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

Appendix to Chapter 3
DERIVATION AND CALCULATION OF ATT, XTT AND
AREA SEMI-WIDTH
1. CALCULATION EXAMPLES FOR DME/DME XTT AND ATT AND THE AREA SEMI-WIDTH
WHEN DME STATIONS COMMISSIONED PRIOR TO 1 JANUARY 1989 ARE USED
1.1 Calculation examples in case of two DME stations available
Area semi-width en-route:
(Maximum DME distance of 370.4 km (200 NM) is applicable)
SI units Non-SI units
DTT = (0.0125 x 370.4) + 0.463 = 5.09 km DTT = (0.0125 x 200.0) + 0.250 = 2.75 NM
ST = 0.46 km ST = 0.25 NM
FTT = 3.70 km FTT = 2.00 NM
BV = 3.70 km BV = 2.00 NM
ATT = [(1.29d) 2 +0.46 2 ]½ = 6.58 km ATT = [(1.29d)2 + 0.252]½ = 3.56 NM
XTT = [(1.29d) 2 + 3.72 + 0.46 2 ]½ = 7.55 km XTT = [(1.29d)2 + 2.02 + 0.252]½ = 4.08 NM
½A/W = 1.5 x XTT + BV = 15.03 km ½A/W = 1.5 x XTT + BV = 8.12 NM
Area semi-width at initial approach 1 500 m (5 000 ft):
SI units Non-SI units
DTT = 0.0125 x 4.11 (1 500)½ + 0.463 = 2.45 km DTT = 0.0125 x 1.23 (5 000)½ + 0.25 = 1.34 NM
ST = 0.46 km ST = 0.25 NM
FTT = 1.90 km FTT = 1.00 NM
BV = 1.90 km BV = 1.00 NM
ATT = 3.19 km ATT = 1.75 NM
XTT = 3.69 km XTT = 2.01 NM
½A/W = 7.39 km ½A/W = 4.02 NM
III-1-3-App-1 23/11/06