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

II-1-3-8 Procedures — Aircraft Operations — Volume II
c) the missed approach surface. This is a sloping surface which:
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1) starts at a point 900 m past threshold at threshold elevation;
2) rises at a 2.5 per cent gradient; and
3) splays so as to extend between the transitional surfaces.
It extends with constant splay to the level of the inner horizontal surface. Thereafter, it continues at the same
gradient but with a 25 per cent splay until the termination of the precision segment; and
d) the extended transitional surfaces, which continue longitudinally along the sides of the approach and missed
approach surfaces and up to a height of 300 m above threshold elevation.
3.4.7.3 Determination of OCA/H with basic ILS surfaces
3.4.7.3.1 Where the basic ILS surfaces specified in 3.4.7.2 are not penetrated, the OCA/H for Category I and
Category II is defined by the margins specified in Table II-1-3-2, and Category III operations are not restricted.
Obstacles may be excluded when they are below the transitional surface defined by Annex 14 for runways with code
numbers 3 and 4, regardless of the actual runway code number (i.e., the surfaces for code numbers 3 and 4 are used for
the obstacle assessment on runways with code numbers 1 and 2).
3.4.7.3.2 If the basic ILS surfaces listed above are penetrated by objects other than those listed in Table II-1-3-3
the OCA/H may be calculated directly by applying height loss/altimeter margins to obstacles (see 3.4.8.8.2,
“Calculation of OCA/H values with OAS”).
3.4.7.3.3 The obstacles in Table II-1-3-3 may only be exempted if the following two criteria are met:
a) the nominal course has the standard width of 210 m (see 3.1.3, “Standard conditions”); and
b) the MLS Category I decision height is not less than 60 m (200 ft) or the MLS Category II decision height is not
less than 30 m (100 ft).
3.4.7.3.4 An object which penetrates any of the basic ILS surfaces and becomes the controlling obstacle, but
which must be maintained because of its function with regards to air navigation requirements, may be ignored under
certain circumstances in calculating the OCA/H with the following provision. It must be established by the appropriate
authority that the portion which penetrates the surface is of minimum mass and frangibly mounted and would not
adversely affect the safety of aircraft operations.
3.4.8.1 General
3.4.8 Obstacle clearance in the precision segment using obstacle
assessment surface (OAS) criteria
3.4.8.1.1 This section describes the OAS surfaces, the constants which are used to define these surfaces, and the
conditions under which adjustments may or must be made. The OAS dimensions are related to:
a) the MLS geometry (azimuth antenna-threshold distance, MLS RDH, azimuth antenna sector width), glide path
(elevation angle);
b) the category of MLS operation; and