Book Description

This report discusses techniques for evaluating the efficacy of Visual Approach Slope Indicators (VASIs) intended for transport aircraft landing at major runways. The discussion is predicated on the assumption that VASI signals should act as a substitute for the information the pilot sees in the natural scene, and a list of design requirements is developed accordingly. Several testing techniques and the utility of information likely to be obtained from each one are outlined. Various aspects of experimental design including the choice of aircraft, pilots, treatments and statistical analysis which can influence the validity of conclusions are highlighted. In many published evaluations to date there has been undue reliance on the subjective opinions of pilots instead of measurements describing flight paths in objective terms. Similarly, operational evaluations have been preferred to more informative experimental tests. Adequate testing of current VASIs could enable substantial improvements to be incorporated into VASI designs of the future, but unfortunately, previous tests have not always been adequate, restricting the pertinence of the findings and limiting the generality of conclusions which might otherwise have influenced subsequent designs. (Author).