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Correct CHOICE is (c) HIGH maintenance

Easiest explanation: Micro machined VIBRATING mass rate gyros exploit semiconductor MANUFACTURING technology for mass production. They are extremely reliable and rugged devices with low power consumption and offer the major advantage of RELATIVELY low cost. They also do not require the very high maintenance that spinning rotor gyros require.

The correct option is (B) FLEXURE pivot accelerometer

To explain: The flexure pivot accelerometer is the most commonly used in AIRCRAFT systems. The SENSITIVE element consists of a pendulum with a torquer coil and a PICK off supported by torsional spring or flexure.

Right choice is (c) Linear motion of the vehicle

For EXPLANATION I WOULD say: The ability of stable element to REMAIN non-rotating relative to a space or EARTH coordinate frame DEPENDS on drift rate of the reference gyros, accuracy of gyro torquers, linear motion of the vehicle, orthogonality of the components on the platform.

The correct ANSWER is (d) Middle gimbal APPROACHES 90°

To elaborate: The condition in which the middle gimbal ANGLE approaches 90° is CALLED gimbal lock. In this condition, the innermost and outermost axis coincide, thus depriving the platform one of its degrees of freedom.

Correct answer is (b) Euler ANGLES are not easily READABLE from the gimbals

Explanation: One of the main purposes of gimballed SYSTEM is to provide a convenient readout of vehicle attitude by reading each of the gimbals angles separately, THEREBY yielding convenient Euler angle outputs.

Right choice is (a) True

The explanation is: In the presence of rotation and acceleration know as sculling, this approximation leads to errors referred to as sculling errors. It can be avoided by executing the velocity TRANSFORMATION at LEAST four times faster than the ANTICIPATED frequency of vibration.

The correct OPTION is (a) Coning algorithm

To elaborate: Pre-processing the gyro data at a HIGHER rate than the quaternion iteration IMPROVES the approximation in the VECTOR change in angle in order to follow the actual motion of the rotation axis closely. The pre-processing algorithm is also called as coning algorithms.

Correct choice is (d) LIMIT vibration errors

Best explanation: The gyros and ACCELEROMETERS are rigidly mounted on a block with temperature sensors. The block is USUALLY shock mounted to the vehicle to control the BANDWIDTH of the motion sensed at the instruments. Shock mounting limits vibration RECTIFICATION errors within the errors themselves.

The correct CHOICE is (C) Coning error

To ELABORATE: Coning refers to a motion in which the axis of rotation is itself moving in space. In this TYPE of motion, the axes of the BODY trace a cone in space.

The correct option is (c) QUATERNION

For explanation I would SAY: Describing rotation motion in the strapdown system employ more than the minimum three parameters. A quaternion is a four element entity ting of a scalar part and a vector part. It DEFINES the INSTANTANEOUS axis of rotation.

Correct option is (b) Normalization constraint

Explanation: Quaternion integration algorithms USUALLY make use of the normalization constraint to control ERROR GROWTH in the COMPUTATIONS. The sum of the SQUARES of the quaternion elements are subtracted from unity to yield the normalization error.

Right choice is (d) Provide inputs to air data computer

Easiest EXPLANATION: The purpose of strapdown computations are to CALCULATE the vehicle’s attitude RELATIVE to the navigational coordinates using the gyro measurements, to transform the ACCELEROMETER measurements from vehicle axes into navigational coordinates, and to perform the dead-reckoning computations. Air data computer is independent of inertial navigation system.

The correct option is (a) Angular rate sensors

Easy explanation: In a strapdown system, the GYROS do not act as NULL sensors as in a gimballed system but act as INERTIAL angular rate sensors. Angle and orientation are computed from the measured angular rates by the algorithms that CALCULATE heading and orientation.

The correct option is (c) Strapdown system

The best EXPLANATION: In a strapdown NAVIGATOR, Gyroscopes and ACCELEROMETERS are rigidly mounted to a sensor assembly that is usually mounted to the vehicle on a set of STRAP mounts. The gyroscopes track the rotation of the body and compute the orientation of the body.

Right answer is (B) Rate biasing

Explanation: The method of rate biasing employs a turntable that APPLIES a CONSTANT rotation to the gyro. An angular encoder measures the relative angle between the INSTRUMENT and its base.

Right answer is (a) True

To ELABORATE: Two mode RLGs are planar by DESIGN so that only linearly polarized modes can be resonant in the cavity. SUPPRESSION of one of the two modes of POLARIZATION ensures stable OPERATION.

Right choice is (C) Interference intensity

To elaborate: In a fiber optic gyro, The counterpropagating BEAMS are launched into an OPTICAL path and are RECOMBINED as they EXIT. The interference generated by the recombination depends on the optical phase difference between the two beams and therefore provides a measure of rotation.

Correct choice is (a) Ring laser GYRO

Explanation: In a Ring laser gyro, the counterpropagating beams form RESONANT nodes within the gyro cavity and create an electromagnetic STANDING wave that remains fixed with inertial SPACE. When the housing of the gyro rotates, a detector can count nodes of the standing waves, each of which represents an angle.

Right option is (c) Sagnac EFFECT

Explanation: The Sagnac effect is a relativistic phenomena of LIGHT in a rotating reference system. When LASER beams circulate in a closed path that is rotating in an inertial SPACE, the optical length seen by the co-rotating BEAM appears longer than that seen by counter rotating beam.

The correct option is (a) RING laser gyro

Explanation: Optical gyroscopes such as the ring laser gyro and the fibre optic gyro measure angular rate of rotation by sensing the resulting difference in the transit times for laser light waves travelling AROUND a closed PATH in OPPOSITE directions.

The correct answer is (b) HALTERES

For explanation: Every flying object needs to maintain its ORIENTATION and INSECTS that fly use halteres. Halteres WORK in the same principle as MEMS gyro, the VIBRATE and use Coriolis force to know their orientation.

Right answer is (a) Reduce base motion

Best explanation: The vibrating mass rate GYRO is a simple instrument suffers from the unacceptable characteristic that the smallest linear motions applied to its base cause UNACCEPTABLY large errors. To overcome the effect of base motion, it is necessary to use balanced oscillations in which the oscillations of one mass are counter-balanced by equal and opposite motion of a second equal mass as in the case of TUNING FORK gyro.

The correct choice is (a) Space launch vehicles

Easiest EXPLANATION: MEMS gyros are being exploited not only in avionic applications such as flight control, standby attitude and heading reference systems, and missile mid-course guidance but ALSO in the automobile INDUSTRY in car STABILITY enhancement systems. Space launch vehicles use RING laser gyros which are more accurate.

Right CHOICE is (a) True

Best EXPLANATION: In an FBW aircraft, the rate GYROS and accelerometers PROVIDE the aircraft motion feedback which enables a manoeuvre command control to be achieved and an aerodynamically unstable aircraft to be stabilized by the flight control SYSTEM.

The correct option is (c) Low run up time

The best EXPLANATION: The major disadvantage of spinning WHEEL or spinning rotor gyros is that they are mechanically complex and have a high probability of failure due to the moving components. They also require high powers and have high run up time. Run up time is the time TAKEN for the gyro to start spinning at the REQUIRED RPM after engine start.

The correct ANSWER is (b) Electrostatically suspended TDF gyro

The EXPLANATION: In electrostatically suspended TDF gyro, the spinning wheel is suspended electrostatically hence reducing friction and ACHIEVING 0.001 deg/hr ACCURACY but at COSTS orders of magnitude higher than the floated TDF gyros.

Right option is (b) High drift rate

To elaborate: Gyroscopes are used as heading references. The spinning WHEEL, LARGE angle, unfloated instruments with ball bearings that have drift rates on the order of 50deg/hr . and HENCE are USELESS for NAVIGATION.

The correct answer is (b) 8.5

To EXPLAIN I would say: A gyroscope on a military AIRCRAFT must sense angular RATES as LOW as 0.005 deg/hr and as high as 400deg/sec, a RANGE of 8.5 orders of magnitude. Strapdown gyros in civil aircraft need only sense an 8 order of magnitude range of angular rates.

Right ANSWER is (a) Space-STABILIZE the accelerometer

The explanation is: The purpose of gyroscope or gyro in an inertial navigation system is to space stabilize the ACCELEROMETERS. In gimballed PLATFORMS, the gyros measure the rotation of the platform, which is angularly ISOLATED from the vehicle’s motion.

Right answer is (b) Voltage forcing

Best explanation: In potential forcing, a potential is applied to the PENDULUM and to one or both the electrodes. The voltage establishes electric fields that induce the CHARGE of the nonconducting pendulum. This causes a NET force to ACT on the proof mass.

Correct OPTION is (a) Heating

For explanation I WOULD say: Heating of torquer coil due to rebalance current can LEAD to rectification of vibration inputs and MUST often be compensated. A pulse rebalance torquer maintains CONSTANT heating.

The correct choice is (a) FLEXURE MUST provide maximum resistance in the DIRECTION of INPUT axis

Best EXPLANATION: The pivot or flexure supporting the pendulum must provide minimal restraint for the pendulum in the direction of the input axis while exhibiting high stiffness in the other two directions. The spring constant of the flexure or pivot generates a restoring force that reduces the gain of the electronic restoring loop.

Correct option is (a) True

The BEST I can explain: An ACCELEROMETER can only measure acceleration in one axes. In navigational systems COMPRISING of accelerometers, THREE separate accelerometers are places with each on the three body axes of the aircraft.

Right option is (d) Thermal characters

To explain I would SAY: Accelerometers that INCLUDE fluid damping exhibit reduced bandwidth and ADDITIONAL thermal sensitivity due to changes in fluid characteristics. Thus FLEXURE pivoted accelerometers are better than floated instruments.

Right answer is (b) 8g

Easy explanation: Accelerometer is USED to measure acceleration of the VEHICLE and thus must be corrected for the Earth’s gravitational effect. If the accelerometer is being ACCELERATED upward with an acceleration of 7g, then (a-G) = 7g – (-1g), and the instrument READS 8g.

The correct answer is (a) True

To explain: The torquer COIL in the accelerometer RESTORE the pendulum to null, the torquer current being a measure of the RESTORING torque and, hence, of the ACCELERATION.

Right ANSWER is (b) Acceleration

Best explanation: The accelerometer is a type of inertial instrument that measures the acceleration in any given AXES. The measured acceleration can be INTEGRATED over time to obtain velocity and DISTANCE.

The CORRECT OPTION is (b) UTC(Moscow)

The explanation: The GPS segment provides correlations so that GPS time can be related to UTC(USNO) MODULO 1sec to within 90nsec, WHEREAS the GLONASS control segment provides correlations so that GLONASS time can be related to UTC(Moscow) to within 1μsec.

Right ANSWER is (a) 437.5kHz

Explanation: The unique frequency for L2 signal in the GLONASS system is GIVEN by the formula f= 1246.0 +0.4375i MHz where I=0,1,2,….,24. The separation between each of these SATELLITES is 437.5kHz.

Right CHOICE is (B) False

The explanation is: GPS time does not follow the leap SECOND correction that UTC occasionally MAKES. GLONASS time does.

Right option is (b) i=+5 and +6

To explain: The GLONASS use i= +5 and +6 frequency channels as a technical channel. They are only USED for a limited periods of time during orbital INTERSECTIONS or other periods of exceptional circumstances.

The correct choice is (a) ECEF COORDINATES

For explanation: The GLONASS ephemeris DATA are BROADCAST as ECEF or Earth Center Earth Fixed coordinate system cartesian coordinates in position and VELOCITY with lunar and solar acceleration perturbations parameters that are VALID about 0.5 hour.