NLR conducted trials with this new speedometer using its Cessna Citation laboratory aircraft as part of the European Seventh Framework Project DANIELA (Demonstration or InstrumEnt based on Laser ANemometry). Flight tests took the Citation as far afield as the North Pole and the Equator.
The new generation speedometer, developed by Thales and other consortium partners, consists of a laser system that measures the Doppler-shift occurring when particles in the atmosphere stream past the aircraft hull. The particles can be anything from tiny dust particles to ice crystals or raindrops. The aim of the tests was to plot the impact of the speed, size and density of these particles on the recorded speed. Flight safety is improved by using the new system as backup alongside the Pitot system.
An earlier version of the system was also tested in the NLR Cessna Citation in a previous project, called NESLIE. That made it possible to install all the new trial equipment largely on the basis of the technical design and components produced for that earlier project, which had all undergone rigorous certification. Tests began as soon as NLR technicians had mounted the test equipment in the plane’s escape hatch. Flight trials took place in the North Pole region, operating from a base at Longyearbuyen on Spitsbergen, primarily to test DANIELA in air that was virtually free of particles. Surprisingly, the Citation also encountered equally particle-free air above the Sahara, while on the way to another test area above West Africa. Operating from a base in Ghana the laboratory plane collected data in tropical rain showers above Sao Tomé and in a sandy and dusty atmosphere over the Mali desert. The maximum altitude flown during the tests was 12 kilometres, the normal cruising altitude of civil aircraft. These trials confirmed confidence in this new generation of speedometers.
Airspeed is still measured with the Pitot tube, a relatively old piece of technology that works on the basis of pressure differences. NLR performed tests with a new type of speedometer using laser technology