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UK – EU Transition, and UK Civil Aviation Regulations

To access current UK civil aviation regulations, including AMC and GM, CAA regulatory documents, please use this link to UK Regulation. Please note, if you use information and guidance under the Headings, the references to EU regulations or EU websites in our guidance will not be an accurate information or description of your obligations under UK law. These pages are undergoing reviews and updates.

The CAA carried out a Safety Review of offshore public transport helicopter operations in support of the exploitation of oil and gas, which was published in CAP 1145. One of the areas subject to review was Critical Parts; as these must be identified on rotorcraft certified to both CS 27 and CS 29.

CAP1145 made a recommendation (R24) which stated “EASA to provide additional guidance material to improve standardisation in the approach to the classification of Critical Parts1 to minimise inconsistencies in the instructions for continuing airworthiness and where appropriate to require revisions to existing Instructions for Continued Airworthiness”.

In 2016 the CAA issued Information Notice IN 2016/026 advising organisation managing and or maintaining Critical Parts for additional training and raising awareness. This information supersedes IN 2016/026, broadening the scope of applicability to all rotorcraft and their operational types and providing further information relating to Critical Part management.

Since the publication of CAP1145 the CAA has issued updates on the actions and recommendations made within. CAP1243 and CAP1386 reflected the status of these actions and recommendations. In 2019, as part of the CAA Safety Assurance model a post implement review has been completed. As part of the review the CAA has highlighted the need to continue its work on raising awareness regarding Critical Parts management and handling.

The Onshore Helicopter Review Report published in CAP1864 also highlights issues with the premature failure or removal of Critical Parts. Action 7 of this report includes the 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.

Critical parts are listed, as applicable on the basis for certification, within the Instructions for Continued Airworthiness (ICA). Dependent upon the Type Certificate Holder these parts may include, but not limited to, components such as bearings, gearboxes and sub-assemblies, flight controls, and tail rotor drive systems. The CAA advises 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.

FAA Advisory Circulars (AC) AC27-1B, for CS27, and AC29-2C for CS29 provide further information. Below is extracted from these ACs and states that the ICA procedures should cover care of critical parts including the following:

  • 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.
  • Emphasize 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.

In order to support the CAA’s on-going surveillance of Critical Part performance it should be noted that operators, approved organisations and licenced personnel should 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, in accordance with Regulation (EU) No. 376/2014 and Regulation (EU) 2015/1018 as retained (and amended in UK domestic law) under the European Union (Withdrawal) Act 2018. Reports can be submitted by following the CAA's occurrence reporting process. Please also refer to CAA Safety Notice SN-2022/003

As part of the CAA Performance Based Oversight it should be noted that the CAA has amended its organisational surveillance to take in to account the continuing airworthiness management and maintenance of Critical Parts.

Required actions

Organisations who provide rotorcraft continuing airworthiness management, maintenance and/or maintenance training 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 the following actions are considered necessary:

  • Part M/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’2 published by the relevant Type Certificate Holders and Supplemental Type Certificate Holders.
  • Part M/Part-CAMO organisations should identify Critical Parts in their aircraft maintenance programmes and where the system allows, also in the electronic airworthiness control systems.
  • Part M/Part-CAMO organisations should update their CAME procedures to ensure it includes Critical Parts training, competence assessment, airworthiness management, including the application of Penalty Factors (if applicable).
  • Part 145 organisations should ensure that their staff fully understand the concept of Critical Parts and how to apply the relevant ICA.
  • Part 145 organisations should ensure that personnel competency assessments include competence in respect to storage, handling and maintenance involving Critical Parts.
  • Part 145 organisations should update their MOE procedures to ensure it includes Critical Parts training, competence assessment, storage and handling.
  • Where possible, Part 145 organisations should 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.
  • To aid stores and maintenance staff with identifying Critical Parts when moving them from the stores to the hangar / line and finally the aircraft, Part 145 organisations are encouraged to have an appropriate labelling system in place which differentiates Critical Parts from other parts.
  • 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.
  • 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.
  • All approved organisations and licence holders should be able to provide demonstratable methods of how Critical Parts rejections are reported through the requirements of the reporting regulation, UK Reg (EU) No. 376/2014.

Organisations should note that to achieve the above, consideration should  be given to utilising the initial induction and Continuation Training programme.

The organisation should consider how the effectiveness of the training is measured.

For further information please contact airworthiness@caa.co.uk.

1 A critical part is 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 (Refer to CS 29.602)

 2 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. 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.

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