failure Mode Metrics (4.9.1.1)
• Worksheet Summary (4.9.1.2)
• Technical Feasibility Assessment (4.9.1.7)

4.9.3.1 Cost Metrics

Same as 4.9.1.5 Cost Metrics, except: ability to enter detection cost.

4.9.3.2 Maintenance Action Details

Same as 4.9.1.6 Maintenance Action Details, except:

• Ability to define action as continuous monitoring
• Ability to enter Inspection Interval
• Inspection tabs (Tasks and Personnel, Equipment and Consumables)

Note: Maintenance interval is set by default to Model-Based value and is calculated as a factor of Item MTTF. The interval factor can be set by navigating to Preferences > Application Preferences > RCM.

• To enter a custom value: click the Model-Based drop-down, select Direct Entry, enter a value

4.9.4 Scheduled Restoration

A restoration task is necessary to return the item to a specific standard.

The following sections in this worksheet are the same as described above:

• Failure Mode Metrics (4.9.1.1)
• Worksheet Summary (4.9.1.2)
• Technical Feasibility Assessment (4.9.1.7)

4.9.4.1 Cost Metrics

Same as 4.9.1.5 Cost Metrics, except: ability to enter detection cost.

4.9.4.2 Maintenance Action Details

Same as 4.9.1.6 Maintenance Action Details, except:

• Ability to choose between continuous monitoring or not
• Ability to enter Inspection Interval
• Inspection tabs (Tasks and Personnel, Equipment and Consumables)

Note: Maintenance interval is set by default to Model-Based value and is calculated as a factor of Item MTTF. The interval factor can be set by navigating to Preferences > Application Preferences > RCM.

• To enter a custom value: click the Model-Based drop-down, select Direct Entry, enter a value

4.9.5 Scheduled Discard

A discard task includes removal of an item from service at a specified life limit.

The following sections in this worksheet are the same as described above:

• Failure Mode Metrics (4.9.1.1)
• Worksheet Summary (4.9.1.2)
• Technical Feasibility Assessment (4.9.1.7)

4.9.5.1 Feasibility Metrics

This section helps identify the appropriate replacement interval by utilizing cost minimization or availability maximization methods.

To calculate the Scheduled replacement interval:

1. Click the calculator icon
2. Select a calculation method from the drop-down (Figure 80)
3. Enter appropriate parameters for the selected method — item failure distribution type and failure rate are captured from the FMEA source. The failure rate is set by default to Model-Based value.
   • To enter a custom value: click the Model-Based drop-down, select Direct Entry
4. Click Ok
5. Enter a narrative for the interval

4.9.5.2 Cost Metric

Same as 4.9.1.5 Cost Metrics, except: ability to enter detection cost.

4.9.5.3 Maintenance Action Details

Same as 4.9.1.6 Maintenance Action Details, except:

• Ability to choose between continuous monitoring or not
• Ability to enter Inspection Interval
• Inspection tabs (Tasks and Personnel, Equipment and Consumables)

Note: Maintenance interval is set by default to Model-Based value and equals the Scheduled Replace Interval.

• To enter a custom value: click the Model-Based drop-down, select Direct Entry, enter a value

4.9.6 Run-To-Failure

Run-to-failure is a reactive maintenance action that is implemented on an unscheduled basis to address a failure mode.

Note: The failure mode decision logic always concludes with either a redesign or a task combination. If an item is permitted to fail, assign a Run-to-Failure task manually.

The following sections in this worksheet are the same as described above:

• Failure Mode Metrics (4.9.1.1)
• Worksheet Summary (4.9.1.2)

4.9.6.1 Cost Metric

Same as 4.9.1.5 Cost Metrics, except: ability to enter detection cost.

4.9.6.2 Maintenance Action Details

Same as 4.9.1.6 Maintenance Action Details, except:

• Ability to choose between continuous monitoring or not
• Ability to enter Inspection Interval
• Inspection tabs (Tasks and Personnel, Equipment and Consumables)

Note: Maintenance interval is set by default to Model-Based value and is calculated as a factor of Item MTTF. The interval factor can be set by navigating to Preferences > Application Preferences > RCM.

• To enter a custom value: click the Model-Based drop-down, select Direct Entry, enter a value