Localizer

Question 1

What is the Localizer Standard Service Volume?

Answer 1

18 NM, 10 degrees either side of centerline; 10 NM, 35 degrees either side of centerline.

Question 2

Where is Localizer sector 1?

Answer 2

10 degrees either side of centerline.

Question 3

Where is Localizer sector 2?

Answer 3

From 10 to 35 degrees either side of centerline.

Question 4

Where is Localizer sector 3?

Answer 4

From 35 to 90 degrees either side of centerline. All of sector 3 is outside of the SSV.

Question 5

What must be done if the coded identifier is not received in any part of the standard service volume?

Answer 5

That area must be restricted.

Question 6

What does the term modulation mean for a localizer frequency.

Answer 6

It refers to the frequency modulation of the signal in two lobes at 90 and 150Hz.

Question 7

Describe how the CDI deflection is determined.

Answer 7

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.

Question 8

If a dual frequency antenna does not provide enough clearance power to measure modulation on centerline, what should be done?

Answer 8

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.

Question 9

What does modulation equality measure?

Answer 9

Modulation equality checks that the 90 and 150Hz signals are modulating the carrier equally.

Question 10

What is the modulation level tolerance for On-Course on path?

Answer 10

36-44%

Question 11

What is the modulation level tolerance for the service volume of a localizer?

Answer 11

30-60% for antennas installed or reconfigured after 1/1/2000.

Question 12

What does power ratio measure and what is the tolerance?

Answer 12

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.

Question 13

What is the purpose of the width and symmetry check?

Answer 13

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.

Question 14

What distance may width and symmetry be measured on periodic checks and what is the optimum distance?

Answer 14

Distance on periodic checks may be 6-14 miles from the antenna. 10 NM is the optimum distance.

Question 15

Where is width measured?

Answer 15

Width is measured in degrees between where the crosspointer crosses the 90Hz and 150Hz 150uA points.

Question 16

What are the tolerances for localizer width (maximum, commissioning, periodic)?

Answer 16

Maximum width - 6.0; Commissioning +/- .1 degree of commissioned width; Periodic - within 17% of the commissioned width.

Question 17

How is symmetry determined?

Answer 17

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.

Question 18

What does clearance measure?

Answer 18

Clearances ensure that the facility provides adequate off-course indications throughout the facilities service volume.

Question 19

What do clearances provide and how are they measured?

Answer 19

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.

Question 20

What are the clearance tolerances?

Answer 20

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.

Question 21

How often must clearances be verified at LSA?

Answer 21

Every 1080 days.

Question 22

What is clearance comparability?

Answer 22

Clearance comparability allows localizer width, symmetry, and clearances to be measured at altitudes higher than LSA.

Question 23

What does alignment and structure measure?

Answer 23

These checks measure the quality and alignment of the on-course signal.

Question 24

When must the reference transmitter meet initial maintenance tolerances?

Answer 24

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.

Question 25

What are the alignment tolerances?

Answer 25

Commissioning: within 3uA of the designed procedural azimuth. Periodic: CAT 1: 15uA, CAT II 11uA, CAT III 9uA

Question 26

How is phasing flown?

Answer 26

If requested, the check is normally flown between between 5-10 degrees off-course. Fly inbound toward the antenna at an altitude and azimuth determined by maintenance between 10 and 3 miles.

Question 27

What CDI deflection corresponds to the 150uA point on either side of centerline?

Answer 27

Full deflection.

Question 28

What is the symmetry tolerance?

Answer 28

45-55%

Question 29

As equipment ages, what tends to happen to the localizer course width?

Answer 29

It widens.

Question 30

What does high angle clearance measure and how do we fly it?

Answer 30

It measures proper off-course indications at the upper limit of the service volume. Fly an ILS-1 at 4500 feet above the localizer antenna. If OT, conduct additional checks at decreasing altitudes to determine the highest altitude at which the facility can be used.

Question 31

What is polarization, how do we measure it, and what’s the tolerance?

Answer 31

Polarization check determines the effects of vertical polarization on the course structure. It is measured prior to the FAF during the ILS-3 maneuver by banking the aircraft 20 degrees to each side. Only required on one transmitter.

Question 32

Why do we measure monitor references?

Answer 32

These checks determine that the localizer meets specified tolerances while in abnormal configurations.

Question 33

Where is course alignment measured?

Answer 33

The last mile prior to the threshold.

Question 34

What must be done on one of the ILS-3 maneuvers if commissioning a CAT III ILS?

Answer 34

At least one of the ILS-3 maneuvers must be modified to include a landing and rollout along the centerline to point E (2000 ft from end) to evaluate both alignment and structure in Zones 4 and 5. The data gathered on the roll-out is compared to that recorded while flying at 50 ft above the runway.

Question 35

How do we fly the ILS-3 maneuver on a LOC only procedure?

Answer 35

After passing the FAF at procedural altitude, descend to 100 ft below the MDA and maintain this altitude to point C (MAP). Then perform 50 foot RWY update.

Question 36

What is RF power and how do we measure it?

Answer 36

Fly an arc across the localizer at 18nm (25 for ICAO) at 4500 above the antenna elevation throughout Sector 1. Then fly an arc at the same distance from the antenna at 2000 feet above the threshold or 1000 feet above the intervening terrain whichever is higher. Fly inbound on course from the service volume at 2000 feet above the threshold elevation, or 1000 feet above intervening terrain whichever is higher until reaching 7 degrees above the horizontal or pt C, whatever occurs last. Fly a 10nm (17 for ICAO) arc across the localizer from 35 to 35 at the LSA.

Question 37

If there is a way to identify a fix on a transition other than just the localizer CDI deflection, must we verify clearances?

Answer 37

No.