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The US Navy is evolving a strategy to develop and demonstrate prognostics and health management for propulsion and mechanical systems. How this overall strategy has evolved and its current status are presented. The SH-60 program was initiated as the first proof-of-concept effort to develop, demonstrate, and integrate available and advanced mechanical diagnostic technologies for propulsion and power drive system monitoring. Included in these technologies were various rule based and model based analysis techniques which were applied to demonstrate and validate various levels of diagnostic and prognostic capabilities. These are discussed and updated. Using past and recent "seeded faults" tests as case examples, various diagnostic methods were used to identify the faults, and various means of applying prognostics and health management are discussed. The most recent examples of "seeded faults" and related tests are also discussed as case studies, demonstrating various degrees of diagnostic, prognostic and health management capabilities. The current philosophy and thinking in respect to prognostics for mechanical systems is embellished, using examples from past and more recent "seeded fault" databases. Of particular interest is discussions of tests focused on demonstrating the understanding of fault to failure progression characteristics and the physics of failures. Accomplishments are discussed and additional needed testing and demonstration requirements are defined. Finally, status and future planned efforts for the USN Helicopter Transmission Test Facility (HTTF) and other related test resources are presented.

The Naval Air Warfare Center has developed a Helicopter Integrated Diagnostic System (HIDS) which performs mechanical diagnostics on a helicopter's drive system. Diagnostic indicators indicative of the mechanical health of the drive system components are derived from vibration data through a combination of statistical and signal processing methods. This paper discusses the application of a multivariate statistical process known as Hotelling's T2 analyysis to HIDS diagnostic indicators. Multivariate analysis uses a composite function of multiple quality indicators to produce a single, trendable indicator that characterizes the state of the monitored process. A statistically valid method of creating and adjusting an alarm threshold for the resultant composite indicator is inherent in the method. When applied to mechanical diagnostic indicators from helicopter drive system seeded fault tests, the method produced timely and unambiguous fault identification with a reduced number of false alarms as compared to current diagnostic methods.

The SH-60 Helicopter Integrated Diagnostic System (HIDS) program was initiated as a proof-of-concept effort to develop, demonstrate, and integrate available and advanced mechanical diagnostic technologies for propulsion and power drive system monitoring. Included in these technologies were various rule based and model based analysis techniques which were applied to demonstrate and validate various levels of diagnostic and prognostic capabilities. These will be discussed. Since spalling of the SB 2205 roller bearing integral inner race is the most common dynamic component cause for gearbox removal in the SH-60, it was tested as part of the HIDS effort. Using this as a case example, diagnostic methods are used to identify the fault, and means of applying prognostics are discussed. Other more recent examples of "seeded faults" are also discussed as case studies demonstrating various degrees of diagnostic and prognostic capabilities. Relative rating of the performance of the different analysis techniques evaluated will also be discussed. As used in this paper, prognostics is the capability to provide early detection of the precursor and/or incipient fault condition to a component or sub-element failure condition; and to have the technology and means to manage and predict the progression of this fault condition to component failure. This prognostic philosophy is further embellished; using examples from the HIDS past and current "seeded fault" data base to define accomplishments and discuss additional demonstration requirements. Finally, a full description, major accomplishments, status and planned efforts for the current Helicopter Transmission Test Facility (HTTF) are presented.

Wideband vibration measurements from seeded fault testing conducted at Pratt and Whitney have been examined to determine the practicality of using such measurements to monitor bearing stress. The measurements were taken using a robust laser interferometer (RLI) in support of technology investigations conducted for prognostic health monitoring (PHM) for the Joint Strike Fighter (JSF) Program. Data from Bearing 1 was examined, where the changes in bearing stress resulted from: changes in operational speed; seeded physical faults and changes in lubrication availability and quality. The RLI measurements were made by measuring the bearing vibrations that were transmitted from the outer race (and its housing) through, or along, the scavenge oil pipe to the outer surface of the engine. Bearing stress and the general health of the 1 bearing were examined from a variety of viewpoints, including the observation of the existence of and character of time series shock pulses, the measurement of enveloped detection bearing fault frequencies, and changes in the amplitude and character of spectrums. While remaining work is required for both RLI system refinement and the development of appropriate analytical tools, it has been demonstrated that acoustic emissions in broadband vibrations should be expected to provide a viable indication of bearing stress.

The evolution of automated diagnostic systems for helicopter mechanical systems has been aided by a Navy program of systematic testing of drive train components having known anomalies (seeded faults) while simultaneously executing a suite of diagnostic techniques to identify and classify the mechanical anomalies. This program, called the Helicopter Integrated Diagnostic System (HIDS) has been carried out using an iron bird test stand (SH-60) at NAWC - Trenton, and SH-60B/F flight vehicles at NAWC - Patuxent River. The SH-60 HIDS program has been the Navy's cornerstone effort to develop, demonstrate, and justify integrated mechanical diagnostic system capabilities for its helicopter fleets. The objectives of the program were to: 1. Acquire raw data for multiple cases of "good" and seeded fault mechanical components on a fully instrumented drive train to support the evaluation of diagnostic algorithms and fault isolation matrices. 2. Analyze vibration and other diagnostic indicators 3. Demonstrate the ability to integrate and automate the data acquisition, diagnostic, fault evaluation and communication processes in a flight worthy system. 4. Integrate and evaluate comprehensive engine monitoring, gearbox and drive train vibration diagnostics, advanced oil debris monitoring, inflight rotor track and balance, parts life usage tracking, automated flight regime recognition, power assurance checks and trending, and automated maintenance forecasting in a well-coordinated on-board and ground-based system. 5. Provide an extensive library of high quality vibration data on baseline and seeded fault components. 6. Provide a "showcase", state-of-the-art, fully functional Integrated Mechanical Diagnostic system to act as a catalyst demonstration. This paper describes the overall program, the goals and objectives, the facilities used, the system evaluated, accomplishments, results and conclusions obtained to date, The results of extensive gearbox and power-train "seeded fault" testing are presented. Lessons learned that can be applied to future Helicopter Usage Monitoring Systems (HUMS) and/or Integrated Mechanical Diagnostic (IMD) systems are also discussed.

A US Navy strategy was generated and is still evolving to develop and demonstrate diagnostics and prognostics for helicopter drive trains. The SH-60 program was initiated as a proof-of-concept effort to develop, demonstrate, and integrate available and advanced mechanical diagnostic technologies for propulsion and power drive system monitoring. Included in these technologies were various rule based and model based analysis techniques which were applied to demonstrate and validate various levels of diagnostic and prognostic capabilities. Since spalling of the SB 2205 roller bearing integral inner race is the most common dynamic component cause for gearbox removal in the SH-60, it was tested as part of the original HIDS effort. Using this as a case example, diagnostic methods are used to identify the fault, and means of applying prognostics are discussed. Other more recent examples of "seeded faults" are also discussed as case studies demonstrating various degrees of diagnostic and prognostic capabilities. These include the evaluation of an epicyclic planet gear separation algorithm developed by the DSTO, Australia. Multivariate analysis reasoners, and information fusion requirements and approaches are also discussed. Most recently a strategy is evolving to more fully develop and demonstrate the predictive aspects of prognostics. Finally a full description, recent accomplishments, status and plans for the NAWCAD Helicopter Transmission Test Facility is presented.