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Laser air speed sensor can enhance aerospace safety, stealth and economy
Article Type: Safety topics and notes From: Aircraft Engineering and Aerospace Technology: An International Journal, Volume 21, Issue 6
BAE Systems is leading a combined industry and academic team in the development of the next generation of air speed sensor. As a result the laser air speed sensor instrument (LASSI) programme has produced a sensor that uses an ultra-violet (UV) laser designed to increase the accuracy of air speed measurement over a much wider range of speeds than traditional methods.
The current method for measuring air speed, the pitot tube, is very accurate at high speeds but is not well suited to the measurement of air speed at low velocities. This causes problems for helicopters, particularly during low speed manoeuvres close to the ground. Additionally, on fixed-wing aircraft, the pitot tube increases the drag on an aircraft and hence fuel consumption.
The new sensor provides significant benefits for all forms of aircraft. For helicopters, LASSI will greatly improve the information provided to pilots during low speed activities, increasing safety. For fixed-wing passenger and transport aircraft, the reduction in drag achieved with the removal of pitot tubes will see fuel savings over long journeys. For military aircraft, LASSI will enable a reduction in the radar cross section of the aircraft and hence improve its survivability in enemy territory.
LASSI exploits the coupling of a new UV laser source with a novel sensor architecture to achieve the required system performance from a compact, power efficient package. The use of fibre optic delivery facilitates system flexibility and deployment. By firing the laser into the atmosphere, the nature of the light reflected from the air molecules will change with speed. This variation is measured by the LASSI system and converted to airspeed.
LASSI has been undertaken by BAE Systems Advanced Technology Centre in collaboration with Advanced Optical Technology Ltd and the Department of Physics at Hull University. The programme is sponsored by the UK Department of Trade and industry (DTI).