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850 

14 CFR Ch. I (1–1–24 Edition) 

§ 171.275 

(iii) The station power emission and 

frequencies of the ISMLS localizer, 
glide path, beacon markers, and associ-
ated 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 ISMLS facility periodi-
cally 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 § 171.275. 

(e) Modifications to an ISMLS facil-

ity may be made only after approval by 
the FAA of the proposed modification 
submitted by the owner. 

(f) The owner or the owner’s mainte-

nance representative must participate 
in inspections made by the FAA. 

(g) Whenever it is required by the 

FAA, the owner must incorporate im-
provements in ISMLS maintenance. 

(h) The owner or his maintenance 

representative must provide a suffi-
cient stock of spare parts, including 
solid state components, or modules to 
make possible the prompt replacement 
of components or modules that fail or 
deteriorate in service. 

(i) FAA approved test instruments 

must be used for maintenance of the 
ISMLS facility. 

(j) The mean corrective maintenance 

time of the ISMLS equipment may not 
exceed 0.5 hours, with a maximum cor-
rective maintenance time of not great-
er than 1.5 hours. This measure applies 
to failures of the monitor, transmitter 
and associated antenna assemblies, 
limited to unscheduled outage and out- 
of-tolerance conditions. 

(k) The mean time between failures 

of the ISMLS equipment may not be 
less than 1,500 hours. This measure ap-
plies to unscheduled outages, out-of- 
tolerance conditions, and failures of 
the monitor, transmitter, and associ-
ated antenna assemblies. 

(l) Inspection consists of an examina-

tion of the ISMLS equipment to ensure 

that unsafe operating conditions do not 
exist. 

(m) Monitoring of the ISMLS radi-

ated signal must ensure a high degree 
of integrity and minimize the require-
ments for ground and flight inspection. 
The monitor must be checked periodi-
cally during the in-service test evalua-
tion period for calibration and sta-
bility. These tests and ground checks 
of glide slope, localizer, and marker 
beacon radiation characteristics must 
be conducted in accordance with the 
maintenance requirements of this sec-
tion. 

§ 171.275 Reports. 

The owner of the ISMLS facility or 

his maintenance representative must 
make the following reports at the indi-
cated time to the appropriate FAA Re-
gional Office where the facility is lo-
cated. 

(a) 

Facility Equipment Performance and 

Adjustment Data 

(

FAA Form 198

). The 

FAA Form 198 shall be filled out by the 
owner or his maintenance representa-
tive with the equipment adjustments 
and meter readings as of the time of fa-
cility commissioning. One copy must 
be kept in the permanent records of the 
facility and two copies must be sent to 
the appropriate FAA Regional Office. 
The owner or his maintenance rep-
resentative must revise the FAA Form 
198 data after any major repair, mod-
ernization, or retuning to reflect an ac-
curate record of facility operation and 
adjustment. In the event the data are 
revised, the owner or his maintenance 
representative shall notify the appro-
priate FAA Regional Office of such re-
visions, and forward copies of the revi-
sions to the appropriate FAA Regional 
Office. 

(b) 

Facility Maintenance Log 

(

FAA 

Form 6030

1

). FAA Form 6030–1 is a per-

manent record of all the activities re-
quired to maintain the ISMLS facility. 
The entries must include all malfunc-
tions met in maintaining the facility 
including information on the kind of 
work and adjustments made, equip-
ment failures, causes (if determined) 
and corrective action taken. In addi-
tion, the entries must include comple-
tion of periodic maintenance required 
to maintain the facility. The owner or 
his maintenance representative must 

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851 

Federal Aviation Administration, DOT 

§ 171.303 

keep the original of each form at the 
facility and send a copy to the appro-
priate FAA Regional Office at the end 
of each month in which it is prepared. 
However, where an FAA approved re-
mote monitoring system is installed 
which precludes the need for periodic 
maintenance visits to the facility, 
monthly reports from the remote mon-
itoring system control point must be 
forwarded to the appropriate FAA Re-
gional Office, and a hard copy retained 
at the control point. 

(c) 

Technical Performance Record 

(

FAA 

Form 418

). FAA Form 418 contains a 

record of system parameters, recorded 
on each scheduled visit to the facility. 
The owner or his maintenance rep-
resentative shall keep the original of 
each month’s record at the facility and 
send a copy of the form to the appro-
priate FAA Regional Office. 

Subpart J—Microwave Landing 

System (MLS) 

S

OURCE

: Docket No. 20669, 51 FR 33177, 

Sept. 18, 1986, unless otherwise noted. 

§ 171.301 Scope. 

This subpart sets forth minimum re-

quirements for the approval, installa-
tion, operation and maintenance of 
non-Federal Microwave Landing Sys-
tem (MLS) facilities that provide the 
basis for instrument flight rules (IFR) 
and air traffic control procedures. 

§ 171.303 Definitions. 

As used in this subpart: 

Auxiliary data 

means data trans-

mitted in addition to basic data that 
provide ground equipment siting infor-
mation for use in refining airborne po-
sition calculations and other supple-
mentary information. 

Basic data 

means data transmitted by 

the ground equipment that are associ-
ated directly with the operation of the 
landing guidance system. 

Beam center 

means the midpoint be-

tween the 

¥

3 dB points on the leading 

and trailing edges of the scanning 
beam main lobe. 

Beamwidth 

means the width of the 

scanning beam main lobe measured at 
the 

¥

3 dB points and defined in angu-

lar units on the boresight, in the hori-
zontal plane for the azimuth function 

and in the vertical plane for the ele-
vation function. 

Clearance guidance sector 

means the 

volume of airspace, inside the coverage 
sector, within which the azimuth guid-
ance information provided is not pro-
portional to the angular displacement 
of the aircraft, but is a constant fly- 
left or fly-right indication of the direc-
tion relative to the approach course 
the aircraft should proceed in order to 
enter the proportional guidance sector. 

Control Motion Noise (CMN) 

means 

those fluctuations in the guidance 
which affect aircraft attitude, control 
surface motion, column motion, and 
wheel motion. Control motion noise is 
evaluated by filtering the flight error 
record with a band-pass filter which 
has corner frequencies at 0.3 radian/sec 
and 10 radians/sec for azimuth data and 
0.5 radian/sec and 10 radians/sec for ele-
vation data. 

Data rate 

means the average number 

of times per second that transmissions 
occur for a given function. 

Differential Phase Shift Keying (DPSK) 

means differential phase modulation of 
the radio frequency carrier with rel-
ative phase states of 0 degree or 180 de-
grees. 

Failure 

means the inability of an 

item to perform within previously 
specified limits. 

Guard time 

means an unused period of 

time provided in the transmitted signal 
format to allow for equipment toler-
ances. 

Integrity 

means that quality which 

relates to the trust which can be placed 
in the correctness of the information 
supplied by the facility. 

Mean corrective time 

means the aver-

age time required to correct an equip-
ment failure over a given period, after 
a service technician reaches the facil-
ity. 

Mean course error 

means the mean 

value of the azimuth error along a 
specified radial of the azimuth func-
tion. 

Mean glide path error 

means the mean 

value of the elevation error along a 
specified glidepath of the elevation 
function. 

Mean-time-between-failures (MTBF) 

means the average time between equip-
ment failures over a given period.