Instrument Landing System (ILS)

Question 1

ILS elements- 3 things

Answer 1

•Guidance Information
•Range Information
•Visual Information

Question 2

Localizer

Answer 2

•Gives us horizontal guidance
•Frequency: 108.1-111.95 MHz
•Always odd number after the decimal
•Ident – I followed by three letters
•Very Sensitive
•Full scale is only 2.5 degrees
•Each dot for a VOR is 2 degrees
•Single Fixed Course
•Will always show same indication regardless of what is set in to the OBS
Yellow sector 90 hz on left and blue sector 150 hz on right

Question 3

Glide slope

Answer 3

•Gives you Vertical Guidance
•Frequency: 329.15-335.00 MHz
•Coupled to ILS (not tuned separately)
•Ground Equipment- Antenna located on the side of runway, 750’ to 1250’ from approach end, offset 250-650 feet from centerline
•Transmits two overlapping lobes
90 hz on top, 150 hz on bottom

1.4 degrees thick
•Normally 2.5 to 3 degree angle up
•Useable distance 10 nm
•Intercept from below
•Avoid false signals

Question 4

Guidance=

Answer 4

Localizer+glideslope

Question 5

Range

Answer 5

Distance information
•Marker Beacons (compass locators)
•Distance Measuring Equipment (DME)
•Used in lieu of OM
•GPS may be used to replace all

Question 6

Marker beacons

Answer 6

•Provides distance information
•Low powered NDBs called compass locators
•VHF signals of 75 MHz transmitted vertically
•Flashing synchronized lights with aural identification
•Three Markers: Outer, Middle and Inner Markers

Question 7

Marker beacons- outer markers

Answer 7

Operates on 400Hz band
•Located 4-7 miles from threshold
•Distance dependent on glide path 2.5-3.2 degrees
•Positioned so aircraft is approximately 1400’ Height Above Touchdown (HAT) when crossing OM.
•dah-dah-dah-dah-dah (- - - - -)
•Flashing blue Light

Question 8

Marker beacons- middle marker

Answer 8

•Operates on 1300 Hz band
•Located 3500 feet from RW Threshold
-approx ½ mile
-200 feet HAT
- near decision height/Missed approach point
•dah-dit-dah-dit-dah-dit (- . - . - .)
•Flashing Amber Light

Question 9

Marker beacons- inner marker

Answer 9

Operates on 3000 Hz band
•Located between Middle marker and RW Threshold.
•Only Used on Category III approaches (lowest minimums)
•Also used for Back course markers or intersection fixes
•dit-dit-dit-dit-dit-dit (…….)
•Flashing White Light

Question 10

Visual information

Answer 10

•Approach Lights, Runway lights & markings
•Aids in the transition of instrument to visual flight
•Fly an ILS down to 200’ and ¼ mile!

Question 11

Localizer type directional aid

Answer 11

•Comparable to the Localizer but not aligned with the runway centerline
•May or may not have a glideslope
•Need to usually do a circle to land approach (30° to runway centerline)

Question 12

Simplified direction finder

Answer 12

Similar to the localizer
•But course width is 6-12 degrees
•But still very accurate
•May not be aligned with the center line
•Lateral limits – 35° of runway centerline
•Identifier not preceded by an “I”