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

Appendix to Chapter 6
REFINED METHOD FOR CALCULATING MAPt AND
TRANSITIONAL TOLERANCES FOR A MISSED APPROACH POINT
DEFINED BY A DISTANCE FROM THE FAF
1. INTRODUCTION
1.1 This appendix shows the full Root Sum Square (RSS) method for calculating:
a) distance from earliest MAPt to nominal MAPt;
b) distance from nominal MAPt to latest MAPt; and
c) distance from nominal MAPt to SOC,
when the MAPt is defined by a distance from the FAF.
1.2 The criteria contained in Part I, Section 4, Chapter 6, 6.1.6.3, “Determining SOC with an MAPt defined by a
distance from the FAF (simplified method)” are conservative in certain cases. To overcome this conservatism,
distances may be calculated precisely using the formulas in this appendix.
1.3 The equations shown in Chapter 6, Table I-4-6-1, “Values for Z (Earliest and latest MAPt for MAPt
determined by distance from the FAF)” and Chapter 6, Table I-4-6-2, “Computation of transitional distance” were
derived by linear interpolation from the accurate RSS calculations at the extreme values quoted (i.e. aircraft Categories
A to D and for all aerodrome elevations up to 4 000 m (13 000 ft)).
2. CALCULATION
2.1 General
The calculation of each of the relevant distances is done in two steps, using the maximum and minimum final approach
speeds for the category of aircraft. The considered distance is the higher of the two found.
2.2 Factors
The empirical RSS method takes into account the following factors:
a) the fix tolerance at the FAF (assumed as 1.9 km (1.0 NM) to develop the simplified equations in the body of
this chapter);
b) the minimum permissible speed at ISA – 10°C or the maximum permissible speed at ISA + 15°C, whichever is
the more critical for each category of aircraft considered;
I-4-6-App-1 23/11/06