874 

14 CFR Ch. I (1–1–19 Edition) 

§ 171.315 

(m) 

False guidance. 

False courses 

which can be acquired and tracked by 
an aircraft shall not exist anywhere ei-
ther inside or outside of the MLS cov-
erage sector. False courses which exist 
outside of the minimum coverage sec-
tor may be suppressed by the use of 
OCI. 

N

OTE

: False courses may be due to (but not 

limited to) MLS airborne receiver acquisi-
tion of the following types of false guidance: 
reflections of the scanning beam, scanning 
beam antenna sidelobes and grating lobes, 
and incorrect clearance. 

§ 171.315

Azimuth monitor system re-

quirements. 

(a) The approach azimuth or back 

azimuth monitor system must cause 
the radiation to cease and a warning 
must be provided at the designated 
control point if any of the following 
conditions persist for longer than the 
periods specified: 

(1) There is a change in the ground 

equipment contribution to the mean 
course error component such that the 
path following error at the reference 
datum or in the direction of any azi-
muth radial, exceeds the limits speci-
fied in §§ 171.313(e)(1) or 171.313(j) for a 
period of more than one second. 

N

OTE

: The above requirement and the re-

quirement to limit the ground equipment 
mean error to 

±

10 ft. can be satisfied by the 

following procedure. The integral monitor 
alarm limit should be set to the angular 

equivalent of 

±

10 ft. at the approach ref-

erence datum. This will limit the electrical 
component of the mean course error to 

±

10 

ft. The field monitor alarm limit should be 
set such that with the mean course error at 
the alarm limit the total allowed PFE is not 
exceeded on any commissioned approach 
course from the limit of coverage to an alti-
tude of 100 feet. 

(2) There are errors in two consecu-

tive transmissions of Basic Data Words 
1, 2, 4 or 5. 

(3) There is a reduction in the radi-

ated power to a level not less than that 
specified in §§ 171.313(a)(4) or 
171.313(g)(4) for a period of more than 
one second. 

(4) There is an error in the preamble 

DPSK transmissions which occurs 
more than once in any one second pe-
riod. 

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

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

(6) A failure of the monitor is de-

tected. 

(b) Radiation of the following 

fuctions must cease and a warning pro-
vided at the designated control point if 
there are errors in 2 consecutive trans-
missions: 

(1) Morse Code Identification, 
(2) Basic Data Words 3 and 6, 
(3) Auxiliary Data Words. 

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