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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