F135 Integrated Engine Prognostics & Health Management

The F135 team has also issued a contract of its own to Diagnostic software maker Qualtech Systems Inc. of Wethersfield, CT to provide real-time on-board diagnostics for its jet engines. The contract calls for Qualtech Systems to provide fault isolation development software tools and an an on-engine "diagnostic reasoner" as part of Pratt & Whitney's Joint Strike Fighter Engine Prognostics & Health Management (PHM) Program.

PHM will make use of electrostatic and other sensors to monitor such parameters as debris generation, vibration, blade health and lubricating-oil quality. The suite of sensors will constantly monitor approximately 500 data streams, which will be integrated with the F-35's own systems. The complete PHM system has been developed in partnership with NASA Ames, which created vital data-fusion algorithms, NASA Dryden and NASA Glenn, with flight development to be carried out with a C-17. As noted previously, the aim is to predict the need for inspection or parts-replacement, so that, via a satellite link, the airbase or aircraft carrier knows the engine health before the aircraft returns from its mission.

NASA wrote:C-17 Wired for the Future by Gray Creech - Dryden Public Affairs

Dryden researchers are investigating an improved, high-tech method of monitoring and diagnosing the status of jet engines, using a U.S. Air Force C-17 transport plane at Edwards Air Force Base.

The effort, known as the C-17 Propulsion Health Monitoring project, seeks to identify and refine aircraft engine technologies aimed at making military and civilian aircraft safer and more reliable.

The C-17 is being used because the aircraft represents modern medium- and large-transport aircraft with quad-redundant digital flight control systems. These features offer maximum flexibility and redundancy for advanced intelligent systems research.

Project objectives include enhancing aircraft safety by enabling early detection of potentially damaging events that would not be discoverable by conventional means, and elimination or minimization of secondary damage.

Advanced engine sensors aboard the C-17 provide ultrasonic stress wave analysis that filters out all normal engine vibration, detecting only friction and shock events.

Electrostatic sensors located in engine inlet and exhaust sections monitor for debris and signal when potential debris passage is detected. The system then diagnoses ingested material in order to determine if a problem exists.

Future additions to the sensor suite include oil debris and engine vibration monitoring, and higher-resolution monitoring of engine compressor stage speeds.

Propulsion health monitoring could provide industry and the military with economic benefits by enabling comprehensive in-flight diagnosis and by eliminating the need for routine engine inspections.

The project is led by Dryden, with NASA funding all development and infrastructure components including aircraft flight time and support.

Other project participants include the U.S. Air Force's C-17 System Program office, Wright-Patterson Air Force Base, Ohio; the Air Force Flight Test Center, Edwards Air Force Base; Ames Research Center, Moffett Field, Calif.; Glenn Research Center, Cleveland; The Boeing Co., Long Beach, Calif., and St. Louis; and Pratt & Whitney, East Hartford, Conn.

The Inlet Debris Monitoring Sensor (IDMS) is mounted in the inlet forward of the FAN and monitors the electrostatic charge associated with debris ingested at the engine inlet. It is designed to detect the size, quantity, velocity and to a limited extent composition of debris (i.e. damaging/non-damaging) entering the inlet.

The Engine Distress Monitoring Sensor (EDMS) is installed in the upper actuator housing of the thrust reverser casing. This sensor monitors the electrostatic charge of debris exiting the engine, which is likely to have been produced by engine distress. This system monitors the exhaust for changes in the level or nature of this debris. Normal healthy engine operation results in a small amount of erosion of various engine components that show up as fine particulate within the gas path. Changes in the nature or quantity of this exhaust debris have the potential for being an early warning of excessive wear or incipient failures.

The Stress Wave Analysis Sensor (SWAN) is a lightweight integrated circuit piezoelectric transducer that monitors structurally borne ultrasonic sound vibrations to measure the energy created by shock or friction events. It is an external sensor that requires a mount point that provides a mechanical sound path to the component being monitored. Five of them are mounted on the engine gearbox and flanges.

A set of 3 High Frequency Vibration Sensors (HFVS) are mounted on the engine. One is located on the gearbox, one on engine case flange B (forward), and one on flange P (aft). These sensors will allow the high frequency response of the components of the engine and gearbox to be tracked.

Current State-of-the-Art
The Joint Strike Fighter (JSF) program embodies the state-of-the-art in aircraft IVHM. This program has incorporated prognostics health management (PHM) into its design, using sensors, advanced processing and reasoning, and a fully integrated system of information and supplies management. The on-board JSF PHM system is hierarchical, dividing the aircraft into areas such as propulsion and mission systems. Area data is generated by a mixture of dedicated, purpose-built sensors and analysis on existing control sensors to identify degradation and failures, compiled and correlated by area reasoners, and then correlated by system-level model-based reasoners. Maintenance data-links telemeter vehicle health data to ground-based information systems focused on maintenance and management of the supply chain. Prognostic events are detected by prognostic built-in-test, automated post-flight trending, and reasoning, with an emphasis on disambiguating sources of degradation rather than failure. Ground-based knowledge capture is used to sift through flight data. An autonomic logistics information system provides logistic support to the end user and provides off-board trending across the entire JSF fleet. The JSF PHM system is still in the design phase, and it is widely acknowledged that much work remains to build a reliable, effective health management system. Much of the integration of health management information is done manually after the flight. Commercial health management systems lag the military, but commercial suppliers have a keen interest in applying health management technologies to keep pace with changing market conditions and the need for reduced maintenance costs to ensure economic viability of the operators and equipment manufacturers.