Turbine Engine Predictive Maintenance Solutions
Making our jobs easier while increasing safety and saving money
By Joe Escobar
Predictive maintenance - the ability to plan maintenance tasks before actual failure of an engine or component. Much has been discussed about this topic in recent years. AMT has written about new technologies that are making predictive maintenance a reality. Photon induced positron annihilation (AMT Airframe Technology, November 2002) for example is allowing flaws in the airframe to be detected at the atomic level before actual cracks appear.
But what about engines? Is it possible to predict upcoming maintenance requirements before an actual failure occurs by monitoring engine performance? In the future, can operators rely on predictive maintenance solutions to plan maintenance instead of the traditional TBO?
Actually, there are engine monitoring solutions available today. One system, SmartSignal Equipment Condition Monitoring™ (eCM), allows operators to better plan their maintenance activities based upon real-time monitoring.
How eCM works
The eCM system uses advanced mathematical techniques (algorithms) to identify deterioration in the engine performance. Ted Anderson, in his white paper Enabling Predictive Maintenance: Increasing Asset Availability in the Aviation Industry with SmartSignal's Equipment Condition Monitoring Solution, November 2002, explains that the algorithms used offer a high level of sensitivity (the ability to distinguish between random signal noise, which represents the inherent variation in normal operations and very subtle shifts in system performance, which are the precursors to failure).
Before the user begins utilizing real-time monitoring, the eCM Workbench is used to create an engine or fleet of engines. It defines an empirical model for each engine, and specifies runtime operation. Actual sensor data from normal engine operation is used to "train" an empirical model for each engine. This training step can be done using either historical data or using data collected during actual engine operation.
Once an engine and its corresponding model is created in the system, the engineer configures runtime operating conditions, such as the real-time data collection source. This information is then stored within the eCM database in the server application.
Collecting and monitoring data
In a typical commercial aviation application utilizing SmartSignal, the data is collected by onboard avionics and is then downloaded by telemetry equipment to the SmartSignal eCM server. For those aircraft that are not equipped with the necessary telemetry, an alternate means of collecting data and transmitting it is employed. Once the data arrives at the eCM server, a datafield module prepares the data for analysis by the eCM Run-Time Engine.
Located within the server, the Run-Time Engine analyzes the incoming data. It collects the real-time data signals coming in through the datafeed and matches those signals to the particular engine model stored in the database. For every real-time snapshot of engine performance that is taken, estimated signals are produced for each sensor value (these estimated signals indicate the "normal" value for each sensor).
Next, the system uses algorithms to compare the estimated signals with the actual real-time signals. Very fine differences between the signals normally indicate the system is operating normally. If significant differences occur, then the system evaluates the severity of the condition, identifies where problems are occurring or are about to occur, and perhaps recommends a diagnosis.
SmartSignal is yet another example of how the industry is using technology to enhance safety and save money. In the near future it is quite possible that similar technology will be used to monitor all systems on the aircraft. When the aircraft gets back from a flight, we will know exactly what is wrong and how to fix it. Seems like that would take the fun out of being an A&P.
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