The ILS (16-05-18) Flashcards
What is the emission class of the ILS?
A8W
What is the frequency of the ILS localiser?
108.1 - 111.95MHz
What frequency band does the ILS localiser operate on?
VHF
What frequency band does the glide path of the ILS operate on?
UHF (approx 333MHz)
What are the 4 main components of an ILS system?
LOC
Glidepath
Markers (older systems)
DME (newer systems)
How do we tune in to the LOC and glidepath on an ILS?
We tune to the LOC and get the glideslope automatically
This reduces workload and errors
What is a precision approach?
One where both azimuth and vertical position guidance is given
What is a non precision approach?
One where azimuth guidance is given but not vertical position.
Instead a minimum descent height/altitude will be given
How does a LOC work?
Generates 2 lobes at different AM:
Left lobe 90Hz AM
Right lobe 150Hz AM
The centerline is equisignal from both.
The principle of operation is Difference in Depth Modulation (DDM) or lobe comparison.
How does a glideslope/path work?
2 lobes generated both AM.
Upper 90Hz AM
Lower 150Hz AM
Path where equisignal from both.
Principle of operation is DDM
What is the coverage of a LOC?
35deg either side of centerline up to 17nm
10deg either side up to 25nm
up to 6250ft
What is the coverage of a glidepath?
0.45 of glide angle to 1.75 of glide angle
What frequency do ILS markers operate on?
75MHz
What are the colours, pitch, ident and touchdown range for the different ILS markers?
Outer:
Blue; low; 2 dashes/s; 6.5 - 11.1km
Middle:
Amber; medium; alternate dashes and dots, 3/s; 1050m +/- 150m
Inner:
White; high; 6 dots/s; 75 - 450m
What are the different ILS categories with ground installation and aircraft minima?
CAT 1 - ground installation = 60m above touchdown;
aircraft minima = 200ft on altimeter, RVR 550m.
CAT 2 = Ground installation = 15m above threshold;
aircraft minima = 100ft on radio altimeter, RVR 300m
CAT 3 = ground installation touchdown and beyond;
aircraft minima = 0ft on radio altimeter
A = RVR 200m
B = RVR 75m
C = RVR 0m
What is the ILS critical area?
The area surrounding the glidepath antenna where movement of people and vehicles is forbidden.
What is the ILS senstive area?
The area aroud the glidepath antenna where, during CAT 2 or 3 operations, movement of people and vehicles is restricted.
What is the ILS back course?
Side lobes are created by the main antenna which cause a mirror image behind.
This mirror image causes reverse indication from behind.
How can an ILS back course be flown?
Using HSI with reverse HDG in order to reverse the reversed information
What are false glide slopes and how do we overcome them?
Glide slopes that are caused by the side lobes created by the main ILS system.
to overcome this we always intercept the correct glide slope from below
What are the features of an ILS instrument display - OBI?
There are 2 break lines for horizontal (LOC) and vertical (glideslope)
the full scale LOC deviation is 2.5deg
the full scale glide slope deviation is 0.7deg
Failure flags flip when:
- there is significant distortion of radiation pattern
- the A/C flies out of the ILS service area
- Ground or airborn equipment fails or is turned off.
What is the required accuracy that the pilot has to fly for an ILS approach?
within 1/2 scale deviation from desired track.
Within what deviation from the LOC centerline does an A/C have to be before starting the descent onto the glide path?
1/2 full scale deviation.
To remain within protected airspace what glidepath deviation must the pilot remain within?
1/2 full scale deviation.
What happens to deviation sensitivity as you get closer to the LOC?
It gets more sensitive
What errors are associated with ILS?
Beam bending from ground reflection
Scalloping reflection
Beam noise, distorting the beam
Commerical radios, FM interference
Siting error
What are the disadvantages of ILS?
Only striaght approach
Only 1 glide path
Snow on aerial can affect the signal
Only 40 channels
