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Technical Paper

H-1 Upgrade Program: A Team Approach to System Safety

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.
Technical Paper

Large Displacement Stability by Design for Robust Aircraft Electric Power Systems

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.
Technical Paper

Developing Analysis for Large Displacement Stability for Aircraft Electrical Power Systems

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.
Journal Article

Aircraft DC Power Quality Characteristics of a PCTRU

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.
Journal Article

Prismatic Li-Ion Cell for Unmanned Aircraft

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.