aerospace

Learning from the eagle

Over a period of 20 years, Liebherr-Aerospace has built up a worldwide network for manufacturing precision landing gear that includes 13 Starrag machines, with the aim of mimicking the accuracy of the eagle. In a short YouTube video clip from Liebherr-Aerospace, viewed 7,300 times, an eagle lands calmly and precisely on rocky ground, accompanied by the slogan: “The best landing gears are built by nature. But we are working on it.”

A harmonious image, however, the requirements in aviation are far more complex. The eagle weighs barely 11 lb. (5 kg), reaches 99 mph (160 km/h) in a dive, and carries only itself. A modern landing gear, on the other hand, must be able to reliably handle over 300 tonnes of flying weight, regardless of the weather, surface, or time of day. The film nevertheless underlines the important point: safe landing under almost all conditions. Together with Starrag, Liebherr is striving to manufacture landing gear systems that function safely, precisely, and reliably over time, even under extreme conditions. The nucleus of this philosophy lies in Lindenberg in the Allgäu region, around 12 mi (20 km) east of Lake Constance. The site has been a center for aviation technology and precision metalworking for decades. Liebherr founded a repair company here in 1960, which has developed into today’s Liebherr-Aerospace Lindenberg GmbH, a leading global system supplier for flight control systems and landing gear.

High loads on the “legs” of the aircraft

Landing gear components are among the most heavily stressed parts of an aircraft, even though they are hardly noticeable compared to the engine or wings. Their job is to safely support the full weight of the aircraft, including passengers, luggage, and fuel, when it touches down. On every landing, in any weather, and on any surface. The requirements in terms of material, geometry and production quality were high from the outset: over 80% of parts requiring machine cutting, complex component geometries, machining strategies with μm tolerances, supplemented by process-reliable automation. This is also reflected in the production process. New landing gears are made of high-strength titanium or steel alloys. In the future, stainless steel alloys could also be introduced, and Liebherr is ideally prepared for their demanding machining properties with its powerful and stable Droop+Rein machines. Production takes place in up to 40 steps, and comprises complex external contours, multiple drill holes with close tolerances, and heat treatment.

A special feature is the design of the landing gear. “As soon as a machining feature protrudes from the cylinder housing, it is no longer possible to rotate in on a turning machine – it has to be milled”, explained Lee Scott, Director Sales and Applications for Starrag UK. “And it’s almost like mold construction: complex external contours, tight tolerances, lots of drill holes – all in one clamping operation.”

Support covers the entire life cycle from development to maintenance.

High level of vertical integration with machining in a single clamping operation

In order to be able to manufacture components of this complexity in-house, Liebherr-Aerospace Lindenberg GmbH relies on a high level of vertical integration. “We attach great importance to quality and availability. That’s why we manufacture the main components of our landing gear ourselves”, says Bernd Molinari, Group Leader in landing gear manufacturing.In 2004, the decision was made to opt for the first Droop+Rein FOGS M40, a machine which offers impressive stability, precision, and flexibility. One of the decisive factors was the similarity of the component geometries to tool and mold construction. The complex contours and drill holes of the landing gear could be machined economically and precisely on the Droop+Rein FOGS in a single clamping operation, thereby forming the foundations of a long-term partnership.

Between 2004 and 2014, Liebherr-Aerospace built up a dynamic production network in Lindenberg, centered on four Droop+Rein FOGS machines. The machines were gradually expanded, modernized, and specifically automated to include robot-supported tool handling, laser measuring systems and tool magazines for up to 250 tools.

At least 95% availability guaranteed

This network was not only designed for productivity, but also for maximum availability. “Since the first installations, we have been working with a contractually guaranteed technical availability of over 95%”, explains Heiko Quack, Sales Director for Large Projects at Starrag’s product range Droop+Rein in Bielefeld. “In addition to Starrag’s renowned high-quality mechanical engineering with modern and proven technology, we also achieve this through close cooperation: maintenance contracts, regular service workshops, coordinated maintenance. Partnership and advanced planning are key to how Liebherr operates the machines.” And successfully so: the machines from the first few years are still in use, and still providing technical availability of over 95%. The production structure at the site thus became a blueprint for other partner plants worldwide. Standardized processes and reliable machines form the foundation. The period up to 2014 marked not only the expansion of the in-house machinery, but also the start of a strategic network with a high degree of automation, which forms the basis for today’s global production strategy. After the pandemic-related slump and the subsequent market ramp-up, Liebherr-Aerospace has been focusing on the targeted expansion of its global network. In addition to the four Droop+Rein FOGS machines in Lindenberg, a further nine machines were installed at partner sites in China, India, France and – until 2022 – also in Russia. “Liebherr has carefully selected its partners worldwide”, explains Quack. “Together with Liebherr, we have transferred our technology to these locations – wherever new plants have been built or existing production facilities have been made suitable for landing gear manufacturing, we have been involved right from the start.” Another Droop+Rein FOGS machine is currently on its way to Liebherr-Aerospace’s latest manufacturing partner and is scheduled to start production in the course of 2025.

Cooperation on an equal footing: partnership between two market leaders

Since the first installations, we have been working with a technical availability of over 95%.

This close co-operation takes place on an equal footing – not least because Starrag is regarded as the world’s leading machine supplier in the field of landing gear manufacturing. Today, around 60 Droop+Rein machining centers are being used for this task. Around one in seven of them work directly or indirectly in the Liebherr-Aerospace production network. Quack emphasizes: “We are the manufacturer of choice in this market segment, not only because of the technology, but also because of our reliable, global partnership and position in this demanding segment.”

Starrag will be putting the spotlight on the resulting product for the first time at EMO 2025: a fully assembled nose landing gear (NLG) for the Airbus A350, manufactured at Liebherr-Aerospace in Lindenberg. This component not only features eye-catching technology, it is also the largest landing gear Liebherr has developed until now. Since the Airbus A350- 900 entered service in 2016, Liebherr has supplied the system for all A350 variants. The nose landing gear of the Airbus A350-1000, which completed its maiden flight on 24 November 2016, has been redesigned – partly due to the higher maximum take-off weight of 308 tonnes. Liebherr was able to contribute its highly specific experience gained from the A350-900 program.

In addition to the nose landing gear, Liebherr-Aerospace also supplies other systems for the Airbus A350, such as components for controlling slats and landing flaps, load measurement and damping. Support covers the entire life cycle from development to maintenance.

The housing of the landing gear on display is produced on a Droop+Rein FOGS machine in Lindenberg. Unlike the much larger main landing gear, the nose landing gear accounts for only a small proportion of the aircraft’s weight but is just as critical to safety. It is subjected to heavy loads during take-off and landing and must be able to absorb extreme shocks and cope with changes of direction. A high-precision landing gear, such as that exhibited, therefore not only ensures safe operation, but also reduces maintenance costs over the life cycle.

The A350 landing gear, exhibited for the first time, completes the circle: what began symbolically in Liebherr’s YouTube clip – the flight and precision landing of an eagle – can be experienced in technical form at EMO 2025. Because although nature still designs the best landing gear, technology is getting amazingly close.

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