ATPL Instrument Landing System Quiz

Questions and Answers

What angle provides azimuth coverage for an ILS Glide Path to a distance of 10 NM from the threshold?

35°

5°

8° (correct)

25°

Which frequency band does an ILS glide slope operate in?

UHF (correct)

SHF

VHF

EHF

What action should be taken if more 90 Hz modulation than 150 Hz modulation is received on an ILS approach?

Fly right and up

Fly left and down

Fly right and down (correct)

Fly left and up

If the HSI compass rose is stuck on 200 degrees while aligned with the ILS localiser for runway 25, what will be the position of the localiser needle?

Centred Signup and view all the answers

To regain centreline and glide path on an ILS approach while receiving more 90 Hz modulation, the correct action would be to:

Increase rate of descent and fly right Signup and view all the answers

What is the reliable navigation information angular coverage for a 3° ILS glide path reaching 10 NM?

1.35° above to 5.25° above and 8° each side Signup and view all the answers

Where is the ILS localiser transmitting aerial normally situated in relation to the runway?

On the non-approach end about 300m from the runway Signup and view all the answers

If an aircraft is outside the published ILS coverage angle, what may occur?

False course indications Signup and view all the answers

What is the aural frequency of an outer marker transmitting on 75 MHz?

400 Hz Signup and view all the answers

Which option is an ILS localiser frequency?

109.15 MHz Signup and view all the answers

What is the minimum accuracy a category III ILS system provides for landing guidance?

The surface of the runway Signup and view all the answers

What frequency does the OUTER MARKER of an ILS facility transmit on?

75 MHz with Morse modulation at two dashes per second Signup and view all the answers

What is the approximate change in rate of descent when the ground speed drops from 150 kt to 120 kt on a 3° glidepath?

A decrease of 50 FT/MIN Signup and view all the answers

How does a 10 kt decrease in ground speed affect the required rate of descent on a 3° ILS glide path?

Decrease in rate of descent of 50 FT/MIN Signup and view all the answers

What is the rate of descent necessary to maintain a 3.25° glide slope at a ground speed of 140 kt?

800 FT/MIN Signup and view all the answers

What ILS indication will show when an aircraft receives more 90 Hz modulation than 150 Hz?

Fly right and fly down Signup and view all the answers

Which of these statements about ILS systems is incorrect?

The OUTER MARKER broadcasts at 200 MHz. Signup and view all the answers

What consequence does an increase in modulation from the localiser indicate?

The aircraft is too low. Signup and view all the answers

What is the expected height of an aircraft on a 3 degree glide path when it is 4.5 NM from touchdown?

1370 ft Signup and view all the answers

What visual and aural indications are associated with the ILS outer marker?

A blue light and 2 dashes per second of 400 Hz modulated tone Signup and view all the answers

How is the middle marker of an ILS facility identified both audibly and visually?

Alternate dots and dashes and an amber light flashing Signup and view all the answers

What is the required rate of descent to maintain a 3 degree glide path at a ground speed of 120 knots?

600 FT/MIN Signup and view all the answers

While lined up on the ILS of runway 25, if the heading rose of an HSI is frozen on 200 degrees, where will the localiser needle be positioned?

Centred Signup and view all the answers

When may aircraft not enter the sensitive area of an ILS?

During category II/III ILS operations Signup and view all the answers

What is the approximate rate of descent required to maintain a 3.3 degree glide path at a ground speed of 115 knots?

641 ft/min Signup and view all the answers

ILS is subject to false glide paths primarily due to which of the following reasons?

Multiple lobes of radiation patterns in the vertical plane Signup and view all the answers

What is the colour sequence when passing over the Outer, Middle, and Inner Marker beacons?

Blue – amber – white Signup and view all the answers

What is the coverage of the ILS glide slope in relation to the localiser centreline?

+/- 8 degrees to 10 nm Signup and view all the answers

What is the approximate altitude of an aircraft at the outer marker when the glide slope height is 50 FT above the threshold?

1,450 FT Signup and view all the answers

How is the operation principle of an ILS localiser transmitter characterized regarding its frequencies?

The same frequencies with different phases Signup and view all the answers

What is the maximum height above the runway provided by a Cat III ILS glide path transmitter?

Surface of the runway Signup and view all the answers

What is the required rate of descent to maintain a 3° glide path at a ground speed of 90 kt?

600 FT/MIN Signup and view all the answers

What frequency range is assigned to all ILS marker beacons?

108-112 MHz at odd tenths Signup and view all the answers

If the glide path is not operating, what is the typical response of the ILS?

The ILS will be switched off Signup and view all the answers

What height must an ILS category II ground installation be capable of providing guidance to?

15m above the horizontal plane Signup and view all the answers

How far must a localiser provide horizontal coverage?

17 nm over a sector of 35° each side of centre line Signup and view all the answers

When looking at modulations of 150 Hz and 90 Hz on a localiser, which statement is correct?

The 150 Hz modulation predominates to the right of the centre line Signup and view all the answers

What is the upper limit of vertical coverage required for a localiser?

Not less than 7° above the horizontal Signup and view all the answers

Which of the following describes the correct radiation pattern of the Instrument Landing System (ILS) localiser?

Two overlapping lobes on the same VHF carrier frequency Signup and view all the answers

Which statement is true regarding false beams on a glide path?

False beams will only be found above the correct glide path Signup and view all the answers

Which facility associated with the ILS may be identified by a two-letter identification group?

Locator Signup and view all the answers

Which elements of an ILS transmit in the VHF band?

Localiser and marker beacons Signup and view all the answers

What is true with respect to marker beacons?

An airway marker and an ILS inner marker carry the same modulation Signup and view all the answers

Why do ILS marker beacons not interfere with each other?

They transmit in narrow vertical beams Signup and view all the answers

How is the outer marker of ILS identified in an aeroplane?

Low-pitched dashes; blue light Signup and view all the answers

What is the azimuth and area coverage of a CAT I ILS localiser?

35o at 17 nm, 10o at 25 nm Signup and view all the answers

To maintain a glide slope of 32.5 degrees at a ground speed of 140 knots, what is the approximate required rate of descent?

800 fpm Signup and view all the answers

An ILS localiser can provide reverse sense indications at which condition?

At any time Signup and view all the answers

What is the ILS glide path coverage in elevation for a 3o glide path?

An angle 1.35o to an angle of 5.25o above the horizontal Signup and view all the answers

Which sequence of marker colours is correct for flying an ILS approach?

blue, white, amber Signup and view all the answers

Where is the ILS localiser typically positioned?

300 m from the upwind end of the runway Signup and view all the answers

What CDI indications can be expected when an aircraft is flying downwind outside the coverage of the ILS?

unreliable in azimuth and elevation Signup and view all the answers

What is the frequency band of the ILS glide path?

UHF Signup and view all the answers

In which band does the ILS glide path operate?

Decimetric Signup and view all the answers

What are the minima for a CAT II ILS approach?

Height: 100 ft ; RVR: 400 m Signup and view all the answers

What kind of identification does the middle marker of an ILS have?

Alternating dots and dashes (3 per second) with an amber light Signup and view all the answers

How should the rate of descent (ROD) be adjusted when reducing speed on a 3o ILS approach from 150 knots to 120 knots?

150 fpm Signup and view all the answers

What causes errors in the ILS localiser beam?

Ground reflections Signup and view all the answers

What is the required rate of descent to maintain a 3o glide path at an approach speed of 150 kts?

750 feet per minute Signup and view all the answers

When using a CDI, what must be done to ensure proper navigation on the ILS?

Set the course arrow to the localiser course Signup and view all the answers

What altitude does a Category 1 ILS provide accurate guidance down to?

200 feet above the runway threshold Signup and view all the answers

What is the maximum safe deviation below the glide path during an ILS approach as per ICAO 8168?

Half scale deflection Signup and view all the answers

Assuming a five dot display on an ILS localiser, what does each dot represent approximately?

0.5 degrees Signup and view all the answers

What does full deflection on a glide slope indicator indicate?

0.7o above or below the correct glide path Signup and view all the answers

Full scale deflection of the localiser needle indicates that the aircraft is approximately how many degrees offset from the localiser centre line?

2.5o offset Signup and view all the answers

What frequency does the inner marker transmit?

3000 Hz Signup and view all the answers

What modulation frequencies are used on an ILS approach?

90 HZ and 150 HZ Signup and view all the answers

What audio frequency does the inner marker utilize?

3000 Hz Signup and view all the answers

What is the angle on either side of the extended centerline for a CAT 1 ILS at 17 nm that results in reverse sense indications?

35°, can Signup and view all the answers

What is the maximum safe ‘fly-up’ indication on the glide path needle with a 5-dot indicator?

2.5 dots Signup and view all the answers

Using the 1 in 60 rule, what is the approximate height of an aircraft 3 nm from touchdown on a 2.9° glide slope?

880 ft Signup and view all the answers

What is the rate of descent in ft/min for a 3° glide slope at a ground speed of 140 kt?

710 Signup and view all the answers

What VHF frequency range does the ILS localiser transmit between?

108 and 111.95 MHz Signup and view all the answers

The ILS localiser signal is made up of two lobes that are on which of the following?

Same frequency with different modulations Signup and view all the answers

What is the audio frequency of the outer marker and its cockpit light color?

400 Hz; amber Signup and view all the answers

In which band does the ILS glide path operate?

Decimetric Signup and view all the answers

What is the typical range and audio frequency of the middle marker?

1 km, 1300 Hz, amber Signup and view all the answers

What is the maximum glide path angle above which accurate signals cannot be guaranteed?

1.75 x the glide path angle Signup and view all the answers

Study Notes

ILS Systems Overview

Category III ILS provides accurate guidance down to the runway surface.
The Outer Marker transmits on 75 MHz, modulated by Morse at two dashes per second.
An aircraft on a 3-degree glide path reduces ground speed from 150 kt to 120 kt, decreasing the rate of descent by approximately 50 FT/MIN.

Glide Path and Descent Rates

A 10 kt decrease in ground speed on a 3-degree glide path requires a decrease in the aircraft's rate of descent by 50 FT/MIN.
For a 3.25-degree glide slope at a ground speed of 140 kt, the approximate rate of descent is 800 FT/MIN.
Maintaining a 3-degree glide path at 120 kt requires a rate of descent of about 600 FT/MIN.
Each dot on a five-dot display represents an approximate angular deviation of 0.5 degrees.

Indications and Marker Beacons

The ILS outer marker features a blue light and emits a low-pitched 400 Hz modulated tone.
The middle marker is identified audibly by alternate dots and dashes with an amber light flashing.
The identification of the outer marker consists of low-pitched dashes accompanied by a blue light.

Operational Characteristics

The ILS sensitive area is restricted when category II/III operations are in progress.
Localiser coverage extends to a distance of 17 nm, with an angle coverage of approximately 35 degrees on either side of the centreline.
Specific frequencies are used for each ILS element, with localiser frequencies typically ranging around 108-112 MHz.

False Glide Paths and Interference

ILS can experience false glide paths due to multiple lobes in radiation patterns.
False beams are primarily found above the correct glide path, presenting a risk during approaches.
Marker beacons do not interfere with each other as they operate on different modulation frequencies.

Descent Calculations

Using the 1 in 60 rule, height can be calculated for various glide paths and distances from the touchdown point.
The height of an aircraft 4.5 NM from touchdown on a 3-degree glide path is approximately 1370 ft.

Instrument Landing System (ILS) Frequencies

The glide slope transmits in the UHF band, while marker beacons operate on 75 MHz.
The modulation frequencies for localiser signals are 90 Hz and 150 Hz.
The amplitude modulation for the outer marker is 400 Hz with a blue light indication.

An HSI must have its course set to the localiser course for correct navigation during ILS approaches.
Pilots must correct their flight path based on modulation signals received; more 90 Hz indicates a left and down adjustment.
The maximum safe deviation below the glide path during approach is typically half scale deflection.

Miscellaneous

The upper vertical coverage of the localiser should be not less than 7 degrees above the horizontal plane.
ILS equipment and markers are identified through synchronized audio and visual signals in the cockpit.
Localiser back beams should only be used if there is a published procedure due to potential risks associated with false indications.### ILS Localiser Coverage and Specifications
Cat I ILS localiser azimuth and area coverage: 35° at 17 nm, 10° at 25 nm.
ILS glide path is effective for maintaining a 32.5° glide slope at 140 knots; the approximate rate of descent is 800 fpm.
Back beams from ILS may be received when approaching from behind the localiser aerial.
Reverse sense indications can occur outside protected coverage on the approach side of the localiser.
Typical localiser frequency characteristics include A8W at 110.30 MHz.

Glide Path Coverage and Minima

ILS glide path elevation coverage is precise from 1.35° to 5.25° for a 3° glide path.
Marker colours during an ILS approach follow: blue, amber, white.
ILS localiser is usually positioned 300 m from the upwind end of the runway.
Outside ILS coverage, CDI indications are unreliable in azimuth and elevation.

ILS glide path frequency operates in the UHF band, specifically in the decimetric range.
For CAT I ILS, minima are specified as: Height 200 ft; RVR 550 m.
CAT II ILS minima: Height 100 ft; RVR 300 m.
ILS outer marker emits 400 Hz and illuminates a blue light.

Approach and Indications

Indicators reveal approach status: If high, the glide path needle shows above; if low, it indicates below.
The maximum "fly-up" indication on the glide path needle is 2.5 dots.
At the outer marker, an ILS approach at a 3° slope requires a rate of descent of 710 ft/min at a ground speed of 140 knots.
Errors in ILS localiser beams are primarily due to ground reflections.

Marker Frequencies and Operations

Middle marker is typically located at 1 km, with an audio frequency of 1300 Hz, illuminating an amber light.
Outer marker emits 400 Hz audio frequency.
ILS localiser signals comprise two lobes on the same frequency but utilize different modulations.

Glide Path Angle and Coverage

The ILS provides reliable navigation within specified angles: generally, 0.7° above and below the glide path, with 8° on either side of the localiser.
Accurate glide path signals are unreliable beyond 1.75 times the glide path angle.

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Description

Test your knowledge of Category III ILS systems and the Outer Marker frequency used in Instrument Landing Systems. This quiz is essential for aspiring pilots and those preparing for the ATPL and IR exams. Challenge yourself and see how well you understand these critical aviation concepts.