Optical Ice Detector Lite: Initial Flight Test Results

In response to safety regulations regarding aircraft icing, Collins Aerospace has developed and tested a new generation of optical ice detectors (OID Lite) intended to discriminate among icing conditions described by Appendix C and Appendix O of 14 CFR Part 25 and Appendix D of Part 33. The OID Lite is a flush-mounted, short-range, polarimetric optical sensor that samples the airstream up to two meters beyond the skin of the aircraft. The intensity and polarization of the backscatter light correlate with bulk properties of the cloud, such as cloud density and phase. Drizzle-sized droplets, mixed within a small droplet cloud, appear as scintillation spikes in the lidar signal when it is processed pulse-by-pulse. Scintillation in the backscatter (in combination with the outside air temperature monitored by another probe) signals the presence of supercooled large droplets (SLD) within the cloud—a capability incorporated into the OID Lite to meet the requirements of Appendix O. Recent laboratory and flight tests have demonstrated the ability of the OID Lite to discriminate among the various icing conditions. In addition, the OID Lite has discriminated mixed phase in a flight test aboard the Weather Modification International Cessna Citation-II research aircraft. The threshold for detection as defined by SAE AS5498B is 0.5 g/m³ IWC, while that for liquid water cloud detection is 0.05 g/m³ LWC [1].