ILS Flashcards
Where is the localiser antenna located?
The localiser antenna is located on the extended centreline of the runway, approximately 300 metres from the upwind, and in line with the runway centre line.
When on approach, on which side will the yellow sector of an ILS be and at what frequency?
The left hand side, modulated at 90 hz
When on approach, on which side will the blue sector of an ILS be and at what frequency?
The right and side, modulated at 150 hz
What is the localiser course width?
5 degrees, 2.5 degrees either side of the centreline.
How does the two localiser sector lobes guide an aircraft unto the runway centreline?
If an aircraft, which approaching the runway in the landing direction, receives more of the 90 hz modulated signal than the 150 hz modulated signal, then the aircraft is in the yellow sector, or left of the localiser centreline. The greater the amount of 90 hz signal or difference in depth of modulations(DDM) will activate the localiser needle.
What are the ICAO localiser coverage requirements
Localiser signals must be sufficient to provide coverage from the centre of the localiser transmitter to:
- 25 nm within 10 degrees either side of the centreline
- 17 nm within 35 degrees either side of the centreline
If coverage greater than 35 degrees is provided, it must extend to?
10 nm
what are the localiser frequencies and transmission type?
VHF band between 108 and 111.95 Mhz, only odd decimals are used and transmission are A2A
Fill the blanks:
Localiser _______ must be maintained up to __ nm from the transmitter, whilst protection of the localiser signal form interference must be maintained up to __ nm from the transmitter and up to a height of _250ft.
Localiser accuracy must be maintained up to 10 nm from the transmitter, whilst protection of the localiser signal form interference must be maintained up to 25 nm from the transmitter and up to a height of 6250ft.
Where are the glide path transmitter and aerial located?
Generally located 150 metres to one side of the runway centreline and approximately 300 metres upwind from the landing threshold of the ILS runway.
Glide path type of polarisation, frequency band, and transmission type?
Horizontally polarised signal, UHF band, A2A.
When imagining a glide path, which modulation lobe is the highest?
The 90 Hz lobe.
When imagining a glide path, which modulation lobe is the lowest?
The 150 Hz lobe
According to ICAO recommendation, what is the angle from the surface to the point of equal modulation(glide path centreline)?
3 degrees, but a farther recommendation is that the glide path equipment should be capable of producing a glide path angle of between 2 and 4 degrees to accommodate local terrain conditions
ICAO required minimum horizontal glide path coverage?
Glide path equipment must be capable of providing signal coverage in sectors of 8 degrees either side of the ILS glide path centreline to a distance of 10nm.
ICAO required vertical glide path minimum and maximum coverage?
Vertical coverage must be multiplied by 0.45 for the minimum and 1.75 for the maximum
Glide path frequency band and frequency range?
UHF between 328.6 MHz - 335.4 MHz
At what angle can the first false glide path be encountered?
6 degrees
The 3 reasons why false glide paths not a danger to aircraft?
- If an aircraft descends on a false glide path its rate of descent would be excessive and obvious.
- In normal conditions the GP is intercepted from below, not from above, so the false GP will not be encountered.
- Signals received on a false GP will be very weak and warning flags should operate.
At what distance is the outer marker, visual indication and aural indication & modulation?
+/- 4 nm, blue and 2 dashes/sec, 400Hz
At what distance is the middle marker, visual indication and aural indication & modulation?
+/- 3500ft, amber and alternate dots/dashes, 1300Hz
At what distance is the inner marker, visual indication and aural indication & modulation?
+/- 250 to 1500ft, white and 6 dots/sec, 3000Hz
At what height is the ILS reference datum?
50ft vertically above the intersection of the runway centreline.
ILS FACILITY PERFORMANCE:
Define CAT 1 accuracy
Accurate guidance down to 200 feet above the ILS reference point
ILS FACILITY PERFORMANCE:
Define CAT 2 accuracy
Accurate guidance down to 50 feet above the ILS reference point
ILS FACILITY PERFORMANCE:
Define CAT 3 accuracy
Accurate guidance down to and along the surface of the runway
Rate of descent formula for ILS glide slope?
ROD = GP angle x GS x 100 / 60
Does the rate of descend need to be increased or decreased if TAS is to be kept constant during an increased groundspeed?
ROD needs to be increased
Is the localiser back course lobes reversed or not?
The are reversed, one would have to disobey the localiser needle.
Does a localiser back beam posses a GS and markers?
No, it does not.
What is the Trig phrase for calculating triangles?
SohCahToa
How to calculate the angle with an adjacent of 3 and a opposite of 2?
Toa:
O / A = 1,5
Since 1,5 is tan, use 1,5 and press the TAN inverse button on your calculator
The ILS fan marker beacon frequency is?
75 MHz
Th ILS localiser has its accuracy checked at?
10 nm
What frequency band does the ILS markers use?
Same as the ILS localiser, 75 MHz VHF.
An aircraft tracking to intercept the Instrument Landing System (ILS) localiser inbound on the approach side, outside the published ILS coverage angle:
may receive false course indications
