Sustaining and maintaining aging shipboard electronics (i.e. radar and communications) equipment is a considerable challenge for the Navy.  As electronics systems age, degradation can occur affecting the reliability of these systems.    The need for these systems to be easily maintained and upgraded is critical to the safety and effectiveness of the warfighter.  

Redesigning electronic equipment can be a difficult task if technical documents are not readily available to fully understand how the equipment operates in a system.  Often, obtaining the documentation and test equipment needed for redesign is not possible.  Technical questions to the original equipment manufacturer (OEM) cannot be answered since in many cases that resource may no longer be available. Additional requirements such as military electro-magnetic interference (EMI) and environmental qualification can also cause setbacks in the redesign schedule.

Case Study
One such electronic system that the EMPF has recently improved the maintainability and affordability of is the C6533/ARC Intercommunication Control System (ICS).  The ICS is a communication system that is currently deployed in the field, was originally designed in the late 1960s, and has seen service in many types of helicopter platforms including the AH-1, CH-47D, OH-58A/C, UH-1H/1V, and UH-60A/L. To allow the DoD to sustain the C6533/ARC for an additional twenty years, the EMPF has successfully re-engineered the C65533/ARC to improve reliability, increase availability, improve maintainability, and reduce total ownership cost.

Over twenty percent of the parts needed to build and repair the unit were obsolete and extremely difficult to procure. The unit also presented some other unique repair challenges since there were five sub-assemblies which were assembled and hard-wired between boards. Over time, severe aging had caused breaks in the internal wiring and brittle solder joints had a tendency to fracture during disassembly.  The redesign of the ICS unit was mostly internal which allowed for the conversion of five separate printed circuit boards (that were assembled by hand soldering between the boards and an E terminal (Figure 5-1)), into two boards with surface mount technology. Unlike the original design which used all discrete components, the redesigned intercom uses commercial-off-the-shelf (COTS) parts including a microcontroller, an op-amp, and integrated components.  The use of current technology reduced both the weight of the unit and the assembly and repair cost.

Lessons Learned
When considering changes to deployed systems to meet new requirements, it is critical to identify areas that can impact the system right at the interface to the platform. Power, interface, and control lines may contain few implementations of proper line filtering. New designs must make use of advanced line filtering to eliminate AC noise.  For a typical system, these noise frequencies which can be problematic may range from 400 to 1000Hz.  As an example of problems caused by insufficient filtering for audio application, unwanted sidetones within this frequency range of interest will be audible at the headset.  

When designing new systems to deployed systems’ requirements, it is important to take into account environmental and EMI testing standards that were in place when the system was designed. In many cases, the environmental EMI requirements for today’s electronic systems are more stringent. In order to have final platform qualification acceptance, the redesign needs to conform to military standards such as MIL-STD-810F, MIL-STD-461E, MIL-STD-901D, and MIL-STD-704E. MIL-STD-810F is an environmental testing guideline that includes standards for temperature cycling, humidity, fungus, salt fog, sand & dust, vibration, explosive atmosphere, and rain. MIL-STD-461E establishes the interface and associated verification requirements for the emission and susceptibility control of EMI. MIL-STD 901D  verifies the ability of shipboard installations to withstand shock loadings which may be incurred during wartime service due to the effects of nuclear or conventional weapons. MIL-STD-704E lists a set of requirements that ensure compatibility between the aircraft electric system, external power, and airborne utilization equipment. It also defines the requirements and characteristics of aircraft electric power provided at the input terminals of equipment to control electromagnetic interference and voltage spikes induced by lightning, electromagnetic pulses and power switching.

For most redesigns of deployed systems, using ferrite beads and technologies such as embedded wafer bypass capacitor connectors on all input and output lines will enable the new system to meet EMI requirements. Other implementations such as utilizing EMI gaskets and seals can augment the mechanical design and prevent the system internal circuitry from being adversely affected by EMI test signals which are radiated into the enclosure. 

Whether the system is designed to perform a navigational, electronic warfare, or communication function, it must be designed to ensure that the equipment is both maintainable and affordable for the Navy platform into which it is inserted.

In conclusion, the EMPF has re-engineered aging electronics equipment to extend its life, improve reliability, and make it more maintainable. This has resulted in a deployed system that is much easier to manufacture (by reducing five sub-assemblies down to two), has fewer moving parts, and has a reduced labor cost for repair and assembly.  Stringent environmental and EMI testing has proven that COTS components can meet tough military requirements and field testing in the target environment has proven that the redesigned unit operates and performs equal to or better than the original design.    Although the hardware in this case was designed for a communications system, the maintenance challenges and solutions are definitely applicable to shipboard sustainment

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