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S3C11 - DEFERMENT OF REQUIRED MAINTENANCE

Table of Contents

INTRODUCTION

DEFERMENT OF REQUIRED MAINTENANCE PROCESS

CARRIED FORWARD UNSERVICEABILITY COMPETENCY STANDARDS AND DELEGATION

Competency Standards

Delegation of CFU Authority

CARRIED FORWARD UNSERVICEABILITY PROCESS

CFU Considerations

CFU Documentation, Authorisation and Management

CFU Presentation

CFU Re-assessment

Annex

A. Example of a Carried Forward Unserviceability Authorisation Form

INTRODUCTION

1. Approved Maintenance Organisations (AMOs) are often required to operate aircraft at high tempo and in harsh environments, which can be detrimental to the serviceability state of the aircraft. In order to meet the demands of operational availability and increase maintenance efficiency, it may be appropriate to defer required maintenance. The deferment of required maintenance process allows an aircraft to operate prior to rectification of the required maintenance.

2. This chapter prescribes the requirements to effectively manage the deferment of required maintenance.

DEFERMENT OF REQUIRED MAINTENANCE PROCESS

3. Deferment of required maintenance is achieved through the Carried Forward Unserviceability (CFU) process.

4. CFU authority is administered in accordance with the DGTA–ADF approved Maintenance Management System (MMS) described in the AMO Maintenance Management Plan (MMP).

CARRIED FORWARD UNSERVICEABILITY COMPETENCY STANDARDS AND DELEGATION

Competency Standards

5. All CFUs must be authorised by the SMM or delegate within the scope of their authority. Prior to delegating the authority to authorise CFUs, the SMM must ensure that designated personnel have attained and retained, as a minimum, the following competency standards:

  1. exhibit a clear appreciation of operational and technical airworthiness management and the technical airworthiness regulatory framework
  2. understand the engineering rigour and expertise required for CFU assignment, and be capable of assessing the operational and technical airworthiness significance of CFUs within their authority
  3. be competent, based on qualifications, training and experience to make CFU decisions within the scope of authorisation
  4. understand the AMO Engineering Support Network
  5. understand the AMO procedures and processes for CFU assessment, operational endorsement, recording, authorisation and review.

Delegation of CFU Authority

6. The SMM may delegate CFU authority to the following personnel:

  1. Navy. SMM delegate, FSMS and Aircraft Captains.
  2. Air Force and Army. Maintenance personnel holding the rank of Flight Sergeant(E) and above, Artificers, Flight Engineers holding a minimum of Category ‘C’ authorisation on aircraft type, and Aircraft Captains.
  3. Contractor AMOs. Senior maintenance personnel specified within the MMP.
  4. Maintenance Manager. The only time a Maintenance Manager can be the CFU authority is for the transfer of a Maintenance Test Flight or an Air Test in accordance with Section 3 Chapter 5—Maintenance Test Flight and Air Tests.

7. Promulgation of CFU Delegates. The AMO is responsible for the promulgation of a list of personnel with CFU authority in local instructions. Personnel authorised with CFU Authority must be monitored by the SMM to ensure competence is maintained and authorisation remains valid.

8. Scope of CFU Authorisation. The scope of the CFU authorisation must be defined in local instructions and must be based on the delegates:

  1. trade and/or professional training
  2. aircraft system(s) proficiency
  3. competency on applicable aircraft types.

9. Withdrawal of CFU Authority. Withdrawal of CFU authority must be conducted in accordance with Section 2 Chapter 1—Maintenance Authorisations.

CARRIED FORWARD UNSERVICEABILITY PROCESS

CFU Considerations

10. Before the rectification of an unserviceability is carried forward, the Senior Maintenance Manager (SMM) or delegate must consider the following:

  1. opportunities to rectify the unserviceability within the resources under AMO control prior to the next flight and without other significant impact
  2. replacement aircraft availability
  3. opportunities to reschedule operations/missions
  4. the impact on crewing or local circumstances
  5. the impact on other CFUs
  6. the impact on operational airworthiness of the aircraft
  7. the impact on the technical airworthiness of the aircraft.

11. Seeking CFU Advice. The SMM or delegate may seek advice to inform their CFU assessment. They may seek advice from anyone considered as value adding to their decision. People providing advice do not need to be authorised to do so.

12. Technical advice that would assist the SMM or delegate in making the CFU decision include risk-relevant advice on the:

  1. consequence of failure or partial performance of the relevant system
  2. likelihood of failure or partial performance of the relevant system
  3. appropriate deferment period of the CFU
  4. evaluated level of risk in authorising the CFU
  5. potential risk treatments to reduce residual risk
  6. impact of the CFU on the capability of the aircraft, including mission effectiveness.

13. The SMM or delegate may also seek:

  1. technical data to inform their decision, including component performance and reliability data
  2. to have another person comment on their thought processes, without requiring specific information or other advice from that person.

14. The SMM or delegate who seeks advice from another person is not transferring the CFU decision responsibility to the person providing the advice. The person asked to provide advice will never have complete understanding of all the relevant considerations. In many situations the person giving advice will be geographically distant and cannot see the unserviceable component or even photographs or diagrams of it. Receiving advice in no way diminishes the responsibility of the SMM or delegate for the CFU decision.

15. The extent to which good advice can be provided to support the SMM or delegate in their CFU assessment depends on the information provided to the person from whom advice is sought, and the questions asked by the SMM or delegate when seeking advice.

CFU Assessment Process

16. The SMM or delegate must ensure that they have:

  1. the competence and expertise to make the appropriate assessment
  2. sufficient technical data to make the assessment.

17. If the SMM or delegate does not have the competence or expertise to make the appropriate assessment, assistance must be sought from the relevant Systems Program Office (SPO).

18. Before authorising a CFU which affects the handling or operating characteristics of an aircraft, the SMM or delegate must obtain an operational endorsement from an appropriately authorised aircrew representative.

19. Prior to accepting the aircraft, the Aircraft Captain will also make an independent assessment of its mission worthiness. The final decision on whether an aircraft is acceptable for an intended mission lies with the Aircraft Captain. If an aircraft is not accepted because of an outstanding CFU, the matter must be referred to the SMM for direction.

20. CFU Pre-assessment. To simplify the CFU process and to allow greater delegation of CFU authority within the AMO, unserviceabilities may be pre-assessed. Pre-assessment involves the SMM or other authority considering possible unserviceabilities, completing the engineering and operational and technical airworthiness analysis, and promulgating the outcomes in a local instruction. The concept of referring to an unserviceability with a pre-assessed impact simplifies the decision making process for the SMM or delegate. Unserviceabilities with pre-assessed impacts on operational and technical airworthiness include:

  1. Deviations Approved by SPOs. Deviations are specific written authorisations to depart from the current approved configuration or maintenance practice.
  2. Permissible Non-Conformances. These unserviceabilities have a pre-determined acceptability within specified limits. The aircraft Maintenance Manual may allow continued operation of the aircraft whilst carrying specified unserviceabilities. For example, missing rivets from a particular skin section may be deemed acceptable within specified limits, as long as regular inspection is carried out in accordance with an authorised Maintenance Manual.
  3. Minimum Equipment List. A document approved by the responsible SPO that contains the conditions under which a specified aircraft may operate with particular aeronautical product and/or systems temporarily inoperative or removed.
  4. Locally Developed List of Permissible Unserviceabilities. A list of common unserviceabilities that are known to have an acceptable operational and technical airworthiness impact. These lists are promulgated by the AMO for reference by delegates when considering an unserviceability for deferment.

21. Lists of pre-assessed unserviceabilities are not an automatic authority to carry forward an unserviceability and must be treated in the same way as advice when making a CFU decision. Additionally, the SMM or delegate must consider the combined impact of the unserviceability on operational and technical airworthiness.

CFU Documentation, Authorisation and Management

22. The reasoning and justification leading to authorising of a CFU must be documented. The minimum recording requirements must address:

  1. the details of the unserviceability
  2. why the unserviceability cannot be rectified
  3. the impact of the unserviceability on operational and technical airworthiness, and the subsequent limitations/ restrictions applied
  4. how the impact was assessed
  5. the deferment period; based on events, airframe hours, date or out of phase based figures
  6. follow-on tasks/special maintenance requirements
  7. certification by the CFU authorising authority.

23. An example CFU Authorisation Form is illustrated in Annex A. CFU authorisation forms may be tailored to meet specific AMO requirements. The form and the procedures for its use must be promulgated in local instructions.

NOTE

Original CFU authorisations forms must not travel with the parent aircraft.

24. Electronic CFU Management. For CFU management in electronic recording and certification systems, deferment periods may be scheduled maintenance events.

25. Paper-based CFU Management. The practice of using ‘Until Spares Available’ (‘TSA’), ‘Next Rx’ or similar annotations must not be used as they do not provide a valid period of deferment. However, ‘30 Jul 03 (TSA)’, ‘1234.5 hrs (Next R1)’ is acceptable as a definite period of deferment has been specified.

26. Electronic CFU Authorisation Forms. Entries in an electronic recording and certification system must be in accordance with the relevant system approved instructions.

27. Paper-based CFU Authorisation Forms. Current CFU authorisation forms must be filed by Aircraft Tail Number in a dedicated CFU folder and kept readily accessible, eg flight line area, so the SMM and Aircraft Captains can easily access all CFU decisions. Closed CFU authorisation forms must be retained in the applicable Aircraft Log Pack in CFU order.

28. CFU Traceability. AMOs must develop and promulgate in local instructions a process in that, all CFUs are traceable to the original Serial Number of Work (SNOW) and any subsequent authorisation ‘SNOW’.

CFU Administration

29. If the unserviceability is authorised for deferment, the unserviceability must be transferred to the CFU Section in accordance with the recording and certification system instructions.

30. The CFU authorisation form ‘Registration Number’ must be referenced against the applicable unserviceability in the recording and certification system.

CFU Presentation

31. The CFU section is a consolidated record of all current approved CFUs for the aircraft and any associated limitations. CFUs must be presented in a format that displays their impact on operational and technical airworthiness to the aircraft captain on acceptance of the aircraft. If, as a result of a CFU, there are limitations effecting aircraft role capability, the limitation must be identifiable.

CFU Re-assessment

32. CFUs must be re-assessed when:

  1. conditions affecting a current CFU have changed or are likely to change
  2. the period of deferment expires, or
  3. any doubt exists as to the appropriateness or circumstances relating to the CFU decision.

33. When the CFU is to be re-assessed, the CFU must be administered in accordance with the recording and certification system instructions. The CFU must be completely re-assessed and revised decisions must be developed in accordance with this chapter.

Annex:

  1. Example of a Carried Forward Unserviceability Authorisation Form
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