853
Federal Aviation Administration, DOT
§ 171.309
inspect the facility and its operation
whenever necessary.
(5) The owner must assure the FAA
that he will not withdraw the MLS fa-
cility from service without the permis-
sion of the FAA.
(6) The owner must bear all costs of
meeting the requirements of this sec-
tion and of any flight or ground inspec-
tion made before the MLS facility is
commissioned.
(b) [Reserved]
§ 171.309 General requirements.
The MLS is a precision approach and
landing guidance system which pro-
vides position information and various
ground-to-air data. The position infor-
mation is provided in a wide coverage
sector and is determined by an azimuth
angle measurement, an elevation angle
measurement and a range (distance)
measurement.
(a) An MLS constructed to meet the
requirements of this subpart must in-
clude:
(1) Approach azimuth equipment, as-
sociated monitor, remote control and
indicator equipment.
(2) Approach elevation equipment, as-
sociated monitor, remote control and
indicator equipment.
(3) A means for the encoding and
transmission of essential data words,
associated monitor, remote control and
indicator equipment. Essential data
are basic data words 1, 2, 3, 4, and 6 and
auxiliary data words A1, A2 and A3.
(4) Distance measuring equipment
(DME), associated monitor, remote
control and indicator equipment.
(5) Remote controls for paragraphs
(a) (1), (2), (3), and (4) of this section
must include as a minimum on/off and
reset capabilities and may be inte-
grated in the same equipment.
(6) At locations where a VHF marker
beacon (75 MHz) is already installed, it
may be used in lieu of the DME equip-
ment.
(b) In addition to the equipment re-
quired in paragraph (a) of this section
the MLS may include:
(1) Back azimuth equipment, associ-
ated monitor, remote control and indi-
cator equipment. When Back Azimuth
is provided, a means for transmission
of Basic Data Word 5 and Auxiliary
Data Word A4 shall also be provided.
(2) A wider proportional guidance
sector which exceeds the minimum
specified in §§ 171.313 and 171.317.
(3) Precision DME, associated mon-
itor, remote control and indicator
equipment.
(4) VHF marker beacon (75 MHz), as-
sociated monitor, remote control and
indicator equipment.
(5) The MLS signal format will ac-
commodate additional functions (e.g.,
flare elevation) which may be included
as desired. Remote controls for para-
graphs (b) (1), (3) and (4) of this section
must include as a minimum on/off and
reset capabilities, and may be inte-
grated in the same equipment.
(6) Provisions for the encoding and
transmission of additional auxiliary
data words, associated monitor, remote
control and indicator equipment.
(c) MLS ground equipment must be
designed to operate on a nominal 120/
240 volt, 60 Hz, 3-wire single phase AC
power source and must meet the fol-
lowing service conditions:
(1) AC line parameters, DC voltage,
elevation and duty:
120 VAC nominal value—102 V to 138 V (
±
1
V)*
240 VAC nominal value—204 V to 276 V (
±
2
V)*
60 Hz AC line frequency—57 Hz to 63 Hz (
±
0.2
Hz)*
*N
OTE
: Where discrete values of the above
frequency or voltages are specified for test-
ing purposes, the tolerances given in paren-
theses indicated by an asterisk apply to the
test instruments used to measure these pa-
rameters.
Elevation—0 to 3000 meters (10,000 feet)
above sea level
Duty—Continuous, unattended
(2) Ambient conditions within the
shelter for electronic equipment in-
stalled in shelters are:
Temperature,
¥
10
°
C to + 50
°
C
Relative humidity, 5% to 90%
(3) Ambient conditions for electronic
equipment and all other equipment in-
stalled outdoors (for example, antenna,
field detectors, and shelters):
Temperature,
¥
50
°
C to + 70
°
C
Relative humidity, 5% to 100%
(4) All equipment installed outdoors
must operate satisfactorily under the
following conditions:
854
14 CFR Ch. I (1–1–24 Edition)
§ 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