ILS Flashcards
What does ILS stand for?
Instrument Landing System
Is an ILS approach Precision or Non-Precision?
ILS is a Precision Runway Approach
What makes an approach a Precision Approach?
Accurate guidance in both Glide Path, as well as Azimuth
Where is the localiser transmitter sited?
Sited beyond the upwind end of the runway, approximately 300m.
Where is the glidepath transmitter sited?
Sited approach 300m from the landing threshold and offset between 100 and 200m from the centreline.
What does the localiser define and indicate?
Defines the extended centreline of the instrument runway.
Indicates deviation from the optimum lateral approach path.
What does the glidepath define and indicate?
Defines the safe descent slope.
Indicates deviation from the optimum vertical approach path.
What is the normal angle of a safe glidepath?
3 Degrees
What are the two beacons installed on an approach and what do they do?
Outer Marker
Middle Marker
They define ranges from the threshold
What does a DME Transponder attached to an ILS do?
Provides range information zero referenced to the runway threshold instead of Marker Beacons
Which band does the localiser operate in?
108-112MHz VHF
What is the coverage of a localiser?
Coverage out to 35 Degrees either side of the centreline out to 17nm, up to maximum range.
Which Annex do ILS facilities conform to?
ICAO Annex 10 unless otherwise indicated in the AIP.
What is the ILS protected range?
Coverage out to 35 Degrees either side of the centreline out to 17nm, reducing to 10 Degrees thereafter up to 25nm.
What are the two modulation frequencies of the localiser and glidepath?
90Hz and 150 Hz
What is the ILS Reference Point?
The Glidepath Aerial
What is the Glidepath protected range?
8° of azimuth each side of the Localizer centreline to a distance of 10 nm from threshold.
What does the location of the Glidepath Aerial and the Approach Angle depend on?
Aircraft likely to use the aerodrome
Terrain
Obstacles within the approach and missed approach areas
Local Meteorological conditions
Runway Length
What is the rate of height loss for a 3 Degree approach?
300ft per nm
What is the ILS Reference Datum?
A point at a specified height, located at the intersection of the centreline and threshold, through which ths ILS glidepath passes.
What height should the ILS Reference Datum be close to?
50ft
If the ILS monitoring equipment detects a malfunction, what happens?
The ILS automatically ceases to transmit navigation information.
Is the LOC only approach Precision or Non-Precision?
Non-Precision because an accurate glidepath is not available
How is the ILS station identified?
By modulating a three letter Morse identifier onto the localizer carrier wave
On what instruments can ILS information be displayed?
Horizontal Situation Indicator (HSI)
Omni-Directional Bearing Indicator (OBI)
What do each horizontal and vertical dot on the ILS display indicate?
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.
When will both ILS needles remain central?
The receiver is switched off.
No signals are being received
The aircraft is on the centreline of both localiser and glidepath beams.
What is ILS Cat I?
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.
What is EU OPS Lower than Standard CAT I Operation?
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.
What is ILS CAT II?
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.
What is ILS Other than Standard CAT II
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.
What is ILS CAT IIIA?
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.
What is ILS CAT IIIB?
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.
What is ILS CAT IIIC?
A precision instrument approach and landing with no decision height, and no runway visual range limitations.
What are the ILS categories based on?
Mainly based on runway lighting and protection from infringements, but also the aircraft equipment and class of ILS installation.
