Chapter 6 - Navigation Systems and Aids 2

Question 1

Name some common HSI inputs.

Answer 1

Mag hdg
VOR/ILS
DME
TACAN
NDB

Can also display:
TCAS, weather radar, moving map, etc

Question 2

Note - Go to 4-6-1 and learn the labelled HSI display diagrams.

Answer 2

Remember -
Course Deviation Scale/Lateral Deviation Scale = Dots
Glidepath Deviation Scale = Dots

Amount represented changes with distance from the target/ILS runway.

Deviation shown on these dots/scales by:
Course deviation bar/lateral deviation bar
Glidepath deviation pointer

Question 3

What does an Instrument Landing System (ILS) comprise of?

Answer 3

Ground installation (localiser and glidepath transmitters)

Airborne receiver

Question 4

What does the Localiser (LLZ) signal provide?

Answer 4

Azimuth information

Question 5

What does the Glidepath (GP) signal provide?

Answer 5

Elevation information

Question 6

Where is the LLZ transmitter positioned?

Answer 6

300m beyond the upwind end of the runway

Aligned with the runway centre

Question 7

Where is the GP transmitter positioned?

Answer 7

100m to the side of the runway

250m from the runway threshold

Question 8

What frequency does the LLZ transmitter operate on?

Answer 8

Single VHF frequency

Question 9

What are the LLZ Right hand and Left hand lobes amplitude modulated at?

Answer 9

Right = 150Hz

Left = 90Hz

Question 10

What is the Localiser coverage?

Answer 10

18nm within +/- 10 degrees of the centreline

10nm between 10 degrees and 35 degrees from the centreline

Question 11

What should you always do when tuning into an ILS?

Answer 11

Listen to the transmitted morse code signal (transmitted every 10 seconds) to identify that you are tuned into the correct installation.

Question 12

LLZ range can differ from one aerodrome to another. Where can precise coverage details be found?

Answer 12

In the UK AIP

Question 13

Where should you fly to if either the course deviation bar or the glidepath deviation pointer are not centred?

Answer 13

Fly towards the bar, i.e. course bar off to the right - adjust course to the right.

Question 14

What frequency band does the GP transmitter operate in?

Answer 14

UHF and paired with the VHF LLZ frequency

Question 15

What are the upper and lower GP lobes modulated at?

Answer 15

Upper = 90Hz

Lower = 150Hz

Question 16

What is the range of the GP signal?

Answer 16

10nm at 2000ft within +/-8 degrees of the localiser front course.

Can differ depending on requirements, details in the UK AIP.

Question 17

What is the beamwidth of the GP signal?

Answer 17

Lower edge = 0.45 x glidepath angle

Upper edge = 1.75 x glidepath angle

Question 18

Note - Learn (if reqd.) the table of ILS performance categories with decision height and RVR.

Answer 18

Look in end of Nav systems and aids 2.

Question 19

What errors can affect ILS systems?

Answer 19

Reflections, weather and multipath interference.

Scalloping - Rapidly oscillating indications

Beam bend - Gentle curve in the approach path

FM Transmissions - Frequencies just below 108Hz can produce ‘spillage’ into LLZ frequency band causing interference

Weather - Heavy snow or rain may attenuate the ILS signals, reducing range and degrading accuracy