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A flexible Data Model for Parts Interchangeability and Supersession in SAP SCM

In an ongoing SCM project, we had to implement global ATP and supply chain planning for interchangeable parts. In the military supply chain, this issue seems quite common, so it’s maybe worth to write down our current findings and invite others to discuss. In this blog, I will explain our current SCM master data model.


At first, it was quite tricky to identify the relevant I&S data feeds. We deal with some distributed system landscape, where knowledge around parts interchangeability is decentral and widespread. We identified feeds from own engineering and maintenance systems, from the manufacturers, from kits and assemblies management and finally a variety of I&S information collected manually by the MRP controllers and procurement. The spectrum of materials spans over both consumables and spares. Material values span from low value commodities to complete aircraft replacement units. Not all, but most feeds are utilized at the moment.


Along with the SAP implementation, some of the material management was shifted to manufacturer part numbers. MPN tracking delivers another standard class of I&S information.  The existing Supersessions and Form-Fit-Function equivalencies are just extended by MPN explosion. Thus, we found a quite standardized mix of one-way and two-way material master relationships to tackle with. These build up a relationship network composed of FFF nodes and SSC edges.


We were then quite successful with mapping these I&S relations into the existing SCM master data solution. Check out /INCMD/UI transaction in APO. In the pic below, you can see such a mix of FFF and SSC relationships modeled into a network. In SAP terminology, this is called a Product Substitution Procedure composed of FFF and SSC.


Product Substitution Procedure with FFF and SSC


We use these master data in gATP and CTM planning. gATP traverses the network depending on the exact start node. CTM utilizes the network more generally as a set. When one-way relations are contained in the network, there are adjustments on how stocks are incorporated into the planning run. Basically, stocks of superseded material is counted less than 100%, since it’s only partially usable.


There was some minor development work around this solution using existing SCM Badi’s, but no modification of the APO standard code was needed so far.


In future, we plan to extend the solution towards gATP ‘by tail number’. Even in a distributed landscape, it seems feasible to map individual weapon system configurations into SCM and build an exact provisioning solution. Basically, the existing Badi’s allow you to switch the edges in the product graph shown. We can turn nodes and edges on and off by weapon system or even by individual equipment.


Remark, there are ‘many ways to Rome’. The ideas presented here are just one. I tried to focus on more general findings, which may also apply to other planning mechanics like SPP or A&D rotables planning. The master data model should be adaptable to other environments.

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      Author's profile photo Former Member
      Former Member
      Wolfgang, I am very interested in the discussion area of your blog.  I spent 3 years working on this issue with Navy ERP. We were significantly handcuffed by the Navy decision not to implement APO, since the Navy supply organization insisted they had to keep using Manugistics APS.  The Navys I&S and the DLA's requirements were vastly more complex and they were successfull in having the DEIG push their requirements for a long term solution. 
      It became obvious, after a period of time, that the "complexity" came from or was a result of organizational issues within the Navy.  The Navy engineering organizations, had passed off the responsibility for Interchangeability and Substitutability, to the Navy supply organization (NAVSUP).  Part of the Navy supply is managed by DLA, and part by NAVSUP.  The whole thing was an exercise in frustration. The existing system is so disfunctional that the fleets deploy with billions of dollars worth of unusable inventory. (large quantities of which are now on the ocean floor).    Your comment .........."it seems feasible to map individual weapon system configurations into SCM and build an exact provisioning solution"... is right on the mark. Until the Navy gets a handle on the configuration managment of thier individual weapons systems, and makes thier Engineering Organizations responsible for Interchangeability,  they will never solve this problem.  Building a solution in SAP that incorporates their current SCM philosophies will streamline a horrible process, that will keep feeding the ocean foor.  
      Author's profile photo Former Member
      Former Member
      Blog Post Author
      Hello Hugh,

      thank you for your valuable comment. Indeed, we faced and still face exactly the same issues here in Europe. SAP ERP isn’t powerful enough to cover supply chain issues under complex engineering restrictions. SAP SCM master data is well prepared to capture this.

      However, the key driver for an engineering I&S Solution is within ERP. In SAP, it’s CCM Asset Configuration control. The new DEIG triggered SAP solution will deliver first integration of PM order, Config Control and APO gATP. More seems in the pipeline for 2008. You always need an engineering change system (ECM) as the lead system for I&S. Then you can feed a SCM replica database with the supply chain I&S information and the supply restrictions “by tail number”. The ECM system may be SAP, as in our simple case, or maybe some vendor owned system tightly integrated by webservices.

      We try to grab engineering data as directly as possible. A lot of tricky constructs like FFF jump-to-codes have their origin in ECM and are somehow flattened. It’s easier to shake-thru an individual aircraft config in the ECM system and just feed its allowed parts list into SCM. For an aircraft carrier, you do this around 100 times for each aircraft and get an exact overview on feasible spares. Aircraft LRU/SRU MTBF data delivers the quantities. That's all we need.

      What I presented in the blog is the first step towards such a SCM replica system. We will go live in june 2008 with the gATP solution. During 2008, engineering restrictions within our FFF networks will be added, eg. the allowed parts per individual config. In 2009, rotables planning and I&S for planning will be added.

      If you’re interested in our solution, DEIG might be a platform to further discuss the approach. But remark, we are still just in the middle of a long way to go. Don’t expect miracles.

      Best regards,