891 

Federal Aviation Administration, DOT 

§ 171.325 

operation if the primary power fails. A 
trickle charge must be supplied to re-
charge the batteries during the period 
of available primary power. Upon loss 
and subsequent restoration of power, 
the battery must be restored to full 
charge within 24 hours. When primary 
power is applied, the state of the bat-
tery charge must not affect the oper-
ation of the MLS ground station. The 
battery must allow continuation of 
normal operation of the MLS facility 
for at least 2 hours without the use of 
additional sources of power. When the 
system is operating from the battery 
supply without prime power, the ra-
dome deicers and the environmental 
system need not operate. The equip-
ment must meet all specification re-
quirements with or without batteries 
installed. 

(h) There must be a means for deter-

mining, from the ground, the perform-
ance of the system including antenna, 
both initially and periodically. 

(i) The facility must have, or be sup-

plemented by, ground, air, or landline 
communications services. At facilities 
within or immediately adjacent to con-
trolled airspace, that are intended for 
use as instrument approach aids for an 
airport, there must be ground air com-
munications or reliable communica-
tions (at least a landline telephone) 
from the airport to the nearest FAA 
air traffic control or communication 
facility. Compliance with this para-
graph need not be shown at airports 
where an adjacent FAA facility can 
communicate with aircraft on the 
ground at the airport and during the 
entire proposed instrument approach 
procedure. In addition, at low traffic 
density airports within or immediately 
adjacent to controlled airspace, and 
where extensive delays are not a fac-
tor, the requirements of this paragraph 
may be reduced to reliable communica-
tions from the airport to the nearest 
FAA air traffic control or communica-
tions facility. If the adjacent FAA fa-
cility can communicate with aircraft 
during the proposed instrument ap-
proach procedure down to the airport 
surface or at least down to the min-
imum en route altitude, this would re-
quire at least a landline telephone. 

(j) The location of the phase center 

for all antennas must be clearly 
marked on the antenna enclosures. 

(k) The latitude, longitude and mean 

sea level elevation of all MLS anten-
nas, runway threshold and runway stop 
end must be determined by survey with 
an accuracy of 

±

3 meters (

±

10 feet) lat-

erally and 

±

0.3 meter (

±

1.0 foot) 

vertically. The relative lateral and 
vertical offsets of all antenna phase 
centers, and both runway ends must be 
determined with an accuracy of 

±

0.3 

meter (

±

1.0 foot) laterally and 

±

0.03 

meter (

±

0.1 foot) vertically. The owner 

must bear all costs of the survey. The 
results of this survey must be included 
in the ‘‘operations and maintenance’’ 
manual required by section 171.325 of 
this subpart and will be noted on FAA 
Form 198 required by § 171.327. 

[Doc. No. 20669, 51 FR 33177, Sept. 18, 1986, as 
amended by Amdt. 171–16, 56 FR 65665, Dec. 
17, 1991] 

§ 171.325 Maintenance and operations 

requirements. 

(a) The owner of the facility must es-

tablish an adequate maintenance sys-
tem and provide MLS qualified mainte-
nance personnel to maintain the facil-
ity at the level attained at the time it 
was commissioned. Each person who 
maintains a facility must meet the 
FCC licensing requirements and dem-
onstrate that he has the special knowl-
edge and skills needed to maintain an 
MLS facility, including proficiency in 
maintenance procedures and the use of 
specialized test equipment. 

(b) In the event of out-of-tolerance 

conditions or malfunctions, as evi-
denced by receiving two successive 
pilot reports, the owner must close the 
facility by encasing radiation, and 
issue a ‘‘Notice to Airmen’’ (NOTAM) 
that the facility is out of service. 

(c) The owner must prepare, and ob-

tain approval of, an operations and 
maintenance manual that sets forth 
mandatory procedures for operations, 
periodic maintenance, and emergency 
maintenance, including instructions on 
each of the following: 

(1) Physical security of the facility. 
(2) Maintenance and operations by 

authorized persons. 

(3) FCC licensing requirements for 

operations and maintenance personnel. 

892 

14 CFR Ch. I (1–1–24 Edition) 

§ 171.325 

(4) Posting of licenses and signs. 
(5) Relations between the facility and 

FAA air traffic control facilities, with 
a description of the boundaries of con-
trolled airspace over or near the facil-
ity, instructions for relaying air traffic 
control instructions and information, 
if applicable, and instructions for the 
operation of an air traffic advisory 
service if the facility is located outside 
of controlled airspace. 

(6) Notice to the Administrator of 

any suspension of service. 

(7) Detailed and specific maintenance 

procedures and servicing guides stating 
the frequency of servicing. 

(8) Air-ground communications, if 

provided, expressly written or incor-
porating appropriate sections of FAA 
manuals by reference. 

(9) Keeping the station logs and other 

technical reports, and the submission 
of reports required by § 171.327. 

(10) Monitoring of the MLS facility. 
(11) Inspections by United States per-

sonnel. 

(12) Names, addresses, and telephone 

numbers of persons to be notified in an 
emergency. 

(13) Shutdowns for periodic mainte-

nance and issuing of NOTAM for rou-
tine or emergency shutdowns. 

(14) Commissioning of the MLS facil-

ity. 

(15) An acceptable procedure for 

amending or revising the manual. 

(16) An explanation of the kinds of 

activities (such as construction or 
grading) in the vicinity of the MLS fa-
cility that may require shutdown or re-
certification of the MLS facility by 
FAA flight check. 

(17) Procedures for conducting a 

ground check of the azimuth and ele-
vation alignment. 

(18) The following information con-

cerning the MLS facility: 

(i) Facility component locations with 

respect to airport layout, instrument 
runways, and similar areas. 

(ii) The type, make and model of the 

basic radio equipment that provides 
the service including required test 
equipment. 

(iii) The station power emission, 

channel, and frequency of the azimuth, 
elevation, DME, marker beacon, and 
associated compass locators, if any. 

(iv) The hours of operation. 

(v) Station identification call letters 

and method of station identification 
and the time spacing of the identifica-
tion. 

(vi) A description of the critical parts 

that may not be changed, adjusted, or 
repaired without an FAA flight check 
to confirm published operations. 

(d) The owner or his maintenance 

representative must make a ground 
check of the MLS facility periodically 
in accordance with procedures ap-
proved by the FAA at the time of com-
missioning, and must report the results 
of the checks as provided in § 171.327. 

(e) The only modifications permitted 

are those that are submitted to FAA 
for approval by the MLS equipment 
manufacturer. The owner or sponsor of 
the facility must incorporate these 
modifications in the MLS equipment. 
Associated changes must also be made 
to the operations and maintenance 
manual required in paragraph (c) of 
this section. This and all other correc-
tions and additions to this operations 
and maintenance manual must also be 
submitted to FAA for approval. 

(f) The owner or the owner’s mainte-

nance representative must participate 
in inspections made by the FAA. 

(g) The owner must ensure the avail-

ability of a sufficient stock of spare 
parts, including solid state compo-
nents, or modules to make possible the 
prompt replacement of components or 
modules that fail or deteriorate in 
service. 

(h) FAA approved test instruments 

must be used for maintenance of the 
MLS facility. 

(i) Inspection consists of an examina-

tion of the MLS equipment to ensure 
that unsafe operating conditions do not 
exist. 

(j) Monitoring of the MLS radiated 

signal must ensure a high degree of in-
tegrity and minimize the requirements 
for ground and flight inspection. The 
monitor must be checked daily during 
the in-service test evaluation period (96 
hour burn in) for calibration and sta-
bility. These tests and ground checks 
or azimuth, elevation, DME, and mark-
er beacon radiation characteristics 
must be conducted in accordance with 
the maintenance requirements of this 
section.