Aircraft Operations. Volume II - Construction of Visual and Instrument ...

Part II — Section 1, Chapter 1, Appendix D II-1-1-App D-3
3.2.2 Where the OAS surfaces are below P1 or P2, they become the PAOAS. Where the Z surface is above the
PAOAS, it becomes the PAOAS. A typical example of the layout of combined OAS and PAOAS surfaces is depicted
in Figure II-1-1-App D-1. The surfaces terminate at a height of 300 m (1 000 ft) below minimum altitude/height
associated with tactical radar vectoring.
3.3 Calculation of PAOAS height
To calculate the height z of P1 or P2 surfaces at a location x’, y’, the appropriate constants should be obtained from
Table II-1-1-App D-1 and substituted in the equation z = Ax’ + By’ + C. Similarly, the height of the OAS surfaces
should be calculated according to Chapter 1, 1.4.8. The height of the PAOAS is then determined as specified in 3.2,
“Definition of surfaces,” above.
3.4 Obstacle assessment
3.4.1 The obstacle elevation/height in the area to be considered shall be less than the PAOAS height as specified
in 3.2, “Definition of surfaces,” above. Obstacles below the Z surface, or its extension, need not be considered. PAOAS
penetrations shall be identified and considered for electronic mapping on controller displays.
3.4.2 If possible, obstacles should be removed. Where obstacle removal is not feasible, air traffic operational rules
shall be established to avoid obstacles, and a risk assessment shall be required to provide guidance on whether
independent simultaneous ILS/MLS operations to parallel runways should be approved.
Table II-1-1-App D-1. Constants for calculation of PAOAS
PAOAS A B C
P1
P2
tan θ
0
0.091
0.091
θ = ILS glide path angle or MLS elevation angle
PAOAS coordinates in metres
5
15
23/11/06