1. Instrument Landing Systems
Instruments and Avionics
Blake Crosby

2. 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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Instrument Landing Systems

3. Instrument Landing Systems
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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Instrument Landing Systems

4. Instrument Landing Systems
History
Tests of the first ILS began in 1929
The first scheduled passenger airliner to land using ILS was in A Pennsylvania-Central Airlines Boeing 247-D from Washington to Pittsburgh.
Unlike the original system developed by the CAA, the US Army standard was not prone to static and had straighter glideslopes and localizer beams.
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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Instrument Landing Systems

5. Instrument Landing Systems
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Instrument Landing Systems

6. Instrument Landing Systems
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Instrument Landing Systems

7. Instrument Landing Systems
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Instrument Landing Systems

8. Instrument Landing Systems
How It Works
Glideslope
Provides vertical navigation
Localizer
Provides horizontal navigation
NDB/ADF or DME
Provides distance from runway
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Instrument Landing Systems

9. Instrument Landing Systems
How It Works
Localizer
Antenna is located on the opposite end of the runway.
Both the localizer and and glideslope emit two “tones” one at 90 hertz and the other at 150.
Glideslope
Antenna is located on one side of the runway at approx. touch down point.
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Instrument Landing Systems

10. Glideslope Antenna Array
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Instrument Landing Systems

11. Localizer Antenna Array
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Instrument Landing Systems

12. Instrument Landing Systems
NDB Antenna
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Instrument Landing Systems

13. 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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Instrument Landing Systems

14. 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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Instrument Landing Systems

15. Instrument Landing Systems
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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Instrument Landing Systems

16. Instrument Landing Systems
Videos
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Instrument Landing Systems