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

Part II — Section 1, Chapter 3 II-1-3-15
e) obstacle data: obstacle boundaries (either as x and y coordinates relative to the runway threshold or as map grid
coordinates) and obstacle height (either above threshold elevation or above MSL). For density assessment, all
obstacles penetrating the basic ILS surfaces described in 3.4.7.2 must be included.
3.4.9.3 Output and application. The output of the programme is:
a) the overall (total) risk of collision with obstacles for aircraft operating to a specified OCA/H; and
b) the minimum OCA/H which will provide the target level of safety.
These options are detailed in Doc 9274, Manual on the Use of the Collision Risk Model (CRM) for ILS Operations. The
user, by rerunning the ILS CRM with the appropriate parameters, can assess the effect on the safety of operations of
any alteration in the parameters, typically varying the glide path, elevation angle or remaining obstacles.
3.5 MISSED APPROACH SEGMENT
3.5.1 General
3.5.1.1 The criteria for the final missed approach are based on those for the general criteria (see Part I, Section 4,
Chapter 6). Certain modifications have been made to allow for the different areas and surfaces associated with the MLS
precision segment and for the possible variation in OCA/H for that segment with aircraft category. Area construction is
according to the navigation system specified for the missed approach.
3.5.1.2 The datum used for calculation of distances and gradients in obstacle clearance calculations is termed
“start of climb” (SOC). It is defined by the height and range at which the plane GP’ — a plane parallel with the glide
path (elevation angle) and with origin at –900 m at threshold level — reaches an altitude OCA/H – HL (OCA/H and
HL must both relate to the same category of aircraft).
3.5.1.3 Where obstacles identified in the final missed approach segment result in an increase in any of the OCA/H
calculated for the precision segment, a higher gradient of the missed approach surface (Z) may be specified in addition
if this will provide clearance over those obstacles at a specified lower OCA/H (see Part I, Section 4, Chapter 6, 6.2.2.1,
“Climb gradient in the intermediate phase”).
3.5.2 Straight missed approach
3.5.2.1 General. The precision segment terminates at the point where the Z surface reaches a height 300 m above
threshold. The width of the Z surface at that distance defines the initial width of the final missed approach area which
splays at an angle of 15 degrees from that point, as shown in Figure II-1-3-16. There are no secondary areas.
3.5.2.2 Straight missed approach obstacle clearance. (See Figure II-1-3-17.) Obstacle elevation/height in this
final missed approach area shall be less than
where:
(OCA/Hps –HL)+do tan Z
a) OCA/H of the precision segment (OCA/Hps) and HL (Table II-1-3-2 value) both relate to the same aircraft
category;
23/11/06