The HALO system-applying the "safe wing" concept to airline operations in ground icing conditions

A process has been developed to improve upon the existing "Clean Aircraft" concept as currently defined by FAA guidelines for airline operations. The new "Safe Wing" concept works with existing airline programs for operations in icing conditions. It adds a contamination detection and classification system to the current procedural system. This addition improves overall system safety while eliminating burdensome checks, reducing delays and saving deicing/anti-icing fluid costs. By eliminating unnecessary deicings, if also reduces the environmental impact of using excessive deicing fluid. The HALO contamination detection system is comprised of ultrasonic sensors, processing electronics and a cockpit display. This multisensor system automatically and continuously monitors critical wing areas. The ultrasonic sensors provide area coverage and sensitivity to a variety of contaminants. These sensors are integrated into a HALO system design based on correlating contamination roughness, location and extent with aerodynamic performance. The HALO system development passed a major milestone with an in-service evaluation on a Northwest MD-80 during the 1994-95 winter season. This evaluation was designed to show technology viability in the demanding environment of airline winter operations. The single-sensor evaluation system showed a correct classification rate of greater than 95 percent and sensitivity to a variety of contaminants. A multi-sensor, broad coverage prototype system will be tested in the 1995-96 winter season.