Localizer Flashcards
What is the Localizer Standard Service Volume?
18 NM, 10 degrees either side of centerline; 10 NM, 35 degrees either side of centerline.
Where is Localizer sector 1?
10 degrees either side of centerline.
Where is Localizer sector 2?
From 10 to 35 degrees either side of centerline.
Where is Localizer sector 3?
From 35 to 90 degrees either side of centerline. All of sector 3 is outside of the SSV.
What must be done if the coded identifier is not received in any part of the standard service volume?
That area must be restricted.
What does the term modulation mean for a localizer frequency.
It refers to the frequency modulation of the signal in two lobes at 90 and 150Hz.
Describe how the CDI deflection is determined.
The ratio of 90 to 150Hz signal received determines deflection. If equal amounts are received, the CDI is centered; if only one is received and the other is absent, the CDI is fully deflected to the corresponding side.
If a dual frequency antenna does not provide enough clearance power to measure modulation on centerline, what should be done?
Measure the clearance-only modulation level while inbound between 5 and 10 degrees off-course at the LSA with the clearance transmitter in modulation balance configuration.
What does modulation equality measure?
Modulation equality checks that the 90 and 150Hz signals are modulating the carrier equally.
What is the modulation level tolerance for On-Course on path?
36-44%
What is the modulation level tolerance for the service volume of a localizer?
30-60% for antennas installed or reconfigured after 1/1/2000.
What does power ratio measure and what is the tolerance?
It measures the power ratio of between the course and clearance transmitters. The course transmitter power level must be at least 10 dB greater than the clearance transmitter.
What is the purpose of the width and symmetry check?
To establish and maintain a course sector width and ratio between half-course widths that will provide the desired displacement sensitivity at the procedural missed approach point or threshold, and is within the limitations of the procedural protected area.
What distance may width and symmetry be measured on periodic checks and what is the optimum distance?
Distance on periodic checks may be 6-14 miles from the antenna. 10 NM is the optimum distance.
Where is width measured?
Width is measured in degrees between where the crosspointer crosses the 90Hz and 150Hz 150uA points.
What are the tolerances for localizer width (maximum, commissioning, periodic)?
Maximum width - 6.0; Commissioning +/- .1 degree of commissioned width; Periodic - within 17% of the commissioned width.
How is symmetry determined?
Symmetry is determined by comparing the 90Hz half width (the width in degrees from the 90Hz 150uA to the 0uA point) to the localizer width.
What does clearance measure?
Clearances ensure that the facility provides adequate off-course indications throughout the facilities service volume.
What do clearances provide and how are they measured?
Clearances ensuer that the facility provides adequate off–course indications throughout the service volume. They are measured on the ILS-1 maneuver (up to 14 miles on a periodic) and correspond to the lowest crosspointer uA value between service volume and the course sector 1 linear increase.
What are the clearance tolerances?
Sector 1 - 175uA, 2 & 3 150uA. Clearances are reduced 15 uA from the clearance required in normal for alarm configurations. Deviations less than 100uA are not acceptable. Momentary crosspointer deflections to less than the tolerance are acceptable in sectors 2 and 3, provided the aggregate area does not exceed 3 degrees of arc in one quadrant.
How often must clearances be verified at LSA?
Every 1080 days.
What is clearance comparability?
Clearance comparability allows localizer width, symmetry, and clearances to be measured at altitudes higher than LSA.
What does alignment and structure measure?
These checks measure the quality and alignment of the on-course signal.
When must the reference transmitter meet initial maintenance tolerances?
Except USAF facilities, the reference transmitter must meet the “Iniital” maintenance tolerance any time alignment is adjusted, or at the end of a periodic with monitors inspection.
