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14 CFR Ch. I (1–1–19 Edition)

§ 171.313

and Auxiliary Data C. Auxiliary Data
A contents are specified below, Auxil-
iary Data B contents are reserved for
future use, and Auxiliary Data C con-
tents 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 orga-

nization and timing of digital auxiliary
data must be as specified in Table 7b.
Data containing digital information
must be transmitted with the least sig-
nificant bit first. Alphanumeric data
characters must be encoded in accord-
ance with the 7-unit code character set
as defined by the American National
Standard Code for Information Inter-
change (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 aux-
iliary 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 an-
tenna phase center and the vertical
plane containing the runway center-
line.

(ii)

Approach azimuth to MLS datum

point distance

shall represent the min-

imum distance between the Approach
Azimuth antenna phase center and the
vertical plane perpendicular to the cen-
terline 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 coordi-

nate system

shall represent the coordi-

nate system (planar or conical) of the
angle data transmitted by the ap-
proach azimuth antenna.

(v)

Approach elevation antenna offset

shall represent the minimum distance
between the elevation antenna phase
center and the vertical plane con-
taining the runway centerline.

(vi)

MLS datum point to threshold dis-

tance

shall represent the distance

measured along the runway centerline
from the MLS datum point to the run-
way threshold.

(vii)

Approach elevation antenna

height

shall represent the height of the

elevation antenna phase center rel-
ative 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 center-
line.

(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 be-
tween the back azimuth antenna phase
center and the vertical plane con-
taining 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 perpen-
dicular to the centerline which con-
tains 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.

§ 171.313

Azimuth performance re-

quirements.

This section prescribes the perform-

ance requirements for the azimuth
equipment of the MLS as follows:

(a)

Approach azimuth coverage require-

ments.

The approach azimuth equip-

ment must provide guidance informa-
tion in at least the following volume of
space (see Figure 9):

ABLE

8b—A

UXILIARY

ATA

ORD

DDRESS

ODES

No. I

1. 0 0 0 0 0 1 1 1
2. 0 0 0 0 1 0 1 0
3. 0 0 0 0 1 1 0 1
4. 0 0 0 1 0 0 1 1
5. 0 0 0 1 0 1 0 0
6. 0 0 0 1 1 0 0 1
7. 0 0 0 1 1 1 1 0
8. 0 0 1 0 0 0 1 0

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