ILS

Question 1

What does ILS stand for?

Answer 1

Instrument Landing System

Question 2

Is an ILS approach Precision or Non-Precision?

Answer 2

ILS is a Precision Runway Approach

Question 3

What makes an approach a Precision Approach?

Answer 3

Accurate guidance in both Glide Path, as well as Azimuth

Question 4

Where is the localiser transmitter sited?

Answer 4

Sited beyond the upwind end of the runway, approximately 300m.

Question 5

Where is the glidepath transmitter sited?

Answer 5

Sited approach 300m from the landing threshold and offset between 100 and 200m from the centreline.

Question 6

What does the localiser define and indicate?

Answer 6

Defines the extended centreline of the instrument runway.

Indicates deviation from the optimum lateral approach path.

Question 7

What does the glidepath define and indicate?

Answer 7

Defines the safe descent slope.

Indicates deviation from the optimum vertical approach path.

Question 8

What is the normal angle of a safe glidepath?

Answer 8

3 Degrees

Question 9

What are the two beacons installed on an approach and what do they do?

Answer 9

Outer Marker
Middle Marker

They define ranges from the threshold

Question 10

What does a DME Transponder attached to an ILS do?

Answer 10

Provides range information zero referenced to the runway threshold instead of Marker Beacons

Question 11

Which band does the localiser operate in?

Answer 11

108-112MHz VHF

Question 12

What is the coverage of a localiser?

Answer 12

Coverage out to 35 Degrees either side of the centreline out to 17nm, up to maximum range.

Question 13

Which Annex do ILS facilities conform to?

Answer 13

ICAO Annex 10 unless otherwise indicated in the AIP.

Question 14

What is the ILS protected range?

Answer 14

Coverage out to 35 Degrees either side of the centreline out to 17nm, reducing to 10 Degrees thereafter up to 25nm.

Question 15

What are the two modulation frequencies of the localiser and glidepath?

Answer 15

90Hz and 150 Hz

Question 16

What is the ILS Reference Point?

Answer 16

The Glidepath Aerial

Question 17

What is the Glidepath protected range?

Answer 17

8° of azimuth each side of the Localizer centreline to a distance of 10 nm from threshold.

Question 18

What does the location of the Glidepath Aerial and the Approach Angle depend on?

Answer 18

Aircraft likely to use the aerodrome
Terrain
Obstacles within the approach and missed approach areas
Local Meteorological conditions
Runway Length

Question 19

What is the rate of height loss for a 3 Degree approach?

Answer 19

300ft per nm

Question 20

What is the ILS Reference Datum?

Answer 20

A point at a specified height, located at the intersection of the centreline and threshold, through which ths ILS glidepath passes.

Question 21

What height should the ILS Reference Datum be close to?

Answer 21

50ft

Question 22

If the ILS monitoring equipment detects a malfunction, what happens?

Answer 22

The ILS automatically ceases to transmit navigation information.

Question 23

Is the LOC only approach Precision or Non-Precision?

Answer 23

Non-Precision because an accurate glidepath is not available

Question 24

How is the ILS station identified?

Answer 24

By modulating a three letter Morse identifier onto the localizer carrier wave

Question 25

On what instruments can ILS information be displayed?

Answer 25

Horizontal Situation Indicator (HSI)
Omni-Directional Bearing Indicator (OBI)

Question 26

What do each horizontal and vertical dot on the ILS display indicate?

Answer 26

Each horizontal dot indicates 0.5° deviation from the centre of the localizer.

Each vertical dot indicates 0.15° deviation from the centre of the glidepath.

Question 27

When will both ILS needles remain central?

Answer 27

The receiver is switched off.
No signals are being received
The aircraft is on the centreline of both localiser and glidepath beams.

Question 28

What is ILS Cat I?

Answer 28

A precision instrument approach and landing with a decision height not lower than 60m (200ft).

Runway visual range (RVR) not less than 550m.

Visibility not less than 800m.

Question 29

What is EU OPS Lower than Standard CAT I Operation?

Answer 29

A Cat I instrument approach and landing operation using
Cat I decision height (DH).

With a runway visual range (RVR) lower than would normally be associated with the applicable DH but not lower than 400m.

Question 30

What is ILS CAT II?

Answer 30

A precision instrument approach and landing with a decision height lower than 60m (200ft), but not lower than 30m (100ft).

Runway visual range (RVR) not less than 300m.

Question 31

What is ILS Other than Standard CAT II

Answer 31

A precision instrument approach and landing operation using ILS or MLS where some or all of the elements of the precision approach Category II light system are not available, and with:

Decision height (DH) below 200ft but not lower than 100ft.

Runway visual range (RVR) of not less than 350m.

Question 32

What is ILS CAT IIIA?

Answer 32

A precision instrument approach and landing with either a decision height lower than 30m (100ft), or with no decision height and a runway visual range not less than 200m.

Question 33

What is ILS CAT IIIB?

Answer 33

A precision instrument approach and landing with either a decision height lower than 15m (50ft), or with no decision height, and a runway visual range less than 200m but not less than 75m.

Question 34

What is ILS CAT IIIC?

Answer 34

A precision instrument approach and landing with no decision height, and no runway visual range limitations.

Question 35

What are the ILS categories based on?

Answer 35

Mainly based on runway lighting and protection from infringements, but also the aircraft equipment and class of ILS installation.