843
Federal Aviation Administration, DOT
§ 171.311
Wind Velocity: The ground equipment shall
remain within monitor limits with wind
velocities of up to 70 knots from such di-
rections that the velocity component
perpendicular to runway centerline does
not exceed 35 knots. The ground equip-
ment shall withstand winds up to 100
knots from any direction without dam-
age.
Hail Stones: 1.25 centimeters (
1
⁄
2
inch) diame-
ter.
Rain: Provide required coverage with rain
falling at a rate of 50 millimeters (2
inches) per hour, through a distance of 9
kilometers (5 nautical miles) and with
rain falling at the rate of 25 millimeters
(1 inch) per hour for the additional 28 kil-
ometers (15 nautical miles).
Ice Loading: Encased in 1.25 centimeters (
1
⁄
2
inch) radial thickness of clear ice.
Antenna Radome De-Icing: Down to
¥
6
°
C (20
°
F) and wind up to 35 knots.
(d) The transmitter frequencies of an
MLS must be in accordance with the
frequency plan approved by the FAA.
(e) The DME component listed in
paragraph (a)(4) of this section must
comply with the minimum standard
performance requirements specified in
subpart G of this part.
(f) The marker beacon components
listed in paragraph (b)(4) of this section
must comply with the minimum stand-
ard performance requirements specified
in subpart H of this part.
§ 171.311
Signal format requirements.
The signals radiated by the MLS
must conform to the signal format in
which angle guidance functions and
data functions are transmitted sequen-
tially on the same C-band frequency.
Each function is identified by a unique
digital code which initializes the air-
borne receiver for proper processing.
The signal format must meet the fol-
lowing minimum requirements:
(a)
Frequency assignment.
The ground
components (except DME/Marker Bea-
con) must operate on a single fre-
quency assignment or channel, using
time division multiplexing. These com-
ponents must be capable of operating
on any one of the 200 channels spaced
300 KHz apart with center frequencies
from 5031.0 MHz to 5090.7 MHz and with
channel numbering as shown in Table
1a. The operating radio frequencies of
all ground components must not vary
by more than
±
10 KHz from the as-
signed frequency. Any one transmitter
frequency must not vary more than
±
50
Hz in any one second period. The MLS
angle/data and DME equipment must
operate on one of the paired channels
as shown in Table 1b.
T
ABLE
1a—F
REQUENCY
C
HANNEL
P
LAN
Channel No.
Fre-
quency
(MHz)
500 ...........................................................................
5031.0
501 ...........................................................................
5031.3
502 ...........................................................................
5031.6
503 ...........................................................................
5031.9
504 ...........................................................................
5032.2
505 ...........................................................................
5032.5
506 ...........................................................................
5032.8
507 ...........................................................................
5033.1
508 ...........................................................................
5033.4
509 ...........................................................................
5033.7
510 ...........................................................................
5034.0
511 ...........................................................................
5034.3
*
*
*
*
*
598 ...........................................................................
5060.4
599 ...........................................................................
5060.7
600 ...........................................................................
5061.0
601 ...........................................................................
5061.3
*
*
*
*
*
698 ...........................................................................
5090.4
699 ...........................................................................
5090.7
T
ABLE
1b—C
HANNELS
Channel pairing
DME parameters
DME No.
VHF freq.
MHz
MLS angle
freq. MHz
MLS Ch.
No.
Interrogation
Reply
Freq.
MHz
Pulse codes
Freq.
MHz
Pulse codes
µ
s
DME/N
µ
s
DME/P Mode
IA
µ
s FA
µ
s
* 1X ....................
....................
....................
..............
1025 12
..............
..............
962
12
** 1Y ..................
....................
....................
..............
1025 36
..............
..............
1088
30
* 2X ....................
....................
....................
..............
1026 12
..............
..............
963
12
** 2Y ..................
....................
....................
..............
1026 36
..............
..............
1089
30
* 3X ....................
....................
....................
..............
1027 12
..............
..............
964
12
** 3Y ..................
....................
....................
..............
1027 36
..............
..............
1090
30
* 4X ....................
....................
....................
..............
1028 12
..............
..............
965
12
** 4Y ..................
....................
....................
..............
1028 36
..............
..............
1091
30
* 5X ....................
....................
....................
..............
1029 12
..............
..............
966
12
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