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.
Required actions
Part-CAO/Part-CAMO
Organisations who provide rotorcraft continuing airworthiness management, should establish procedures and processes to ensure that their staff fully understand the information produced by the relevant Type Certificate Holders and Supplemental Type Certificate Holders relating to Critical Parts.
To achieve this objective Part-CAO/Part CAMO organisations should:
- Establish that their staff are competent to manage the airworthiness of Critical Parts using the applicable ICA, including where applicable the application of any ‘Penalty Factors' published by the relevant Type Certificate Holders and Supplemental Type Certificate Holders.
Please note:
In the context of this information, a ‘Penalty Factor’ is a fatigue damage calculation applied to reduce the airworthiness life limit, or maintenance task period, of an aircraft or aircraft component at a rate that is different from the normal life count of the aircraft due to operational factors.
Different Type Certificate Holders use a variety of terms, including but not limited to:
Life Penalty Factor;
Retirement Index Number;
Corrective Multiplication Factor; and
Flight Count Factor.
- Identify Critical Parts in their aircraft maintenance programmes and where the system allows, also in the electronic airworthiness control systems.
- Update their CAE / CAME procedures to ensure it includes Critical Parts training, competence assessment, airworthiness management, including the application of Penalty Factors (if applicable).
- Provide demonstrable methods of how Critical Parts rejections are reported through the requirements of the reporting regulation, UK Reg (EU) No. 376/2014 and UK Reg (EU) 2015-1018.
- Consider how the effectiveness of the training is measured.
To achieve the above, consideration should be given to utilising the initial induction and Continuation Training programmes.
Part 145
Organisations who provide rotorcraft maintenance should establish processes to ensure that their staff fully understand the information produced by the relevant Type Certificate Holders and Supplemental Type Certificate Holders relating to Critical Parts.
To achieve this objective Part 145 organisations should:
- Ensure that their staff fully understand the concept of Critical Parts and how to apply the relevant ICA.
- Ensure that personnel competency assessments include competence in respect to storage, handling and maintenance involving Critical Parts.
- Update their MOE procedures to ensure it includes Critical Parts training, competence assessment, storage and handling.
- Identify Critical Parts in their inventory management systems to enable goods in and stores personnel to ensure the correct storage and handling procedures are complied with.
- Have an appropriate labelling system in place which differentiates Critical Parts from other parts to aid stores and maintenance staff with identifying Critical Parts when moving them from the stores to the hangar / line.
- Be able to provide demonstrable methods of how Critical Parts rejections are reported through the requirements of the reporting regulation, UK Reg (EU) No. 376/2014 and UK Reg (EU) 2015/1018.
- Consider how the effectiveness of the training is measured.
To achieve the above, consideration should be given to utilising the initial induction and Continuation Training programmes.
Part 147
Organisations who provide rotorcraft maintenance training should establish processes to ensure that their staff and where applicable, their students, fully understand the information produced by the relevant Type Certificate Holders and Supplemental Type Certificate Holders relating to Critical Parts.
To achieve this objective Part 147 organisations should:
- Ensure that helicopter type courses include information to explain the concept of
- Critical Parts and how this is applied through the ICAs applicable to the aircraft type.
- Consider how the effectiveness of the training is measured.
Independent Certifying Staff
Independent Licensed Engineers holding Rotorcraft type ratings should ensure that they understand the concept of Critical Parts and how to apply the relevant ICA for each rotorcraft type rating included in the scope of their licence.
Independent Certifying Staff should report Critical Parts rejections through the requirements of the reporting regulation, UK Reg (EU) No. 376/2014 and UK Reg (EU) 2015-1018.