Level Of Repair Analysis

Level Of Repair Analysis
Life Cycle Cost
Logistics Support Analysis
Maintenance Task Analysis
Spares Modeling
FMECA
Reliability Centered Maintenance Analysis

The Level Of Repair Analysis (LORA) is instrumental in providing an optimized maintenance philosophy based upon a cost rational. This analysis can be implemented as a standalone analysis, but is generally integrated in the Logistics Support Analysis on an iterative basis. The LORA can be considered as a two-stage process that determines where an item is destined to be repaired and to what level. The results of the LORA process are based upon an economic and non-economic rational. The LORA can be conducted as a economical or non economical LORA, or both. If an economical LORA (ELORA) is implemented, then as a pre-requisite an non-economical (or screening) process would be implemented. This screening process will minimise the candidates, who are subject to a ELORA.

Generally the candidates would be selected and worked in conjunction with the maintenance concept. The maintenance concept would provide details about the lines (or level) of maintenance and what type of maintenance activities are to be implemented at each line of maintenance.

The objective of the ELORA, when performed correctly, is to determine the optimum cost of repair of an end item/equipment, by taking into consideration all associated support cost drivers (e.g., manpower, support equipment, training, transportation, etc.) that would be required at each line of maintenance. There is an element in the LORA process that must not be overlooked, that is the Sensitivity Analysis. Varying different LCC cost drivers will determine their impact on the model's repair decisions.

Non-Economical LORA

The non-economic LORA is based upon a set of predefined questions, as given in the example Logic Chart below. This logic could be modified to take into consideration, other maintenance constraints, as dictated by a customer, or criteria such as operational environmental restriction.

Using the Logic Tree, a response is made to each question (as given below), following the logic. This process will lead itself to establish the maintenance strategy and level of repair for each corrective maintenance task. The questions identify which of the failed units can be removed from their operational positions with a minimum amount of support resources.

When determining if an item or sub-item should be replaced and/or repaired at 1st line, consideration must be given to all aspects of the maintenance task. These include fault diagnostic techniques, accessibility requirements, task verification, elapsed task times, disruption to the operational environment etc.

Questions 1) Is the design of the item such that repair is feasible? 2) Are the item's maintenance characteristics and installation such that a remove/replace strategy is feasible at first line? 3) Does the item have lower level sub-assemblies? 4) Does item's maintenance characteristics permit a replacement action of the sub-item? 5) Does the item's configuration consist of subassemblies from multiple vendors?

Logic for the Level of Repair Analysis (CM Tasks - Non-Economical Criteria)

Economical Level Of Repair Analysis (ELORA)

Following the LORA, the ELORA provides a recommended repair strategy based upon economic rational. Consideration is also given to an item's maintainability and physical characteristics.

There are many ELORA models available that can be used for simple and complex applications. For example MIL-STD-1390 contains several model such as an Avionics Model. In the case of this model it focuses on the following six major cost drivers:

• Inventory cost - includes inventory administration cost, attrition cost, transportation, etc.
• Support Equipment (SE) - the cost of providing the necessary SE (other than standard tools and SE) for completing a particular CM task at a given level of maintenance.
• Space - required for inventory.
• Labour cost - the associated cost for personnel to complete each repair task.
• Training cost - the cost for upgrading and providing the necessary training to personnel performing a maintenance task at a given maintenance site and/ or shop.
• Documentation - the cost for developing the required documentation for each of the maintenance options.

These algorithms require specific input data for the system inherent supportability characteristics and its intended "Use" or deployment profile. System level data includes the system's expected operational life, operational profile, and site data (distances between operational centers and repair shop, including the total number of these facilities.). The item data includes Mean Time Between Failures (MTBF), cost, repair time, procurement lead times etc. It is these data elements provide the life-cycle cost data and system data used for the ELORAs.

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