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The correct choice is (a) True

To explain: Even with narrow beamwidth antennas, the RADAR TRANSMITTER requires from 5kW to 50KW of output power. When coupled with an antenna of 25 dB, this combination can result in an EFFECTIVE power more than a million watts.

Right option is (d) 4FT

The best explanation: With RADAR system OPERATING in EXCESS of 5KW output, the minimum safe approach distance to weather radar is about 4ft.

Right OPTION is (c) 25 dB

Easiest explanation: The signal STRENGTH of ECHOES from storms located at a distance from the aircraft is very low, which requires the transmitter to OPERATE at very high power levels and that the antenna have a gain of more than 25 dB.

The correct choice is (d) 200 nmi

Easiest explanation: The USE of airborne weather RADAR is one METHOD of STORM avoidance. A weather radar system can SHOW centers at a distance of up to 200 nmi.

The correct answer is (a) True

The explanation is: TCAS uses two different METHODS to avoid GARBLING. One is whisper shout and the other is using directional INTERROGATIONS.

The correct option is (d) 4 min

The best I can EXPLAIN: The range of a GENERAL TCAS system is around 4 MINUTES before collision. At 45 seconds before collision TCAS gives traffic advisory and at 25 seconds before collision provides resolution advisory.

Correct choice is (a) True

To explain I would say: TCAS I provide only PROXIMITY warning and aids the PILOT in visual identification of POTENTIAL THREAT AIRCRAFT.

Right option is (d) MANEUVERABILITY of the aircraft

Easiest explanation: the threshold NUMBER for Tau, whether it is 10 SEC or 100 sec depends on the ability of the aircraft to maneuver and avoid a COLLISION.

The CORRECT choice is (a) True

Explanation: Mode S system and ATCRBS have the same INTERROGATION frequency and the same REPLY frequency. The transmitter power output is SIMILAR to the ATCRBS transponder as is the receiver sensitivity which ensures that mode S TRANSPONDERS will have similar service ranges as ATCRBS transponders.

Right option is (b) False

Easy explanation: USUALLY, a transponder REMAINS SILENT when not interrogated. However, being an integral part of TCAS requires the occasional spontaneous mode S TRANSMISSIONS.

The correct option is (a) Garble

For EXPLANATION I WOULD say: If several aircraft are within the range of the secondary radar and REPLY to the same interrogation pulse there is a chance that TWO reply pulses can overlap each other and cause an error in the values of interfere with DIFFERENT aircraft.

The correct option is (B) Squitter

To EXPLAIN: An important transponder characteristic that aids TCAS is the transmission of a MODE S reply at quasi-random intervals of about 1 sec, which is CALLED squitter.

Right answer is (a) Unique code for each transponder

Easiest explanation: Unlike the ATCRBS where a squawk code is dialed into the transponder, a MODE S transponder has a unique identity PERMANENTLY assigned to it. The mode S RADAR system can have more than 16 million different identities, enough for each airplane in the world to have a unique identity.

The correct option is (d) MODE S

Best explanation: Different modes have its own unique features; mode A GIVES only identity, mode c gives identity and ALTITUDE, mode B is used in European operations and mode S is used for selective CALLING of transponders.

Right option is (c) 1030 MHz

Explanation: The interrogation pulse is TRANSMITTED at 1030 MHz and the REPLY pulse by the AIRCRAFT transponder is given at 1090 MHz. Since the reply is coded information, it does not interfere with other transponders that are using the same frequency.

Right choice is (a) 8 μs

Easy explanation: The time delay between P1 and P3 determines the type of INTERROGATION. When the Time lag is 8μs, it CORRESPONDS to mode A WHEREAS a SEPARATION of 21 μs corresponds to mode C.

Correct ANSWER is (c) Clutter

The best I can EXPLAIN: The PRIMARY radar pulse is reflected by BUILDINGS and clouds and cause undesirable effects in the actual identification. These are called as clutter and can be eliminated by combing primary radar with secondary radar.

The correct choice is (a) MODE A

The explanation: There are two TYPES of interrogations in the ATCRBS: mode A and mode C. Mode A provides IDENTITY only and mode C provides identity and altitude of the aircraft.

Correct option is (a) True

Best explanation: In SECONDARY radar the transponder present in the aircraft reply for the interrogation pulse with information of the aircraft such as FLIGHT name and some of the important flight PARAMETERS like AIRSPEED and altitude.

Correct ANSWER is (a) Second

The explanation: In the secondary RADAR, the strength of the COMMUNICATION system varies inversely with DISTANCE to the second power, compared with primary radar which reduced with the fourth power.

The correct answer is (c) Capture area

The explanation is: The ability of the antenna to TURN radiated ENERGY into CONDUCTED energy is called a capture area. As an example, if a power density of mw/m2 illuminates an antenna with 1 m2 capture area, then the antenna provides 1 mw power at the output CONNECTOR.

Right choice is (a) Requires more power than primary radar

To explain: Secondary radar requires LESS power than primary radar for the same amount of coverage area. This is because in secondary radar the pulse is one way; it triggers a REPLY pulse in the transponder of the AIRCRAFT which replies with some of the important flight PARAMETERS of the aircraft.

Correct answer is (a) The objects RCS

The BEST explanation: When radar pulse strikes the AIRCRAFT some radio pass through the object whereas some get reflected back. The amount of radio energy that gets reflected back depends UPON the Radar CROSS section of the aircraft. RCS depends on size, material on the SURFACE of the aircraft and many more parameters.

Correct answer is (b) False

To explain I would say: The radio energy has to travel TWO WAY: to the aircraft and back to the RECEIVER, this caused attenuation by the atmosphere. In ADDITION to this, only a part of the actual transmission radio energy is reflected back to the receiver.

The correct CHOICE is (a) Pulse

To EXPLAIN: The primary radar uses pulse techniques. It sends out short bursts of pulse and the AIRCRAFT SURFACE reflects the radio energy BACK to the radar antenna. It is possible to measure the elapsed time and determine the range or distance of the aircraft.

Right OPTION is (d) interleaving radar modes

To elaborate: BEAM agility makes it possible for one phased array radar to act as multiple radars each with its own beam shape and scan PATTERN! This is referred to as interleaving radar modes. The same radar can be tracking for airborne threats using one beam shape and scan pattern while SEARCHING for GROUND targets using another beam shape and scan pattern.

Correct choice is (b) Computer

The best explanation: The beam SHAPE and direction is CONTROLLED by an on-board computer which gives the NECESSARY PHASE shift to the phase shifters to change the beam direction and shape.

The correct answer is (a) Friend or foe identification is possible

For explanation: Friend or foe identification is not possible in primary radar and hence it is hard to determine if the aircraft is an enemy or friend. It has a WIDE RANGE and REQUIRES HIGH transmitting power due to the TWO way travel of the radar signal.

Correct OPTION is (a) Height of the aircraft

Explanation: One of the major disadvantages of the PRIMARY radar is that it cannot provide a three dimensional FIX, that is position and ALTITUDE. They are radars that can find the height of the aircraft but can only be used for short distances.

Correct OPTION is (a) AESA

Best explanation: AESA radars can produce multiple radar frequencies with multiple beams. This ALLOWS the radar to have faster scan RATES and can track multiple targets with EASE.

Correct choice is (a) True

Best explanation: In AESA a new control VARIABLE is introduced. The GAIN of each Tx and Rx module can be controlled and hence the array radars can adaptively alter their transmit and RECEIVE ANTENNA pattern to maximize system performance.

Right option is (a) True

Explanation: An AESA solves MANY of the reliability and maintainability problems DUE to TWT and POWER supply problems. 4 to 6% of the T/R module could fail without NOTICEABLE degradation in ANTENNA performance.

Right OPTION is (d) ELECTRONIC scanning capability

For explanation I would say: One of the basic common features between the AESA and PESA is that both provide electronic scanning. This allows the use of narrow BEAMS since the rate of scanning is very high.

Right option is (b) 1000 to 2000

To explain I would SAY: A typical airborne active ARRAY contains 1000 to 2000 transmitting MODULES, each capable of transmitting 5 to 20 WATTS of power.

The correct OPTION is (c) Because it uses a, multiple frequencies, it is less susceptible to enemy JAMMERS

To EXPLAIN I would say: In a PESA only one TRANSMITTER DRIVES the whole antenna and hence only one frequency can be achieved at a time. This allows it to be more susceptible to jammers.

The CORRECT option is (a) Pulse

To explain I would say: Both AESA and PESA that are currently in use are pulse RADARS. Its basic principle is that shorts bursts of RADIO pulse are emitted which reflect off a target and the reflected pulse gives the information about the object.

Right answer is (c) PHASE shifter

Explanation: The ESA has no mechanical moving parts, such as antenna gimbals, POTENTIOMETERS, rotary joints, or hydraulic/electronic motors. It USES phase SHIFTERS to ELECTRONICALLY steer the beam.

The correct ANSWER is (a) MICROSECONDS

The best I can explain: SINCE the antenna’s phase shifter SETTINGS can be CHANGED in a few microseconds, an ESA’s beam can be repositioned almost instantly.

The correct choice is (c) Slope of the phase taper

The best I can EXPLAIN: The ESA controls the beam by phase shifters. The slope of the phase taper determines the direction in which the ANTENNA beam will be POINTED.

The correct ANSWER is (a) Phase shift

Explanation: In ESA, the antenna’s beam is moved electronically by setting the phase angles of phase shifters located at each radiating element to provide a linear phase taper across the ARRAY SURFACE.

The CORRECT answer is (b) Situation awareness

The explanation is: The fundamental limitation in military radars is situation awareness. This limitation is overcome by the ELECTRONICALLY scanned array which has a very HIGH RATE of SCANNING.