Instrument Landing Systems

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Instrument Landing Systems

• Instruments and Avionics
• Blake Crosby

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What Is An Instrument Landing System?
The ILS is designed to provide an aircraft with a
precision final approach with horizontal and
vertical guidance to the runway. The ground
equipment consists of a localizer, a glide path
transmitter and an NDB along the approach path. A
DME fix may replace the NDB.
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Why?

• Scheduled service would be impossible without a
  way to land in poor weather.
• Provide a standard way to land and take off from
  any airport in the world.
• Additional safety and situational awareness.

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History

• Tests of the first ILS began in 1929
• The first scheduled passenger airliner to land
  using ILS was in 1938. A Pennsylvania-Central
  Airlines Boeing 247-D from Washington to
  Pittsburgh.

• In 1949, ICAO adapted an ILS standard developed
  by the US Army as a standard system for all of
  its member countries.

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How It Works

• Glideslope
• Provides vertical navigation
• Localizer
• Provides horizontal navigation
• NDB/ADF or DME
• Provides distance from runway

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How It Works
Localizer Antenna is located on the opposite end
of the runway.
Glideslope Antenna is located on one side of the
runway at approx. touch down point.
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Glideslope Antenna Array
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Localizer Antenna Array
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NDB Antenna
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Course Deviation Indicator
Signal Integrity Flag Indicates if instrument is
unreliable
Dots Each dot on the instrument represents 2
of deviation
Localizer Deviation from runway centre line
Glideslope Deviation from optimal glide path
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Limitations of current ILS

• Localizer is sensitive to obstructions like
  buildings and terrain.
• Glideslope errors can occur if terrain is sloping
  or is uneven infront of the antenna.
• Since antennas point in a single direction, only
  straight approaches are available.
• Can be costly.

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Other types of ILS

• Microwave Landing System
• Curved approaches are possible
• Less interference and more accurate than
  traditional ILS
• Used mostly in Europe
• Being replaced by GPS approaches
• Transponder Landing System
• Easy and quick to deploy in remote locations
• Only one airplane can use the system at a time.
• No additional equipment needed on aircraft.
• Similar system used by the military.

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Videos
http//www.youtube.com/watch?vM3wnl1Ut--o
http//www.youtube.com/watch?vZnEtr6Ei1sc