InterviewSolution
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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
What happens if a satellite is launched vertically and released at its design altitude?(a) Continue to orbit the earth(b) Fall back(c) Overshoots the altitude and moves at a constant speed(d) Stays where it was released |
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Answer» Correct choice is (b) Fall back Best explanation: If a satellite were launched vertically from the earth and then released, it would fall back to earth because of gravity. For the satellite to go into orbit around the earth, it must have some forward motion. For that reason, when the satellite is launched, it is given both vertical and forward motion. |
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| 52. |
Why does the orbit take the shape of an ellipse or circle?(a) Position can be easily determined(b) Consume less fuel(c) Most efficient geometry(d) Better coverage on earth |
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Answer» Correct option is (a) Position can be easily determined Easiest explanation: A satellite rotates about the earth in either a circular or an elliptical path. Circles and ellipses are geometric figures that can be accurately described mathematically. Because the orbit is either circular or elliptical, it is possible to calculate the position of a satellite at any given time. |
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| 53. |
Which of the following type of direction finder has a system that rotates the loop, using a servo system until a null is found?(a) Fixed loop(b) Rotatable loop(c) Rotating loop(d) Fixed, crossed loop |
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Answer» The correct choice is (c) Rotating loop Best explanation: The rotating loop is driven by a motor and forming part of a servo system that rotates the loop until a null is found and then stops. They are sometimes referred to as the radio compass and are housed inside plastic structures that do not reflect radio waves. |
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| 54. |
The direction of orbit in the same direction of earth rotation is called ______(a) Retrograde(b) Posigrade(c) Perigee(d) Apogee |
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Answer» Correct option is (b) Posigrade For explanation: The direction of satellite rotation may be either in the same direction as the earth’s rotation or against the direction of earth’s rotation. In the former case, the orbit is said to be posigrade, and in the latter case, retrograde. Most orbits are posigrade. |
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| 55. |
What is the function leading edge range tracker servo loop?(a) Provide range to the nearest return(b) Speed measurements(c) Vertical speed measurement(d) Automatic ground navigation |
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Answer» Correct answer is (a) Provide range to the nearest return Easiest explanation: To provide a range to the nearest return within the bounds of the antenna beam, many modern radar altimeters incorporate the gate in a pulse modulated radar or a filter in a frequency modulated radar over the leading edge of the return. |
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| 56. |
Differential GPS corrects for satellite errors.(a) True(b) FalseThis question was addressed to me in unit test.The query is from Orbital Mechanics and Clock Characteristics topic in division Satellite Radio Navigation & Inertial Navigation of Avionics |
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Answer» Right answer is (a) True Easy explanation: Satellite clock errors, including those caused by SA dithering, are completely eliminated by DGPS, except for the SA dithering effects due to delays in estimating, broadcasting, and making the DGPS corrections. |
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| 57. |
Which coordinate system is used in satellite based radio navigation?(a) Earth centered, Earth fixed(b) Earth centered inertial(c) Geodetic spherical coordinates(d) Geodetic wander azimuth |
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Answer» Correct option is (a) Earth centered, Earth fixed For explanation: Satellite based radio navigation system uses ECEF coordinated to calculate satellite and aircraft position. The origin is at the mass center of the earth and its axis lies along the earth’s spin axis. |
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| 58. |
What is the frequency designated to radar altimeters?(a) 4.2 to 4.4 GHz(b) 2.4 to 4.2 GHz(c) 500 to 1 GHz(d) 13 to 14 GHz |
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Answer» The correct choice is (a) 4.2 to 4.4 GHz The best explanation: The frequency band of 4.2 to 4.4 GHz is assigned to radar altimeters. This frequency band is high enough to result in a reasonable small sized antenna to produce 40° to 50° beam but significantly low so that attenuation by rain is minimum. |
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| 59. |
What is the point on the surface of the earth that is directly below the satellite called?(a) Satellite point(b) Subsatellite point(c) Supersatellite point(d) Overhead point |
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Answer» Correct answer is (b) Subsatellite point To elaborate: The satellite location is specified by a point on the surface of the earth directly below the satellite. This point is known as the subsatellite point (SSP). The subsatellite point is then located by using conventional latitude and longitude designations. |
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| 60. |
What is the nominal accuracy of radar altimeters below 100ft?(a) 5 ft(b) 10 ft(c) 20 ft(d) 1.5 ft |
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Answer» Correct answer is (d) 1.5 ft For explanation I would say: Low range radar altimeters have a nominal accuracy of 1.5 ft below 100ft altitude and 2% of full scale at higher altitude. They have a low noise output that allows the derivation of vertical rate information. |
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| 61. |
The angle between the line from the earth station’s antenna to the satellite and the line between the earth station’s antenna and the earth’s horizon is called as ___________(a) Angle of inclination(b) Angle of elevation(c) Apogee angle(d) LOS angle |
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Answer» The correct choice is (b) Angle of elevation Best explanation: The angle of elevation of a satellite is the angle that appears between the line from the earth station’s antenna to the satellite and the line between the earth station’s antenna and the earth’s horizon. If the angle of elevation is too small, the signals between the earth station and the satellite have to pass through much more of the earth’s atmosphere. Because of the very low powers used and the high absorption of the earth’s atmosphere. |
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| 62. |
What is the approximate time taken by the GPS for one complete orbit?(a) 11 minutes(b) 45 minutes(c) 5 hours(d) 12 hours |
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Answer» The correct option is (d) 12 hours Explanation: The GPS satellites are in approximately 12 hour orbits( 11 hours, 57 minutes, 57.27 seconds) at an altitude of approximately 11,000 nmi. At any point on Earth, 4 satellites are visible at all times. |
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| 63. |
What percentage of the earth can communication satellites see?(a) 20(b) 50(c) 70(d) 40 |
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Answer» Right option is (d) 40 To elaborate: Most communication satellites in use today are of the geosynchronous variety. Approximately 40 percent of the earth’s surface can be “seen” or accessed from such a satellite. Users inside that area can use the satellite for communication. |
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| 64. |
_____ acts as a coarse tuning device for the antenna?(a) Loop(b) Helix(c) Amplifiers(d) Filters |
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Answer» Right choice is (b) Helix To explain I would say: The RF signal that is to be transmitted is transferred to the ‘Helix,’ a large helical coil that acts as a coarse tuning device for the antenna. The helix is equipped with separate taps for each signal frequency transmitted. |
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| 65. |
Which of the following is not true with respect to Loran-C?(a) Loran stands for Long range navigation(b) Uses ground waves(c) Uses pulse techniques(d) Subjected to site errors |
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Answer» The correct option is (d) Subjected to site errors Easy explanation: The Loran stands for Long range navigation and uses ground waves with pulsed technique to avoid sky wave contamination. Being a hyperbolic system, it is not subjected to the site errors of point source systems. |
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| 66. |
What is the number of systems used for redundancy in a transmitting station?(a) 2(b) 1(c) 5(d) 3 |
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Answer» The correct option is (a) 2 For explanation: Each transmitter station is physically divided into two groups of units to provide system redundancy. At the appropriate interfaces switching units are provided between them. |
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| 67. |
Which of the following derives all the signals needed by the transmitter from the timer?(a) PATCO(b) ECD(c) HCG(d) TOPCO |
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Answer» Right answer is (a) PATCO Explanation: Dual redundant pulse amplitude and timing controllers or PATCO accept timing signals from the timer and derive from this all the signals needed by the transmitter. Signals generated by the PATCO include start triggers, charging triggers, digital amplitude reference signals, amplitude compensation signals, and megatron reference trigger. |
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| 68. |
Which one of the following is not a hyperbolic radio system?(a) Loran-C(b) Omega(c) Chayka(d) VOR |
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Answer» Correct option is (d) VOR For explanation I would say: Loran-C, Omega, Decca, and Chayka are the hyperbolic navigational systems whereas the VOR, DME falls under the point source navigational systems. |
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| 69. |
Which of the following type is not used in an Omega system?(a) Grounded tower(b) Insulated tower(c) Hanging tower(d) Valley span |
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Answer» The correct option is (c) Hanging tower The best I can explain: Since the Omega stations transmit in very low frequencies, the antennas are the largest physical structures in the stations. Three types of antennas are employed in the Omega system: grounded tower, insulated tower, and the valley span. |
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| 70. |
What type of transmission is used in Omega system?(a) Amplitude modulated wave(b) Continuous wave(c) Phase modulated wave(d) Frequency modulated wave |
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Answer» Correct answer is (b) Continuous wave For explanation I would say: At each Omega station, continuous wave signals on four common frequencies and one station unique frequency. The signal frequencies are time shared among the stations so that a given frequency is transmitted by only one station at any given time. |
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| 71. |
Which of the following is not true?(a) Battery is only used as a back up(b) When in orbit, solar power is always available(c) Battery is used for initial satellite orientation and stabilization(d) The batteries are charged using solar power |
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Answer» Right option is (b) When in orbit, solar power is always available Best explanation: When a satellite goes into an eclipse or when the solar panels are not properly positioned, there is a temporary cut in solar power supply. In situations like this the batteries take over temporarily and keep the satellite operating. The batteries are not large enough to power the satellite for a long time; they are used as a backup system for eclipses, initial satellite orientation and stabilization, or emergency conditions. |
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| 72. |
Why is it not possible to provide transmit function by wideband amplifier and mixer circuits?(a) Heavy attenuation(b) High power output over wideband is not possible(c) Economically not profitable(d) Weight of the system increases five fold |
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Answer» Right option is (b) High power output over wideband is not possible Explanation: it is generally not possible to generate very high output power over such wide bandwidth. The fact is that no components and circuits can do this well. The high-power amplifiers in most transponders are traveling-wave tubes that inherently have limited bandwidth. They operate well over a small range but cannot deal with the entire 500-MHz bandwidth allocated to a satellite. |
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| 73. |
What the model of transmission line that appears as a distributed low-pass filter consisting of series inductors and resistors and shunt capacitors and resistors called?(a) Impedance model of transmission line(b) Lumped model of distributed line(c) Capacitative model of transmission line(d) Complex resistive model of transmission line |
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Answer» Correct answer is (b) Lumped model of distributed line Easiest explanation: The sum of the complex impedance by the parallel wires, resistance of the wires and the shunt capacitance results in a transmission line that appears as a distributed low-pass filter consisting of series inductors and resistors and shunt capacitors and resistors. This is called a lumped model of a distributed line. |
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| 74. |
What is the reason for shifting from c band to ku band in satellite communication?(a) Lesser attenuation(b) Less power requirements(c) More bandwidth(d) Overcrowding |
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Answer» The correct option is (d) Overcrowding To elaborate: Most new communication satellites will operate in the Ku band. This upward shift in frequency is happening because the C band is overcrowded. Many communication satellites are in orbit now, most of them operating in the C band. However, there is some difficulty with interference because of the heavy usage. The only way this interference will be minimized is to shift all future satellite communication to higher frequencies. |
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| 75. |
Which of the following is not a unit of the magnetic field?(a) Gamma(b) Gauss(c) Tesla(d) Maxwell |
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Answer» Right option is (d) Maxwell To elaborate: The magnetic fields B are measured in Gauss and Tesla(10^4 Gauss). In geomagnetism, Units of “Gamma”(10^-5 )are used. |
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| 76. |
Which of the following is false with respect to GPS?(a) Active system(b) All weather system(c) Continuous system(d) Space based system |
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Answer» Correct option is (a) Active system Explanation: The GPS is an all weather global navigational system. It is passive, survivable, continuous, space based system that provides any suitable equipped user with highly accurate three dimensional position, velocity, and time information anywhere on or near the Earth. |
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| 77. |
The refractivity of the troposphere is not a function of ________(a) Frequency(b) Temperature(c) Pressure(d) Partial pressure of water vapour |
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Answer» The correct answer is (a) Frequency The explanation is: Unlike the refractivity of the ionosphere, the refractivity of the troposphere is not the function of carrier frequency. At a given altitude it is determined from where P is total pressure, T is the absolute temperature, and e is the partial pressure of water vapour. |
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| 78. |
What is the load on a transmission line?(a) 0 Ω(b) Infinity(c) Some value between 0 and infinity(d) Some value between0 and 1 |
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Answer» Right answer is (c) Some value between 0 and infinity Explanation: In practice, however, the load on a transmission line is neither infinite nor 0Ω; rather, it is typically some value in between. The load may be resistive or may have a reactive component. |
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| 79. |
Calculate the physical length of the transmission line for an operating frequency of 450MHz and 3⁄8λ long.(a) 0.45(b) 0.84(c) 0.82(d) 0.41 |
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Answer» Correct option is (c) 0.82 For explanation I would say: λ = 984/450 = 2.19 ft (3/8)λ = 2.19(3)/8 = 0.82 ft. |
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| 80. |
Which of the following is true with respect to ionospheric scintillation effects?(a) It causes signal fading(b) Occurs at the equatorial and polar regions(c) Occurs mostly at day(d) Occurs when high solar activity is present |
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Answer» Right answer is (c) Occurs mostly at day Best explanation: Ionospheric scintillation causes signal fading and effects in the equatorial and the Polar Regions. Strong scintillation effects are rare localized at certain times during the night, and usually occurs during periods of high solar activity. |
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| 81. |
Cables that carry RF signal are not ______(a) Capacitors equivalents(b) Inductors equivalents(c) Simple resistive conductors(d) Covered |
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Answer» Correct choice is (c) Simple resistive conductors The explanation: Cables used to carry RF energy are not simply resistive conductors but are complex equivalents of inductors, capacitors, and resistors. If simple resistive conductors are used then undesirable effects such as noise, power loss occurs. |
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| 82. |
Which of the following is not true regarding standing wave?(a) In a standing wave the energy moves towards the power source(b) In a standing wave power loss occurs(c) Standing waves do not affect signal strength(d) Standing waves are not desirable |
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Answer» Correct answer is (c) Standing waves do not affect signal strength For explanation I would say: Standing waves are not desirable. Some of the energy is reflected from the end of the line and actually moves back up the line. This reflection indicates that the power produced by the generator is not totally absorbed by the load. When there is a power loss naturally the strength of the signal goes down. |
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| 83. |
What is the number of GPS satellites used?(a) 54(b) 12(c) 5(d) 24 |
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Answer» The correct answer is (d) 24 Best explanation: The fully operational GPS satellite constellation comprises 24 satellites, 4 each in six 55° inclined orbit placed 60° apart in longitude. The number of satellites is limited mainly due to budget restrictions. |
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| 84. |
Which of the following does not cause standing waves?(a) Short circuit(b) Open circuit(c) High frequency high power signal(d) Impedance is not matched |
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Answer» The correct option is (c) High frequency high power signal To elaborate: If the load at the end of a line is an open circuit or a short circuit or has an impedance other than the characteristic impedance of the line, the signal is not fully absorbed by the load. This causes the signal to get reflected back the line and cause a standing wave. |
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| 85. |
Only L2 signal carries the encrypted precise code.(a) True(b) FalseThe question was asked during an online exam.This interesting question is from NAVSTAR GPS in chapter Satellite Radio Navigation & Inertial Navigation of Avionics |
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Answer» Correct answer is (a) True Easiest explanation: Precise codes are required to correct for the international degradation of signals. Only the L2 signal carries the p code and only authorized users can access them. |
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| 86. |
What type of transmission line is used to intentionally delay the signal?(a) Parallel lines(b) Serial lines(c) Delay lines(d) Transit lines |
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Answer» The correct answer is (c) Delay lines For explanation I would say: A signal applied at one end of a line appears some time later at the other end of the line. This is called the time delay or transit time for the line. A transmission line used specifically for the purpose of achieving delay is called a delay line. |
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| 87. |
A current carrying conductor is only called a transmission line if the length of the line is _____ long at the signal frequency?(a) 0.1λ(b) 0.3λ(c) 1.2λ(d) 1.5λ |
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Answer» Right option is (a) 0.1λ Best explanation: A pair of current carrying conductors is not considered to be a transmission line unless it is at least 0.1λlong at the signal frequency. |
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| 88. |
The intentional degradation of GPS signal in specific areas is called ________(a) Selective degradation(b) Selective availability(c) Distributed GPD(d) Signal jamming |
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Answer» Right answer is (b) Selective availability To elaborate: The intentional degradation of GPS signal is meant to deny accuracy to unfriendly forces. It is known as selective availability. SA also denies accuracy to unauthorized users who are friendly, which is the entire civil community. |
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| 89. |
Which of the following is the most necessary for an electric field to exist?(a) Current(b) Potential difference(c) Dielectric material(d) Metal conductor |
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Answer» The correct option is (b) Potential difference For explanation I would say: The most important thing for an electric field to exist is a potential difference between two conductors. It is not that only metal conductors can produce an electric field, potential difference between fluids also produces electric fields. |
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| 90. |
Which of the following methods breaks the signal into finite segments to find the ASF?(a) Millington’s method(b) Bill’s method(c) Differential method(d) Table look up process |
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Answer» The correct choice is (a) Millington’s method Best explanation: In Millington’s method, the signal between the transmitter and the receiver is broken down into finite segments of different conductivity levels, based on conductivity maps. The incremental phase delay is then computed as a function of range and conductivity for each path segment summed and averaged to provide an estimate of ASF. |
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| 91. |
Where are self-aligning pitot tubes used?(a) Bomber planes(b) Commercial airliners(c) High angle of attack fighter aircraft(d) General aviation |
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Answer» Right option is (c) High angle of attack fighter aircraft Explanation: When the angle of attack and the sideslip angle are under 10°, they do not affect the pressure measurements much. In applications such as high angle of attack fighters, special self-aligning pitot tubes are used to measure the stagnation pressure. |
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| 92. |
The absolute pressure of the still air surrounding the aircraft is called as______(a) Static pressure(b) Stagnation pressure(c) Constant pressure(d) Absolute pressure |
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Answer» Right choice is (a) Static pressure Explanation: static pressure is the pressure of the still air surrounding the aircraft body even when the aircraft is moving. It is measured using static ports placed along the aircraft skin. |
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| 93. |
The undesirable responses from buildings and clouds for the radar pulse are called as __________(a) Noise(b) Disturbance(c) Clutter(d) Radio error |
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Answer» 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. |
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| 94. |
How is the velocity of an aircraft measured by passive radio systems?(a) Doppler shift(b) Velocity data is transmitted by the aircraft and received by the station(c) Secondary surveillance method(d) Satellite mapping |
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Answer» Correct choice is (a) Doppler shift For explanation: The aircraft’s velocity is measured from the Doppler shift of the transmission or from a sequence of position measurements. Since the aircraft is continuously moving, each interrogation pulse when it is received will have different phase shift which corresponds to the aircraft’s velocity. |
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| 95. |
Why is heating necessary in pitot-static tube?(a) Ice formation(b) Force the flow away from tube(c) Force the flow towards the flow(d) Increase the sensitivity |
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Answer» Right answer is (a) Ice formation To explain I would say: Pitot-static tubes are generally placed with heating elements to stop the formation of ice in the orifice of the probe. Formation of ice on the probes causes erroneous readings and has lead to fatal air crashes. |
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| 96. |
Why is the static source errors compensated in helicopters?(a) Due to difference in rotor down wash(b) Not economical(c) Requires high computational power(d) Static source error does not matter |
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Answer» Correct answer is (a) Due to difference in rotor down wash Best explanation: Static-source errors in helicopters tend to be difficult to compensate because of rotor downwash that differs significantly in and out of ground effect. Fixed wing aircraft do not compensate for static source errors in ground effect, and neither do helicopters. |
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| 97. |
Which of the following cannot be used to obtain an approximate velocity?(a) GPS(b) Doppler radar system(c) Inertial navigation system(d) Primary radar |
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Answer» Correct option is (d) Primary radar For explanation: Velocity from Doppler, inertial and GPS can be used as an approximation for velocity. It is possible for the radio controller on the ground to obtain the velocity of the rotorcraft but it is not possible for the pilot to get velocity data from primary radar. |
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| 98. |
The distance the aircraft climbs to clear an obstacle of particular height during takeoff is called as?(a) Ground roll(b) Take off distance(c) Runway length(d) Airborne distance |
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Answer» The correct answer is (d) Airborne distance For explanation I would say: The extra distance the aircraft covers airborne but before it covers an obstacle of particular height is called airborne distance. Airborne distance is also added with the ground roll to give the total takeoff distance. |
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| 99. |
The conventional pitot tube cannot be used under______(a) 100 knots(b) 40 knots(c) 2 knots(d) 80 knots |
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Answer» The correct answer is (b) 40 knots The explanation: The conventional pitot tube and the pressure transducer become ineffective as airspeed drops below 40 knots. At the lower speeds, impact pressure is equal to dynamic pressure q, and the sensitivity of this pressure to a change in velocity is minimal. |
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| 100. |
What is the approximate accuracy of laser velocimeter?(a) 1 knot and below(b) 2.5 knots(c) 10 knots(d) 0.14 knots |
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Answer» Right choice is (a) 1 knot and below The best explanation: Test results show an accuracy of 1 knot or better at altitudes where the particle density is adequate. Aerosol densities and particle densities vary with altitude, time and volcanic eruptions. |
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