Better main­tenance planning with Engine Trend Monitoring

Running a practiced eye over the data, Ivaylo Krastev, engine engineer at MTU Main­tenance Han­nover, sees that an engine is experi­encing a drop in effi­ciency while cruising. The outlet tem­pera­ture has risen, the high-pres­sure spool is speeding up and the engine is consuming more fuel. A warning is immedi­ately sent to the air­line, which has its entire fleet of engines looked after by MTU Maintenance. At the air­craft’s next stop, the engine is exam­ined while still on the wing by two of the airline’s main­tenance mechanics using a borescope.

They discover that a foreign body has found its way into the compressor. The engine is im­medi­ately removed from the wing and sent to the MTU Maintenance shop for repair. There, the fears are confirmed: the foreign body has damaged several blades. Had this comparatively minor damage gone unnoticed, it could have caused major conse­quential damage to the engine and led to costly repairs— the air­line is now spared both of these.

This early detection and analysis of abnor­malities is thanks to MTU Maintenance’s Engine Trend Monitoring (ETM): a com­pre­hensive software solution devel­oped by MTU in house for moni­toring engine para­meters. “During flight, the air­craft computer records the key engine para­meters including speed, pres­sure, tem­pera­ture and vi­bration,” says Norman Schwarz from Perfor­mance Engineering at MTU Main­tenance Hannover. The ETM system evaluates these parameters at certain points during a flight cycle—typically during takeoff and cruising—by comparing the data with expected values for a corre­sponding engine model. “This means that we can detect abnormal changes, such as in the engine’s thermo­dynamic behavior, and identify even the tiniest of deviations,” Schwarz says.

Thanks to the early detection system, MTU experts can analyze the data and look into potential abnorma­lities long before a serious problem surfaces. If they notice a deviation, they recom­mend a clear course of action for the necessary main­tenance.

Fleet under control

ETM is a key component of the fleet manage­ment service that MTU Main­tenance offers its customers. The concept ensures that all the fleet’s engines have maximum avail­ability and efficiency and can be operated as cost-effec­tively as possible. Performance Engineer Schwarz explains: “ETM also offers a forecast function that can predict the number of remaining cycles. This helps im­prove the planning of more compre­hensive engine over­hauls and to optimize shop visit intervals from both a tech­nical and an economic perspective.

Two more benefits for fleet customers is that all engine types can be monitored with a single tool and that MTU Main­tenance is in a position to tailor its expertise to indi­vidual cus­tomer require­ments, and new alert rules can be intro­duced that focus on certain parameters.

24/7 engine monitoring

ETM and its fully automatic alert function for deviations are active around the clock, seven days a week. Schwarz says, “For many of the new kinds of engine and air­craft, data analysis can already begin during the flight. Trend analyses can be called up online 24 hours a day, virtually in real time. Specialists at MTU’s Hannover, Zhuhai or Vancouver locations can then evaluate them.

Developed in house by MTU experts, the flexible system has been in use since 2006 and is continuously being expanded and optimized. And in the future, customers will benefit from further innovations.

Mobile and straightforward

“We’re currently preparing to change platforms and use new soft­ware so that we can track the data not only on PCs, but in the future also on tablets and with a smart­phone app,” says Christian Preuss, who is respon­sible for test systems and ground support equip­ment at MTU Aero Engines. IT specialists in Munich and Rzeszów are handling the program­ming. The new inter­face will be more cutting edge, more stream­lined and more straightforward—genuine added value for customers.

And there’s a further optimization in the pipeline. “With the current system, we can ascertain the loss in efficiency of the engine as a whole, but we’re developing the ETM so that it will show which engine modules are contri­buting to the loss in efficiency,” says Jürgen Mathes from MRO Perfor­mance Support at MTU Aero Engines. “Analysis at the modular level offers the benefit of allowing main­tenance to be planned in a more targeted way. This is because it lets our main­tenance specialists know which compo­nents to concentrate on during the shop visit.”

One dataset every second

In the future, engine data is to be recorded, trans­mitted and stored through­out the flight—in essence, one dataset every second. “This means that trend deviations can be detected even earlier compared to the current system, which can do just two to three snapshots per flight,” Mathes says. As such, main­tenance experts will be able to react even faster to trend deviations. It’s all about predictive main­tenance, or in other words efficiency through advance knowledge.

“New avionics can continuously record and transmit data. The necessary hard­ware is already installed on newer air­craft types,” Mathes says. And it can be retro­fitted to older models. However, the future ETM system does pose certain challenges for the IT experts. The sheer volume of data that is con­tinu­ously being received must not only be stored, but analyzed and evaluated as well. Alongside sufficient storage space, the effi­cient analysis method is the key to success for targeted and predictive main­tenance. As Preuss puts it: “We’re testing various data analysis concepts, such as machine learning, so that we can then offer our customers an ideal early detection system.”