Liebherr Uses Steinmeyer Ballscrew In Sukhoi Jet
Liebherr-Aerospace has specified a Steinmeyer ballscrew for the horizontal stabiliser trim actuator of the Sukhoi Superjet 100, which will be introduced at the Paris Air Show in June. Liebherr-Aerospace, from Lindenberg, Germany, is responsible for the fly-by-wire flight control system of the Sukhoi Superjet 100.
The jet, produced by Russian aerospace firm Sukhoi Civil Aircraft Company, will contain between 75 and 95 seats. An aeroplane must be in balance longitudinally to fly. This means that the net effect of all the forces acting on the aeroplane must not produce an overall pitching moment about the centre of gravity. Without a horizontal stabiliser there would be only one combination of speed and centre-of-gravity position where this requirement was met.
The horizontal stabiliser provides a balancing force to maintain equilibrium for different speeds and centre-of-gravity positions. The ballscrew is part of an actuator that moves the horizontal tail surface of the plane up and down to accommodate the changing centre of gravity. The ability to withstand stress is an important factor in the design of flight-critical components. All structural parts must be tested under maximum stress levels. For that purpose, design engineers at Steinmeyer simulated different load scenarios.
An example is the runaway check. During a runaway, a malfunction of an electronic or electrical part causes the actuator to run against its end stop at full speed and full motor torque. Another scenario could be a gear box jamming, leaving all parts locked under inertia. The components of the actuator must withstand these load conditions without causing the actuator to fail.
Should the actuator be damaged during flight, or should wear to the mechanical parts exceed certain limits, a sensor triggers an alarm. The part can then be identified and replaced during an inspection, rather than operating the aircraft with the help of the backup system for any length of time. Solidworks software was used to model all parts of the horizontal stabiliser trim actuator in 3D.
Various load conditions for all structural parts were analysed with finite element method (FEM) stress analysis and the design adjusted accordingly where necessary, especially where safety was concerned. Every time the design was changed, tests were carried out under a range of load conditions. The ballscrew in the actuator has a special fail-safe feature that triggers an alarm if the load limit is exceeded only once. The design was only finalised when the achieved safety margin was satisfactory. The ballscrew operates 60,000 flight cycles safely and accurately. It is made from Cronidur30 steel, a stainless steel developed for aerospace applications.
To make the component fit for the flight-critical application, special care had to be taken during the manufacturing process, which involves the grinding of the steel parts and can lead to grinder burn with dangerous consequences. Grinder burn is caused by excessive heat generation during the grinding of hardened steel parts. This induces tensile stresses into the material, which can lead to micro cracks and subsequent part-failure. Although sometimes a blackened surface is an obvious sign of grinder burn being present, there is often no visible sign.
Conventional tests for the detection of grinder burn destroy the part. Steinmeyer, in cooperation with Liebherr-Aerospace Lindenberg, has developed a non-destructive method to detect grinder burn using the Barkhausen effect. It involves sending an alternating magnetic field through the part. Changes in the magnetic noise indicate stress conditions in the material. To interpret the results correctly, each new part and the slightest design change needed a new calibration sensor.
This is a complicated and time-consuming process, but, once calibrated, the Barkhausen noise inspection allows complete, reliable and quick scanning of each ballscrew. The horizontal stabiliser trim actuator is only one aerospace application for Steinmeyer ballscrews. The company has set up an aerospace division with its own dedicated design engineers, assembly and inspection staff. Work on a number of prototypes, to be used in civil and military aerospace applications, is currently under way.
Liebherr-Aerospace has specified a Steinmeyer ballscrew for the horizontal stabiliser trim actuator of the Sukhoi Superjet 100, which will be introduced at the Paris Air Show in June. Liebherr-Aerospace, from Lindenberg, Germany, is responsible for the fly-by-wire flight control system of the Sukhoi Superjet 100.
The jet, produced by Russian aerospace firm Sukhoi Civil Aircraft Company, will contain between 75 and 95 seats. An aeroplane must be in balance longitudinally to fly. This means that the net effect of all the forces acting on the aeroplane must not produce an overall pitching moment about the centre of gravity. Without a horizontal stabiliser there would be only one combination of speed and centre-of-gravity position where this requirement was met.
The horizontal stabiliser provides a balancing force to maintain equilibrium for different speeds and centre-of-gravity positions. The ballscrew is part of an actuator that moves the horizontal tail surface of the plane up and down to accommodate the changing centre of gravity. The ability to withstand stress is an important factor in the design of flight-critical components. All structural parts must be tested under maximum stress levels. For that purpose, design engineers at Steinmeyer simulated different load scenarios.
An example is the runaway check. During a runaway, a malfunction of an electronic or electrical part causes the actuator to run against its end stop at full speed and full motor torque. Another scenario could be a gear box jamming, leaving all parts locked under inertia. The components of the actuator must withstand these load conditions without causing the actuator to fail.
Should the actuator be damaged during flight, or should wear to the mechanical parts exceed certain limits, a sensor triggers an alarm. The part can then be identified and replaced during an inspection, rather than operating the aircraft with the help of the backup system for any length of time. Solidworks software was used to model all parts of the horizontal stabiliser trim actuator in 3D.
Various load conditions for all structural parts were analysed with finite element method (FEM) stress analysis and the design adjusted accordingly where necessary, especially where safety was concerned. Every time the design was changed, tests were carried out under a range of load conditions. The ballscrew in the actuator has a special fail-safe feature that triggers an alarm if the load limit is exceeded only once. The design was only finalised when the achieved safety margin was satisfactory. The ballscrew operates 60,000 flight cycles safely and accurately. It is made from Cronidur30 steel, a stainless steel developed for aerospace applications.
To make the component fit for the flight-critical application, special care had to be taken during the manufacturing process, which involves the grinding of the steel parts and can lead to grinder burn with dangerous consequences. Grinder burn is caused by excessive heat generation during the grinding of hardened steel parts. This induces tensile stresses into the material, which can lead to micro cracks and subsequent part-failure. Although sometimes a blackened surface is an obvious sign of grinder burn being present, there is often no visible sign.
Conventional tests for the detection of grinder burn destroy the part. Steinmeyer, in cooperation with Liebherr-Aerospace Lindenberg, has developed a non-destructive method to detect grinder burn using the Barkhausen effect. It involves sending an alternating magnetic field through the part. Changes in the magnetic noise indicate stress conditions in the material. To interpret the results correctly, each new part and the slightest design change needed a new calibration sensor.
This is a complicated and time-consuming process, but, once calibrated, the Barkhausen noise inspection allows complete, reliable and quick scanning of each ballscrew. The horizontal stabiliser trim actuator is only one aerospace application for Steinmeyer ballscrews. The company has set up an aerospace division with its own dedicated design engineers, assembly and inspection staff. Work on a number of prototypes, to be used in civil and military aerospace applications, is currently under way.
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