852
14 CFR Ch. I (1–1–24 Edition)
§ 171.305
Microwave Landing System (MLS)
means the MLS selected by ICAO for
international standardization.
Minimum glidepath
means the lowest
angle of descent along the zero degree
azimuth that is consistent with pub-
lished approach procedures and obsta-
cle clearance criteria.
MLS Approach Reference Datum
is a
point at a specified height located
vertically above the intersection of the
runway centerline and the threshold.
MLS back azimuth reference datum
means a point 15 meters (50 feet) above
the runway centerline at the runway
midpoint.
MLS datum point
means a point de-
fined by the intersection of the runway
centerline with a vertical plane perpen-
dicular to the centerline and passing
through the elevation antenna phase
center.
Out of coverage indication (OCI)
means
a signal radiated into areas outside the
intended coverage sector, where re-
quired, to specifically prevent invalid
removal of an airborne warning indica-
tion in the presence of misleading guid-
ance information.
Path Following Error (PFE)
means the
guidance perturbations which could
cause aircraft displacement from the
desired course or glidepath. It is com-
posed of the path following noise and of
the mean course error in the case of
azimuth functions, or the mean glide-
path error in the case of elevation
functions. Path following errors are
evaluated by filtering the flight error
record with a second order low pass fil-
ter which has a corner frequency at 0.5
radian/sec for azimuth data or 1.5 radi-
ans/sec for elevation data.
Path following noise (PFN)
means that
portion of the guidance signal error
which could cause displacement from
the actual mean course line or mean
glidepath as appropriate.
Split-site ground station
means the
type of ground station in which the azi-
muth portion of the ground station is
located near the stop end of the run-
way, and the elevation portion is lo-
cated near the approach end.
Time division multiplex (TDM)
means
that each function is transmitted on
the same frequency in time sequence,
with a distinct preamble preceding
each function transmission.
§ 171.305 Requests for IFR procedure.
(a) Each person who requests an IFR
procedure based on an MLS facility
which that person owns must submit
the following information with that re-
quest:
(1) A description of the facility and
evidence that the equipment meets the
performance requirements of §§ 171.309,
171.311, 171.313, 171.315, 171.317, 171.319,
and 171.321 and is fabricated and in-
stalled in accordance with § 171.323.
(2) A proposed procedure for oper-
ating the facility.
(3) A proposed maintenance organiza-
tion and a maintenance manual that
meets the requirements of § 171.325.
(4) A statement of intent to meet the
requirements of this subpart.
(5) A showing that the facility has an
acceptable level of operational reli-
ability and an acceptable standard of
performance. Previous equivalent oper-
ational experience with a facility with
identical design and operational char-
acteristics will be considered in show-
ing compliance with this subparagraph.
(b) FAA inspects and evaluates the
MLS facility; it advises the owner of
the results, and of any required
changes in the MLS facility or in the
maintenance manual or maintenance
organization. The owner must then
correct the deficiencies, if any, and op-
erate the MLS facility for an in-service
evaluation by the FAA.
§ 171.307 Minimum requirements for
approval.
(a) The following are the minimum
requirements that must be met before
the FAA approves an IFR procedure for
a non-Federal MLS facility:
(1) The performance of the MLS facil-
ity, as determined by flight and ground
inspection conducted by the FAA, must
meet the requirements of §§ 171.309,
171.311, 171.313, 171.315, 171.317, 171.319,
and 171.321.
(2) The fabrication and installation of
the equipment must meet the require-
ments of § 171.323.
(3) The owner must agree to operate
and maintain the MLS facility in ac-
cordance with § 171.325.
(4) The owner must agree to furnish
operational records as set forth in
§ 171.327 and agree to allow the FAA to
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: