Laser Gyroscopes and Interference Patterns

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Questions and Answers

What is the function of the partially transparent mirror in the laser gyro?

To tune the path length and adjust the frequency of the laser beam

To reflect the laser beam towards the photocell detectors

To amplify the laser beam intensity

To allow some laser light to reach the photocell detectors (correct)

What is the purpose of the mode selector unit and control display unit in the IRS?

To sense the Earth's rotation rate

To adjust the path length of the laser beam

To provide user interfacing with the inertial reference unit (correct)

To control the laser gyro's frequency

What is the role of the three ring laser gyros in the IRS?

To control the servo motor

To sense the Earth's rotation rate

To provide sensing input to the computer section (correct)

To measure the aircraft's altitude

What is the benefit of using IRS and INU systems in aircraft?

To replace several conventional equipment with a single system Signup and view all the answers

How does the laser gyro sense the Earth's rotation rate?

By detecting the frequency change of the laser beam Signup and view all the answers

What is the alignment requirement for the inertial reference unit in the IRS?

It must be hard mounted to the airframe and critically aligned with it Signup and view all the answers

What is the primary factor that affects the liability of error in a radio compass?

Intensity of indirect waves Signup and view all the answers

At what distance over land does the ground wave transmission predominate, making the NDB range dependable?

60 miles Signup and view all the answers

What is the effect of the nighttime range on the bearing indications of an NDB?

Bearing indications become erratic Signup and view all the answers

What is the name of the phenomenon that causes errors in the radio compass at night?

Night effect Signup and view all the answers

What is the primary cause of system errors in an automatic direction finder?

Night effect Signup and view all the answers

What is the range of an NDB over sea under reasonable propagating conditions?

100 miles Signup and view all the answers

What is the approximate altitude of an aircraft above the runway when it is on a glide path at the MM?

200 feet Signup and view all the answers

What is the primary function of the marker beacons in an ILS installation?

Providing an indication of position along the glide path Signup and view all the answers

What is the component of the ILS airborne equipment that displays localiser and glideslope deviation?

Indicator Signup and view all the answers

What is the point of decision for a category II approach?

IM Signup and view all the answers

What is the typical configuration of the localiser and glideslope receivers in an ILS airborne equipment?

One radio unit containing both localiser and glideslope receivers Signup and view all the answers

What is the purpose of the glideslope transmitter in an ILS ground installation?

Producing a radio beam for vertical guidance to the runway threshold Signup and view all the answers

What is the typical altitude range of RADALT systems?

2500 feet Signup and view all the answers

How many antennas are used in some RADALT systems?

One Signup and view all the answers

What is the primary function of the transmitter/receiver in a RADALT system?

To generate the transmission signal Signup and view all the answers

What is the frequency of operation for RADALT systems?

4.3 GHz Signup and view all the answers

Where are the RADALT antennas typically mounted?

Along the aircraft centreline on the underside of the fuselage Signup and view all the answers

What is the principle behind RADALT system height measurement?

Measuring the time delay between transmission and reception Signup and view all the answers

What is the purpose of Mode 1 in the GPWS?

To warn the crew of an excessive sink rate Signup and view all the answers

What is the location of the GPWS INOP warning lamp?

On the instrument panel directly in front of the pilot and co-pilot Signup and view all the answers

What is the classification of the initial message provided by the GPWS in a potentially hazardous situation?

Advisory Signup and view all the answers

What triggers a warning message from the GPWS in Mode 3?

Descent after take-off Signup and view all the answers

How many warning lamps are located on each side of the instrument panel for the GPWS?

Two Signup and view all the answers

What is the purpose of Mode 6 in the GPWS?

To alert the crew of descent below the decision height Signup and view all the answers

Study Notes

When flying at altitude, pilots must allow for drift due to wind.

Automatic Direction Finder (ADF)

Errors in ADF readings are more common and of greater magnitude at night due to the 'night effect'.
The night effect is caused by the strength of indirect waves being greater at night, affecting the ratio of indirect to direct waves.
The range of an NDB is only dependable over distances where the ground wave transmission predominates (approximately 60 miles over land and 100 miles over sea).
Beyond these ranges, bearing indications may become erratic, and ADF reception should be treated with caution.

Instrument Landing System (ILS)

A complete ILS installation consists of a glideslope transmitter, localiser transmitter, and marker beacons.
The glideslope transmitter provides vertical guidance, while the localiser transmitter provides lateral guidance to the runway threshold.
Marker beacons produce vertical, fan-shaped radio beams, indicating position along the glide path.

Instrument Landing System Airborne Equipment

The airborne equipment portion of the ILS system includes a VHF localiser receiver, glideslope receiver, marker beacon receiver, control unit, antennae, and an indicator displaying localiser and glideslope deviation.

Ground Proximity Warning System (GPWS)

There are six modes of GPWS operation:
- Mode 1: excessive sink rate
- Mode 2: excessive ground closure rate
- Mode 3: descent after take-off
- Mode 4: proximity to the ground with landing gear in the up position or flaps not in the landing position
- Mode 5: descent below glideslope
- Mode 6: descent below the decision height selected on the RADALT

Laser Gyro

A laser gyro uses three mirrors and two photocell detectors to sense the Earth's rotation rate of 15 degrees per hour, causing a laser beam frequency change of 4 Hz.

Inertial Reference Units (IRUs)

An IRU consists of three ring laser gyros and three accelerometers, providing sensing input to the computer section.
IRU outputs can replace equipment used in conventionally equipped aircraft, including vertical axis gyroscope, rate gyroscopes, and remote-sensing compass systems.

Radar Altimeter (RADALT)

RADALT systems determine height by measuring the time delay between signal transmission and reception after reflection from the Earth's surface.
Typical altitude range of RADALT systems is 2500 feet, with output power levels ranging from 5 to 100 milliwatts.
RADALT systems operate on a frequency of 4.3 GHz.

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Description

This quiz covers the principles of laser gyroscopes, including their components, functionality, and applications. Learn how they accurately sense the Earth's rotation rate. Explore the role of mirrors, photocell detectors, and interference patterns in these devices.