Data-first digital twins

Hayley Everett

Ben Wilkinson explains how a data-driven approach to digital twins can revolutionise maintenance and repair operations and extend time-on-wing for aerospace engines.

Time-on-wing (TOW) is a measure of the operational reliability of an engine or aircraft system. The higher the TOW of an aircraft engine the better, particularly for airline operators for whom keeping an aircraft fleet operational is crucial not only for their passengers but also for minimising costly and timely maintenance and repair (MRO) operations.

Rolls-Royce Civil Aerospace has an extensive history in the aviation industry, having developed and supplied its aircraft engines and systems to the sector for decades. Improving TOW of its engines is an integral focus for the business, prompting a complete overhaul of its business model in the 1990s. At Manufacturing and Engineering Week 2023 in June, Ben Wilkinson – Head of Digital Technology at Rolls-Royce Civil Aerospace – explained how the company pivoted its approach to MRO in order to maximise TOW of its engines, and how implementing innovative digital twin technology is aiding the company in this endeavour.

The introduction of total care

Back in the 1990s, Rolls-Royce’s business model was based on the sale and maintenance of its aircraft engines; the airlines paid for the engine and then also paid Rolls-Royce to fix it when it broke. However, this relationship was not the most synergistic one, Wilkinson admitted, and so the company started looking at how they could transform this arrangement to align the outcomes for both itself and its airline customers.

“We developed a new contract type called Total Care, which at the time was transformational,” he said. “Total Care essentially transferred risk. So before, if one of the engines broke the airlines carried the risk and would incur downtime while the engine was repaired, and would have to pay us to fix it. With Total Care, we take on this risk and cover the cost of maintenance, meaning the airlines pay us when the engine is working in what we call engine flying hours.”

Fast forward to today, and the company’s service business now generates more revenue than its manufacturing business. However, as the company covers the cost of MRO for its engines, it had to look at how it could make this a profitable part of its business and ensure that its MRO operations were as efficient as possible. Part of this was reducing the amount of maintenance events entirely; by keeping the engines operational as much as possible, TOW is increased and therefore revenue, too.

“We looked at TOW as a combination of time between our maintenance events, and the time between maintenance events is our revenue earning opportunity,” Wilkinson explained. “The fewer maintenance events in a contract, the more profitable that contract can be. This business case drove the creation of digital twins: how can we better understand the condition of the engine? How can we make sure that we can keep the engine going for as long as possible within the safety and efficiency tolerances?”

Data is king

The company realised that in order to extend TOW, it needed to collect as much data from its engines as possible. Previously, the engines were generating huge swathes of data content, but this was too much for Rolls-Royce’s processing systems to cope with. The firm embarked upon improving its data transmission capacity, prompting the creation of a new big data and Internet of Things (IoT) platform called the Intelligent Engine. Using a combination of cloud technology, artificial intelligence (AI) and self-learning analytics, the Intelligent Engine allows the company to monitor the data transmitted by its engines in real-time during flights.

“The first digital twin we created, the Intelligent Engine was something that looked at the whole engine system,” said Wilkinson. “Within this, we could create an ecosystem of digital twins, one of which looked at engine level failure modes. This was our first approach to being able to know whether something was wrong with an engine, and led to a whole new service we now offer called engine health monitoring. By understanding the condition of the parts within an engine, we’re able to minimise the amount of maintenance that we do. If you don’t know much about the data coming from the engines, then you have to be pessimistic. However, with digital twins we can create models that accurately reflect the actual condition of parts and make a case backed up by data-led evidence about extending the TOW. This has been a massive step change – in certain cases we have been able to extend the TOW for critical parts by over 70%.”

The firm has also used digital twins to predict how its engines will be operated by different airlines in various parts of the world – factors that can have a significant impact on the amount of MRO an engine may need over the course of its lifetime.

“Using this as a predictive model, we can simulate how those engines will be operated in the future, allowing us to optimise our maintenance,” Wilkinson explained. “By knowing everything about the engine, you can predict the future and create a ‘crystal ball’ digital twin that tells you when the engine is going to fail and allows you to plan for maintenance.”

In addition to optimising its service offering, the company is also using digital twins to improve its manufacturing operations, he added. “Some of the metrics we’re looking at are around reducing rework, reducing scrap, and improving the sustainability of our operations. You can see the pattern here: Look at a particular area, generate a digital platform based on certain value stream business cases, and then develop digital twins on top of it. We are creating a digital thread throughout the organisation all the way from the source systems into a unified 360-degree data platform that brings data from manufacturing, engineering design and the aftermarket all together for unified optimisation.”