AU778804B2 - Repairable item management process and system - Google Patents

Description

Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT APPLICANT: PS MANAGEMENT CONSULTANTS PTY LTD Invention Title: REPAIRABLE ITEM MANAGEMENT PROCESS AND SYSTEM The following statement is a full description of this invention, including the best method of performing it known to me: "REPAIRABLE ITEM MANAGEMENT PROCESS AND SYSTEM" Technical field This invention relates to a repairable item (RI) management process and system.

SThe nen';n h pa'icua but not exciuSive dppiication to repairaole item management processes and systems for logistic support. The preferred embodiment will be described in a defence context, but it will be understood that the system and mpthM nf thoe t is pi,, o ,,ay cv iaan app;;iillvi where there is the need tor sophisticated management techniques to control the supply of repairable items. The mining industry is one example of a civilian application of the invention.

Background of Invention There are many known systems to provide repairable items in a timely and cost effective manner.

RIs are generally relatively expensive items of varying degrees of complexity. Frequently they incorporate two or more levels of internal hierarchical build structure which may include items which are RIs in their own right.

Ultimately though, all RIs consist of assemblies of discrete breakdown spares (BOS). Maintenance/repair of RIs therefore requires access to a suitable range of BDS and the infrastructure necessary to assemble and test them.

All RIs by definition have a maintenance policy which provides for some maintenance action to be performed cost-effectively. Each maintenance action performed on a RI should be subject to these same cost-effectiveness considerations and, where the cost exceeds the defined parameters for uneconomic repair, the item will be considered for throwaway. Notwithstanding, the non-availability of a new replacement item may still indicate that repair must be performed.

RIs will normally go through repeated cycles of use and maintenance. As the number of RIs is limited, these cycles must be managed to provide the correct proportion of items in a serviceable state at any given time.

Management of these proportions requires an accounting system which provides visibility of all assets on a continuous basis to ensure the correct proportions are maintained.

There are two categories of RI worthy of special consideration: Items which are subject to scheduled maintenance and SItems which are maintained on an unscheduled basis (repair on-condition).

The significant difference between these two is the level of confidence with which maintenance events and 30 related BDS requirements can be predicted. The parameters which drive maintenance events for these two categories are dissimilar in most instances and therefore require separate management techniques by the RI Manager (RIM).

A typical RI System is illustrated in FIG 1.

RI systems can be regarded as aggregation of management, maintenance, logistics, administrative, and financial functions toward a common goal of cost-effective mission generation without deference to organisational boundaries. At the overview level, RI systems can be regarded as comprising requirements, policies, procedures.

"goods, services and information systems operating in a distributed environment which transgress organisational boundaries of authority and responsibility.

At the working level, RI systems can be regarded as having personnel performing operational maintenance and support activities to generate missions at the locations and times required. Operational availability depends to a great extent on the availability of serviceable RIs at Operational Units. Therefore it is the availability of these Units which provides the ultimate validation of the effectiveness of the RI System.

Support personnel provide the link between geographical locations to allow distribution of equipment according to need and serviceability status. The ability to provide mission ready end items (aircraft, ground support *equipment etc) when and where required is directly dependent on this distribution function. Further, the ability of 45 technical personnel to perform the maintenance activities on RIs which make them serviceable is almost entirely dependent on the availability and distribution of sub assemblies and BOS which support maintenance processes.

Engineering services such as maintenance engineering analysis (MEA) and maintenance requirements determination (MRD) are closely related to the RI System in terms of assisting both effectiveness and efficiency.

Implicit in the working level considerations of RI management are the availability of suitable facilities, technical documentation, training materials, trained personnel, transport infrastructure and information systems.

It is evident that, unless there is an unlimited number of end items, it is the timely availability of resources for each of the RI System functions which provides mission generation capability.

The RI repair pipeline is the most obvious component of the RI System in that it is the vehicle by which unserviceable items have their status changed to serviceable. Indeed many consider the RI pipeline per se to be the RI Sysierrl. The Ri pipeline is the major instrument by which the proportions of unserviceable to serviceable items can be altered. It is where much of the managerial leverage will be applied to adapt between peak usage and routine usage rates, ,provii g botu". effective d id eficieni outcomes.

The RI pipeline comprises administrative, logistics and maintenance functions. In design of the RI System, these ultimately manifest themselves as turnaround time (TAT) comprising administrative delay time (ADT), logistic delay time (LDT) and time to repair (TTR) elements. Each element will be separately considered as each has the potential to enhance or degrade the RI Pipeline, and hence the RI System as a whole.

An idealised RI repair pipeline is displayed at FIG 1 to demonstrate the inter-dependencies between activities.

This pipeline (the bottom loop in FIG 1) depicts only a single level of maintenance being performed and none of the additional complexities which may occur when there are additional maintenance venues for sub-assemblies or multiple repair venues for the same maintenance level for a single item.

From FIG 1, it can readily be seen that the number of maintenance arisings is a primary function of Rate of Effort (ROE) (inc!uding mission type considerations) and mean time between failures (MTBF) (or scheduled life in the case of "lifed" items). These parameters lead to a calculated mean time between arisings/forecast repair arisings (MTBA/FRA). When a repair pipeline is established, the repair facility must be able to repair unserviceable items at a rate (turnaround time or TAT) equal to or faster than failures occur. In these circumstances, provided that the MTBA/FRA is not exceeded, there should always be a serviceable RI available to replace an unserviceable (US) item submitted to the repair pipeline. The timely provisioning of BDS is a critical factor in achieving TAT.

As an example, an RI System which was based on a MTBA of 30 days with a TAT of 30 days would not work in practice. This is because the variations which occur in end item usage patterns (ROE) and short term fluctuations in time between failure (which may not ultimately reflect any variation in "mean" time between failure) dictate that the arising rate may in fact generate 3 failures in 60 days (MTBA equals 20 days) and no more failures for 30 days. Overall MTBA for the time period is as expected however, the 3 failures during the first 60 days may exceed the capacity of the repair facility to provide a one for one exchange as the planned TAT is 30 days.

Normally, these short term variations in arising rate, or other parameters are accommodated by provision of buffer stock at some holding location. The buffer stock is used to provide one for one replacement at the operational level while the repair facility "catches up" during periods of lower than normal failure rate. While effective, this strategy can be extremely expensive due to the typically high cost of RIs.

From the above scenario, it is clear that while MTBAIFRA and TAT are important criteria when designing a RI repair pipeline, they are only useful in providing general guidelines as to the overall capacity required. The normal variability within these parameters requires a great deal more consideration of their impact on Ao.

Operational Availability MTBM MTBM MDT 40 Where MTBM the mean time between maintenance, either scheduled or unscheduled.

and Where MDT maintenance downtime MDT comprises the time required to effect Operation Maintenance or OM repairs (Mom) assuming all spares (RIs in this consideration) are available.

45 In the event that no spares were to be available. OM repair would then be dependent on the evacuation, repair and return of the failed RI. The time taken to achieve this is known as turnaround time (TAT) and is the prime design consideration for a RI repair pipeline and RI System. The availability equation now is: Ao= MTBM MTBM Mom +TAT If one assumes that Mom is the same whether spares are immediately available or not, when spares are unavailable. TAT alone determines Ao. It also provides clear indication that there is a direct relationship between Ao, serviceable RI numbers and TAT. The fact that the vast majority of serviceable RIs are physically located in Operational Units leaas to me conclusion that me Ri System considerations extend into OM and therefore (need to) transgress organisational boundaries between deep maintenance (DM) and OM.

ii ia dia i iildi tliiiidl ifUedba e iviTBMvi or decreased MviDT wiii improve avaiiaoiiity. MTBM is suDstantially determined by initial design and manufacturing, although poor maintenance standards may have a negative impact on MTBM. Each of the individual components which comprise MDT provide discrete opportunities for improving availability.

MTTR is the actual time spent performing maintenance actions on the RI. MTTR is the direct product of maintainability decisions and is substantially determined by the design and construction of the RI. Nonetheless.

particularly for RIs subject to on-condition maintenance, significant repair time can be saved by having an efficient repair process and suitably trained and experienced technical staff. Additionally, workshop production planning may contribute to significant reductions in MTTR.

ADT is the delay time associated with administrative tasks related to the management of a RI in the repair pipeline. The ADT tends to increase in direct proportion to the number of agencies involved in managing items through the pipeline due to the need for accounting, data recording and handling at each discrete point of management responsibility or intervention. Careful design of RI Systems will lead to minimisation of ADT and concomitant reduction in MDT for most RIs.

LDT is the time spent waiting for access to resources such as spares (these spares may be subordinate RIs or BDS), test equipment, transportation or facilities required for maintenance. Although all of the components of LDT can contribute to overall delay, for a well designed RI System, the main variability results from spares and transport delays. Both of these components are relatively simple to manage for scheduled maintenance while transport is also relatively simple for unscheduled maintenance.

The most difficult variable to manage for LDT is provision of spares for unscheduled maintenance. The spares referred to are the BDS as, ultimately, repair of all RIs is dependent on availability of BDS.

FIG 1 displays the role of BDS in supporting TAT at the repair venue. Ideally, BDS would be procured on a just-in-time basis to support repairs in progress and RIs would be produced within the defined TAT. This approach would minimise the investment and ownership costs of BDS inventory while still meeting required operating parameters of the RI repair pipeline. In practice, the lead time for some BDS precludes just-in-time procurement however, this strategy should be applied to the extent possible.

Obviously, BDS procurement should not be viewed in isolation from the remainder of the RI pipeline as it is an integral part of the RI System and influence upon, the MDT. Moreover, the issue of whether to stock more BDS in order to improve MDT, thereby reducing the need for line replacement units (LRUs) in buffer stock, is far from simple.

Questions arising include the following: What is the cost to assess, procure warehouse and distribute BDS when and where required to produce sufficient reduction in MTTR to allow reduction in RI pipeline spares? How does this cost compare to the cost of procuring one or more additional RIs? It is doubtful that anyone can assign the true cost to the BDS inventory management function with any degree of accuracy although it is unarguable that the true cost far exceeds the purchase cost of the stock at hand for many items. Nonetheless, it is important to understand the relative merits of the strategies of lay-in (procurement in advance of an actual requirement) of BDS versus just-in-time procurement.

The optimum method of BDS procurement lies somewhere between the two extremes of buy everything in advance and buy everything just-in-time and the design and operation of an efficient RI System with minimum delays at 45 all other points will provide increased opportunity for just-in-time BDS procurement for any given end item availability.

Many of the critical parameters used in the initial design of a RI pipeline are mean values. MTBF, MTBA, MTTR are all elements which, for fielded systems with significant history, can all be determined with reasonable confidence. Even ROE and mission profile data are provided on an annual basis with little attempt made to factor in variations to effort over a shorter timeframe.

These mean figures provide a sound basis on which to plan facilities floorload capacities, staff numbers, transport infrastructure requirements, warehouse floor/shelf space, packaging and handling equipment/materials requirements. Unfortunately, mean values do not represent the real world in terms of delivering mission availability.

Operationally, it is not sufficient to have achieved an average Ao equal to the target figure over a one year period if none of the missions were available when required. The inadequacy of this type of Ao is even more apparent when considered in the context of contingency operations.

Ideally HI Systems provide the maximum opportunity to deliver the required Ao at all times, regardless of short term fluctuations in failure rate, time to repair, ROE and mission profiles, and to do this in the most cost-effective way possible.

Summary of Invention The present invention aims to provide an alternative to known repairable item management systems and processes.

This invention in one aspect resides broadly in a repairable item management process for a logistic support system in which unserviceable items from a plurality of item types are repaired to become serviceable items, the process being controlled in accordance with a logistic model utilising a plurality of model parameters representative of operating characteristics of the system, at least one of the parameters being a mean value of an operating characteristic, the process including:monitoring the operating characteristic; modifying the mean value of the operating characteristic in response to the monitoring, and adaptively controlling the repairable item management process by revising the logistic model to include the modified mean value as a modified parameter.

It is preferred that the monitoring and the adaptive control is in substantially real time.

It is also preferred that one of the parameters is, for each item type, the mean turnaround time between the arising of the need to repair an item of that type and when the item is repaired, and that the process includes:monitoring the elapsed time between the arising of the need to repair an item and when the item is repaired, the elapsed time being the turnaround time for repairing the item: modifying the mean turnaround time for that item type in response to the elapsed time thus monitored, and revising the logistic model to include the thus modified mean turnaround time for that item type.

It is also preferred that for a given operating characteristic the parameters include:a' a first parameter indicative of the mean value of the operating characteristic during routine conditions, and a second parameter indicative of the mean value of the operating characteristic during peak use conditions.

In another aspect this invention resides broadly in a method of controlling a repairable item management process for a logistic support system in which unserviceable items from a plurality of item types are repaired to become serviceable items, the process being controlled in accordance with a logistic model utilising a plurality of model parameters representative •of operating characteristics of the system, at least one of the parameters being a mean value of an operating characteristic, the method including:utilising the logistic model to predict the parameter value representative of an operating characteristic given at least one known other parameter value; monitoring the operating characteristic to determine the actual parameter value thereof; comparing the predicted parameter value with the actual parameter value, and modifying the logistic model to cause the predicted parameter value to correspond with the actual parameter value.

In another aspect this invention resides broadly in a method of controlling a repairable item management process for a logistic support system in which unserviceable items from a plurality of item types are repaired to become serviceable 45 items, the process being controlled in accordance with a logistic model utilising a plurality of model parameters representative of operating characteristics of the system, at least one of the parameters being a mean value of an operating characteristic, the method including:determining a desired parameter value of at least one operating characteristic: monitoring the at least one operating characteristic to determine the actual parameter value thereof; comparing the desired parameter value with the actual parameter value, and modifying the system to cause the actual parameter value to correspond with the desired parameter value.

In another aspect this invention resides broadly in a method of designing a logistic model for controlling a repairable item management process for a logistic support system in which unserviceable items from a plurality of item types are repaired to become serviceable items, the logistic model utilising a plurality of model parameters representative of operating characteristics of the system, at least one of the parameters being a mean value of an operating characteristic, the method including:monitoring the operating characteristic to determine the actual parameter value thereof; building the logistic model with the parameter value equal to the actual parameter value.

monitonng other operating characteristics; modifying the mean value of the operating characteristics in response to the monitoring, and adaptively modifying the logistic model by including the thus modified parameters.

In a further aspect this invention resides broadly in a repairable item management system for logistic support in which unserviceable items from a plurality of item types are repaired to become serviceable items, the process being controlled in accordance with a logistic model utilising a plurality of model parameters representative of operating characteristics of the system, at least one of the parameters being a mean value of an operating characteristic, the system including:monitor means for monitoring the operating characteristic, and a computer programmed to include the logistic model, to modify the mean value of the operating characteristic in response to the monitoring, and to adaptively control the repairable item management process by revising the logistic model to include the thus modified parameter.

The monitor means may be any suitable time recording means or system.

In another aspect this invention resides broadly in a repairable item management system for logistic support in which unserviceable items from a plurality of item types are repaired to become serviceable items, the process being controlled in accordance with a logistic model utilising a plurality of model parameters representative of operating characteristics of the system, at least one of the parameters being, for each item type, the mean turnaround time between the arising of the need to repair an item of that type and when the item is repaired, the system incJuding:monitor means for monitoring the elapsed time between the arising of the need to repair an item and when the item is repaired, the elapsed time being the tumrnaround time for repairing the item, and l .a computer programmed to include the logistic model, to modify the mean tumrnaround time for that item type in response to the elapsed time thus monitored, and to adaptively control the repairable item management process by revising S-the logistic model to include the thus modified mean tumrnaround time for that item type.

Description of Drawings In order that this invention may be more easily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention, wherein:- FIG 1 is a schematic diagram illustrating an RI system in general terms; FIG 2 is a schematic diagram illustrating the RI cycle in general terms; FIG 3 is a schematic diagram illustrating a number of higher level processes in the system and method of the present invention, and the interaction of these processes, and S 40 FIG 4 is a schematic diagram illustrating an organisational structure suitable for implementing the present invention.

Description of Preferred Embodiment of Invention RI systems have already been described in general terms with reference to FIG 1 in the Background to the 45 Invention.

Tumrning now to FIG 2 which illustrates the RI cycle in general terms and indicates why it is preferred to monitor both serviceable and unserviceable RIs. Traditional RI Management has used reactive techniques monitoring serviceable RIs in only one stock location to detect a stock out situation. This method almost inevitably leads to a reduction in Ao before remedial action is begun. In the present invention, early warning coupled with swift and effective management intervention will avoid the stock out and lost Ao under most circumstances.

The RI Cycle illustrated in FIG 2 is a graphical depiction at the highest level of the distribution of RI assets. It displays distribution of RIs according to their potential to support Ao, i.e. whether they are serviceable or not. All unserviceable RIs within the RI System are considered to be within the repair pipeline and therefore subject to TAT management objectives.

From FIG 2 it can be seen that, as all RIs are either serviceable or unserviceable at any given time, therefore: Z X+Y where Z is the total number of RIs in the RI System X is the number of serviceable RIs, and Y is the number of unserviceable Ris It is clear from Figure 2 that as Z is a fixed number X-1 Y+1. Thus numbers of serviceable and unserviceable RIs are directly linked.

FIG 2 is also useful in displaying the direct relationship between the rate at which successive failures occur and the immediate impact that this has on RI spares availability. Thus, the MTBF (long term rate of failure) is not the critical factor in determining Ao: it is the time between failures relative to the TAT. By monitoring the rate of changes of status and distribution of assets it is possible to obtain the maximum possible warning of an impending threat to Ao.

Reference will now be made to FIG 3 which illustrates in broad terms a number of higher level processes in the system and method of the present invention, and the interaction of these processes. The name PRISM is the applicant's trade mark used in relation to the invention. It is used in FIG 3 and through the following text to refer to the overall system in which the invention is utilised.

In an overall operational system utilising the various aspects of the present invention, there are nine high level processes, each with lower level subprocesses. The processes are: Direct PRISM Provide the high level RI system performance requirements and overall direction.

The purpose of the Direct PRISM process is to provide high level performance requirements and direction for the RI System. It is performed by the Logistics Preparedness Management Board and includes the following four subprocesses DP1 Specify Preparedness requirements 30 DP2 Specify Logistics priorities oDP3 Identify Changes in operational parameters DP4 Review RI System Performance Initiate PRISM Allocate responsibilities and set up the initial system requirements.

The purpose of the Initiate PRISM process is to allocate responsibilities and set initial requirements for the •,system. It is the responsibility of the Board but the Logistics Support Manager performs most of the work. It includes the following three subprocesses: IP1 Appoint Logistics Preparedness Board IP2 Appoint Logistics Support Manager 40 IP3 Define Preparedness Requirements Design PRISM Design the overall RI system, pipelines and spares requirements.

The purpose of the Design PRISM process is to provide the overall design of the pipelines, the spares requirements, the trigger points and to develop the procedures. It is the responsibility of the Logistics Support Manager -45 with assistance from the RI Managers. It includes the following eight subprocesses: DEl Design PRISM management structure DE2 Design RI Pipeline DE3 Determine OLOC parameters DE4 Determine MLOC parameters DE5 Determine RI Spares Requirements DE6 Determine Trigger Points DE7 Design Support Information Systems DE8 Develop procedures Implement PRISM Put the design into practice.

The purpose of the Implement PRISM process is to put the design into practice by implementing the physical design and loading data and design parameters into the supporting implementation tools. It is the responsibility of the Logistics Support Manager with the support of the RI Managers. It includes the following five subprocesses: IM1 Appoint staff IM2 Implement RI Pipeline IM3 Purchase Spares IM4 Execute contracts IMS Implement support information systems Operate PRISM Perform the day to day management of the RI System.

The purpose of the Operate PRISM process is to perform the day to day control of the RI System. It is performed by the RI Managers and includes the following six subprocesses: OP1 Monitor Operational Demand OP2 Monitor Automatic Triggers OP3 Monitor System Performance OP4 Manage LDT/ADT Manage Throughput OP6 Report Deficiencies Manage RI Repairs Manage the day to day repairs of RIs.

The purpose of the Manage RI Repairs process is to perform the day to day management of RI repairs within a maintenance venue. It is the responsibility of the repair venue managers based on priorities set by the RI Managers and includes the following four subprocesses: MR1 Control Production (Throughput) 30 MR2 Forecast Facility Workload MR3 Forecast BDS Requirements MR4 Assign Workshop Priorities Manage Distribution Manage the distribution of RIs into the repair venues and back to operational units.

The purpose of the Manage Distribution process is to perform the day to day management of the distribution of RIs between the operational units and the repair venues. It is the responsibility of the distribution managers based on priorities set by the RI Managers. It has no subprocesses.

Monitor RI System Performance Monitor the overall performance of the RI system to meet short term :40 and long term requirements.

The purpose of the Monitor RI System Performance process is to manage the overall performance of the RI system to ensure that it meets operational requirements in the both the short and long terms, and remains cost effective.

The Logistics Support Manager performs this function based on operational requirements and assessment of the o performance of the RI System. It includes the following four subprocesses MP1 Assess operational demand MP2 Assess RI System performance MP3 Initiate PRISM redesign MP4 Initiate Engineering/ Maintenance Review 9 Review Design parameters Identify deviations from the PRISM design parameters that require redesign considerations.

The purpose of the Review Design Parameters process is to identify situations where the RI system performance is outside the PRISM design parameters and therefore the design parameters need to be updated. This cih tinn i uwhere the maan or varianrA. vale for narmntp.r. (en TAT ;ari.inn rate have varipd) and not when the system is displaying normal variability. It is the responsibility of the Logistics Support Manager and includes the followina two suborocesses: RD1 Monitor system design parameters RD2 Identify candidate items for review To assist in a fuller understanding of the invention and its practical implementation, a more detailed analysis of the above process levels commences on page 12 under the heading "Detailed Analysis of Higher Level PRISM Processes.

In use, effective management of the process of the present invention requires a defined organisation structure with roles and associated responsibilities. An organisational structure suitable for use with the present invention will now be described briefly with reference to FIG 4.

The organisation can be closely aligned with known approaches in that it defines structure and responsibilities in terms of roles, has a four layer structure with the top layer a Management Board having three roles and has provision for an independent Assurance role to assist the Management Board.

The organisation is defined in terms of roles for which responsibilities are assigned. Characteristics of Roles are: Roles can be shared or combined in that the responsibilities associated with one role may be divided between two or more individuals (or organisations) or one individual may perform more than one role.

All roles must be filled and can be filled on a full time or part time basis.

The terminology for positions within an organisation does not have to align with the role terminology used herein but positions need to be aligned with role responsibilities.

S. As can be seen in FIG 4, the four layers of the preferred Organisation are: Logistics Preparedness Management Board. The Board has overall responsibility for the preparedness of the operational system from a logistics perspective. It sets the overall priorities for management of RIs.

The Logistics Preparedness Management Board has overall responsibility for the preparedness of the operational system from a logistics perspective. It may form part of a higher management structure with responsibility for the overall preparedness management of the operational system in question.

The management board objective is to ensure that both the long and short-term preparedness objectives for the operational system can be achieved cost effectively within the available resources.

The Board represents three separate interests: The Operation Authority. The Operations Authority represents the users of the operational system and has generally has the overall responsibility for meeting the capability outcomes.

The Operations Authority represents the operators of the operational system. The Operations Authority is *b 40 responsible for: Ensuring that the operational System can meet the Preparedness requirements set by senior management Providing operational requirements and information for the design and operation of the RI System.

Assigning priorities for operational availability of the operational System sub-systems.

The Supply Authority. The Supply Authority represents the organisations responsible for satisfying defined RI availability requirements to achieve the operational availability targets.

The Supply Authority represents the organisation responsible for meeting the RI availability targets. The Supply A0thciht is -n ihle fcr.

Ensuring that the RIs meet the specified quality standards.

Ensuring that RI availability targets are achievable.

The Supplier Business Case.

The Logistics Authority. The Logistics Authority has overall responsibility for meeting the RI availability targets and controls the resources (primarily funds) to support the requirements.

The Logistics Authority has overall responsibility for the logistics elements of Preparedness for the operational system. To achieve this the Logistics Authority: Is responsible for Logistics support resourcing Chairs the Preparedness Management Board Assigns the Preparedness targets Takes advice from the Operations Authority and Supply Authority Logistics Support Manager. The Logistics Support Manager has responsibility for the day to day performance of the logistic support for the complete operational system.

The Logistics Support Manager (LSM) has responsibility for the day to day performance of the logistics support for the entire operational system. This includes the RI Management function and other functions such as supply support for Break Down Spares (BDS), Engineering and Configuration Management.

The LSM is responsible to the Management Board and reports to the Logistics Authority, usually through the Supply Authority.

The LSM takes advice from RIMs about the impact of Engineering and BDS issues affecting performance of the RI System and is responsible for managing the overall system to achieve the Preparedness targets authorised by the Board.

The LSM is responsible for notifying the Board as soon as he or she identifies that preparedness targets may not be achieved.

S RI Manager. The RI Manager is the'hands on' manager of the RI system for the operational system or subsystem.

The Repairable Item Manager (RIM) manages a range of Rls on behalf of the LSM.

In most situations several RIMs will be responsible to the one LSM and each RIM will have a range of RIs to manage.

••"The RIM is responsible for managing the RI availability and distribution to ensure that serviceable target levels are maintained. To achieve this the RIM: Ensures that the design of the RI System is appropriate to achieve availability targets.

Monitors the operational requirements provided by the Operations Authority to identify when exception action or system redesign is required.

11 Monitors the dynamic performance of the RI System for each RI type and initiates exception action when required to achieve availability targets.

Monitors the average performance of the RI system for each RI type and initiates: RI system redesign when required.

Advice to the LSM that Enqineering action may be required for an RI tvoe.

Provides work priorities to the Repair Venue Managers.

Repair Venue Manager. The Repair Venue Manager is responsible for managing the actual repairs of RIs.

The Repair Venue Manager (RVM) is responsible for managing the throughput of RIs in a maintenance workshop. The RVM sets short term workshop priorities to achieve the RI System Design Time To Repair which is the time from when the item enters the Repair Venue until it leaves. This includes the actual Time To Make Serviceable (TMS) (ie hands on repair time) plus administrative and logistics delays within the Repair Venue. The RVM is responsible to the RIM for achieving reduced TTR to meet short term priorities.

It will be appreciated that the present invention has a number of advantages over known RI processes, disadvantages of which variously include the following:- Known RI processes are based on initial modelling using sophisticated software modelling tools. The modelling tools are very good but often the data used as the basis of the models is 'generic' particularly 'Tumrn Around Time This results in predicted spares requirements which are at best questionable and not optimal.

Known management techniques are normally based on the modelling but not monitored against the original model parameters which results in largely ad hoc management. Management intervention usually occurs only after a problem has eventuated (eg spares required are not available). The process to recover the situation is expensive and the damage has already been done.

Typical management systems are fragmented with different organisations responsible for different parts of the process and no single organisation has management responsibility for the full process. The lack of active monitoring of the system means that there is no process in place to identify significant ,deficiencies in the system or opportunities for improvement.

Known RI processes comprise complex and fragmented processes, information and responsibilities. People are focused on their own micro-element with no one having overall understanding, visibility or responsibility. With the fragmented process people aim at local performance measures which often detract from the overall RI performance.

There can be excessive delays in known systems, particularly Logistics and Administrative delays because of the fragmented system.

Inadequate analysis and reactive responses to short term problems have resulted in additional spares being purchased and in many cases there are too many spares in known systems allowing even less discipline in management, exacerbating the problem.

With some few exceptions the primary focus in known systems is on meeting routine requirements with little consideration of how the system can cope during peak use periods.

RIs are not managed as a total system but separately for in-use and spare items. The RI System is considered to be the RI repair pipeline (excluding the installed items) RI spares requirements are determined using sophisticated software models but the models are based on a single Tumrn Around Time (TAT) and the TAT used is generally based on routine usage rates.

Typical spares modelling in known systems uses a range of simplistic inputs which do not reflect real word variability. These limitations often result in suboptimal outputs.

S A typical known RI process uses the number of spares as the primary variable to manage the RI system. This is difficult to correct after the initial purchase and is a poor means of controlling the RI system, it being difficult to vary the number of spares once they are purchased. Normally there is no way to recover costs if excess spares have been procured initially.

The preferred embodiments of the several aspects of the present invention variously consider all the disparate elements of RI related processes as an RI System as a whole. It then optimises the overall process with consideration of routine and peak use requirements. It documents the overall process and responsibilities in a realistic and holistic way. It facilitates pipeline design and eliminates avoidable Logistics and Administrative delays in the system.

The system of the present invention continues to use the software modelling tools currently in use but adds a new level of sophistication by allowing variable Turn Around Times (TAT) to be used. This enables determination of initial spares purchase and/or allows optimisation of the system with existing spares. The system defines how the spares will be managed for peak and routine usage rates. Furthermore. by using variation in TAT as the primary means of controlling the RI system, it proactively manages the RI System using near real time monitoring to dynamically control TAT to satisfy variations in demand.

The system monitors the overall performance of the RI system against the original design parameters to enable validation of the initial design parameters as necessary to reflect real world events, and considers whether engineering design changes should be implemented to improve system performance.

Consequently the preferred embodiments of the several aspects of the present invention variously have a number of advantages over known RI systems including the following:- The present invention optimises the number of spares required and will result in fewer (or at worst the same number) of spares being required as current models, for any given scenario. It may however, highlight that the spares predicted by the current models are inadequate to support peak usage rates. However, even in this case it will require less spares than would be predicted by other models.

For any given number of spares, the present invention enables a higher level of equipment availability to be achieved because the inherent efficiency of the RI repair pipelines will increase the ratio of serviceable items to unserviceable items within the RI system, and the near real time monitoring coupled with dynamic feedback controls will, in most cases, enable potential problems to be identified and resolved using predetermined processes before an actual spares shortage occurs.

Monitoring of actual RI system performance will enable validation of the original system design parameters. If these were wrong or have changed, the design needs to be revised to accord with the actual parameters. If the actual performance of the system is considered unacceptable, engineering design changes can be considered to improve its performance.

Design of the system to meet peak usage rates means that organisations can better sustain high rates of usage.

It will of course be realised that whilst the above has been given by way of an illustrative example of this •invention, all such and other modifications and variations hereto, as would be apparent to persons skilled in the art, are deemed to fall within the broad scope and ambit of this invention as is herein set forth.

DETAILED ANALYSIS OF HIGHER LEVEL PRISM PROCESSES Initiate PRISM Principle The RI System must work within Preparedness requirements defined by individuals with the appropriate authorities.

The authority of individuals must be assigned and these individuals must define the overall Preparedness requirements for the weapon system that the RI system is required to meet.

99 Without formal appointment of authorities, there can be no external accountability for the RI system and the definition of performance requirements is essential for the design and assessment the system.

Context Initiating PRISM is the first process and is instigated to assign responsibilities and the high level system performance requirements.

(SEE FIG Process Description

C~JIH'

0 .1 1 of -,I;tIC RS COG to a!Cct an oc .c-.rmc t c c the responsibility of the Board but the Logistics Support Manager performs most of the work. It includes the following !!hree s ,hnrnccses P1 Appoint Logistics Preparedness Board.

Appropriate individuals are appointed to the Logistics Preparedness Management Board. This requires senior management to formally appoint the individuals to positions and for the appointees to sign off on their responsibility statements.

P2 Appoint Logistics Support Manager.

The Supply Authority appoints the Logistics Support Manager on behalf of the Logistics Authority. The Logistics Support Manager may belong to the customer organisation (Defence) or the suppler organisation (contractor).

P3 Define Preparedness Requirement--.

The Logistics Preparedness Management Board provides the overall requirements for the RI System to meet. This is defined in terms of the Preparedness requirements contingencies and the peacetime Rates of Effort (ROE) Design PRISM Principle The RI System must be designed to meet the specified Preparedness Requirements. The primary objective is to be able to sustain the wartime operational requirements (OLOC). However, there is also an imperative to be able to operate cost effectively in peacetime.

Context This process is fundamental to PRISM as it is where the system design and the associated parameters are determined.

The Logistics Support Manager appointed in Initiate PRISM (1P) takes the Preparedness Requirements provided by the Logistics Preparedness Requirements also in Initiate PRISM (1P) and follows the Design PRISM (DE) process develops the overall design for the RI System.

Design PRISM (DE) provides the input for Implement PRISM (IF) and sets the parameters against which the RI System performance will be monitored in Operate PRISM (OP) and Review Design Parameters (RD).

*30 The Design PRISM (DE) is revisited whenever a system redesign is initiated from Monitor RI System Performance (MP).

(SEE FIG 6) *****Process Description The purpose of the Design PRISM process is to provide the overall design of the pipelines and the control processes and parameters. It is the responsibility of the Logistics Support Manager It includes the following eight subprocesses: DEl Design PRISM Management Structure People need to be appointed to undertake the work and to make decisions. The RI System management structure is designed based on the PRISM Organisation Structure. This process includes the development of responsibility statements for appointments. Some appointments may belong to the customer organisation (ie Defence) and some to the supplier organisation (contractors).

DE2 Design RI Pipeline.

The RI pipeline is designed. This includes identification of the repair venues and associated repair times transport arrangements and delay times.

DE3 Determine OLOC Parameters.

The operational usage, logistics and engineering data required to predict OLOC RI requirements is determined.

DE4 Determine MLOC Parameters.

The operational usage, logistics and engineering data required to predict MLOC RI requirements is determined.

Determine RI Spares Required.

The number of spares required is determined. Normally this would include the use of a modelling tool such as OPUS and PRISM Tools.

DE6 Determine Trigger Points.

The trigger points where intervention will be required are determined using the PRISM Tools.

DE7 Design Support Information System.

The RI system needs to be managed. In particular the location of all RIs must be readily available at all times. Normally a maintenance or logistics management information system is used.

DE8 Develop Procedures.

The procedures for managing the RI system must be developed. These will often be dependent on the type of information system tool selected.

Guidance Note Most of this to move to the DE subprocesses.

RI Pipeline Design Principles All RIs which are to be maintained at DM venues must have a defined method by which unserviceable items can be evacuated from the operational level to one or more repair venues. The repair pipeline for each item must be designed with conscious consideration of each attribute of that pipeline.

For each individual RI, the repair pipeline should: Identify the shortest practical TAT for normal operation; Identify the shortest possible TAT, achievable using manual intervention by the RI Manager from the time an item is first made unserviceable; Separately identify normal administrative, logistics and maintenance time (ADT, LDT and MTTR) components of .*°the TAT; S° 30 Separately identify the shortest possible ADT, LDT and MTTR using manual intervention by the RI Manager from the time the items is first made unserviceable on CAMM2: Provide for minimal accounting and handling of the RI between the user Unit and the maintenance facility; Allow transfer of sub-Contract items direct from the user Unit to the sub-Contract facility and back again after o completion of maintenance; Automate data capture for tracking of RI Movements, to the maximum extent practical; Ensure a high level of integrity for all data used to track RI distribution and status; Provide the earliest possible warning of deviations from critical pipeline design parameters using continuous monitoring techniques; and Expedite processes related to RI pipeline operation such as clarification of configuration issues, Engineering approvals °40 (deviations, waivers, non-standard repairs).

Determination of OLOC Requirements Overview Determination of preparedness requirements for OLOC requires operational usage, logistics and engineering data to make predictions, the accuracy of which are limited by the scope and validity of the data. In simple terms, usage data, maintenance policy and reliability data will support prediction of maintenance arisings while maintainability and logistics data will allow prediction of repair rates and spares requirements. Collectively, the predictions will allow determination of infrastructure requirements to support the predicted work throughput at OLOC (readiness). Additionally, predictions will ensure that the rate of (OLOC) arisings is less than OLOC TAT, thus ensuring sustainability. PRISM has preparedness for OLOC as a primary outcome and is therefore clearly "structured for war".

Operational Inputs As the primary goal of the RI System is to ensure the required level of preparedness, initial system design must confirm the capacity to support operations at OLOC. Thereafter, there is a consideration of how to move from MLOC to OLOC.

Accordingly, the single most important task to be performed once the RI repair pipeline design is completed is to model throughput using OLOC rates of effort, mission profiles/roles and venues.

Although these may not be well defined, it is imperative that every effort is made to quantify these to the maximum extent possible. Close consultation with operational authorities will allow use of the most authoritative data available.

Logistics Inputs Logistics inputs describe equipment design parameters pertinent to support, and the support environment. The design parameters provide reliability and maintainability data as primary modelling inputs while the description of the (OLOC) support environment wiil allow consideration of support venues arnd Lheir iocations, transport arrangements, resourcing levels (particularly manpower) and how these affect RI repair pipeline design. It is important to note the impact of removal of embedded MRU staff during OLOC activities.

Engineering Inputs The primary engineering inputs to OLOC considerations are maintenance policy considerations, possible variations to scheduling of maintenance activities being a prime criterion. However, consideration of time delays associated with approvals for battle damage repairs and non-standard repairs should also be considered if possible. At the least, the effect on TAT of additional delays of this type should be considered. In practice, most of these delays would probably be offset by additional resourcing levels although, qualified human resources may be scarce if the OLOC scenario is one involving all FEGs.

OLOC Throughput Using usage and reliability data, the number and rate of maintenance arisings, both scheduled and unscheduled, is •:*calculated. All elements of the repair pipeline must then be reviewed to ensure sufficient capacity exists to handle this level of throughput at the standard design TAT. Additionally, the ability to manage throughput for arising rates not less 30 than TAT (normal), see FIG 3, must be confirmed.

In the event that the repair venue are unable to sustain operations at the OLOC rate of usage, a plan to create a: additional capacity within the warning period is required as a minimum. Alternatively, to provide a higher level of assurance of preparedness, immediate investment could be made to create the additional capacity.

Where infrastructure (facilities, equipment and manpower) are shared across multiple RIs, the OLOC requirements S 35 review must consider all RI throughput from all FEGs to be at OLOC at the same time. Additional information should be sought from operational authorities when conflict is imminent to determine whether all FEGs will assume OLOC at the same time: this seems improbable.

OLOC Spares Requirements The determination of OLOC spares requirements will, after separation of those items required for serviceable stock floor and wartime contingency requirements, provide the opportunity to use other excess assets in order to speed turnaround time. This would involve breakdown to subordinate build level to allow rapid changeout at the LRU level. The benefit to LRU TAT flows to both OLOC and MLOC and improves overall cost-effectiveness. This is an important consideration where excess assets already exist but there is little opportunity to sell the excess. Increased stocks of subordinate items may also allow smaller levels of BDS inventory to be carried, or none at all (using just-in-time procurement techniques) further reducing support costs Determination of MLOC Requirements Overview no;.rn;natiCn ,f nronr dnmoce ro9,,,iromontc fnr MI lC roi iro nnorntinnal I IsnP. Inniktir and Pnninerino data to make predictions, as per OLOC. The major difference from OLOC requirements is that the rate of effort will be innifir'fntly nlwer Other potential effects include the use of embedded MRU within contractor facilities, possible restrictions on the resourcing available for transport, administration and packing/handling.

The operational data for MLOC is more predictable than OLOC and there can also be a higher level of confidence in the validity of TAT due to the more stable repair pipeline. Equipment reliability data is not expected to change significantly between OLOC and MLOC. Overall, the data used to determine throughput, arising and repair rates should be more predictable and, in deference to asset preservation, there will be a more rigid approach to performance of scheduled maintenance activities.

Operational Inputs As the determination of OLOC requirements has confirmed the capacity to sustain OLOC, or at least quantified the shortfalls, the primary aim of MLOC design is to adapt for peace in the most cost effective way possible.

This includes modelling probability of RI spares availability with a view to minimising the number of spares required and the cost to operate the repair pipeline. At the same time, the repair pipeline is adapted for the applicable operational venues and all RI movements between in-use and maintenance locations are expedited wherever cost-effective.

PRISM design principles will be applied to all aspects of RI management to minimise ADT and LDT effects on TAT.

Use of these design principles will significantly enhance the overall efficiency and cost effectiveness of the repair pipeline during OLOC and MLOC although cost effectiveness may be traded for availability assurance at OLOC.

Additionally, benefits can be expected to accrue with regard to data integrity due to the use of continuous data capture and regular review of design parameters. Improved confidence in data used for modelling spares and pipeline operations will inevitably allow for better management of RIs and therefore, higher levels of operational capability for a given level of resourcing.

Logistics Inputs os The logistics design parameters for the MLOC support environment will most likely involve the same support support venues and locations although transport arrangements are expected to be somewhat different. Additionally, resourcing levels for both manpower and spares can be traded against availability if desired. Careful use of failure distribution *30 probability in conjunction with pipeline design parameters such as TAT will support this type of value judgement.

Engineering Inputs The primary engineering inputs to MLOC considerations are maintenance policy and lifing criteria. The relatively benign operating environment associated with MLOC provides the opportunity to analyse failure data and identify candidates for reliability or maintainability improvements. The PS Management Consultants RI System supports the identification of these candidates by using the data captured at both OM and DM venues.

MLOC Throughput As throughput capability for OLOC is expected to exceed that of MLOC, throughput considerations are restricted to those necessary to determine resource levels and sparing. RI spares requirements will have been determined by OLOC considerations but there is an opportunity to minimise MLOC support costs by judicious use of just-in-time BDS procurement. The use of subordinate RIs (SRUs) is critical to the success of this approach.

Management of Obsolescence Management of obsolescence is an increasingly important issue in RI management which requires careful analysis of risk and cost. This is particularly true for avionics equipment which typically has a large number of lines of BDS with a high turnover rate (ie the rate at which items are replaced by alternative items of similar or upgraded performance).

Most OEMs propose a low risk, high cost strategy to manage obsolescence. Normally, the proposal is for the customer to purchase a comprehensive range of BOS for LOT, at the same time as RIs are purchased. These are then maintained in a "bonded store" for the customer and used as required. Frequently, the quantity and type of spares proposed by the OEM lacks analytical rigour; the numbers may have no relationship to the number fitted or the individual component reliability. Moreover, for new equipment, the reliability of the equipment and many of the components are unproven making it almost impossible to accurately predict LOT requirements.

PRISM incorporates consideration of obsolescence management risks into the BIDS procurement strategy and in~torr.ace t*Mis wrilh onninoflflf m~nnamant fn nht2in fAct affartisv *nro Determine Tolerance for Pipeline Parameters Overview In the event that all parameters affecting RI repair pipeline operation were totally quantifiable, design of the RI System would be a simple matter of applied mathematics. In practice, for fielded systems, data is of variable reliability because of anomalies in reporting and collection. Moreover, the statistical validity of data sets must also be considered.

As equipment reliability improves and failure events decrease, the timeframe required to gather a valid failure data set also increases. Other aberrations such as changes to reliability/maintainability brought about by modification or redesign must also be considered, although these would normally be expected to enhance pipeiine operation and therefore not impact negatively on availability.

Arising Rate and TAT Variation The most critical aspects of repair pipeline design and operation are arising rates and TAT. Those data sets which support analysis of the extent of variation of arising rate and TAT from the mean values must be carefully assessed for accuracy and validity. For fielded systems, maximum possible use is to be made of historical data from CAMM/MAARS while new systems must be modelled using OEM supplied data (either fielded data from different users or predicted).

For the future, the RI Management System will make extensive use of the highly reliable data on both OM and DM activities provided by CAMM2. Progressively, CAMM2 data will accumulate and become statistically more significant leading to higher confidence in key data.

Ultimately, regardless of the source of pipeline design data, tolerances must be placed on Arising Rate and TAT. These tolerances represent the level of confidence in the data used and the modelling method chosen. The tolerances will be ~o a subjective judgement based on the aggregate risk associated with each contributory data element. Pipeline design then considers the probability of failures occurring within these tolerances such that availability remains unaffected. A so design target will be applied which equates to a probability of availability of the RI. Achievement of availability of 100% 0.0 30 is not cost effective so the actual target will be a negotiation issue between support and operational agencies.

.The probability of failures occurring outside of the prescribed tolerances, and therefore affecting availability, are the inherent level of risk for that RI Management System. As data collected by CAMM2 is applied to repair pipeline design, see* 0: and as each repair pipeline matures with the concomitant reduction in performance variability, the inherent risk should diminish.

Arising Rate Tolerance The probability of failure curve represents the number of expected maintenance arisings plotted against elapsed time.

Care must be taken to map this figure accurately using recorded failure data wherever possible. For items with scheduled maintenance, this curve represents the aggregate of the scheduled and unscheduled arisings. For "oncondition" items, the curve is simply probability of failure.

.40 The availability design target is represented by the Ait line. The shaded area between Ait and the origin of the failure curve represents those failures which vary so much from the mean arising rate that the Commonwealth is prepared to accept a loss of availability rather than fund additional pipeline capacity or buffer stocks. TAT(min) is capable of repairing items slightly faster than the arising rate for items failing at Ait. In practice, TAT(min) may exceed the arising rate for items at Ait and availability will be provided by buffer stock. In this circumstance, a succession of items at this increased rate of failure would rapidly lead to consumption of all buffer stock: additional failures beyond this point would lead to lost availability.

Regarding the relationship of arising rate, TAT and buffer stock to RI availability, it is readily apparent that, as the total number of assets in the RI System remains constant, the asset distribution reflects the ability of the repair pipeline to respond dynamically to failure rate variations. Buffer stock provides assurance against short term variability of arising rates.

The options of funding reduction in TAT (normal) toward TAT(min), purchasing additional buffer stock or accepting a A;,r rrzc d rsign rncjertrntons I ttimata, here are nprctirni limitz tA tha Amnnt that TAT C-qn hp rpdifprl and then buffer stock is the only alternative to lost availability.

Implement PRISM Principle Once the system has been designed and a decision taken to proceed the system must be put into place. This requires the staff to be appointed, the maintenance, storage and transport arrangements and information systems to be implemented.

Context In this process the RI System design developed in Design PRISM (DE) is put into place.

(SEE FIG 7) Process Description The purpose of the Implement PRISM process is to put the design into practice by implementing the physical design and loading data and design parameters into the supporting implementation tools. It includes the following four subprocesses: IM1 Appoint Staff to Positions.

IM2 Implement RI Pipeline.

IM3 Execute Maintenance Contracts.

25 IM4 Implement Support Information Systems.

Operate PRISM Principle The RI system must be continuously monitored and controlled to ensure that appropriate action can be taken as soon as any of the design parameters exceed system tolerances. This process comprises the RIMs day to day process Context (SEE FIG 8) 35 The RIM monitors the system performance against the design parameters and initiates corrective action to keep the system functioning. Deficiencies beyond the control of the RIM are reported to the Logistics Support Manager.

Process Description The purpose of the Operate PRISM process is to perform the day to day management of the RI System. It is the S responsibility of the RI Manager. It includes the following six subprocesses: OP1 Monitor Operational Demand.

The RIM monitors information passed from the operational units to identify predicted surges or other changes in operational usage which might impact on RI requirements.

OP2 Monitor Automatic Triggers.

The RIM monitors asset levels at locations against the system design triggers to identify whether any exception actions is required.

OP3 Monitor System Performance.

All parameters which have been or will be captured using operational and maintenance management databases will be used in the initial design using PRISM. For aviation, it is expected that CAMM2 will progressively become the prime software tool for data capture. Other suitable software includes MIMS. Monitoring serves two main purposes; to provide the warnings necessary for management of throughput and to provide the data with which to identify continuous improvement opportunities. Major considerations are to verify throughput, demand rate, asset distribution, actual failure rate and achieved TAT (normal and minimum). Longer term considerations include monitoring parameters for use in the vaiidate System Design process. The critical issue with performance monitoring is the timeframe in which it is conducted. Real time monitoring is the optimum and system responsiveness (and efficiency) will inevitably decrease as delays in failure and asset distribution data increase.

OP4 Manage Administrative Delay Time and Logistics Delay Time.

Manage Throughput.

OP6 Report Deficiencies.

Guidance Automatic Trigger Values The Basic RI Repair Pipeline All RI Repair pipelines are designed around mean arising rates and mean TAT. Items in use do not fail individually at these values. Buffer stock is used to even out the availability of spares to operational agencies and smooth the workflow requirements within the repair venues. The size of the buffer stock is normally limited by cost considerations thus generating the requirement to assess risk to availability for a given level of financial constraint Tolerances are applied to parameters to define the level of risk considered acceptable for normal pipeline operation. Beyond these tolerances, managerial intervention is required to reduce the risk of lost RI availability.

Pipeline Health Indicators Assessment of the health of a repair pipeline has two main points of focus. Does it meet operational availability requirements and does it meet logistics agency requirements. This dual focus results in the need for multiple indicators, not just achievement of Ait. It is clear that operational availability is relatively simple to achieve if unlimited funds are available.

A repair pipeline can be considered to be healthy, and therefore require no outside intervention (or re-design), if the distribution of assets within the RI System provides: 30 an uninterrupted flow of serviceable assets to the operational user(s); and a consistent flow of work to the repair venue, such that work priorities are not regularly rescheduled.

eeeee Additionally, in achieving these two aims, the buffer stock level may fluctuate between zero and the design maximum but not reach a minus stock level (ie an unsatisfied demand from operational users which is outside of the design limit, the Ait).

Clearly, the relative distribution of assets is a simple and reliable indicator of health. It provides ready visibility of buffer stock capability to absorb fluctuations in failure rate and an immediate indicator of the probability of future operational availability. Therefore, asset distribution is a useful tool to use as an automatic trigger for RI manager intervention in the repair pipeline, should this become necessary. The asset level trigger shall operate whenever buffer stock levels reach •a point which, after consideration of TAT(normal) indicates a probability that buffer stocks may fall to zero. At this point 40 the RI Manager would intervene to invoke a high priority repair at the repair venue with a view to restoring buffer stock levels before the next failure occurs.

Use of asset distribution alone is insufficient to avoid buffer stock levels falling to zero. There is a finite period of time required for repair and, if failures occur at a rate greater than TAT(normal), buffer stock levels will progressively fall.

Under these circumstances, RI manager intervention may reduce the restocking time to TAT (min) if required. Provided that the rate of failures is less than the rate of repair at TAT (min), buffer stock levels will rise.

Arising rate may therefore be a harbinger of ill health in the repair pipeline. It provides earlier, though less reliable indication that intervention may be warranted, well in advance of critical asset distribution levels being reached. For pipelines with limited throughput capacity and long TAT, arising rate triggers may provide warning of an impending stock out situation many months in advance of the event. Arising Rate trigger points will be set based on the RI Managers understanding of the repair pipeline (particularly whether items can be repaired serially or in parallel), throughput capacity and, TAT(min) compared with the rate at which items are committed to the repair pipeline.

It is important to note that, prediction of arisings for RIs subject to scheduled maintenance may also provide warning in advance of throughput excesses. Modification and STI action may also produce similar outcomes. Immediate prioritisation of existing work, prior to these extraordinary workloads may alleviate later throughput and floorload problems within maintenance venues.

Manage RI Reoairs Context (SEE FiG 9) Process Description The purpose of the Manage RI Repairs (MR) process is to to ensure the effective throughput of RIs through each maintenance venue. It is the responsibility of the Venue Repair Manager. It includes the following four subprocesses: MR1 Control Production (Throughput).

The balance of throughput against customer demand will occur routinely if the RI System is properly designed. Only when failure or repair patterns are outside of the design tolerance should there be a requirement for RI Manager intervention. This intervention will take the form of a direction for priority action at one or more (previously identified high leverage) points in the repair pipeline for one or more unserviceable RIs. Intervention will normally only be instigated o because of operation of one of the automatic triggers which continuously monitor system performance and business case requirements. Management of throughput should be identical for both OLOC and MLOC but there will inevitably be a requirement for more intervention during ramp-up as it is uneconomic to manage ramp-up in a fully sustainable way. Buffer stock and more frequent intervention will be used in lieu of a large investment in overall system capacity increase.

MR2 Forecast Facility Workload.

This process is the responsibility of the RI Manager and is designed to allow forward planning of maintenance resource requirements. This will allow facilities infrastructure maintenance, GSE maintenance and calibration, workforce development and human resource management activities to be co-ordinated to the maximum extent possible. A forecast will be produced quarterly covering one year's predicted workload. Forecast updates will be issued whenever warranted for abnormal or unforeseen requirements such as STIs or Modifications.

MR3 Forecast breakdown spares (BDS) Requirements.

For scheduled maintenance, BDS Requirements forecasts (BOMs) flow directly from scheduled maintenance forecasts and will be issued quarterly or as required in concert with STIs and Modification Orders. BDS requirements for unscheduled maintenance activities are much less predictable and are outside of the jurisdiction of the RI manager.

BDS provisioning responsibilities will however normally come under the same Supply Authority as the RI Management.

Accordingly, BDS provisioners will be provided with forecasts of predicted unscheduled maintenance arisings at least S"annually. These should be used in concert with organisational BDS provisioning strategies to ensure that LDT does not exceed design parameters, on average, for all unscheduled maintenance arisings.

MR4 Assign Workshop Priorities.

This process is one of the management techniques used to control throughput. It will require re-scheduling of work within the repair facility and may also require overtime to be worked. It has variable potential to alter total TAT depending on the nature of the work to be performed and will normally result in some drop in efficiency within the workshop. This process is the least preferred method of altering TAT and will normally only be used when TAT(min) is the desired outcome.

Manage Distribution Context S (SEE FIG Process Description The purpose of the Manage RI Repairs (MR) process is to to ensure the effective throughput of RIs through each maintenance venue. It is the responsibility of the Venue Repair Manager. It includes the following four subprocesses: MD1 Manage Distribution.

Monitor RI System Performance Context (SEE FIG 11) Process Description The purpose of the Monitor RI System Performance process is to manage the overall performance of the RI system to ensure that it meets operational requirements in the both the short and long terms, and remains cost effective. It is the responsibility of the Logistics Support Manager. It has the following four subprocesses: MP1 Assess Operational Demand.

MP2 Assess RI System Performance.

MP3 Initiate PRISM Redesign.

25 MP4 Initiate Engineering/Maintenance Review.

25 Review PRISM Desian Parameters Context 30 (SEE FIG 12) Process Description The purpose of the Review Design Parameters process is to identify situations where the RI system performance is outside the PRISM design parameters and therefore the design parameters need to be updated. This situation is where the mean or variance values for parameters (eg TAT, arising rate have varied) and not when the system is displaying normal variability. It is the responsibility of the Repairable Item Manager It includes the following two subprocesses: RD1 Monitor System Design Parameters.

The RI Manager will use data gathered through system performance monitoring to validate the system design and the input parameters used. The data used to predict, the mean demand rate and the probability of variations, and the 40 throughput, will be validated against the design figures not less than annually. These are the key drivers for overall system performance although statistical analysis of the frequency with which automatic triggers are activated will also be a useful indicator of validity of the system design itself as opposed to the input data used within the system software models.

RD2 Identify Candidate Items for Review.

This process delivers candidate lists for MRD/MEA review. Data captured from the Monitor System Performance process will be analysed against defined criteria to identify items with deteriorating reliability or maintainability, or items with wear characteristics which are inconsistent with the scheduled maintenance activity being performed on them. To 22 ensure that engineering analysis is cost-effective, item cost data will also be included in the selection criteria. Items subject to scheduled maintenance activities will also be considered for review.

Guidance RI Manager Intervention Criteria Overview The RI Manager will design a pipeline which requires intervention only rarely. The challenge is to have the RI System operate as efficiently as possible which means that occasionally, repair at the TAT (normal) rate will be inadequate. The philosophy is to resource to the normal and manage for the abnormal.

Under abnormal circumstances, the RI manager will intervene to change priorities within the repair venue, expedite BDS replenishment, arrange priority transport and expedite all administrative activities associated with the pipeline. These actions and the effect which they can have should have all been pre-determined during pipeline design as part of the determination of TAT (min) Frequent intervention though, is also inefficient because of the disruption it causes to production planning activities.

Parameters Out of Tolerance There will also be occasions when the RI Manager will intervene in RI System activities because review of RI System performance criteria indicates one or more parameters are outside of tolerance. This will inevitably lead to lost availability at one end of the scale, or wasted resources at the other.

Intervention in these circumstances will aim to establish the nature, extent and reason for the variation(s). Remedial action or re-design will be implemented for those variations which inhibit effective RI System operation. Those variations which arise from efficiency improvement in one or more areas of system operation will result in re-design of the RI System to ensure that maximum benefits are realised.

Candidate Items S2 The RI Manager will monitor OM and DM maintenance activities actively seeking candidates for reliability and maintainability improvement. Scheduled maintenance items which routinely fail prematurely, and those which never display expected wear characteristics at the scheduled maintenance event are equally candidates for MEA. Items with deteriorating MTBF or ever lengthening repair times would also be reviewed.

S- Reduced Support Costs This type of intervention aims to improve or maintain airworthiness and mission effectiveness while, at the same time, reducing MDT and support costs. The success of this initiative depends to a large extent on the willingness of engineering authorities to perform MEA and/or fully investigate the cost effectiveness of re-design/modification as suggested by the maintenance data. This can be an expensive exercise but the rewards would almost inevitably be far greater. The ability of the PS Management Consultant RI System to then translate improved equipment reliability and' maintainability into tangible preparedness and support cost reductions is unique.

35 The full extent of benefits resulting from this approach is normally underestimated. Improved equipment reliability and (justified) extended scheduled maintenance intervals in particular result in an immediate reduction in MDT and improved Ao. Moreover, there is also a reduction in the manpower requirement at the operational level, or an increase in flexibility and surge capacity if the manpower is retained. These are highly desirable attributes at all times but most particularly at o OLOC.

Direct PRISM Context (SEE FIG 13) 23 Process Description The purpose of the Direct PRISM process is to provide high level performance requirements and direction for the RI System. It is the responsibility of the Logistics Authority with the support of the other members of the Logistics Preparedness Management Board. It includes the following four subprocesses: DP1 Specify Preparedness Requirements.

DP2 Specify Logistics Priorities.

DP3 Identify Changes in Operational Parameters.

DP4 Review RI System Performance.

*a ee

Claims (13)

1. A repairable item management process for a logistic support system in which unserviceable items from a plurality of item types are repaired to become serviceable items, the process being controlled in accordance with a logistic model utilising a piuraiity of mudei parameters rep.- nrn, c n har-C',t- cs of the syste.m nt least one of said parameters being a mean value of an operating characteristic, said process including:- modifying the mean value of said operating characteristic in response to said monitoring, and adaptively controlling the repairable item management process by revising the logistic model to include said modified mean value as a modified parameter.

2. A repairable item management process as claimed in claim 1, wherein said monitoring and said adaptive control is in substantially real time.

3. A repairable item management process as claimed in claim 1, wherein one of said parameters is, for each item type, the mean turnaround time between the arising of the need to repair an item of that type and when the item is repaired, said process including:- monitoring the elapsed time between the arising of the need to repair an item and when the item is repaired, said elapsed time being the turnaround time for repairing the item; modifying the mean turnaround time for that item type in response to the elapsed time thus monitored, and revising the logistic model to include the thus modified mean tumaround time for that item type.

4. A repairable item management process as claimed in claim 1, wherein for a given operating characteristic said parameters include:- a first parameter indicative of the mean value of the operating characteristic during routine conditions, and a second parameter indicative of the mean value of the operating characteristic during peak use conditions.

5. A method of controlling a repairable item management process for a logistic support system in which unserviceable items from a plurality of item types are repaired to become serviceable items, the process being controlled in accordance with a logistic model utilising a plurality of model parameters representative of operating characteristics of the system, at least one of said parameters being a mean value of an operating characteristic, said method induding:- utilising said logistic model to predict the parameter value representative of an operating characteristic given at least one known other parameter value; monitoring said operating characteristic to determine the actual parameter value thereof; 35 comparing said predicted parameter value with said actual parameter value, and omodifying the logistic model to cause the predicted parameter value to correspond with the actual parameter value.

6. A method of controlling a repairable item management process for a logistic support system in which :unserviceable items from a plurality of item types are repaired to become serviceable items, the process being controlled in accordance with a logistic model utilising a plurality of model parameters representative of operating characteristics of the system, at least one of said parameters being a mean value of an operating characteristic, said method including:- determining a desired parameter value of at least one operating characteristic: monitoring said at least one operating characteristic to determine the actual parameter value thereof, -comparing said desired parameter value with said actual parameter value, and modifying the system to cause the actual parameter value to correspond wth the desired parameter value.

7. A method of designing a logistic model for controlling a repairable item management process for a logistic support system in which unserviceable items from a plurality of item types are repaired to become serviceable items, the logistic model utilising a plurality of model parameters representative of operating characteristics of the system, at least one of said parameters being a mean value of an operating characteristic, said method including:- monitoring said operating characteristic to determine the actual parameter value thereof; building the logistic model with the parameter value equal to the actual parameter value. monitoring other operating characteristics: modifying the mean value of said operating characteristics in response to said monitoring, and mnrdifvinn t h p Irnnitir. mnrp.l hv indlrling the thus modified parameters. a.

A rpnairmhle item management system for loqistic support in which unserviceable items from a plurality of item types are repaired to become serviceable items, the process being controlled in accordance with a logistic model utilising a plurality of model parameters representative of operating characteristics of the system, at least one of said parameters being a mean value of an operating characteristic, said system induding:- monitor means for monitoring said operating characteristic, and a computer programmed to include said logistic model, to modify the mean value of said operating characteristic in response to said monitoring, and to adaptively control the repairable item management process by revising the logistic model to include the thus modified parameter.

9. A repairable item management system for logistic support in which unserviceable items from a plurality of item types are repaired to become serviceable items, the process being controlled in accordance with a logistic model utilising a plurality of model parameters representative of operating characteristics of the system, at least one of said parameters being, for each item type, the mean turnaround time between the arising of the need to repair an item of that type and when the item is repaired, said system induding:- monitor means for monitoring the elapsed time between the arising of the need to repair an item and when the item is repaired, said elapsed time being the turnaround time for repairing the item, and a computer programmed to include said logistic model, to modify the mean turnaround time for that item type in response to the elapsed time thus monitored, and to adaptively control the repairable item management process by revising the logistic model to include the thus modified mean turnaround time for that item type.

:10. A repairable item management process for a logistic support system substantially as described with reference to the drawings.

11. A method of controlling a repairable item management process for a logistic support system substantially as •described with reference to the drawings.

12. A method of designing a logistic model for controlling a repairable item management process for a logistic support system substantially as described with reference to the drawings.

13. A repairable item management system for logistic support substantially as described with reference to the drawings.