Set 4

Question 1

Difference between Continuous Wave (CW) & Pulsed Radar antenna requirements?

Answer 1

Pulsed radar uses a single antenna for both receiving and transmitting through a duplexer.
CW uses 2 antennas, one for receiving and one for transmitting.

Question 2

Function & Principle of operation for TCAS

Answer 2

Purpose: Designed to reduce danger of mid-air collisions between aircraft by monitoring the airspace around the aircraft, independent of air traffic control, and warns pilots of the presence of other aircraft which may present a threat of Mid-Air Collision (MAC).

Operation: Each TCAS equipped aircraft interrogates all other aircraft in a determined range about their position (via 1030 MHz), and all other aircraft reply to interrogation (via 1090 MHz). This interrogation-and-response cycle may occur several times per second, by which the TCAS system builds a three-dimensional map of aircraft in the airspace, incorporating their bearing, altitude and range. Then, by extrapolating current range and altitude difference to anticipated future values, it determines if a potential collision threat exists.

Question 3

Principle of operation of Glideslope

Answer 3

The glideslope deviation instrumentation compares the signal levels of 90 Hz & 150 Hz tones as localizer deviation instrumentation but the produced difference signal is applied to drive the vertical deviation course pointers of Attitude Director Indicator.
Every 0.35 degrees in slope deviation will produce 75 micro Amps.

Question 4

GPS Errors

Answer 4

Satellite Clock Error (2 ft) - due to minor inaccuracies in synchronizing the satellite atomic clocks.
Ephemeris Errors (2 ft) - caused by slight variations in satellites position as it orbits the earth.
Atmospheric Propagation Errors (2 ft) - caused by distortion of the transmitted signal as it travels from the satellite to the receiver. Most of these errors are created as the radio signals travel through the ionosphere
Receiver Errors (4 ft) - caused by local electrical noise, computational errors, and errors in matching the pseudorandom digital codes.

Question 5

Loop Swing

Answer 5

Function - procedure for determining the sign and size of errors in an ADF installation
Air Swing carried out in smooth air conditions in order to eliminate drift errors.
Ground carried out at a site known not to introduce bearing errors