ILS

Question 1

What does the ILS provide aircraft?

Answer 1

• Course guidance and glideslope.

Question 2

What are the requirements of a Category I ILS approach?

Answer 2

• Visibility requirements have to be met at not lower than 200 ft height above threshold.
• A visibility of not less than 800m
• RVR not less than 550 m

Question 3

What are the three main components of the ILS?

Answer 3

1. VHF localiser
2. UHF glideslope
3. DME or low powered NBDs used for range information.

Question 4

What are the characteristics of the localiser transmitter?

Answer 4

• VHF frequencies from 108.10 to 111.95 MHz
• Two overlapping lobes
• when lobes are of equal strength, aircraft is on track.

Question 5

What are the frequencies of the glideslope?

Answer 5

90 Hz and 150 HZ signals that when are of equal strength, correspond to correct glideslope (normally 3 deg).

Question 6

What are the various range information provided during an ILS approach?

Answer 6

1) ILS DME
2) DME
3) Marker Beacons
4) Compass Locator

Question 7

What are approach lights used for?

Answer 7

To provide visual references and cues to assist landing from an ILS approach.

Question 8

What are the two types of approach lights for ILS?

Answer 8

• Distance coded centrelines

- Barrett centreline

Question 9

What is the process for tuning the ILS?

Answer 9

1) Tune Nav receiver to LOC frequency
2) Listen to Morse code to confirm
3) By identifying LOC, you will also identify glideslope for the ILS
4) No red NAV off flags should be visible.

Question 10

On ILs instrument, what does one lateral deviation equate to off the inbound track?
What about for glideslope?

Answer 10

1. 25 degrees off the inbound track.

0. 35 deg off glideslope

Question 11

What is the localiser signal coverage?

Answer 11

• 25 NM at 2,000 ft and within +-10 deg of the localiser centreline.
• Reliable indications are available within +-35 of the LOC centreline at 17NM from the runway touchdown point.

Question 12

What distance is the glideslope only considered accurate to?

Answer 12

• Out to 10 NM

- More accurate above than below glideslope

Question 13

What angle can false glideslope a occur?

Answer 13

Normally fined at 12.5 degrees glideslope

Question 14

What should be done to verify the accuracy of the glideslope?

Answer 14

Verify the glideslope with a TACAN or other method.

Question 15

What can affect ILS?

Answer 15

Interference and insufficient signal.

Question 16

What will often display if there is insufficient signal?

Answer 16

Red flags on ILS display.