ILS Oral Questions

Question 1

What guidance does the localizer provide?

Answer 1

It provides lateral guidance (side-to-side).

Question 2

How is the aircrafts lateral position interpreted with a localizer?

Answer 2

90 and 150 Hz signals are carried over the VHF frequency and used by the receiver interpret the aircraft’s lateral position.

Question 3

What is the width of the localizer? What is the width at the threshold? What is the sensitivity?

Answer 3

Between 3°- 6° so that the width at the threshold would be 700 feet.

Usually 5° total width. (2.5 full deflection to each side, 4 times more sensitive than a VOR).

Question 4

What is the coverage range of the localizer?

Answer 4

• 35° to each side of the centerline for the first 10NM
• 10° up to 18NM from the antenna and up to an altitude of 4500’.

Question 5

What guidance does the glideslope provide?

Answer 5

• It provides Vertical Course Guidance

Question 6

How is the vertical position of the aircraft located with the glideslope?

Answer 6

The vertical position is interpreted by the intensity of 90 and 150 Hz signals carried over the UHF frequency and directed above and under the slope.

Question 7

How is the glidesloped tuned with the localizer?

Answer 7

It is automatically tuned with the Localizer.

Question 8

What is the width of the of the glideslope?

Answer 8

• 1.4 Degrees (full deflection is 0.7 Degrees in either direction).

Question 9

What is the range of the Glideslope?

Answer 9

• Typically up to 10 NM.

Question 10

What is the slope in degrees for the Glide Slope?

Answer 10

• Typically 3 Degrees

Question 11

What are the Errors of the Glide Slope?

Answer 11

False glide slope above the normal glide slope.

Question 12

What are Marker Beacons? How many MHz do they transmit?

Answer 12

Provide range information over specific points along the approach.

Transmits at 75 MHz.

Question 13

What is an Outer Marker? What color is it? How many miles out is it? What is the morse code?

Answer 13

• Indicate the position at which the aircraft should intercept the GS at the appropriate interception altitude ±50ft.
• BLUE.
• 4-7 miles out.
• “- - -“

Question 14

What is an Middle Marker? What color is it? How many feet from the runway is it? What color is it? What is the morse code?

Answer 14

• Indicates the approximate point where the GS meets the decision height.
• 3500ft from the runway.
• Amber
• “. - . -”

Question 15

What is an Inner Marker? What color is it? Where is it located? What is the morse code?

Answer 15

• Indicates the point where the glide slope meets the DH on a CAT II ILS approach.
• White.
• It is located between the MM and the runway threshold.
• “. . .”

Question 16

What is the Back Course Marker? What color is it? Is it apart of the ILS approach?

Answer 16

• Indicates the FAF on selected back course approaches.
• No, it is not a part of the ILS approach.
• White,

Question 17

What is the ALS?

Answer 17

Approach Light System

Provides basic visible means to transition between instrument-guided flight into a
visual approach.

Question 18

What is the ALS?

Answer 18

Approach Light System

Provides basic visible means to transition between instrument-guided flight into a
visual approach.

Question 19

How far does the ALS extend from the landing threshold into the approach area for a precision instrument runways?

Answer 19

• 2,400-3,000 feet for precision instrument runways.

Question 20

How far does the ALS extend from the landing threshold into the approach area for non-precision instrument runways?

Answer 20

• 1,400-1,500 feet for non-precision instrument runways.

Question 21

What kind of lighting is included in the ALS?

Answer 21

May include sequenced flashing lights, which appear to the pilot as a ball of light traveling towards the runway at twice a second (AKA “The Rabbit”).

Question 22

What can visible parts of the ALS help indicate?

Answer 22

• The visible parts of the ALS configuration can help the pilot estimate flight visibility.

Question 23

How is the Touchdown Zone Elevation determined?

Answer 23

The highest elevation in the first 3000’ of the runway

Question 24

What is a Localizer Type Directional Aid (LDA)?

Answer 24

More precise than an SDF because the course is usually between 3°- 6° just like a localizer (hence, localizer type). An LDA may also provide a glideslope for vertical guidance in some instances. These are published as LDA/Glideslope and are characterized as APVs (approaches with vertical guidance).

So what makes this different from a localizer or ILS? An LDA is NOT aligned with the runway. Upon arriving at the MDA/DA, the pilot will have to maneuver the aircraft into position to make a normal landing. LDAs may have straight in minimums, however, if the alignment is within 30° of the runway centerline.

Question 25

What is a Simplified Directional Facility (SDF)?

Answer 25

It provides lateral guidance similar to a localizer but less accurate because the course is fixed to either 6° or 12°. The SDF antenna may be offset from the runway centerline but usually not by more than 3°. There is no vertical guidance.

Question 26

Where is the glideslope equipment located?

Answer 26

Between 750’-1250’ from the approach end of the runway and 400-600’ to one side of the centerline

Question 27

What is the sensitivity differences between the CDI tuned to a VOR and a CDI tuned to a LOC?

Answer 27

Full scale deflection represents at least 10° when tuned to a VOR and only 2.5° when tuned to the localizer.

Question 28

What are substitutes for an ILS outer marker?

Answer 28

Compass locators, DME, VOR, GPS, Precision Approach Radar (PAR), or Airport Surveillance Radar (ASR)

Question 29

What are the components of the ILS?

Question 30

What is FDE?

Answer 30

Fault Detection and Exclusion

RAIM detects an error but does nothing about it except give you a warning. FDE is a function of some RAIM capable GPS. It requires 6 satellites so that info from the faulty satellite can be excluded.