Optical-based gearbox monitoring to make helicopters safer

18 May 2021

Via a new Royal Society Industry Fellowship at the Zepler Institute at ORC; optical sensing to lead to safer, more reliable flight.

Optical sensing techniques will measure helicopter gearbox health in real-time in a new UK Royal Society Industry Fellowship at the Zepler Institute for Photonics and Nanoelectronics in Southampton.

The fellowship, led by Dr. Christopher Holmes in partnership with GE Aviation, will build understanding of potentially-fatal mechanical failures and feed the information into machine learning models.

The University of Southampton's Zepler Institute is home to the Optoelectronics Research Centre, one of the world's leading institutes for photonics research. Improved helicopter monitoring can be achieved through photonics, leading ultimately to safer and more reliable flight.

In 2016, a fatal air crash of a Super Puma helicopter in Norway was attributed to the mechanical failure of the main gearbox. In addition to a tragic loss of life, aircraft grounding affected search and rescue, military and off-shore oil and gas operations.

No room for error

Dr. Holmes, ORC Senior Enterprise Fellow, said, “While a twin-engine passenger jet can fly on one engine, the failure of a key component on a helicopter, such as the main gearbox, often proves fatal. In no other type of aircraft is so much criticality placed on a single component. Approximately 16 percent of all mechanical failures and 30 percent of the total maintenance cost for helicopters can be attributed to the main gearbox.

“This new fellowship with GE Aviation will develop fresh understanding of planetary gear trains by targeting new scalable monitoring techniques. The approach will be the first that monitors the casing of an epicyclical gear box optically, monitoring for changes in vibration and temperature. This process will be validated experimentally to ensure the accuracy, efficiency and practicality of the innovation,” Dr. Holmes added.

A helicopter's main gearbox uses an epicyclic system, where outer gears revolve around a central sun wheel. This offers a compact structure, large transmission ratios and strong load-bearing capacity, compared with traditional fixed-shaft gearing. However, the monitoring of these systems are underdeveloped, due to their complexity.

Dr Holmes's fellowship will investigate integrating an optical sensor platform onto the casing of an epicyclical gearbox, helping develop reliable digital fault diagnosis methods. Several indicators will be used in order to detect mechanical abnormalities based on kinematic analysis and signal processing techniques.

“Optical fiber sensors are an attractive alternative as they are the size of a human hair, electrically non-conductive, immune to electromagnetic interference and can contain multiple sensors along one stretch of fiber,” said Dr Holmes. “Fully localised optical sensing can become a cost effective, quantitative, high-speed, high sensitivity solution. Working with GE Aviation, we will isolate any gear damage in its early stages and formulate a complete virtual representation in a so called digital twin.”

Epicyclic gears are also found in wind turbines, mining machines and many other engineered systems. This research could directly improve integrity and efficiency of all these systems. The new Royal Society fellowship could support the reduction of energy consumption and provide more efficient structures for transportation and power generation, ultimately reducing carbon emissions.