摘要: |
An air data system usually consists of a primary system that includes three redundant channels and has, in addition, a separate stand-by channel. Traditional air data standby channels are composed of pitot tubes and pressure ports, which deliver parameters such as airspeed and pressure altitude. The standby channel has generally neither a temperature probe nor an angle of attack probe. The standby static pressure probe location on the fuselage is selected so as to limit the influence of sideslip. Air data standby channels are therefore composed of equipment very similar to that encountered on the primary channels: pitot probes, static probes and pneumatic tubing. The main reason for aircraft accidents to be linked to air data systems is probe obstruction due to icing problems, volcano ash or bugs, although some accidents have occurred due to the failure of pneumatic connection after maintenance operations. Even though efforts are made by manufacturers to design dissimilar air data channels, there is no reason that external aggressions such as ice, ash or bugs will independently affect the primary air data system probe and the standby air data system probe. The purpose of NESLIE is, therefore, to demonstrate that a LIDAR-based (light detection and radar) air data standby channel will help to suppress the major drawbacks of existing pneumatic systems whilst maintaining the performance required by the related standards. The aim of the NESLIE project is to develop a 3-axis laser function for air data standby channel for implementation on civil aircraft on the horizon 2010. Actual air data standby channel is composed of individual probes and pressure sensors. Air data standby channels information delivers vital parameters for the safety of the aircraft's flight such as air speed, angle of attack and altitude. But since primary and standby channels have similar failure modes, the use of laser based standby architecture with drastically different failure modes must increase aircraft's safety by reducing the probability of common failures. |