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

II-1-3-10 Procedures — Aircraft Operations — Volume II
autocoupled operations. The PANS-OPS OAS CD-ROM gives coefficients for glidepath angles between 2.5° and 3.5°
in 0.1° steps, and for any azimuth-threshold distance between 2 000 m and 4 500 m. Extrapolation outside these limits
is not permitted. If an azimuth-threshold distance outside this range is entered, the PANS-OPS OAS CD-ROM gives
the coefficients for 2 000 m or 4 500 m as appropriate, which must be used. For an example of the PANS-OPS OAS
CD-ROM results, see Figure II-1-3-13.
3.4.8.5 Calculation of OAS heights
To calculate the height z of any of the sloping surfaces at a location x’, y’, the appropriate constants should be first
obtained from the PANS-OPS OAS CD-ROM. These values are then substituted in the equation z = Ax’ + By’ + C. If
it is not clear which of the OAS surfaces is above the obstacle location, this should be repeated for the other sloping
surfaces. The OAS height is the highest of the plane heights (zero if all the plane heights are negative).
Note.— The PANS-OPS OAS CD-ROM also contains an OCH calculator that will show the height of the OAS
surface z above any x, y location. It includes all the adjustments specified for MLS geometry, aircraft dimensions,
missed approach climb gradient and MLS approach reference datum height.
3.4.8.6 OAS template construction
Templates, or plan views of the OAS contours to map scale, are sometimes used to help identify obstacles for detail
survey (see Figure II-1-3-12). The OAS data in the PANS-OPS CD-ROM includes the coordinates of the points of
intersection:
a) of the sloping surfaces at threshold level. The intersection coordinates are labeled as C, D and E
(Figure II-1-3-12);
b) at 300 m above threshold level for Cat I; and
c) at 150 m for Cat II.
3.4.8.7 Adjustment of OAS constants
3.4.8.7.1 General. The following paragraphs describe the adjustments that the PANS-OPS OAS CD-ROM makes
to the OAS constants. These adjustments are mandatory when the standard conditions are not met (see 3.1.3, “Standard
conditions”). Optional adjustments may be made when so specified. For examples of calculations see the Instrument
Flight Procedures Construction Manual (Doc 9368).
3.4.8.7.2 Reasons for adjusting constants. The constants may be modified to account for the following:
a) dimensions of specific aircraft (see 3.4.8.7.3, below);
b) the height of the MLS approach reference datum above the nominal value (see 3.4.8.7.4, below);
c) Category I azimuths having a sector width greater than 210 m at threshold (see 3.4.8.7.5, below);
d) use of flight director (manually flown) in Cat II (see 3.4.8.7.6, below); and
e) missed approach climb gradient (see 3.4.8.7.7, below).
23/11/06