GM1 ADR-DSN.M.640 Visual approach slope indicator systems

(a)Factors that should be considered when making a decision on which runway on an aerodrome should receive first priority for the installation of a visual approach slope indicator system are:

(1)frequency of use;

(2)seriousness of the hazard;

(3)presence of other visual and non-visual aids;

(4)type of aeroplanes using the runway; and

(5)frequency and type of adverse weather conditions under which the runway should be used.

(b)With respect to the seriousness of the hazard, the order given in the CS ADR-DSN.M.640 may be used as a general guide. These may be summarised as:

(1)inadequate visual guidance because of:

(i)approaches over water or featureless terrain, or absence of sufficient extraneous light in the approach area by night;

(ii)deceptive surrounding terrain.

(2)serious hazard in approach;

(3)serious hazard if aeroplanes undershoot or overrun; and

(4)unusual turbulence.

(c)The presence of other visual or non-visual aids is a very important factor. Runways equipped with ILS or MLS would generally receive the lowest priority for a visual approach slope indicator system installation. It should be remembered, though, that visual approach slope indicator systems are visual approach aids in their own right and can supplement electronic aids. When serious hazards exist and/or a substantial number of aeroplanes not equipped for ILS or MLS use a runway, priority might be given to installing a visual approach slope indicator on this runway.

(d)Priority may be given to runways used by turbojet aeroplanes.

(e)Where a runway threshold is temporarily displaced from the normal position and one or more of the conditions specified in paragraph (a) above exist, a PAPI should be provided except that where the code number is 1 or 2 either an APAPI may be provided.