Muja, O. and Lamper, D., "Automated Fault Isolation of Intermittent Wiring/Conductive Path Systems Inside Weapons Replaceable Assemblies," SAE Int. J. Aerosp. 5(2):579-589, 2012, doi:10.4271/2012-01-2241.
Automated Fault Isolation of Intermittent Wiring/Conductive Path Systems Inside Weapons Replaceable AssembliesWiring/conductive path faults inside Weapon Replaceable Assemblies (WRAs) that result in No Fault Found (NFF) or intermittent diagnosis are estimated to cost the DoD over $2B annually. To date there is no logistically supportable, standardized capability to reduce this annual cost. This report covers the development of this capability and its subsequent testing and fielding as a means to reduce this component repair costs. This new capability is called the Automated Wiring Test Set (AWTS) intermittent testing capability.To test the new capability, the F/A-18 APG-73 Radar Receiver (RR) chassis was selected due to its high repair cost and its #1 ranking as an avionics mission degrader for this type aircraft.The new capability can automatically test over 3400 conductive paths inside the chosen RR chassis using customized interface cables and replacement dummy circuit card boards for the real boards. All conductive paths can be queried and analyzed in less than a minute for static tests and less than 30 minutes for dynamic (vibration) tests. The new capability can test for opens, shorts, high impedance faults and resistors, capacitors and inductors faults. The new capability will enable the I-level and D-level technicians to quickly diagnose latent wiring faults.The end result of applying this new capability showed that 93% of all RR chassis tested had latent wiring faults; only one RR chassis had no latent wiring faults. Of the wiring faults identified, 74% were diagnosed using static tests and an additional 26% were diagnosed during dynamic testing. The 26% wiring faults revealed during dynamic testing directly contribute to the NFF / intermittent DoD annual costs.The new capability will augment the existing Consolidated Automated Support System (CASS) to eliminate latent wiring/conductive faults; CASS cannot and was not designed to diagnose wiring/conductive path faults. This new capability is scalable and adaptable to other avionic WRAs.