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

II-1-3-14 Procedures — Aircraft Operations — Volume II
3.4.8.8.3.3 Radio altimeter verification. If the radio altimeter OCA/H is promulgated, operational checks shall
have confirmed the repeatability of radio altimeter information.
3.4.8.8.3.4 Height loss (HL)/altimeter margins for a specific speed at threshold. If a height loss/altimeter margin
is required for a specific Vat, the following formulae apply (see also Table II-1-3-4):
Use of radio altimeter:
Margin = (0.096 Vat – 3.2) metres where Vat in km/h
Margin = (0.177 Vat – 3.2) metres where Vat in kt
Use of pressure altimeter:
Margin = (0.068 Vat + 28.3) metres where Vat in km/h
Margin = (0.125 Vat + 28.3) metres where Vat in kt
where Vat is the speed at threshold based on 1.3 times stall speed in the landing configuration at maximum certificated
landing mass.
Note.— The equations assume the aerodynamic and dynamic characteristics of the aircraft are directly related to
the speed category. Thus, the calculated height loss/altimeter margins may not realistically represent small aircraft
with Vat at maximum landing mass exceeding 165 kt.
3.4.8.9 Effect of obstacle density on OCA/H. To assess the acceptability of obstacle density below the OAS, the
ILS CRM described in 3.4.9 may be used. This can provide assistance by comparing aerodrome environments and by
assessing risk levels associated with given OCA/H values. It is emphasized that it is not a substitute for operational
judgement.
23/11/06
3.4.9 Obstacle clearance in the precision segment — application of the ILS collision risk model
(CRM) to MLS operations
3.4.9.1 General. The ILS CRM is a computer program that establishes the numerical risk which can be compared
to the target level of safety for aircraft operating to a specified OCA/H height. A description of the programme and
instructions on its use, including the precise format of both the data required as input and the output results, are given in
the Manual on the Use of the Collision Risk Model (CRM) for ILS Operations (Doc 9274).
3.4.9.2 Input. When applied to MLS operations, the ILS CRM requires the following data as input:
a) aerodrome details: name, runway threshold position and runway orientation in map grid coordinates (optional),
threshold elevation above MSL;
b) MLS parameters: category (the appropriate ILS category as defined in 3.4.8.8.1), glide path (elevation angle),
azimuth-threshold distance, azimuth nominal course width, height of MLS reference datum above threshold;
c) missed approach parameters: decision height (obstacle clearance height) and missed approach turn point;
d) aircraft parameters: type, wheel height (antenna to bottom of wheel), and wing semi-span, aircraft category (A,
B, C, D or DL) missed approach climb gradient; and
Note.— The CRM does not consider Category E aircraft.