8. ILS - N2 Flashcards
What is an ILS?
ILS is a Precision Runway Approach that provides accurate guidance both in azimuth and elevation.
Runways served by ILS are known as Precision Approach nstrument Runways.
It’s a pilot interpreted aid.
What are the components of an ILS?
- The localizer - providing horizontal guidance
- The glide-slope - providing vertical guidance.
Landing information is then supplemented with range information through:
- Marker Beacons
- Compass Locators
- or DME which is simplified via frequency pairing.
What is the ILS Localiser?
It defines the extended centreline of the instrument runway & indicates deviation from the optimum lateral approach path
Situated beyond the upwind end of the runway approx, 300m from the threshold.
A localiser must provide a minimum horizontal coverage to a distance of?
17nm over a sector of 35˚ either side of centreline
What is the GP Transmitter?
Indicates deviation from the optimum vertical approach path - normally 3°
Situated approx. 300m from the landing threshold and offset between
100 & 200m from the centreline., it defines the safe descent slope.
How many Marker Beacons are employed?
Normally two, or occasionally three
Outer Marker 3-6nms from threshold.
Tx 2 dashes per sec at 400Hz. Flashes blue light in cockpit.
Middle Marker 900-1200m from threshold.
Tx alternate dot dash at 1300Hz. Flashes amber light in cockpit.
How is DME used with an ILS?
Range information - is zero referenced to the runway threshold.
Provides range information instead of Marker Beacons.
DME channel is frequency paired with localizer so DME automatically tuned when ILS selected.. Accurate only within localizer coverage and up to 25,000ft.
The ground installation of an ILS has three distinct components, localiser, glide path/slope and DME?
True
if we are including the DME as a part of the ILS.
Some Airports may not have a DME associated with the ILS
How does the Localiser operate?
Radiates two lobes which overlap by 5º.
Flight receives signals of equal intensity from both lobes when on centreline
Deviation left or right results in unequal signals being received.
Transmits a signal in the 108-112MHz VHF band.
What is the ILS Protected range?
Coverage out to 35° either side of centreline out to 17nm, reducing to 10° thereafter up to 25nm.
How does the G/S operate?
Radiates two lobes which overlap by 1° out to a maximum range of 10nms along extended approach path.
The G/S Transmits a signal in the 329.3-335MHz UHF band.
The glidepath aerial is known as the ILS Reference Point. The overlapping area normally subtends an angle of 3° (adjustable by comms for a particular aerodrome) to give continuous descending approach to the
touchdown point.
What is the G/S protected range?
Glide Paths provide coverage in the sectors 8° azimuth each side of
the Localizer centre-line to a distance of 10 nm from threshold.
What is the ILS reference point?
The ILS reference point, or datum, is found above the runway
threshold, at the intersection of the localiser centreline and the GP beam.
What is the height of the ILS ref point (Datum)?
approx 50 ft above the threshold
How are ILS categories established?
This is mainly based on runway lighting and protection from
infringements, but also the aircraft equipment and class of ILS installation.
What best describes the Instrument Landing System (ILS) localiser radiation pattern?
2 overlapping lobes on the same radio carrier freq. but with different modulation
