T-Visual Approach Slope Indicator System (T-VASIS) versus Precision Approach Path Indicator (PAPI) – the debate revisited

Abstract

Two visual approach slope indicator lighting systems are in use in Australasia. These systems are designed to ameliorate and overcome the visual illusions associated with the approach and landing manoeuvre of aircraft. Using a flight simulator, 14 student pilot candidates, with little actual flying experience, ‘flew’ 10 approaches using PAPI and 10 approaches using T-VASIS. The approaches were ‘flown’ in various flight conditions including low visibility. The visual approach slope indicator lighting system was randomly assigned to each experimental condition. Results indicated that overall, there was less deviation from a correct glidepath when the approaches were ‘flown’ using T-VASIS. A post-flight survey indicated that participants found T-VASIS to be more intuitive. The results are discussed with reference to the prevailing preference of PAPI over T-VASIS by aviation authorities.