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ILS influences System Design

January 2, 2014

How can Integrated Logistics Support (ILS) Engineering influence System Design?

System design for defense services should be based on user/customer requirements and basic ILS requirements can and should support minimum LCC (Life Cycle Cost) by meeting the following requirements:-

  1. Number of Maintenance levels
  2. Maintenance Support personals capabilities
  3. Maintenance Training limitations
  4. Technical Manuals limitations
  5. Field Reliability
  6. Mean Time to Repair at each Maintenance level

By my experience, the above list is ordered according to importance.

The first requirement, the number of maintenance levels, should be in place before detail design starts as it is almost impossible to modify later during the detail design stage.

Any fielded system should be supported by existing maintenance personal with known abilities and learning potential and addressed early on in the detailed design phases.

Today, for example, we judge a smart phone on how simple it is to operate and maintain without using a manual or training because this concept is already implemented in modern design, and applies to other consumer products such as cameras and home appliances.   The current crop of maintainers joining the military service today have had this kind of experience.. Thus, the design team needs to be aware of this constraint – detailed, large technical repair manuals and long training should become a thing of the past!

In past years, measureable reliability, MTTR and MTBD (Mean time between Demands) were, traditionally, at the top of support requirements. Today they occupy the bottom of the list.

Today the way the industry predicts reliability is based on methods that were developed and implemented during the Second World War. For example, using these antiquated methods to predict reliability of a family vehicle we would see reliability predictions for less than 10 hours; random failures are rare and we should produce better predictions!

Today, in the defense electronic industry, commercial components are used without screening before assembly to meet military environment requirements while Environment Stress Screening (ESS) is only done at final Acceptance Test Procedure (ATP). Unfortunately the yield achieved in production forecasts the field performance but, in my experience, 100% of failures that popup during final test in production FRACAS also appear in the field while the rest of the field failures are either introduced by the maintainer/operator or Can Not Duplicate (CND).  In short, these types of failures should be eliminated by good design and training.

In practice, during the establishment of the system, the top level configuration support requirement should drive the number of maintenance levels and, additionally, how and by whom the system will be supported and operated. Once these requirements are established, detail design can start, it is difficult to influence the top system configuration once detail design started.

Summary: The first four requirements – Maintenance levels, Maintenance personel capabilities, Maintenance Training and Technical Manuals – should influence the design, through a rigorous system engineering process, at the initial stage of top level system configuration.  The next step should be to push the realization of high yields at final production stage (integration, ESS and final ATP); achieve these high yields by screening components that will be used to assemble the various subassemblies.


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  1. Ben S. Blanchard permalink

    Very nice! Levels of repair (level of repair analysis) for different major subsystems/products should certainly be included and influence item number 1 (perhaps you have already included this). I particularly like the comment pertaining to the “rigorous systems engineering process” as a vehicle for integrating logistics engineering requirements into the system design process.

  2. paul beavis permalink

    Operational requirements and costs to maintain the serviceability of the procured systems has not been placed at a level which the ILS Will be governed by.

  3. MICHEL permalink

    I’m surprised not to see obsolescence risk as a major key design factor. Selection of short life COTS in design integration (with poor after sale support) may have a major impact on in-service costs ?

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