Airworthiness Records (Part V): Life-Limited Parts and Time-Controlled Components Status

Life-limited parts (LLPs) and time-controlled components are subject to defined operational and maintenance limits that cannot be exceeded. Their status ensures that these limits are properly monitored and controlled throughout the component’s service life.

Aircraft Maintenance Programs (AMP) define both life limits and scheduled maintenance requirements for components. These may include mandatory removals, periodic overhauls, or condition-based inspections, depending on the design and certification basis of the component.

At any point in time, the status must provide a clear and unambiguous view of the remaining life, compliance condition, and maintenance status of each affected component.

Component Classification: Life-Limited Parts and Time-Controlled Components

Life-limited parts are parts for which the AMP requires permanent removal from service when, or before, a specified mandatory life limit is reached, based on the applicable controlling parameter(s).

Time-controlled components are components for which the AMP requires periodic removal for maintenance in a workshop, in order to restore the component to a specified standard, replace sub-components of the assembly, or perform inspection or functional testing to confirm continued performance, after a service period controlled at component level based on the applicable parameter(s).

Time-controlled components include:

• Hard time components (periodic restoration or overhaul)

• On-condition components (periodic inspection or testing)

• Condition-monitored components (performance trend monitoring)

Each category requires status tracking aligned with its maintenance philosophy; in practice, life-limited parts, hard time components, and on-condition components are typically managed through separate status records to ensure clarity and correct monitoring of compliance.

Applicability and Scope

The LLP and time-controlled component status is a live record reflecting the current life consumption and compliance condition of components installed on the aircraft.

It covers:

• Life-limited parts subject to mandatory removal at a defined life limit

• Time-controlled components subject to periodic maintenance, overhaul, or inspection

Components may be affected by maintenance tasks controlled at component level without qualifying as time-controlled components; in such cases, their status is still be required to demonstrate compliance with the AMP.

Recording LLP and Component Status

Life-Limited Parts (LLP) Status

The status of LLP indicates the life limitation, the total life accumulated in the applicable parameter(s), and the remaining life before the life limitation is reached.

Each entry typically includes:

• Component identification (part number and serial number)

• Description/functional designation

• Applicability (aircraft, engine, propeller, component, or installation position)

• Installation date (where applicable for traceability)

• Total accumulated life (hours, cycles, landings, or other applicable parameter(s))

• Approved life limit

• Remaining life margin

In practice, LLP status is often structured following major components, assembly, and subassembly breakdowns (e.g. engine and engine modules or landing gear and landing gear assemblies), reflecting their design and certification basis.

Time-Controlled Components Status

The status of time-controlled components refers to the status of compliance with the applicable periodic maintenance tasks defined in the Aircraft Maintenance Program (AMP) at component level.

It shall include the life accumulated by the component since the last accomplishment of the scheduled maintenance task, as well as the applicable controlling parameter(s).

Each entry typically includes:

• Component identification (part number and serial number)

• Description/functional designation

• Applicability (aircraft, engine, propeller, component, or installation position)

• Reference to approved source (e.g. MRBR, ALS)

• Last done:

  • Date of the Certificate of Release to Service (CRS)

  • Reference to the associated work package, work order, or technical log entry

  • Component time at last accomplishment (hours, cycles, landings, or other applicable parameter)

• Next due:

  • Date and/or applicable parameter (hours, cycles, landings, calendar time, or other)

  • Approved limit or maintenance interval (as applicable)

In practice, time-controlled components are usually grouped by system or ATA chapter for reporting and control purposes, although their status remains driven by the applicable requirements.

Special Considerations

Configuration Changes

Component status must be continuously updated following installation, removal, or transfer between aircraft to ensure correct life and utilziation accounting and traceability.

Back-to-Birth Traceability

For life-limited parts in particular, traceability back to manufacture (back-to-birth) is essential to support the accuracy of the accumulated life and remaining life recorded in the status.

This ensures that life consumption is complete and uninterrupted, preventing gaps that could compromise the validity of the component’s life limitation.

For example, a life-limited part installed on different aircraft over time must retain a continuous record of its accumulated life across all installations. Any missing period in its utilisation history may prevent demonstrating that the life limit has not been exceeded.

In practice, this requires maintaining clear records of component movements between installations, ensuring that each removal and installation is properly captured and linked to the component’s life history.

Conclusion

The status of life-limited parts and time-controlled components demonstrates that all affected components are correctly identified, tracked, and controlled within their approved life and maintenance limits.

By linking each component to its configuration, accumulated life, and maintenance history, the status provides a clear and current view of compliance with continuing airworthiness requirements.

Learn more about Component Maintenance Programs →

Airworthiness Records Series — Next: Part VI – Deferred Defect Status (coming soon)