ILS Flashcards
ILS
Instrument Landing System
An ILS provides precise ____________ and ___________ guidance
- Azimuth
- Glide slope
The minima of an ILS will be:
a Decision Height (DH) or Decision Altitude (DA)
Visibility and Height minima for ILS Cat 1?
Vis: 800m
Height: Not below 200ft
Visibility and Height minima for ILS Cat 2?
Vis: 350m RVR
Height: Not below 100ft
Visibility and Height minima for ILS Cat 3A?
Vis: 200m RVR
Height: Below 100ft or 0
Visibility and Height minima for ILS Cat 3B?
Vis: 50m RVR
Height: Below 50ft or 0
Visibility and Height minima for ILS Cat 3C?
Vis: 0
Height: 0
What are the components of an ILS?
- Localiser transmitter & aerials
- Glide slope transmitter and aerials
- DME
- High Intensity Approach Lighting (HIAL)
The localiser provides ___________ guidance
azimuth
The glide path provides __________ guidance
vertical
Where is the localiser aerial located?
Upwind on the extended centreline
The localiser carries the _________ ident
morse
A localiser sends out two overlapping signals. What are they?
- 150Hz tone right of the runway (blue zone)
- 90Hz tone left of the runway (yellow zone)
Where is the glide path aerial positioned?
Adjacent to the aiming point.
What is the frequency range of the glide path?
329 MHz to 335 MHz
What is the frequency range of the localiser?
108MHz to 112 MHz
Based on 3° Glide Path an aircraft will lose ____________ per NM travelled.
approx 300ft (more like 318) per NM travelled.
Of the two signals sent by a glide path, which is the higher (vertically)?
90Hz
Of the two signals sent by a glide path, which is the lower (vertically)?
150Hz
DME may be associated with an ILS to provide a pilot with what?
A cross-check of height/distance-to-run
Where is ILS DME typically located?
With the glide path.
Where no DME is associated with an ILS what can be used instead?
GNSS
What may be located prior to the ILS procedure Initial Approach Fix (IAF)?
An NDB.
Flying over the NDB prior to the IAF ensures what?
That the correct localiser beam is intercepted.
What is the purpose of HIAL?
High Intensity Approach Lighting is designed to assist a pilot in transitioning from flight in IMC to visual conditions
Which categories of ILS require HIAL?
CAT 2 & CAT 3
What is a marker beacon?
A low powered NDB that shoots a signal upwards in a vertical cone.
As an aircraft passes over, lights go off in the cockpit to tell the pilot where they are.
GBAS
Ground Based Augmentation System
How does GBAS work?
- A GPS receiver is placed at a surveyed geographical position
- The position received from the GNSS is compared with the known position and a correction is applied
- Differences are relayed via VHF datalink to aircraft
- Aircraft GPS compensates for errors
How accurate is GBAS?
Can be as accurate as 10cm
What does GBAS enable?
Precision approaches based on GPS
How should HIAL be operated?
a) select initial intensity in accordance relevant table
b) vary settings in accordance with pilot requests; and
c) advise pilots when equipment is operating in visibility of 5000 m or less.
How does NDB failure impact ILS approach?
Aircraft must join the ILS outside the outer marker as directed by NOTAM or ATC
How does Glide Path failure affect ILS approach?
Only localiser procedure is available
How does Marker Beacon failure affect ILS approach?
Aircraft may use the ILS if the alternate fixes nominated on the IAL chart or by NOTAM are used for altimeter checks
How does GBAS failure affect ILS approach?
GLS approaches are not available.
Minimum visibility for CAT 1 ILS approach when HIAL is not available?
1.5km
Minimum visibility for ILS CAT I when high intensity runway edge lighting is not available?
1.2km
Minimum visibility for ILS CAT I when instrumented RVR information in the threshold zone is not available?
0.8km
