• 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.    

    CAP 1145 made a recommendation (R24) which stated “EASA to 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”.

    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 Notice 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 CAP 1145 the CAA has issued updates on the actions and recommendations made within.  CAP 1243 and CAP 1386 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. 

    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 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. 

    EASA AMC refers to FAA Advisory Circulars (AC) AC27-1B, for CS27, and AC29-2C for CS29. The 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 in accordance with Regulation (EU) No. 376/2014. Reports can be submitted by following the CAA's occurrence reporting process.

    As part of the CAA Performance Based Oversight it should be noted that the CAA will be amending its organisational surveillance considering Critical Parts.

    Required actions

    Organisations who provide rotorcraft continuing airworthiness management, maintenance and/or maintenance training must establish processes to ensure that their staff fully understand the information produced by the relevant Type Certificate Holders relating to Critical Parts.

    To achieve this objective the following actions are necessary: 

    • Part M organisations must establish that their staff are competent to manage the airworthiness of Critical Parts using the applicable ICA.
    • Part 145 organisations must ensure that their staff fully understand the concept of Critical Parts and how to apply the relevant ICA.
    • Part 147 organisations must 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 particular type. 
    • Independent Licensed Engineers holding Rotorcraft type ratings must 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 or licence holders should be able to provide demonstratable methods of reporting Critical Parts rejections through the requirements of EU Regulation 376/2014.

    Organisations should note that in order to achieve the above, consideration may be given to utilising the Continuation Training programme.

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

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

  • Related Information