In-flight evaluation of an optical standby air data system

Henk W. Jentink, National Aerospace Laboratory NLR,
Henri Kannemans, National Aerospace Laboratory NLR,
Marcel J. Verbeek, National Aerospace Laboratory NLR,

Abstract

Within the EC project NESLIE (New Standby Lidar Instrument), an innovative air data system was developed, built and tested. The system applies the LiDAR technique to measure air speed. This principle differs from the customary pitot-static one, thereby reducing common failures in the total system and increasing flight safety.

The NESLIE system measures air speed in four different directions. The aircraft’s TAS (True Air Speed), AOA (Angle Of Attack) and SSA (Side Slip Angle) are calculated from these speed measurements.

The development resulted in a first test system. The in-flight evaluation of the system was performed in the NLR Cessna Citation II research aircraft during spring 2009. The performance of the system as a function of the atmospheric conditions was measured and the output of the system was compared with Citation air data.

This paper describes the standby air data system under test as developed in the NESLIE project, describes the integration of the system in the NLR Cessna Citation II research aircraft, gives an overview of the techniques applied during the flight test campaign and presents the results of the analysis of recorded data. Flight testing of the system in an already instrumented and relatively easy-to-modify research aircraft as presented proved to be effective and efficient.