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Meet your future flight mechanic: Amit Katwala investigates new repair robots that can walk, crawl and work inside jet engines.

Tom Danvers has a rare set of skills.

He's one of a handful of people--no more than 20 worldwide--who are qualified to perform 'keyhole surgery' on Rolls-Royce jet engines. These skilled engineers travel all over the world to reach stricken planes, but their exotic lifestyle could soon come to an end.

Rolls-Royce is working with the University of Nottingham to develop mini remote-controlled robots that can snake their way inside engines, allowing Danvers and his colleagues to perform their delicate operations without travelling to the aircraft. It's a fascinating engineering challenge.

When an aircraft owner detects a problem with their plane during routine checks, or suspects damage has been caused by grit rising from the runway or a bird strike, they use a borescope--a long, thin tool like a medical endoscope--to peer inside the engine through tiny access holes, some too small for a pen to fit into.

If they detect a problem, fixing it becomes an immediate priority--ideally without having to take the engine off the wing. "It costs a lot of money, time and effort to take an engine off an aircraft, and also to subsequently reinstall it following any required maintenance action," says Daniel Olufisan, chair of the Royal Aeronautical Society's airworthiness and maintenance specialist group.

The need to find quick fixes has increased since Rolls-Royce changed its business model. "We don't sell engines anymore, we sell 'time on wing'," explains James Kell, an in-situ technology specialist at Rolls-Royce. "By fixing an engine on the wing rather than removing it, we reduce the time and cost of the operation."

Working through small holes, or accessing it through the front, experienced engineers called boreblenders grind and scrape away defects on the engine's blades using special miniaturised tools to leave a smooth finish. A lot of these tools have their roots in the medical world, and there are clear parallels with keyhole surgery performed on humans.

"It's very skilled work," says Danvers. "It can take three or four hours to remove and blend out a feature."

They work on commercial jets, military planes, and sometimes even larger machines. Danvers now works full-time at the Rolls-Royce site in Derby, developing techniques that the boreblenders can use on engines, but he's full of stories from his time in the field.

Once he spent the night on HMS Daring --a Type 45 destroyer powered by a Rolls-Royce engine--as it floated in Plymouth Sound awaiting deployment to the Middle East. He'd been called down from Derby to carry out emergency repairs on the vessel, missed the ferry back, and had to borrow a bed from one of the ship's officers.

For now, the boreblenders are constantly on call, and travel to where they're needed from hubs in London, Indianapolis, Singapore, Abu Dhabi and Derby. When they get a job, they pack up their equipment and head out on the first available flight. But that still takes time and costs money. There can be delays associated with getting visas, or receiving permission from local officials to go airside at tightly-secured airports.

"Sometimes the engine is not where the person is, so we have to manage the fleet a little bit to make sure that they all coalesce," says Kell. " Our fleet is growing rapidly, and with these skills in short supply it makes sense to look at new ways of working."

That's why Rolls-Royce is investing in robots.


On a sunny morning in July, Dragos Axinte walks me through the workshops at the University of Nottingham's Advanced Manufacturing Centre, where strange machines lurk in the corners, and large sections and models of jet engines occupy much of the floor space.

Axinte is working with Rolls-Royce to develop robots with miniature tools on the ends that can be inserted into the engines and controlled remotely by boreblenders, who can then spend less time travelling and more time operating.

"Instead of sending an engineer to Singapore, someone less skilled can mount the robot on the engine, and the robot will insert itself, make observations and measurements and start repairing, everything tele-operated by the guy from Derby," Axinte explains.

The tele-operating robot is an open cylinder about 300mm long, with a tiny stereovision camera and specially developed miniature cutting tool at the business end. It comes to a point that's small enough to fit through one of the ports in the side of an engine. Instead of an 'elbow' controlled by a motor, it moves flexibly using stainless steel tendons. This, explains PhD researcher David Alatorre, allows air to flow through to the cutting surface.

Kell says boreblenders have an advantage over surgeons who use similar technology to perform operations on the human body remotely. "We know a lot more about the thing we're operating on because we designed the engine," he says.

From input from the robot's camera, and existing CAD models, the boreblender can create a digital model of the repair site and a plan for the work. Then they 'record' the movements required to blend away any defects, and send this information to the robot in packets over the internet.

"We don't do the full operation all at once," explains Bilal Nasser, a research fellow at Nottingham. " The reason for this is that we ensure security in the process and the communication, and we also make sure that it's safe and it's producing what it's expected to do."

At the moment, the robot and the control station sit metres apart within the same room, but in the future this technology will allow boreblenders to repair engines from thousands of miles away. Future models could go even further.


The MiRoR (Miniaturised Robotic System for In-Situ Repair) continuum robot looks a bit like the hose of a vacuum cleaner. It's 1.2m long and black, and protrudes from a round plastic base like a grasping tentacle. It's designed to snake its way inside an engine from the front, allowing boreblenders to reach sites that previously would have been impossible to access without dismantling the structure.

The robot is made of a series of discs, a bit like vertebrae in the spine, connected by flexible rods that allow each section to bend in a different way. "By combining the bending of each section, the arm can form very complex shapes," explains research fellow Xin Dong.

The robot starts off coiled around the base, and can release itself into the engine using specially devised algorithms to guide its movement. "This robot has 25 degrees of freedom. If you imagine a normal robot, you could move each motor around with a joystick quite comfortably. If you try and do that with this you'd have 25 different knobs and you'd have to try and turn them simultaneously," explains research associate David Palmer.

The algorithms work either by following a predetermined path, telling the robot to contort itself into a predefined shape, or by the machine feeling its way with cameras and sensors. The idea is that the first time it enters an engine it would do so by sight and feel, and then later on it could move more quickly back to the work site by repeating the same movements if tools needed to be changed--a kind of muscle memory.

Flexibility is important when navigating into the engine, but once the robot gets there it needs to be stable, as it's performing delicate procedures to an accuracy level measured in microns. So the team is also working on a similar snaking prototype that can change stiffness using smart materials. When it's navigating to an area of interest it's flexible, and when it gets there it can be locked into a more rigid state. "It's a thermoplastic," explains Dong. "Whenit heats up it's soft, and when cold it's rigid so we use that material to lock the joints."

These robots still need to be placed by human operators, but the plan is to create models that can move themselves to the right place. The final project the Nottingham team is working on with Rolls-Royce is a hexapod robot or, as Axinte calls it," a walking machine tool".

It has six legs made of rubberised plastic that creates joints which can be soft and pliable during movement, and then locked into place when the cutting or blending work starts. It can walk--very slowly at the moment--but the idea is that, once one of the snaking continuum robots is placed on top of it, it will create a tool that can be positioned and inserted into an engine remotely. Its feet can be locked at different angles for standing on uneven surfaces.

It also opens up the robotic technology for other uses. "We have partners in civil nuclear, civil engineering, and oil and gas for offshore oil rigs," explains Palmer. "Situations where you've got height or clearance or radiation issues where you don't really want to send a person."

Proving cost-effective

There's still plenty of work to be done on the technical and regulatory side (see box, right) before these robots can start making repairs on their own, but they're already saving Rolls-Royce money. In fact, one of the miniaturised tools developed for the robots was used inside an engine within six months. "That alone justifies us being involved in three years of research and development effort," says Kell. "We love being involved with this project," he continues. "Nothing has changed with that blending probe for 20 or 30 years. The industry has been doing it like that for years. But this could help us react to a customer need within hours rather than weeks."

Others in the industry agree. "The industry is always keen to receive any innovative technology or system which has the ability to reduce cost, increase efficiency, and/or mitigate risk," says Olufisan.

"I think the technology is great because its potential benefits are significant and, as long as it is proven to be safe for use on an aircraft, I'm all for it."

These robots are in the early stages of development, but they're feats of high-tech engineering equally as impressive as the engines. In the future, they'll be controlled by skilled engineers to repair aeroplanes quickly.

That means fewer air miles for Danvers and his colleagues, perhaps, but more for the rest of us.


The snaking continuum robot developed at Nottingham University has 25 degrees of freedom. A special algorithm had to be written to control its movements


The size of the stereovision camera in the tele-operated robot that feeds images back to the boreblender in Derby


The number of Rolls-Royce engines in use on 35 different types of aircraft worldwide, for over 400 airlines in 150 countries

RELATED ARTICLE: Who takes responsibility?

When an engineer repairs an engine in person, it's very clear who should sign it off. But Rolls-Royce and Nottingham University are building robots that will be attached to the engine by a mechanic on site, and then operated remotely by a more skilled boreblender back in Derby.

This raises an interesting ethical question about who owns the legal rights to that repair. Who signs off the work when it's been done using a robot?

Daniel Olufisan of the Royal Aeronautical Society thinks that, as per M.A.201(c) of European Commission regulation 1321/2014 on continuing airworthiness, responsibility would lie with the boreblender and Rolls-Royce. "Simply put, if an airline contracts Rolls-Royce to perform on-wing engine repairs on its aircraft, then Rolls-Royce will be responsible for the repair regardless of whether it is carried out remotely or not," he says.

"It's worth noting that the remotely controlled robot in question is essentially maintenance equipment. Also, the methodology and nature of repair carried out by the robot would need to be approved by regulators before they can be used on an aircraft."

Caption: Rolls-Royce robots like this one can snake into jet engines to perform repairs

Caption: James Kell of Rolls-Royce (top left) says boreblending (bottom left) can help the team repair jet engines (right) more quickly
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Title Annotation:AEROSPACE
Author:Katwala, Amit
Publication:Professional Engineering Magazine
Geographic Code:4EUUK
Date:Sep 1, 2017
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