NAV - ILS Flashcards
What is an ILS? (5)
ILS - Instrument Landing System
- Precision approach (azimuth and elevation)
- Runways are known as Precision Approach Instrument Runways
- For poor weather (cloud / visibility)
- Assists in achieving an orderly flow of landing traffic
What is the Localiser Transmitter? (3)
- Situated beyond the upwind end of the runway approx. 300m from the threshold
- Defines the extended centreline of the
instrument runway - Indicates deviation from the optimum lateral approach path
What is the Glidepath Transmitter? (3)
- Situated approx. 300m from the landing threshold and offset between 100 & 200m from the centreline
- Defines the safe descent slope (normally 3°)
- Indicates deviation from the optimum verticalapproach path
What are the 3 Marker beacons? (3)
- Outer marker
- Middle marker
- Inner Marker
What are the characteristics of the Outer Marker? (3)
- 3-6nm from threshold
- Tx 2 dashes per sec at 400Hz
- Flashes blue light in cockpit
What are the characteristics of the Middle Marker? (3)
- 900-1200m from threshold
- Tx alternate dot dash at 1300Hz
- Flashes amber light in cockpit
What are the characteristics of the Inner Marker? (3)
- 300 – 450m from threshold
- TX 6 Dots per sec at 3000hz
- Flashes white light in cockpit
ILS & Marker beacons diagram
How is a DME used for an ILS? (3)
- Paired with ILS - Both auto tuned when selected
- Range info is “0” to the Runway threshold
- Accurate only within localizer coverage and up to 25,000ft
ILS Transmitters WITH DME diagram
What are the characteristics of the Localiser? (5)
- VHF Band: 108-112 Mhz
- Radiates 2 lobes - overlap by 5°
- Modulates 90 & 150 Hz in either centreline side
- Unequal signals indicates left / right of centreline
What is the Localiser protected range? (3)
- Coverage 35° either side of centreline
- 17 nm
- Reduces to 10° thereafter up to 25nm
Which ICAO annex indicates ILS facilities to conform to? (1)
Annex 10
What are the characteristics of the Glidepath? (4)
- UHF band: 329.3 - 335 Mhz
- Radiates 2 lobes - overlap by 1° - Range of 10nm
- Known as ILS Reference Point
- 3° descent angle
- Deviation either above or below results in unequal signals being received
What is the Glidepath protected range? (2)
- Coverage 8° Azimuth side of localiser centreline
- 10 nm from threshold
What does the operation of the GP and angle depend on? (5)
- Aircraft likely to use the aerodrome
- Terrain
- Obstacles within the approach and missed approach areas
- Local meteorological conditions
- Runway length
What is the datum for the Rate of Height Loss? (3)
- 2.5° = 250ft per NM
- 3° = 300ft per NM (Normal setting)
- 3.5° = 350ft per NM
What is the ILS reference datum? (2)
- Glide transmitter is to equate the same height as an A/C flies over the threshold
- Height is 50ft
What are the advantages of frequency pairing? (3)
- Reduces cockpit workload
- Guards against mismatching
- Only the localizer frequency needs to be published and selected on the flight deck
What ILS equipment is monitored? (3)
- Localiser
- Glidepath
- Markers
What happens if the ILS fails? (2)
- ATC & Pilot warned of failure
- System will switch off - If monitoring system fails
How is the ILS station identification achieved? (2)
- Modulating a three letter Morse identifier onto the localizer carrier wave
- When the ILS is undergoing maintenance, or is radiating for test purposes, the identifier is removed or replaced by a continuous tone
What does HSI & OBS stand for? (2)
HSI - Horizontal Situation Indicator
OBS - Omni-directional Bearing Selector
How is an ILS shown on an aircraft display? (3)
- Edge of central ring equates to the first dot of displacement
- Each horizontal dot indicates 0.5° deviation from the centre of the localizer
- Each vertical dot indicates 0.15° deviation from the centre of the glidepath
When would an ILS display both needles in the centre? (3)
- The receiver is switched off
- No signals are being received
- The aircraft is on the centreline of both localizer and glidepath beams
What are the conditions to be allowed to perform an Auto land with the ILS? (3)
- Aircraft being suitably equipped
- Ground transmissions being adequately protected from external interference
- Aircraft movements on the ground in the vicinity of the ILS equipment must therefore be restricted (depending on the category of approach)
What are the ILS categories? (7)
- ILS Category I
- LOWER THAN STANDARD CAT I
- ILS Category II
- OTHER THAN STANDARD CAT II
- ILS Category III A
- ILS Category III B
- ILS Category III C
ILS Category table
