At EADS Innovation Works, the company’s research centre, scientists are working on a system that can identify turbulences and gusts already before the aircraft flies into it.
It is based on the LIDAR sensor principle. LIDAR stands for LIght Detection And Ranging – using light to discover obstacles and measure how far away they are. To this end, the LIDAR sensor designed by EADS Innovation Works radiates ultra-violet (UV) light pulses, typically at a rate of 60 per second, which are scattered by the nitrogen and oxygen molecules present in the air. In this way, a total of four rays measure the motion vector of the air 50 to 200 metres in front of the aircraft’s nose.
Any turbulence that may be present alters the motion profile of the molecules and thus the signature received by the system. In future, the LIDAR could send data to the flight control system, which would then actuate the wing control surfaces to counteract the effect. “We will send the signals to the flight control computer so the aircraft can automatically react.” says Dr. Nikolaus Schmitt of EADS Innovation Works. “What our LIDAR sees is at most a second ahead. That’s long enough for a machine, but not for the human brain. But our measurement of the airflow at that distance in front of the aircraft is extremely accurate, so the aircraft really will be able to automatically react to a vertical or horizontal draft on the basis of our advance information”.
This not only makes it possible to avoid sudden loss of height (clear air turbulences, so called “air pockets”). Equipped with such an early warning system, the aircraft would also be exposed to less stress, as air turbulence causes strong forces to act on the fuselage and the wings.
The system is currently still in the test phase, and Nikolaus Schmitt estimates that it might be ready for series production in about ten years’ time. The LIDAR was successfully tested in flight on an Airbus A340. The researchers are now looking into the possibility of miniaturising the sensors and integrating them in the flight control system. Aircraft builders from Europe as well as the United States are interested in such technology. However, it is open to conjecture who will be the first to deploy the system.
In future the system might not only be used to measure air pockets, but also wake vortices (turbulences caused by aircraft). Thus, LIDAR could help to gauge the position and distance of planes from the wake vortices of aircraft taking off ahead of them. Aircraft typically maintain a prescribed distance from one another in order to avoid encountering the wake vortex produced by the aircraft in front. However, these distances are not based on real-time measurements and presently can vary from one airworthiness authority’s jurisdiction to another. Like air pockets, vortices are invisible. LIDAR technology would make it possible to discern how far the vortices actually extend. This could enable the required safety spacing between take-offs and landings to be accurately determined in real time based on a common global standard. Furthermore, at some airports this could allow the distances to be safely reduced, thus enabling an increase in air traffic frequency. The researchers at EADS Innovation Works are currently examining how the light pulses must be aligned in order to yield a full picture of the position of a wake vortex.
LIDAR technology could also be used to measure key data such as speed, temperature or air pressure and density during flight. Today these parameters are determined by various mechanical methods. Optical data acquisition would provide an additional measuring technique, providing greater safety through additional systems redundancy. Moreover, particles in the air, such as volcanic ash, could be identified and their concentration determined, enabling safe operation in low ash concentration areas in case of volcanic explosions.For more information visit www.eads.com