Originally Posted by Airportdata
PAPI and Localizer Glideslope are not designed to coincide or give the same information.
Originally Posted by ICAO Annex XIV
5.3.5.36 When the runway is equipped with an ILS and/or
MLS, the siting and the angle of elevation of the light units
shall be such that the visual approach slope conforms as
closely as possible with the glide path of the ILS and/or the
minimum glide path of the MLS, as appropriate.
This is flight checked, by the way.
In addition, localizers do not have glide slopes. ILS systems do.
Originally Posted by Airportdata
In most cases The PAPI instalation is installed on a Non Precision approach runway for descent information below MDA. In other words it is for a visual approach.
Originally Posted by ICAO Annex XIV
5.3.5.1 A visual approach slope indicator system shall be
provided to serve the approach to a runway whether or not the
runway is served by other visual approach aids or by nonvisual
aids, where one or more of the following conditions
exist:
a) the runway is used by turbojet or other aeroplanes with
similar approach guidance requirements;
b) the pilot of any type of aeroplane may have difficulty in
judging the approach due to:
1) inadequate visual guidance such as
...