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

Part II — Section 1, Chapter 1 II-1-1-13
Correction for glide path angle:
5 3.5 – 3.2
22 × × = 3.30 m
100 0.1
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.
1.4.8.8.3.2 Exceptions and adjustments to values in Table II-1-1-2. Values in Table II-1-1-2 are calculated to
account for aircraft using normal manual overshoot procedures from OCA/H on the nominal approach path. The values
in Table II-1-1-2 do not apply to Cat III operations. 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 1.4.9 shall be used. Values in Table II-1-1-2 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 ).
1.4.8.8.3.3 Radio altimeter verification. If the radio altimeter OCA/H is promulgated, operational checks shall
have confirmed the repeatability of radio altimeter information.
1.4.8.8.3.4 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-1-1-4):
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.
1.4.8.8.3.5 Height loss (HL)/altimeter margins for a specific speed at threshold (Helicopters). For helicopter
operations the concept of Vat is not applicable. Height loss margins are listed in Table II-1-1-2.
1.4.8.9 Effect of obstacle density on OCA/H. To assess the acceptability of obstacle density below the OAS, the
CRM described in 1.4.9 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