Freiburg, May 2022

Highest safety standards for Airbus Helicopters:
The LCR-350B Attitude and Heading Reference System from LITEF

The open sea is notorious for the rough winds that blow across its waters. Safely manoeuvring a helicopter under such harsh conditions requires sure instinct and years of experience from the pilots. This becomes necessary, for example, when offshore wind farms have to be maintained on the high seas or employees have to be transported to or from their workplace on oil platforms. But apart from the pilots' flying skills, there is another thing that is crucial: the right technology behind everything. It is worth taking a closer look at the interior of the helicopters.

At first glance, there are simply two black boxes built into the helicopter. But without them, the aircraft could not be flown safely: The LCR-350B Attitude and Heading Reference System (AHRS) from LITEF provides vital data necessary for safe flight. "A simple analogy would be likening the device to a sense of orientation and balance for the aircraft," says Klaus Blatter, Product Manager Commercial Aviation at LITEF. "Without these sensors, helicopters or airplanes would be flying only using external visual references. During vertical take-off and landing, the AHRS makes it easier for the pilot to control the helicopter." In addition, during search and rescue operations, for example, helicopters have to hover precisely in mid-air – here too, the LCR-350B plays an important role. "As this hardware and software are critical for safety, the AHRS has been developed to highest safety standards," explains Dr Daniel Martens, Director of Commercial Aviation at LITEF.

Harsh environmental conditions require maximum robustness
The conditions under which the LCR-350B is operated are particularly challenging: The sensors must be resistant to vibrations and reliably provide the necessary data even under significant temperature variations. In the far north, on ships or oil platforms, there is often magnetic interference, which makes it difficult to measure the heading with a magnetic sensor. It is important that sensors also work reliably under these conditions. "Allow me to present an illustrative example for this: The accuracy of the gyroscope built into the AHRS makes it possible to maintain the aircraft's heading even without a magnetic sensor. In other words, the LCR-350B can reliably deliver data even in environments where the magnetic reference is not ideal or disturbed," says Klaus Blatter. "Reliability of the entire product is always at the forefront of the entire design process."
The reliability of the LCR-350B is the result of many years of development: "Our attitude and heading reference system is based on MEMS technology (micro-electro-mechanical-systems). This technology makes it possible to build very small and cost-efficient sensors. However, in principle, the technology is susceptible to vibrations and the sensor accuracy may degrade under such conditions," says Dr Daniel Martens. "But since sensor accuracy and performance are a fundamental requirement for the LCR-350B, this technology was painstakingly developed to create highly complex and sophisticated electronic control circuits to reach our final result, making the LCR-350B so reliable, robust and highly accurate – this is the pinnacle of what our concentrated know-how can achieve." Furthermore, the use of composites in aircraft construction also reduces shielding from electromagnetic interference. Especially for helicopters flying close to such emitters, the requirements for the immunity of the electronic components are even higher. Also in this area, the LCR-350B meets the highest requirements.

More than ten years of research and development pays off
But how does LITEF develop highly complex solutions like this? Generations of design improvements and more than ten years of research and development have led to this sophisticated, compact and lightweight product with inherent reliability. "Of course, we didn't have to start from scratch here, but made good use of existing technologies and our experience," says Klaus Blatter. During development, LITEF worked in close cooperation with Airbus Helicopters early on, who needed a AHRS for their helicopters. Today, various types of Airbus Helicopters use the LCR-350B from LITEF. "By involving a launching customer like Airbus at an early stage, we were able to better incorporate practical requirements into the iterative development process and test them directly," says Dr Daniel Martens. "With the LCR-350B, we have succeeded in developing a product that is not only reliable for military applications in fixed-wing aircraft and helicopters, but also for civilian applications, such as in search and rescue, police and offshore services."
In addition to the very high aeronautical quality standards, an AHRS meeting highest safety requirements must undergo an elaborate certification process. "The underlying data is crucial. For example, we had to prove multi-layered probability calculations using precise specifications that reflect the percentage probability of a possible failure. Redundancy in operation serves as yet another fail-safe: Every helicopter has at least two units installed," explains Dr Daniel Martens. "The practical use of the LCR-350B in the air confirms: There are hardly any failures. The very long development time brings the expected reliability and pays off for us and our customers."

LITEF: Close dialogue with customers and highest quality
LITEF also develops and manufactures high-quality navigation and sensor systems in other areas. Its expertise is based on German technology for mechanical, fibre optic and micro-mechanical inertial sensors. This allows for ITAR-free distribution of LITEF products all over the world. The product range of the company, which was founded in 1961, includes sensors, inertial measurement units, attitude and heading reference systems, inertial navigation systems and
inertial reference systems. In close discussions with the customer, specific product solutions are developed for measurement and navigation tasks with the maximum precision and reliability requirements. Products from LITEF are in use worldwide, with applications ranging from civil and military aviation, land and marine applications, through to industrial applications.