When you think about it, it’s pretty tough for aerospace manufacturers. Not only is there a relentless drive for greater efficiency and keeping costs down to make air travel affordable for the masses, but there’s also the overriding factor of passenger safety to consider. Not surprisingly then is the fact that the engine control system in an aircraft has become one of the key elements in the development of new aero engine programmes. One company that knows a thing or two about such systems is Aero Engine Controls. Dave Tudor reports.

In a nutshell, Aero Engine Controls (AEC) is a designer and manufacturer of harsh environment, safety critical control and power supply systems but the company is somewhat unique in that it only has two customers. However in this case, quality definitely overrides quantity because those two customers just happen to be Rolls-Royce and Goodrich – two of the largest players in the industry and each a household name in its own right.

Actually, the two companies are more than simply customers – they’re shareholders! AEC is the result of a 50/50 joint venture established three years ago between Rolls-Royce plc and Goodrich Corporation. The combination of Rolls-Royce’s engine system and software expertise with Goodrich’s engine controls system design, manufacture, test and support capabilities have created an agile, competitive and innovative company. AEC undertakes the engine control system design, and provides safety critical software, electronic engine controllers, health monitoring systems, fuel pumps and hydro-mechanical controls, fueldraulic actuators and permanent magnet alternators predominantly for Rolls-Royce’s aero-engines. AEC provides aftermarket products and support to Goodrich, as well as supplying a number of products used for other aero-engine and airframe manufacturers.

To paint something of an overall picture, Rolls-Royce designs and manufactures the aero-engine, defining the top level system requirements. A major benefit of the joint venture is that AEC is able to work closely with Rolls-Royce right at the beginning of the design process, from early concepts, all the way through into aircraft service. This helps achieve an optimised system. All the sensors and actuators on the engine are monitored and controlled by AEC’s control system, enabling the engine to respond to the pilot’s instructions whilst ensuring that the engine is operating safely, at optimum efficiency. It also needs to be ready to respond to a wide variety of conditions and events – even the surprise ingestion of a bird!

“A good, albeit simplified, analogy is the human body,” explains Chris Weir, AEC’s vice president of strategy and business development. “Our electronic controller is like the brain of the engine; it receives a wide range of signals from all over the engine and from the cockpit. Based on this information it decides what action should be taken, and sends the appropriate signals back out to drive actuators and valves to appropriate positions. Our hydro-mechanical products are akin to the heart, in that they supply the energy – fuel – to the engine. So in effect, we provide the brain and the heart – which perform important functions to ensure safe and efficient operation.”

Nothing ventured, nothing gained

“Although the joint venture with Rolls-Royce and Goodrich has been established for three years now, AEC’s heritage, in one guise or another actually dates back to the birth of the gas turbine aero engine some 70 years ago,” affirms Mr Weir. “Our core capabilities and technologies include safety critical control systems, designed to operate in harsh conditions, and to manage component and material obsolescence effectively. We have modelling and test facilities that cover a wide range of performance and environmental testing of both individual products and complete systems. Moving forward, the know-how and technologies are clearly transferable to other industry sectors other than aerospace – hence we’ve set up AEC Applied Technologies to access other markets.”

Globally, AEC employs 1,500 people in six worldwide locations with engineering and manufacturing facilities in Birmingham, engineering sites in Belfast and Derby, regional support sites in Dubai and Singapore and a further engineering facility in Indianapolis in the US, with a business turnover of over £200 million. “As AEC we are able to work more openly with our customers,” Mr Weir adds. “Relative to them, we’re a small company, but that makes it easy for us to be dynamic. Each year we’ve challenged ourselves to make significant improvements in quality, cost and delivery targets – and we’ve exceeded them. It’s an exciting place to work.”

Continuous improvement

The aerospace industry is renowned for its forward thinking manufacturing strategies and in this regards AEC has fully embraced Lean Manufacturing principles and Six Sigma methodologies. The company is also very proud to be manufacturing in the UK as Mr Weir reveals: "Our UK manufacturing footprint has to remain highly competitive on quality, delivery and cost. Our manufacturing ethos is centred around material flow, focusing on minimising waste, reducing leadtimes and improving the capabilities of our processes. To achieve this, we've invested in new manufacturing technologies, to reduce the duration and number of processes and to increase the levels of automation. We're working with both the UK's Advanced Manufacturing Research Centre in Sheffield and the Manufacturing Technology Centre in Coventry - where AEC was a founding member.

"This investment in continuous improvement and new manufacturing technologies and equipment has enabled us to retain our core, strategic capabilities in the UK,” he continues. “However, also key to AEC's success is the partnership with our global supply chain, which includes 7,458 different part numbers and bringing in just under 7 million parts a year.

“We’ve learned some lessons in what to outsource and what to retain in-house. In our opinion, with the right strategy, the UK is still a great place to manufacture high end, technically advanced products.”

The relentless pursuit towards improvement has resulted in significant levels of investment: AEC has invested 65% of its capital investment to improve process capability, increase automation and reduce cycle times. These represent serious levels of investment, but AEC is a company that refuses to stand still in terms of improving its manufacturing processes. “Providing we can justify the outlay, Rolls-Royce and Goodrich are more than prepared to back us in the purchase of new equipment,” explains manufacturing engineering manager, Bernard McGillion. “We’re constantly reviewing our processes to see if they can be improved and through Lean and analytical techniques we’re able to identify and hone in on areas of excessive waste or causes of variation, and apply corrective actions.

“We’ve learned much from Rolls-Royce and Goodrich, as well as other businesses,” he says. “We’re all about treating the root cause of a problem, not just the symptoms. For this approach to work it’s essential that the entire workforce understands why we need to continuously improve and what targets we are trying to achieve. Everyone has a role to play, and feels that he or she can have a positive input into a particular manufacturing problem. We use a Policy Deployment Matrix approach to flow down the business improvement strategy. From this, we can define our manufacturing improvement priorities to ensure we support the business goals. This is definitely a marathon rather than a sprint but we’re making good progress.”

Problem solving

AEC manufactures a wide variety of different components on a regular basis and when it encounters a process that constrains either manufacturing or design performance it will analyse the problem to understand whether there is a simple fix, or a thorough Six Sigma investigation is required. Sometimes it is necessary to take a fresh approach to achieve the step up in performance and this is exactly what happened recently with a family of parts used in AEC’s fuel metering units which were causing a real headache in terms of manufacturing bottlenecks.

It was decided that a new mill/turn machining centre would solve the problem. This would significantly reduce the number of operations used to manufacture the parts and more importantly enable the components to be machined in one hit rather than transferring across multiple machines.

As with all of its major purchasing decisions, AEC embarked on a thorough evaluation process before committing to a single supplier. Mr McGillion takes up the story: “It’s a very competitive market, as there are a number of excellent solution providers who we’ve worked with very successfully. Initially there were five companies on the shortlist and to be honest, in terms of machine performance, there was very little to separate them,” he explains. “All offered around 70% cycle time reductions when compared to our previous manufacturing methods, but where one supplier in particular – Mills CNC and its Doosan MX2100ST mill/turn centre – really excelled, was in reducing our set-up times significantly. Previously, this was a real bottleneck for us. The Doosan gives us the flexibility of being able to change jobs quickly which is essential to maintain high levels of productivity.”

He elaborates: “Something that is always a key factor in our decision making process is the total support package. Mills’ has excellent aftersales service, support and training and demonstrated absolute willingness to go the extra mile to ensure we were 100% satisfied. We needed a turnkey solution for the manufacture of a specific family of parts and Mills worked with us all the way from day one. As soon as I visited Mills’ facility in Leamington Spa, saw the machines and experienced the company’s ethos firsthand, I knew this would be a successful partnership. As Mills has been involved from the start, it’s reassuring to know that should we run into any problems, help is only a phone call away – and this will be the case on an ongoing basis.”

By Mr McGillion’s own admission, the previous, specific manufacturing process had been somewhat slow, cumbersome and inefficient. “To make this family of parts previously involved three separate machining operations – two turning processes and a third milling operation,” he advises. “Now the parts are made in one hit and in a fraction of the time.”

Turnkey triumph

Turnkey manufacturing in this context means buying a machine for a specific purpose – in this case manufacturing the aforementioned family of control valve parts. In operation, these parts are critical as they are part of the control system that regulates and stabilises fuel supply to the engine. Being part of an overall complex assembly, the parts have to be right first time every time. Dimensional instability on both geometric and linear tolerances can cause significant problems upstream and ultimately affect engine efficiency so there’s little margin for error.

Some machine tool providers will shy away from turnkey projects simply because of the risks – and subsequent costs – involved. And it is risky because if the solution doesn’t work, the customer simply walks away. In this case, all the trialling and development work done at the front end of the project was orchestrated by Mills’ technical director, Andrew Jack and his team. It took more than six months to complete but as Mills’ managing director Nick Frampton explains, the objective here was to produce a total manufacturing solution rather than simply sell a machine.

“We knew from the start the type of components the machine would be producing and we were 100% confident in terms of specification that the MX2100ST would be up to the job of hitting and maintaining the tight tolerances required,” he says. “But equally as important however was our experience in handling turnkey projects. We have a number of blue chip customers – including several in the aerospace sector – where we have operated similar projects very successfully. I think this gave us a real differentiator against the competition.

“I like to think that we arrived at the eventual solution together,” Mr Frampton expands – and Mr McGillion agrees. “We took great care in the early stages of the project to listen carefully to what Bernard and his team needed to solve their problem. This was the primary driver for the entire duration of the project.”

More of the same

The machine supplied to AEC was a Doosan MX2100ST equipped with a Fanuc 31iTA control system. Installed in August 2011 and comprising an eight inch chuck and 65mm bar capacity the machine features two 22kW/5,000rpm spindles, an integrated B-axis, a Y-axis and lower turret.

The machine was specified with a number of optional extras: thermal compensation for the B-axis; linear scales on the X- and Y-axes of the top milling head and the X-axis on the bottom turret; an FSE filter drum conveyor system with built in refrigeration; a 70 bar coolant pressure upgrade for the B-axis milling spindle; a Renishaw RMP600 inspection probe with Capto C6 back end; and a Renishaw NC4 laser tool breakage detector.

The project has been so successful that a second MX2100ST has been ordered and is due for installation in July 2012.

Aero Engine Controls
www.aeroenginecontrols.com

Mills CNC
www.millscnc.co.uk