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Background

Our Safety Review of offshore public transport helicopter operations in support of the exploitation of oil and gas (CAP1145) included a review of critical parts, as these must be identified on rotorcraft certified to both CS-27 and CS-29.

Recommendation 24 (R24) stated that “EASA provide additional guidance material to improve standardisation in the approach to the classification of Critical Parts to minimise inconsistencies in the instructions for continuing airworthiness and where appropriate to require revisions to existing Instructions for Continued Airworthiness”.

Progress reports (published as CAP1243 and CAP1386) and the subsequent publication of Safety Review of Offshore Public Transport Helicopter Operations in Support of the Exploitation of Oil and Gas (CAP1877) in 2020 highlight the need to continue to raise awareness of the issues around critical parts management and handling.

Our Onshore Helicopter Review Report (CAP1864) also highlights issues with the premature failure or removal of critical parts. Action 7 includes the Civil Aviation Authority (CAA) carrying out focussed oversight of Continuing Airworthiness Management Organisations in respect to verifying compliance with the management of continuing airworthiness of critical and life limited components.

Our Performance Based Oversight approach includes the continuing airworthiness management and maintenance of critical parts.

Critical parts

CS29.602 defines a ‘critical part’ as a part, the failure of which could have a catastrophic effect upon the rotorcraft, and for which critical characteristics have been identified which must be controlled to ensure the required level of integrity.
Critical parts are listed, as applicable on the basis for certification, within the Instructions for Continued Airworthiness (ICA).

Depending on the Type Certificate Holder these parts may include:

  • bearings
  • gearboxes and sub-assemblies
  • flight controls
  • tail rotor drive systems

We advise organisations to review the respective ICA’s for the helicopters operated, managed or maintained to ensure there is an understanding of the parts identified as critical and how these should be maintained and managed in order to protect their integrity.

Further information

Federal Aviation Administration (FAA) Advisory Circulars (AC) AC27-1B, for CS-27, and AC29-2C for CS-29 provide further information and state that the ICA procedures should cover care of critical parts and include:

  • Contain comprehensive instructions for the maintenance, inspection and overhaul of critical parts and emphasize the importance of these special procedures.
  • Indicate to operators and overhaulers that unauthorized repairs or modifications to critical parts may have hazardous consequences.
  • Emphasise the need for careful handling and protection against damage or corrosion during maintenance, overhaul, storage, and transportation and accurate recording and control of service life (if applicable).
  • Require notification to the manufacturer of any unusual wear or deterioration of critical parts and the return of affected parts for investigation, where appropriate.

Reporting

To support our on-going surveillance of Critical Part performance operators, approved organisations and licenced personnel shall report any unusual wear or deterioration of critical parts, or any defect in a life-controlled critical part causing removal before reaching their approved life limit.

Identification of Critical Parts in Operators Maintenance Programmes (SN-2022/003) includes information to establish the effectiveness of an organisation’s AMP and to enable easy identification of removal of life limited critical parts for the purposes of occurrence reporting.

In accordance with occurrence reporting regulations reports should be submitted following the UK Mandatory Occurrence Reporting process.

Contact

For further information email airworthiness@caa.co.uk.

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