Research on a method to measure the optical parameters of a precision approach path indicator

The precision approach path indicator (PAPI) system is installed alongside a runway or at a heliport to provide accurate visual approach path information to pilots of landing aircraft, either day or night. The indicator sends the information through different color combinations. The international standards have very rigid requirements for the intensity distribution and the transition angle from red light to white light of the indicator. These two parameters are the main parameters to judge the accuracy of the indicator. We propose a new method to measure these two optical parameters, which can improve the accuracy of the signals and guarantee safe landing of the aircraft.