An understanding of landing

At the last Aero Engineering Show, Messier-Bugatti-Dowty's Mick White gave visitors to the open forum a heads up on what's going down with the company's latest landing gear technology innovations. Mike Richardson reports. Messier-Bugatti-Dowty (MBD) forms part of the Safran Group and employs over 62,000 people in 57 countries. Safran's aerospace sector accounts for 80% of its revenue and its aerospace division is split into propulsion and aircraft equipment to comprise landing gear and systems. MBD's fully-integrated Gloucester-based manufacturing facility is currently working on the main landing gear for the Airbus A350, which are typically over 5m tall and weigh approximately 3.5tonnes. “We are a global integrated company that covers concept design through to in-service support,” begins MBD's chief engineer of new product development, Mick White. “We're increasingly performing more integrated systems testing - something that was traditionally done by the aircraft constructors themselves. We can construct a full-size, 100% representation of a landing gear assembly, which we then test under every load case of performance and adverse conditions before it goes into service. For example, during our Airbus A350 landing gear drop test, the assembly descends at 12ft per second, which as you can imagine, required the building a huge test rig.” White adds that year on year, airline customer demands are becoming more and more challenging as they look to reduce weight, which is directly connected to the amount of fuel consumption. “We continuously provide innovative ways of reducing the weight of the landing gear by promoting new designs, methodologies and materials,” he continues. “Airlines want ‘fit and forget' solutions, so we manufacture our products as reliably as possible to help extend the maintenance intervals. Every aircraft landing gear is typically overhauled somewhere between 12-14 years. Ideally, we need to increase these periods so the airlines can fit and forget for as long as possible.” <The science of compliance> According to White, MBD knows exactly where it's going regarding the use of environmentally-friendly materials and complying with strict regulations like Registration, Evaluation, Authorisation & restriction of CHemicals (REACH). “We realise that REACH is here, and therefore for new programmes and products we have found alternatives to the chromium plating processes and anything that uses hexavalent chromates in the production process,” he says. “These parts operate in hostile environments with the potential for foreign object damage (FOD) so our parts must remain undamaged and sustainable for 12 years.” Equally, noise regulations are becoming increasingly tougher and the company recognises that in the future, airport authorities will be driving through some very strict regulations in terms of acoustic footprint. “The landing gear isn't the most aerodynamically-shaped part as it's designed to take very high loads and allow the aircraft to manoeuvre on ground,” White clarifies. “However, when the landing gear is extended it does have a significant impact on the overall noise footprint as the aircraft approaches the runway. We're tasked with finding new ways to reduce this impact. Continuous technology evolution and innovation are absolutely vital to the success of our business. We're number one in the world in terms of landing gear, but we need to maintain this position because there is plenty of competition. The only way to keep this position is by investing in technology and innovation.” The hot R&D topics currently at the forefront of MBD's thoughts comprise the broad headings of weight reduction, new and exotic, higher strength materials and developing solutions for All Electric Aircraft (AEA), such as the replacement of traditional hydraulic landing gear components. In addition, the company has invested in providing high strength titanium products in partnership with a number of industry partners, like the AMRC with the intent to get to a stage where it can manufacture high strength titanium parts in a ‘similar' timescale to what it can from a typical 300M alloy steel part. “The titanium we use is high strength compared to conventional variants,” White explains. “This titanium is in service on the Boeing 787 Dreamliner and will soon be in service on the A350 too. Extensive use of new titanium alloys provides a massive weight saving for next generation aircraft. We're developing new titanium technology to increase its strength and enable us to reduce part size and weight, and still contain the benefits that the less corrosive materials we use for landing gear manufacture. Our research is continuing to develop new titanium with increased material properties and working with UK Catapult Centres like the AMRC.” <Send for reinforcements> White adds that the use of carbon fibre composite materials in landing gear manufacture presents a number of real opportunities, but also some challenges. “If you can imagine an aircraft landing at 12ft per second and weighing in the region of 250tonnes then you can appreciate the loads going through composite materials are very high,” he states. “As the pin joints are made from steel, we need to keep the composite envelope as small as possible, otherwise what we gain in weight savings using composite materials we lose by adding weight to the pins. Landing gear assemblies work in very hostile environments, so we must be very aware of the material's damage tolerance. “MBD is the first landing gear manufacturer to use composites on large structured parts. The side and drag braces of the Boeing 787 Dreamliner landing gear are made from carbon fibre composite materials. There are many examples of what we're doing to generate complex shapes using composite materials. We realise they are the future and we're spending a proportional amount of time at Safran group level developing the materials, the technology and the resins so that when the next generation of large landing gear programmes arrive, we'll be able to offer landing gear solutions with a high level of  composite materials.” White believes MBD understands how manufacturing innovation can help profoundly influence technical R&D into landing gear systems. The company continues to work with various technology centres, looking at how different manufacturing techniques can help drive future design. MBD is also aware that additive manufacturing will drive changes in terms of design concepts, whilst reinforced thermoplastic use is another area where it is looking at ways to remove weight. “We must develop methods, tools and processes that actually influence the design from day one,” he concludes. “40,000 take-offs and landings every day with an aircraft landing every 2.2 seconds involve our landing gear. Technology and innovation form our key strategies within MBD and Safran, and both will require further investment to ensure we maintain our number one position as a global landing gear supplier.”  www.safranmbd.com

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