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Naval Aviation has expanded its efforts to eliminate mishaps; especially those linked to human error. This focus was expanded to cover not only aircrew error, but maintainer error as well. To examine maintenance error, the Naval Safety Center's Human Factors Accident Classification System (HFACS) was adapted to analyze eight fiscal years of major maintenance mishaps. The HFACS Maintenance Extension effectively profiled the nature of maintenance errors and depicted the latent supervisory and maintainer conditions that “set the stage” for subsequent unsafe maintainer acts.

An overview of aircraft DC power quality specifications reveals that only minor changes have occurred in recent years within industry standards. Current and future advanced electronic aircraft are requiring significant power quality improvements due to increased use of digital and COTS (commercial off the shelf) systems. Certain electronic systems do not function properly due to various types of electrical disturbances. Some systems shutdown, fault or exhibit operational delays due to power interruptions or “blackout” conditions. Undervoltage or “brownout” conditions also cause this effect. Some electronic systems exhibit critical faults that can affect safety or mission success due to overvoltage conditions. Additional effects of high voltage spikes or overvoltage transients are known to reduce the life of utilization equipment [1], which is directly related to the health of the aircraft's electronic system and creates an economic burden.

An onboard Acoustic Wiring Diagnostic System to monitor the health of aircraft wiring is under development by Innovative Dynamics Inc. The AWDS incorporates passive acoustic sensors to monitor wire chafing. The system operates continuously in-flight so that intermittent wiring fault conditions can be detected as they happen. Trend analysis data can be logged to enable pro-active maintenance prior to catastrophic failure. A key advantage of the in-situ system is to perform the inspection without removing or disconnecting the wiring. Acoustic signatures of representative aircraft wiring have been characterized under simulated damage conditions. Flight ready hardware and software have been developed and flight testing is underway on an H-53 helicopter. This paper will present the wire diagnostic approach, the AWDS flight instrumentation, and some representative lab test results.

Future more electric aircraft (MEA) architectures that improve electrical power system's (EPS's) source and load utilization will require advance stability analysis capabilities. Systems are becoming more complex with bidirectional flows from power regeneration, multiple sources per channel and higher peak to average power ratios. Unknown load profiles with large transients complicate common stability analysis techniques. Advancements in analysis are critical for providing useful feedback to the system integrator and designers of multi-source, multi-load power systems. Overall, a framework for evaluating stability with large displacement events has been developed. Within this framework, voltage transient bounds are obtained by identifying the worst case load profile. The results can be used by system designers or integrators to provide specifications or limits to suppliers. Subsystem suppliers can test and evaluate their design prior to integration and hardware development.

The H-1 Upgrades Program is an Acquisition Category 1D Program executing an Engineering and Manufacturing Development contract with Bell Helicopter Textron Inc. The Upgrades Program will take the existing UH-1N and AH-1W helicopter airframes and provide a common 4-bladed rotor and drive system, a new main transmission, 4-bladed tail rotor, and many changes designed to bring the two airframes into as identical a configuration as possible. The aircraft will also receive integrated cockpits as a part of the modification. The program recently passed its Preliminary Design Review. This paper will discuss some of the program rationale and background information and focus on the advantages of the IPT process in general, and specifically as it relates to system safety.

More electric aircraft (MEA) architectures have increased in complexity leading to a demand for evaluating the dynamic stability of their advanced electrical power systems (EPS). The system interactions found therein are amplified due to the increasingly integrated subsystems and on-demand power requirements of the EPS. Specifically, dynamic electrical loads with high peak-to-average power ratings as well as regenerative power capabilities have created a major challenge in design, control, and integration of the EPS and its components. Therefore, there exists a need to develop a theoretical framework that is feasible and useful for the specification and analysis of the stability of complex, multi-source, multi-load, reconfigurable EPS applicable to modern architectures. This paper will review linear and nonlinear system stability analysis approaches applicable to a scalable representative EPS architecture with a focus on system stability evaluation during large-displacement events.

Analyzing and maintaining power quality in an electrical power system (EPS) is essential to ensure that power generation, distribution, and loads function as expected within their designated operating regimes. Standards such as MIL-STD-704 and associated documents provide the framework for power quality metrics that need to be satisfied under varying operating conditions. However, analyzing these power quality metrics within a fully integrated EPS based solely on measurements of relevant signals is a different challenge that requires a separate framework containing rules for data acquisition, metric calculations, and applicability of metrics in certain operating conditions/modes. Many EPS employed throughout industry and government feature various alternating-current (ac) power systems.

Saft is working on advanced 28V Li-ion batteries for use in NAVY unmanned aircraft applications. This battery employs seven (7) prismatic state-of-the art Li-ion cells connected in series. The battery needs to be less than 40lbs in weight and 600 in3 in volume. This paper presents the performance results of the new prismatic cell. This development is pioneering new technological territories for SAFT since the PL55E cell is the first prismatic cell developed and delivered by SAFT America [1]. The experience gained will be useful and the PL55E cell will be followed by more prismatic cells added to the SAFT Li-ion portfolio. The presentation will give an overall status update of the technology as well as a brief overview of the complete 28V battery.

In the continuing effort to save Fleet Operations and Maintenance (O&M) costs, a united effort was launched to propose the replacement of the Nickel-Cadmium battery on the F-5 aircraft with a valve-regulated, sealed lead-acid battery. The Aging Aircraft IPT (AAIPT) at Naval Air Systems Command, Patuxent River (PAX River), Maryland presented the concept to the Value Engineering group at Defense Supply Center Richmond, Virginia and successfully obtained funding for this and other Aging Aircraft efforts. The AAIPT then approached the Propulsion and Power Division of Naval Air Systems Command (AIR-4.4.4.1) as the cognizant engineering activity over batteries. AIR-4.4.4.1 then requested the assistance of Crane Division of Naval Surface Warfare Center (NSWC Crane) to develop a test plan and a Memorandum of Agreement and to obtain flight test authority as well as conduct the flight test.

This paper will summarize the details of replacing the EA-6B Sealed Nickel-Cadmium (SNC) batteries in an effort to reduce battery maintenance and battery maintenance costs. A flight evaluation program is presently underway at two locations to validate the proposed change from SNC batteries to Valve Regulated Lead-Acid (VRLA) batteries. The EA-6B aircraft currently uses two 26-volt SNC batteries, military part number (MIL PN) D8565/1-1, and one 24-volt SNC battery, part number MS17334-2. The SNC batteries are scheduled for maintenance every 112 days, which requires removal and replacement of the batteries at the O-level and battery maintenance at the I-level (battery shop). A load check is required every 28 days on the aircraft in accordance with the Maintenance Requirement Card (MRC).