Federal Aviation Administration, DOT

Section 171.307

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 published approach procedures and obstacle 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 defined by the intersection of the runway
centerline with a vertical plane perpendicular 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 required, to specifically prevent invalid
removal of an airborne warning indication in the presence of misleading guidance information.
Path Following Error (PFE) means the
guidance perturbations which could
cause aircraft displacement from the
desired course or glidepath. It is composed of the path following noise and of
the mean course error in the case of
azimuth functions, or the mean glidepath error in the case of elevation
functions. Path following errors are
evaluated by filtering the flight error
record with a second order low pass filter which has a corner frequency at 0.5
radian/sec for azimuth data or 1.5 radians/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 azimuth portion of the ground station is
located near the stop end of the runway, and the elevation portion is located 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.

Section 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 request:
(1) A description of the facility and
evidence that the equipment meets the
performance requirements of SectionSection 171.309,
171.311, 171.313, 171.315, 171.317, 171.319,
and 171.321 and is fabricated and installed in accordance with Section 171.323.
(2) A proposed procedure for operating the facility.
(3) A proposed maintenance organization and a maintenance manual that
meets the requirements of Section 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 reliability and an acceptable standard of
performance. Previous equivalent operational experience with a facility with
identical design and operational characteristics will be considered in showing 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 operate the MLS facility for an in-service
evaluation by the FAA.
Section 171.307 Minimum
approval.

requirements

(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 facility, as determined by flight and ground
inspection conducted by the FAA, must
meet the requirements of SectionSection 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 requirements of Section 171.323.
(3) The owner must agree to operate
and maintain the MLS facility in accordance with Section 171.325.
(4) The owner must agree to furnish
operational records as set forth in
Section 171.327 and agree to allow the FAA to

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