Билет №40

1). How does MLS compare with ILS. The time-referenced scanning beam Microwave Landing System (MLS) has been adopted by ICAO as the standard precision approach system to replace ILS. MLS provides precision navigation guidance for alignment and descent of aircraft on approach to a landing by providing azimuth, elevation and distance. The system may be divided into five functions:

• Approach azimuth;

• Back azimuth;

• Approach elevation;

• Range; and

• Data communications.

The Instrument Landing System (ILS) has served as the standard precision approach and landing aid for the last 40 years. During this time it has served well and has undergone a number of improvements to increase its performance and reliability. However, in relation to future aviation requirements, the ILS has a number of basic limitations:

• site sensitivity and high installation costs;

• single approach path;

• multi path interference; and

• channel limitations - 40 channels only.

2). Describe the term RADAR

Radar is an acronym for "radio detection and ranging." A radar system usually operates in the ultra-high-frequency (UHF) or microwave part of the radio-frequency (RF) spectrum, and is used to detect the position and/or movement of objects. Radar can track storm systems, because precipitation reflects electromagnetic fields at certain frequencies. Radar can also render precise maps. Radar systems are widely used in air-traffic control, aircraft navigation, and marine navigation.

3). At what Frequency operate DME

Distance measuring equipment (DME) is a transponder-based radio navigation technology that measures slant range distance by timing the propagation delay of VHF or UHF radio signals. DME frequencies are paired to VHF omnidirectional range (VOR) frequencies and a DME interrogator is designed to automatically tune to the corresponding DME frequency when the associated VOR frequency is selected. An airplane’s DME interrogator uses frequencies from 1025 to 1150 MHz. DME transponders transmit on a channel in the 962 to 1213 MHz range and receive on a corresponding channel between 1025 to 1150 MHz.

Билет №41

1). Give the four Radar Definitions.

1) Pulse length alternatively known as pulse width is the duration of the pulse in microseconds.

2) Pulse repetition frequency is the number of pulse transmitted per second. Otherwise known as the pulse recurrence frequency.

3) Pulse repetition interval is the time interval from the start of one pulse to the start of the next. The pulse repetition (or recurrence) interval is the reciprocal of the pulse repetition frequency. PRI=1/PRF

4) Beam width describes the angular dimension of the radiation pattern. Most radars make use of aerials that concentrate the energy into a narrow beam.

2). Describe the term Primary Radar.

Primary radar relies on reflected energy, that is echoes of its own transmissions.

Examples:

• Airborne Weather Radar (AWR)

• Radar Altimeter

• Precision Approach Radar (PAR)

• Primary Surveillance Radar

Advantage of Primary Radar: it is self-contained and does not require the cooperation of the target.

3). At what Frequency operate NDB.

The source of the radio waves used by ADF is normally a non-directional beacon (NDB) transmitting in all directions, as its name implies. Frequency surface wave range increases as frequency decreases because attenuation is reduced. Frequency bands – LF and MF. Frequencies – 190 kHz to 1750 kHz (most commonly 200-500kHz).