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

III-3-6-12 Procedures — Aircraft Operations — Volume II
Example: Aircraft Category C — Aerodrome elevation:
1 650 m above MSL; glide path angle 3.5°
Tabulated allowances: radio altimeter 22 m
(Table III-3-6-3) pressure altimeter 46 m
Correction for aerodrome elevation:
22 × 2/100 × 1 650/300 = 2.42 m
Correction for glide path angle:
22 × 5/100 × (3.5–3.2)/0.1 = 3.30 m
Total correction 5.72 m rounded up to 6 m
Corrected radio altimeter margin 22 + 6 = 28 m
Corrected pressure altimeter margin 46 + 6 = 52 m
6.4.8.8.3.2 Exceptions and adjustments to values in Table III-3-6-3. Values in Table III-3-6-3 are calculated to
account for aircraft using normal manual overshoot procedures from OCA/H on the nominal approach path. The values
do not consider the lateral displacement of an obstacle nor the probability of an aircraft being so displaced. If
consideration of these joint probabilities is required, then the CRM discussed in 6.4.9 shall be used. Values in Table III-
3-6-3 may be adjusted for specific aircraft types where adequate flight and theoretical evidence is available, i.e. the
height loss value corresponding to a probability of 1 × 10 -5 (based on a missed approach rate 10 -2 ).
6.4.8.8.3.3 Radio altimeter verification. If the radio altimeter OCA/H are promulgated, operational checks shall
have confirmed the repeatability of radio altimeter information.
6.4.8.8.3.4 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 III-3-6-4):
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.
23/11/06