09 Instrument Landing System

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INSTRUMENT LANDING

SYSTEM

ILS


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PRECISION APPROACH

Non-precision approaches supply the pilot withhorizontal guidance only. (VOR, NDB, Localizer,Loc. B/C, GPS without VNAV)

Precision approaches supply the pilot withhorizontal and vertical guidance. (ILS, MLS, PAR,GPS with VNAV)

ILS is the primary international precision approachsystem approved by ICAO and protected until

2010. ILS provides an aircraft with precision horizontal

and vertical guidance to the runway.


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TYPICAL ILS INSTALLATION
http://upload.wikimedia.org/wikipedia/en/7/79/ILS_illustration.jpg


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http://upload.wikimedia.org/wikipedia/en/7/79/ILS_illustration.jpg


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LOCALIZER Localizers operate in the VHF range and provide horizontal

course guidance to runway centerline. Transmitters are locatedon the centerline at the opposite end of the runway from theapproach threshold.

The signal transmitted consists of two fan shaped patterns thatoverlap at the centre. The overlap area provides the on-track

signal. The angular width of the beam is between 3and 6. Normally

width is 5, resulting in full scale deflection at 2.5. The width ofthe beam is adjusted to be 700 feet wide at runway threshold.

The localizer may be offset from runway centerline by up to 3.Localizers offset more than 3 will have an identifier beginning

with X, aligned localizer identifiers begin with I. A cautionary note will be published in the CAP whenever

localizer is offset more than 3.


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Normal reliable coverage of localizers is 18nm within 10 of

either side of course centerline and 10nm within 35. Localizer installations provide back course information, and

non-precision localizer back course approaches may bepublished. (ignore all glide path information on backcourse) Normally glide path will flag off.

Caution: a localizer signal is transmitted differently than aVOR radial. Aircraft receivers are not supplied with azimuthinformation relative to magnetic or true north. It is simply abeam aligned with the runway centerline. For this reasonCDIs will display normal sensing characteristics when

flying in the same direction as front course alignment, butreverse sensing when traveling in the direction of backcourse alignment. (HSI will normal sense anytime frontcourse direction is set on head of track bar.)


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LOCALIZER


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Glide Path

Glide path information is paired with the associatedlocalizer frequency.

The glide path is normally adjusted to an angle of 3 (maybe adjusted 2 to 4.5) and a beam width of 1.4(0.7 for

full scale deflection). The antenna array is located approx. 1000ft from the

approach end of the runway and offset approx. 400ft. (ifglide path is followed to the pavement touchdown point willbe at the 1000ft markers)

In installations with an ILS serving both ends of a runwaythe systems are interlocked so only one can operate at atime.

Note: on a standard 3 glide path 320ft/1nm can be used toverify.


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FINAL APPROACH FIX

Typical final approach fixes are NDBs inCanada, but can also be identified by DMEor VOR radial and DME as published.

Fan Markers are commonly used in the USas a means of identifying aircraft locationalong a localizer. As the marker is reached afan marker light will illuminate in the flightdeck (if equipped).


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ILS CATEGORIES

CAT I: operation down to a minimum of 200ft DH andRVR2600 or sm ground visibility when RVR notavailable.

CAT II: operation down to a minimum of 100ft DH and RVR

1200ft. CAT III: minimums will be prescribed in the carriers

operating specifications, carriers operations manual, or theCAP. (minimums are further broken down into A,B, or Cwith a CAT IIIC minimums being zero-zero).

Requirements: CAT II/III approaches require specificaircraft and airport capabilities. (ex: airport lighting, aircraftautoland)

Note: when CAT II/III approaches are being conducted theCAT II or CAT III hold line must be adhered to.


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RUNWAY LIGHTING AND

TRANSMISSOMETERS The following must be fully serviceable to meet CAT II/III standards:

Airport lighting: approach lights runway threshold lights touchdown zone lights

centerline lights runway edge lights runway end lights all stop bars and lead-on lights essential taxiway lights

ILS components: localizer glide path


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RVR equipment:

CAT II- two transmissometers- approach end, mid-field

CAT III- three transmissometers- approach end, mid-

field, departure end Power source:

Airport emergency power as primary power source forall essential system elements.

Commercial power available within one second as abackup.

09 Instrument Landing System

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