Instrument Landing System (ILS)

Question 1

What are the 3 main components?

Answer 1

• localiser (LOC)
• glide path (GP)
• range information (markers/DME)

Question 2

What frequencies does an ILS operate in?

Answer 2

108.00 - 111.975 MHz

Question 3

What is the LOC centreline determined by?

Answer 3

2 overlapping left and right beams (lobes) modulated at 90 Hz and 150 Hz

Question 4

What is the recommended glide path?

Answer 4

3 degrees above the horizontal

Question 5

What are the scales of maximum deflection?

Answer 5

LOC +/- 2.5 degrees

GP +/- 0.7 degrees

Question 6

What is the LOC plan coverage?

Answer 6

10 degrees either side of centreline out to 25nm

35 degrees either side of centreline out to 17nm

Question 7

What is the GP plan coverage?

Answer 7

8 degrees either side of the LOC centreline out to 10nm

Question 8

When must a missed approach procedure be initiated?

Answer 8

If the a/c deviates by more than half-scale deflection on either LOC or GP

Question 9

What’s the ILS critical area?

Answer 9

Area around the LOC and GP antennas where operations are prohibited during ILS operations

Question 10

What’s the ILS sensitive area?

Answer 10

Area around LOC and GP antennas where operations are controlled during ILS operations

Question 11

What’s the ILS beam bends?

Answer 11

Deviations from nominal LOC and GP centrelines