EASA Proposes Guidance on Extending Component Overhaul Intervals

EASA has published a Notice of Proposed Amendment concerning the treatment of Times Between Overhaul (TBO).  The purpose of the guidance is to harmonize the practices regarding extension of component overhaul periods when those periods are not part of the airworthiness limitations.

The European draft includes recommendations for how to handle extension of the overhaul period:

An owner may prefer not to follow the manufacturer’s recommended periods for component overhaul. The decision to deviate from the manufacturer’s recommendation for TBOs may have safety, economic, operational and other implications. The Agency proposes with this NPA Acceptable Means of Compliance that, when satisfactorily followed by the owner, would lead to the extension of the TBO, if not affecting the airworthiness limitations of the product. Regardless of other considerations and in order not to reduce the level of safety, at the recommended time for component overhaul, the owner intending to exceed the manufacturer’s recommended TBO should observe the following:

  • The TBO extensions to be performed in accordance with this proposal are applicable to components installed in non-powered and piston engine aircraft other than complex motor-powered aircraft when not used for commercial air transport.
  • In order to identify the recommended TBO, the modifications and service bulletins that may affect the components’ TBO limits should be considered.
  • When an AD stated that it has to be complied at the time of overhaul of a certain component, extending the TBO does not alleviate the AD completion at the time originally scheduled for the overhaul for such component.
  • At the time of the component overhaul extension and before the extension is granted, affected components should be inspected in accordance with the maintenance data for obvious defects or abnormal functioning by approved organisations or competent persons and the results should be kept.
  • Tests conditions and pass-fail criteria should be defined for the inspection tests before they are performed, based on the components’ typical parameters provided by the manufacturer. These conditions and criteria should be part of the approved maintenance programme.
  • TBO extensions will be approved and recorded by means of an update to the aircraft maintenance programme. The maintenance programme should identify additional flight hours and/or calendar time inspections required when exceeding the originally recommended TBO for the component(s), so that the aircraft can be operated safely until the new overhaul limit. The new maintenance programme should also set the new limit for the component(s) overhaul.
  • Nevertheless, in the case of privately operated aircraft with a MTOM of 2 730 kg or below, indirect approval of the aircraft maintenance program by a CAMO is possible in respect of the TBO extension as long as this is a recognized procedure in the CAME. The limited use of the aircraft for private operations should be stated in the aircraft’s logbook by the organization granting the extension and affected components should be identified on it.
  • The procedure includes the possibility of two extensions of 20 % of the original TBO provided that the conditions for these extensions are satisfied.
  • No further extensions are possible except for components installed in privately operated aircraft with a MTOM of 2 730 kg or below, for which there is no limit on the number of extensions, provided that the inspections assessments are positive and that there are no safety records that would recommend not to extend these intervals.

The NPA can be found online at http://hub.easa.europa.eu/crt/docs/viewnpa/id_134.

Comments should be submitted to EASA by December 16, 2011.

About Jason Dickstein
Mr. Dickstein is the President of the Washington Aviation Group, a Washington, DC-based aviation law firm. He represents several aviation trade associations, including the Aviation Suppliers Association, the Aircraft Electronics Association, the Aircraft Fleet Recycling Association and the Modification and Replacement Parts Association.

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