Section 171.313

14 CFR Ch. I (1-1-19 Edition)

and Auxiliary Data C. Auxiliary Data
A contents are specified below, Auxiliary Data B contents are reserved for
future use, and Auxiliary Data C contents are reserved for national use. The
address codes of the auxiliary data
words shall be as shown in Table 8b.
(2) Organization and timing. The organization and timing of digital auxiliary
data must be as specified in Table 7b.
Data containing digital information
must be transmitted with the least significant bit first. Alphanumeric data
characters must be encoded in accordance with the 7-unit code character set
as defined by the American National
Standard Code for Information Interchange (ASCII). An even parity bit is
added to each character. Alphanumeric
data must be transmitted in the order
in which they are to be read. The serial
transmission of a character must be
with the lower order bit transmitted
first and the parity bit transmitted
last. The timing for alphanumeric auxiliary data must be as shown in Table
7c.
(3) Auxiliary Data A content: The data
items specified in Table 8c are defined
as follows:
(i) Approach azimuth antenna offset
shall represent the minimum distance
between the Approach Azimuth antenna phase center and the vertical
plane containing the runway centerline.
(ii) Approach azimuth to MLS datum
point distance shall represent the minimum distance between the Approach
Azimuth antenna phase center and the
vertical plane perpendicular to the centerline which contains the MLS datum
point.
(iii) Approach azimuth alignment with
runway centerline shall represent the
minimum angle between the approach
azimuth antenna zero-degree guidance
plane and the runway certerline.
(iv) Approach azimuth antenna coordinate system shall represent the coordinate system (planar or conical) of the
angle data transmitted by the approach azimuth antenna.
(v) Approach elevation antenna offset
shall represent the minimum distance
between the elevation antenna phase
center and the vertical plane containing the runway centerline.

(vi) MLS datum point to threshold distance shall represent the distance
measured along the runway centerline
from the MLS datum point to the runway threshold.
(vii) Approach elevation antenna
height shall represent the height of the
elevation antenna phase center relative to the height of the MLS datum
point.
(viii) DME offset shall represent the
minimum distance between the DME
antenna phase center and the vertical
plane containing the runway centerline.
(ix) DME to MLS datum point distance
shall represent the minimum distance
between the DME antenna phase center
and the vertical plane perpendicular to
the centerline which contains the MLS
datum point.
(x) Back azimuth antenna offset shall
represent the minimum distance between the back azimuth antenna phase
center and the vertical plane containing the runway centerline.
(xi) Back azimuth to MLS datum point
distance shall represent the minimum
distance between the Back Azimuth
antenna and the vertical plane perpendicular to the centerline which contains the MLS datum point.
(xii) Back azimuth antenna alignment
with runway centerline shall represent
the minimum angle between the back
azimuth antenna zero-degree guidance
plane and the runway centerline.
Section 171.313 Azimuth
performance
requirements.
This section prescribes the performance requirements for the azimuth
equipment of the MLS as follows:
(a) Approach azimuth coverage requirements. The approach azimuth equipment must provide guidance information in at least the following volume of
space (see Figure 9):
TABLE 8b - AUXILIARY DATA WORD ADDRESS
CODES
No.
1.
2.
3.
4.
5.
6.
7.
8.

I13

I14
0
0
0
0
0
0
0
0

I15
0
0
0
0
0
0
0
0

I16
0
0
0
0
0
0
0
1

I17
0
0
0
1
1
1
1
0

I18
0
1
1
0
0
1
1
0

I19
1
0
1
0
1
0
1
0

864

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I20
1
1
0
1
0
0
1
1

1
0
1
1
0
1
0
0