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890 

14 CFR Ch. I (1–1–24 Edition) 

§ 171.321 

(4) There is an error in the time divi-

sion multiplex synchronization of a 
particular elevation function such that 
the requirement specified in § 171.311(e) 
is not satisfied and this condition per-
sists for more than one second. 

(5) A failure of the monitor is de-

tected. 

(b) The period during which erro-

neous guidance information is radiated 
must not exceed the periods specified 
in § 171.319(a). If the fault is not cleared 
within the time allowed, radiation 
shall cease. After shutdown, no at-
tempt must be made to restore service 
until a period of 20 seconds has elapsed. 

§ 171.321 DME and marker beacon per-

formance requirements. 

(a) The DME equipment must meet 

the performance requirements pre-
scribed in subpart G of the part. This 
subpart imposes requirements that per-
formance features must comply with 
International Standards and Rec-
ommended Practices, Aeronautical 
Telecommunications, Vol. I of Annex 
10 to ICAO. It is available from ICAO, 
Aviation Building, 1080 University 
Street, Montreal 101, Quebec, Canada, 
Attention: Distribution Officer and 
also available for inspection at the Na-
tional Archives and Records Adminis-
tration (NARA). For information on 
the availability of this material at 
NARA, call 202–741–6030, or go to: 

http:// 

www.archives.gov/federal

_

register/ 

code

_

of

_

federal

_

regulations/ibr

_

loca-

tions.html. 

(b) MLS marker beacon equipment 

must meet the performance require-
ments prescribed in subpart H of this 
part. This subpart imposes require-
ments that performance features must 
comply with International Standards 
and Recommended Practices, Aero-
nautical Telecommuncations, Vol. I of 
Annex 10 to ICAO. 

[Doc. No. 5034, 29 FR 11337, Aug. 6, 1964, as 
amended at 69 FR 18803, Apr. 9, 2004] 

§ 171.323 Fabrication and installation 

requirements. 

(a) The MLS facility must be perma-

nent and must be located, constructed, 
and installed in accordance with best 
commercial engineering practices, 
using applicable electric and safety 
codes and Federal Communications 

Commission (FCC) licensing require-
ments and siting requirements of 
§§ 171.313(b) and 171.317(b). 

(b) The MLS facility components 

must utilize solid state technology ex-
cept that traveling wave tube ampli-
fiers (TWTA) may be used. A maximum 
level of common modularity must be 
provided along with diagnostics to fa-
cilitate maintenance and trouble-
shooting. 

(c) An approved monitoring capa-

bility must be provided which indicates 
the status of the equipment at the site 
and at a remotely located maintenance 
area, with monitor capability that pro-
vides pre-alarm of impending system 
failures. This monitoring feature must 
be capable of transmitting the status 
and pre-alarm over standard phone 
lines to a remote section. In the event 
the sponsor requests the FAA to as-
sume ownership of the facility, the 
monitoring feature must also be capa-
ble of interfacing with FAA remote 
monitoring requirements. This require-
ment may be complied with by the ad-
dition of optional software and/or hard-
ware in space provided in the original 
equipment. 

(d) The mean corrective maintenance 

time of the MLS equipment must be 
equal to or less than 0.5 hours with a 
maximum corrective maintenance time 
not to exceed 1.5 hours. This measure 
applies to correction of unscheduled 
failures of the monitor, transmitter 
and associated antenna assemblies, 
limited to unscheduled outage and out 
of tolerance conditions. 

(e) The mean-time-between-failures 

of the MLS angle system must not be 
less than 1,500 hours. This measure ap-
plies to unscheduled outage, out-of-tol-
erance conditions, and failures of the 
monitor, transmitter, and associated 
antenna assemblies. 

(f) The MLS facility must have a reli-

able source of suitable primary power, 
either from a power distribution sys-
tem or locally generated. Adequate 
power capacity must be provided for 
the operation of the MLS as well as the 
test and working equipment of the 
MLS. 

(g) The MLS facility must have a 

continuously engaged or floating bat-
tery power source for the continued 
normal operation of the ground station 

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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.