Chapter 5.1
Maintenance Policy – General
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Table of contents Paragraph |
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2.1 Maintenance policy for materiel
2.2 Maintenance policy for software
3.3 Condition-based maintenance
4.1 Corrective maintenance of materiel
4.2 Inspect and Repair as Necessary (IRAN)
4.3 Corrective maintenance of software
5.1 Application for concessions
This chapter details the policy for maintenance within the Military Air Environment (MAE), the principles on which it is based and the process by which the policy is promulgated.
Maintenance is a combination of the engineering and supportive administrative actions taken to retain materiel in a serviceable condition or to restore it to serviceability. The function of maintenance within the MAE is to maintain, in the most cost-effective manner, aircraft and related equipment in a condition such that they are capable of fulfilling their declared purpose throughout their required life.
The MAE’s maintenance policies are implemented through a 2-level maintenance construct - Forward and Depth. Chapter 1.4 and Chapter 1.5 give more details of this construct and the roles played by IPTs and FLCs in providing Forward and Depth support.
This chapter is associated with the following publications:
1 43
2 43
3 43
4 DAP 100C-22 – Procedures for Developing Preventive Maintenance.
5 JAP 100E-10 – Military Aviation Ground Support Equipment Management and Policy.
6 AP 100D-10 – Support for Mission Software in RAF Systems.
7 4ASD3 Specification 1000D – International Specification for Technical Publications Utilising a Common Source Database.
8 ASD Specification 2000M – The International Specification for 4Military Materiel Management.3
2.1 Maintenance policy for materiel
Through-life maintenance policy is a judicious balance of preventive and corrective maintenance, supported by appropriate sustainment or enhancement modification action. A policy of wholly preventive maintenance could result in low utilization and over-maintenance. Conversely, a policy based entirely on corrective maintenance could result in unpredictable availability, poor utilization of resources and could generate an unacceptable number of hazardous or expensive failures.
2.2 Maintenance policy for software
Software maintenance involves some concepts that are distinct from those applied to hardware and mechanical systems. Although corrective maintenance still applies, this relates to the removal of software faults rather than the repair of a physical breakdown. The more significant dimensions of software maintenance are the controlled and configured implementation of perfective, adaptive and enhancement change. Chapter 12.8 provides further guidance.
The maintenance policy aims to maintain functionality by optimising the balance of preventive and corrective maintenance in order to:
1 Minimize the engineering manpower and other resources required for the task.
2 Minimize faults that would result in a situation hazardous to aircraft, associated equipment or personnel.
3 Minimize faults that would result in unacceptable loss of operational capability.
4 Minimize faults that would result in expensive repairs and/or lengthy down times.
5 Identify methods to improve operability, reliability and/or maintainability.
6 Retain the condition of equipment until its out-of-Service date and to accommodate periods of intensive use if required.
Preventive maintenance is systematic and prescribed work undertaken at predetermined intervals to reduce the probability of failure, to restore the inherent level of equipment reliability and to ensure that performance is not degraded by time or usage. A more detailed description is provided in Chapter 5.3. Within the MAE there are 3 types of preventive maintenance: servicing, scheduled and condition-based maintenance.
Servicing is that maintenance required to determine the condition of an aircraft or other item of equipment after a period of use and to prepare it for its next period of use. It comprises the checking and replenishment of consumables and may include such minor maintenance as the replacement of bulbs and the identification of obvious signs of unserviceability. The user or operator may carry out servicing.
Scheduled maintenance is that preventive maintenance undertaken at regular, predetermined intervals to keep an aircraft or other item of equipment in a sound overall condition and to minimize the amount of corrective maintenance and other day-to-day attention it requires. For aircraft, the requirements for scheduled maintenance are derived using a version of Maintenance Steering Group logic and Reliability-Centred Maintenance; similar logic techniques may be applied to other equipment.
Scheduled maintenance tasks may be retained as individual tasks (Flexops), allowing completion to coincide with corrective maintenance or other down time as operations dictate. Alternatively, the individual tasks may be grouped by periodicity and allocated to the appropriate level of maintenance. This grouping defines the scheduled maintenance system, which may be based either on units of usage or calendar time and may, if appropriate, have an upper limit specified in the other unit of measure. A grouping may be divided into smaller groups or packages and equalized over the relevant part of the maintenance cycle so that the whole requirement is satisfied within the specified period.
3.3 Condition-based maintenance
Condition-based maintenance is that preventive maintenance initiated as a result of knowledge of the condition of an item gained from routine or continuous monitoring. Where adequate and realistic condition-monitoring techniques are available for a particular item to detect incipient failure (eg wear debris monitoring, NDT techniques and, in some applications, built-in test), condition-based maintenance is applied to the item in preference to routine repair or replacement as part of scheduled or out-of-phase maintenance. Where possible, the requirement for condition monitoring of the item is to be included in the relevant servicing or maintenance schedule; otherwise it is incorporated as out-of-phase maintenance. Additionally, the accuracy of the condition-monitoring technique is normally sufficiently refined to permit anticipation of the need to repair or replace the item concurrent with scheduled or other maintenance opportunities.
4.1 Corrective maintenance of materiel
Corrective maintenance embraces those maintenance activities carried out after a fault has occurred in order to restore an item to a serviceable state. Maintenance activities undertaken when a fault is indicated, but in the event not confirmed, are also corrective maintenance. A fault may be identified from the application of condition-monitoring techniques as part of preventive maintenance. When a fault is reported to, or detected by, the responsible engineering organization, the main equipment concerned becomes unserviceable and the unserviceability is formalized by raising the appropriate work order entry. A more detailed description of corrective maintenance is provided in Chapter 5.4.
4.2 Inspect and Repair as Necessary (IRAN)
IRAN is a methodology intended to ensure that the most cost-effective corrective maintenance activities are undertaken to return an item to a condition to meet operational commitments. It is rarely necessary to return a faulty component to ‘as new’ condition; consideration should always be given to repairing an identified fault, rather than reconditioning whole equipments.
IPTs are to incorporate the IRAN principle in the content of Technical Information, including maintenance schedules, manuals and repair schemes. Repair contracts are also to clearly state that the principle of IRAN is to be followed and is to refer to Def Stan 05-61. Def Stan 05-61 specifies the procedures to be followed when the contractor seeks permission to deliver a product that does not comply in full to the contract requirement. IPTs are also to establish at what point it is more cost-effective to recondition rather than repair a component. In addition, they should also establish at what point the cost of repair is uneconomical and the component should be considered as scrap. IRAN is to be applied by all maintenance organizations unless otherwise directed by the IPT or delegated authority.
4.3 Corrective maintenance of software
Faults in software may require changes to the design and hence are generally corrected as part of pre-planned program updates embodying multiple change requirements.
Concessions are defined as either IPT-approved variations from manufacturing or maintenance specifications, or faults for which repairs have been assessed by the IPT as uneconomic or unnecessary and for which there is no specific timescale for rectification. Concessions are to be recorded on the aircraft or component Engineering Record Card and, for the information of maintenance personnel, on the aircraft Acceptable Deferred Faults (ADF) log. Deferment of all other corrective maintenance is to be logged on the aircraft Limitations Log (Lim) or ADF Log as appropriate; Chapter 5.4.2 provides guidance on completing these forms.
5.1 Application for concessions
Applications for concessions, as described in paragraph 5, are to be made to the relevant IPT. Where an application concerns aircraft equipment, the application is to be copied to affected platform IPTs.
Whenever a new design, modification or process is under consideration, the concept of ‘cost-effective design for whole life supportability‘ should be incorporated in the project as early as possible. Subsequently, Integrated Logistic Support (ILS) should be implemented as described by Def Stan 00-60 or equivalent, supplemented by the 4Acquisition Operating Framework (AOF)3, but it may need tailoring to suit.
6.2.1 4Continuous airworthiness – Integrated Project Team (IPT) responsibility3
4IPTs are responsible for ensuring the continuous airworthiness of their platform and are to provide a system of assessment that ensures the continual analysis of the fault management system. A fundamental part of this system is the Fault Reporting And Corrective Action System (FRACAS), which is to provide for:
1 The monitoring of all significant incidents and faults that have occurred in flight and faults found during maintenance, highlighting any that appear significant in their own right.
2 The continuous monitoring of repetitive incidents and faults occurring in flight and faults found during maintenance and periodic servicing.
3 The continuous monitoring of deferred faults.
4 Analysis of the unscheduled removal of component and the performance of aircraft systems for use as part of the maintenance programme efficiency.
5 The review of schedules and maintenance procedures.
A description of the FRACAS is to be included in the platform Safety Management Plan; JSP 553 Annex P refers.3
6.2.2 Support Policy Statements (SPS)
The maintenance policy for an aircraft or item of equipment, including software, is to be detailed in a multi-disciplinary SPS. The SPS is the executive document specifying the support arrangements for an aircraft or equipment throughout its service life, including disposal, and should be promulgated in either the platform or commodity Topic 2(N/A/R)1 or equipment Topic 5W as determined by the IPT. 4The initial issue SPS will be produced by the ILS Team in conjunction with the contractor; JSP 886 Vol 7 Pt 2 refers.3 An SPS is to be subject to an auditable review by the IPT at least every 5 years4or whenever there is a substantial change to the support policy or there are changes that amend the responsibilities of staffs or formations that provide ILS.3 Additionally, aircraft SPS are to include a breakdown of the aircraft IPT responsibilities and those of any associated commodity IPT, including the reference of the commodity Topic 2(N/A/R)1, if produced.
4Chapter 5.14 and its subordinate chapters provide additional information on SPS layout and the details to be included.3
6.2.3 Contingency maintenance
Contingency maintenance is that maintenance considered essential in times of tension or conflict, when maintenance standards may be relaxed and other forms of scheduled and condition-based maintenance may be suspended. If required, for each aircraft and item of equipment, the contingency maintenance requirements are to be identified in the Topic 2(N/A/R)1, Topic 5 or equipment publication. Additionally, aircraft and equipment expedient repair procedures may be required.
6.2.4 Anti-deterioration maintenance of equipment in store
In the context of anti-deterioration maintenance of equipment in store, the term ‘in store’ means both in store within the supply organization and in forward stores, but excludes:
1 Complete aircraft, for which procedures appear in JAP 100V-21.
2 Equipment governed by other specialist regulations, eg aero-engines, explosives, armament stores and dehumidification.
The use of suitable storage environments and protective packaging should make the need for anti-deterioration maintenance while equipment is in store exceptional. Such maintenance should only be used in instances where ageing, corrosion, growth of mould or other conditions would adversely affect the equipment concerned to an extent that is unacceptable from a cost or operational availability point of view. Shelf life may be authorized and promulgated in the appropriate Topic 5A1 and Topic 5W only when it is known that the equipment concerned will deteriorate with age regardless of any pre-storage maintenance or precautions undertaken, eg lithium battery life.
6.2.5 Modifications
Although sustainment, enhancement, perfective or adaptive modification action is taken primarily to reflect changes in operational requirements or to improve equipment and personnel safety, such action can also improve reliability and maintainability. Modifications are an integral feature of the overall maintenance policy of an aircraft or other item of equipment. However, the costs associated with preparing and embodying a modification are significant and the downtime arising from a modification embodiment programme can affect equipment availability. Detailed procedures for authorizing and monitoring modifications are specified in Chapter 10.2 to ensure that adequate control is maintained.
From conception, consideration should be given to the efficient, effective and safe disposal of assets. Once MOD declares aircraft on the military register to be non-effective, their disposal is to be co-ordinated by SC(i) Disposal and Sales in accordance with 4JSP 886, Vol 9, Pt 4.3 This may result in the aircraft remaining within MOD control, ie as static/flying display aircraft or ground instructional use, or it may lead to its sale, gifting or scrapping. An IPT’s engineering and Safety, Health, Environment and Fire responsibilities will therefore vary according to the disposal arrangements for each aircraft; these responsibilities are detailed in 4JSP 886, Vol 9, Pt 4.3
4Note:
Aircraft retained for static display are not recognized as MAE equipment and therefore JAP 100A-01 policies and regulations do not apply. The owning organization is responsible for providing support procedures and arrangements that address the potential risks presented by aircraft retained for static display.3
This chapter refers to the following publications and websites:
1 4JSP 553 Annex P – Safety Management Plan - Guidance Notes3
2 4JSP 886 – The Defence Logistics Support Chain Manual3
3 Def Stan 00-60 – Integrated Logistic Support
4 Def Stan 05-61 – Quality Assurance Procedural Requirements Pt 1 - Concessions
5 JAP 100V-21 – Aircraft Storage.
6 Topic 2(N/A/R)1 – General Orders and Special Instructions.
7 Topic 5A1 – Master Maintenance Schedule.
8 Topic 5W – Summary of Component Repair Plans.