Led light sources in the approach slope indicators and their visibility in inhomogeneous atmosphere

1) In laboratory measured APAPI light distribution parameters have proved the applicability of SMD LED chips instead of a halogen lamp in the optical unit of the APAPI visual approach slope indicator system. 2) The same thing shows the calculated visibility range values in inhomogeneous environment and applicability of APAPI with 50W SMD LED chip on the airfields belong to the ICAO CAT I. 3) Using a 100W or 150W SMD LED chip in the APAPI optical unit, it can be used on the airfields belong to the ICAO CAT II.