Section 171.309

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

inspect the facility and its operation
whenever necessary.
(5) The owner must assure the FAA
that he will not withdraw the MLS facility from service without the permission of the FAA.
(6) The owner must bear all costs of
meeting the requirements of this section and of any flight or ground inspection made before the MLS facility is
commissioned.
(b) [Reserved]
Section 171.309 General requirements.
The MLS is a precision approach and
landing guidance system which provides position information and various
ground-to-air data. The position information 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 include:
(1) Approach azimuth equipment, associated monitor, remote control and
indicator equipment.
(2) Approach elevation equipment, associated 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 integrated 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 equipment.
(b) In addition to the equipment required in paragraph (a) of this section
the MLS may include:
(1) Back azimuth equipment, associated monitor, remote control and indicator 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 SectionSection 171.313 and 171.317.
(3) Precision DME, associated monitor, remote control and indicator
equipment.
(4) VHF marker beacon (75 MHz), associated monitor, remote control and
indicator equipment.
(5) The MLS signal format will accommodate additional functions (e.g.,
flare elevation) which may be included
as desired. Remote controls for paragraphs (b) (1), (3) and (4) of this section
must include as a minimum on/off and
reset capabilities, and may be integrated 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 following service conditions:
(1) AC line parameters, DC voltage,
elevation and duty:
120 VAC nominal value - 102 V to 138 V (Section1
V)*
240 VAC nominal value - 204 V to 276 V (Section2
V)*
60 Hz AC line frequency - 57 Hz to 63 Hz (Section0.2
Hz)*
*NOTE: Where discrete values of the above
frequency or voltages are specified for testing purposes, the tolerances given in parentheses indicated by an asterisk apply to the
test instruments used to measure these parameters.
Elevation - 0 to 3000 meters (10,000 feet)
above sea level
Duty - Continuous, unattended

(2) Ambient conditions within the
shelter for electronic equipment installed in shelters are:
Temperature, Section10 SectionC to + 50 SectionC
Relative humidity, 5% to 90%

(3) Ambient conditions for electronic
equipment and all other equipment installed outdoors (for example, antenna,
field detectors, and shelters):
Temperature, Section50 SectionC to + 70 SectionC
Relative humidity, 5% to 100%

(4) All equipment installed outdoors
must operate satisfactorily under the
following conditions:

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