At EADS Innovation Works, the company’s research centre, scientists are working on a system that can identifyturbulences 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.