Thales 421 - Monitor Alarm Limits, Width Calculation

LLZ 421
Alignment Procedure LLZ−1F (LPD) Operation and Maintenance
ILS 420
7−20 Ed. 07.08SOAC
7.8 MONITOR ALARM LIMITS, WIDTH CALCULATION
− ILS, Localizer monitor alarm limits
Parameter ICAO Annex 10 Reference−§
Annex 10
Standard setting for
LLZ 421 (DDM)
Nom. values for flight check
course width: 4°
90 Hz Mod. depth 20 % ±2 % (3.1.3.5.1)
150 Hz Mod. depth 20 % ±2 % (3.1.3.5.1)
SDM 40 % ±4 % 40 % ±2 %
Position CAT. I ±10.5 m (±1.52 % DDM) (3.1.3.11.2) ±1.6 %
Position CAT . II ±7.5 m (±1.11 % DDM) (3.1.3.11.2) ±1.1 %
Position CAT . III ±6 m (±0.87 % DDM) (3.1.3.11.2) ±0.9 % 8.3 µA
Width alarm Course ±17 % of nom. width
(±2.6 % DDM)
(3.1.3.11.2) 12.9 % ... 18.1 % wide: 4.82°/ narrow: 3.42°
RF Level
(Integral., Internal)
1F: 71 % (3.1.3.11.2) 71 % ... 110 %
RF Level (Nearfield) 71 % ... 129 %
Alarm delay time CAT I: 10 s; CAT II: 5 s; CAT III: 2 s (preferably 1 s); Nearfield: 20 s.
− Calculation of resulting course width on change of the "Displacement Sensitivity" according
ICAO ANNEX 10 for x %:
Resulting Width = Nominal Width / [(100−x) / 100]
==> for 4° course width:
Width wide = 4° / [(100−17) / 100] = 4.82°;
Width narrow = 4° / [(100+17) / 100] = 3.42°
Nominal DDM at course width:
±15.5 % ==> DDM [%] = (DDM [A] /150) S 15.5
and
±150 A ==> DDM [A] = (DDM [%] /15.5) S 150
7.9 CONVERSION OF RETURN LOSS TO VSWR VALUES
The following table shows the return loss in dB and the correspondent VSWR value.
21 0.089 1.196
22 0.079 1.173
23 0.071 1.152
24 0.063 1.135
25 0.056 1.119
26 0.050 1.106
27 0.045 1.094
28 0.040 1.083
29 0.035 1.074
30 0.032 1.065
31 0.028 1.058
32 0.025 1.052
33 0.022 1.046
34 0.020 1.041
35 0.018 1.036
36 0.016 1.032
37 0.014 1.029
38 0.013 1.025
39 0.011 1.023
40 0.010 1.020
1 0.891 17.391
2 0.794 8.724
3 0.708 5.848
4 0.631 4.419
5 0.562 3.570
6 0.501 3.010
7 0.447 2.615
8 0.398 2.323
9 0.355 2.100
10 0.316 1.925
11 0.282 1.785
12 0.251 1.671
13 0.224 1.577
14 0.200 1.499
15 0.178 1.433
16 0.158 1.377
17 0.141 1.329
18 0.126 1.288
19 0.112 1.253
20 0.100 1.222
Return Loss [dB] Reflection Coefficient VSWR Return Loss [dB] Reflection Coefficient VSWR