861
Federal Aviation Administration, DOT
§ 171.311
T
ABLE
8a—B
ASIC
D
ATA
W
ORDS
Data bit
#
Data item definition
LSB
value
Data bit
value
Basic Data Word No. 1
1 Preamble .........................
N/A
1
2 ..........................................
............
1
3 ..........................................
............
1
4 ..........................................
............
0
5 ..........................................
............
1
6 ..........................................
............
0
7 ..........................................
............
1
8 ..........................................
............
0
9 ..........................................
............
1
10 ..........................................
............
0
11 ..........................................
............
0
12 ..........................................
............
0
13
Approach azimuth to
threshold distance
(Om
¥
630m).
100m 100m
14 ..........................................
............
200m
15 ..........................................
............
400m
16 ..........................................
............
800m
17 ..........................................
............
1600m
18 ..........................................
............
3200m
19
Approach azimuth propor-
tional coverage limit
(negative limit) (0
°
to
¥
62
°
).
2
°
¥
2
°
20 ..........................................
............
¥
4
°
21 ..........................................
............
¥
8
°
22 ..........................................
............
¥
16
°
23 ..........................................
............
¥
32
°
24
Approach azimuth propor-
tional coverage limit
(positive limit) (0
°
to +
62
°
).
2
°
2
°
25 ..........................................
............
4
°
26 ..........................................
............
8
°
27 ..........................................
............
16
°
28 ..........................................
............
32
°
29
Clearance signal type ......
N/A 0 = pulse; 1
= SB
30 Spare ...............................
............
Transmit
zero
31
Parity: (13 + 14 + 15. . .
+ 30 + 31 = odd).
N/A N/A
32
Parity: (14 + 16 + 18. . .
+ 30 + 32 = odd).
N/A N/A
Note 1:
Transmit throughout the Approach Azimuth guidance
sector at intervals of 1.0 seconds or less.
Note 2:
The all zero state of the data field represents the
lower limit of the absolute value of the coded parameter
unless otherwise noted.
Basic Data Word No. 2
1 Preamble .........................
N/A
1
2 ..........................................
............
1
3 ..........................................
............
1
4 ..........................................
............
0
5 ..........................................
............
1
6 ..........................................
............
0
7 ..........................................
............
1
8 ..........................................
............
1
9 ..........................................
............
1
10 ..........................................
............
1
11 ..........................................
............
0
12 ..........................................
............
0
13
Minimum glide path (2.0
°
to 14.7
°
).
0.1
°
0.1
°
14 ..........................................
............
0.2
°
15 ..........................................
............
0.4
°
16 ..........................................
............
0.8
°
T
ABLE
8a—B
ASIC
D
ATA
W
ORDS
—Continued
Data bit
#
Data item definition
LSB
value
Data bit
value
17 ..........................................
............
1.6
°
18 ..........................................
............
3.2
°
19 ..........................................
............
6.4
°
20
Back azimuth status ........
............
see note 4
21
DME status ......................
............
see note 6
22 ..........................................
............
23
Approach azimuth status
............
see note 4
24
Approach azimuth status
............
see note 4
25 Spare ...............................
............
Transmit
zero
26 ......do ...............................
............
Do.
27 ......do ...............................
............
Do.
28 ......do ...............................
............
Do.
29 ......do ...............................
............
Do.
30 ......do ...............................
............
Do.
31
Parity: (13 + 14 + 15. . .
+ 30 + 31) = odd).
N/A N/A
32
Parity: (14 + 16 + 18. . .
+ 30 + 32 = odd).
N/A N/A
Note 1:
Transmit throughout the Approach Azimuth guidance
sector at intervals of 0.16 seconds or less.
Note 2:
The all zero state of the data field represents the
lower limit of the absolute range of the coded parameter
unless otherwise noted.
Basic Data Word No. 3
1 Preamble .........................
N/A
1
2 ..........................................
............
1
3 ..........................................
............
1
4 ..........................................
............
0
5 ..........................................
............
1
6 ..........................................
............
1
7 ..........................................
............
0
8 ..........................................
............
1
9 ..........................................
............
0
10 ..........................................
............
0
11 ..........................................
............
0
12 ..........................................
............
0
13
Approach azimuth beam-
width (0.5
°
¥
4.0
°
) See
note 7.
0.5
°
0.5
°
14 ..........................................
............
1.0
°
15 ..........................................
............
2.0
°
16 Approach
elevation
beamwidth (0.5
°
to
2.5
°
) See note 7.
0.5
°
0.5
°
17 ..........................................
............
1.0
°
18
Note: values greater than
2.5
°
are invalid.
............
2.0
°
19
DME distance (Om to
6387.5m.
12.5m 12.5m
20 ..........................................
............
25.0m
21 ..........................................
............
50.0m
22 ..........................................
............
100.0m
23 ..........................................
............
200.0m
24 ..........................................
............
400.0m
25 ..........................................
............
800.0m
26 ..........................................
............
1600.0m
27 ..........................................
............
3200.0m
28 Spare ...............................
............
Transmit
zero
29 ......do ...............................
............
Do.
30 ......do ...............................
............
Do.
31
Parity: (13 + 14 + 15. . .
+ 30 + 31 = odd).
............
32
Parity: (14 + 16 + 18. . .
+ 30 + 32 = odd).
N/A N/A
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