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Questions on INS and IRS

 
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K.Haroon
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PostPosted: Wed Jun 27, 2012 2:02 pm    Post subject: Questions on INS and IRS Reply with quote

For description see Aircraft Instruments: http://www.theairlinepilots.com/forum/viewforum.php?f=35

Arrow During initial alignment an inertial navigation system is north aligned by inputs from:

a) horizontal accelerometers and the east gyro <-- Correct
b) the aircraft remote reading compass system
c) computer matching of measured gravity magnitude to gravity magnitude of initial alignment
d) vertical accelerometers and the north gyro


Arrow What measurement is used to carry out alignment of an Inertial Navigation System?

a) Acceleration sensed by the east gyro horizontal accelerometer <-- Correct
b) Acceleration sensed by the north gyro horizontal accelerometer
c) Acceleration sensed by the north gyro ertical accelerometer
d) Difference in magnitude of the value of gravity compared with the gravity at the last known position


Arrow During the initial alignment of an inertial navigation system (INS) the equipment:

a) will accept a 10o error in initial latitude but will not accept a 10o error in initial longitude
b) will not accept a 10o error in initial latitude but will accept a 10o error in initial longitude <-- Correct
c) will accept a 10o error in initial latitude and initial longitude
d) will not accept a 10o error in initial latitude or initial longitude


Arrow When initial position is put into an FMS, the system:

a) rejects initial latitude error, but it will accept longitude error
b) rejects initial longitude error, but it will accept latitude error
c) rejects initial latitude or longitude error <-- Correct
d) cannot detect input errors, and accepts whatever is put in


Arrow After alignment of the stable platform of the Inertial Navigation System, the output data from the INS computer to the platform is:

a) rate corrections to the gyros <-- Correct
b) accelerations from the accelerometers
c) attitude
d) latitude and longitude


Arrow After alignment of the stable platform of an Inertial Navigation System, the output data from the platform is:

a) acceleration north/south and east/west and true heading
b) latitude, longitude and attitude
c) acceleration north/south and east/west, attitude and true heading <-- Correct
d) latitude, longitude and true heading


Arrow In an Inertial Navigation System (INS), Ground speed (GS) is calculated:

a) from TAS and W/V from RNAV data
b) from TAS and W/V from Air Data Computer (ADC)
c) by integrating measured acceleration <-- Correct
d) by integrating gyro precession in N/S and E/W directions respectively


Arrow The principle of Schuler Tuning as applied to the operation of inertial Navigation Systems Inertial Reference Systems is applicable to:

a) both gyro-stabilised platform and strapdown systems <-- Correct
b) only gyro-stabilised systems
c) both gyro-stabilised and laser gyro systems but only when operating in the non strapdown mode
d) only to strapdown laser gyro systems


Arrow In an Inertial Reference System, accelerations are measured in relation to:

a) the direction of true north
b) WGS 84 Earth co-ordinates
c) local vertical at the aircraft position
d) aircraft axis <-- Correct


Arrow Inertial Reference System sensors include:

A – one east-west and one north-south gyro; one east-west and one north- south accelerometer
B – accelerometers mounted in the direction of the aircraft axis
C – laser gyros mounted in the direction of the aircraft axis
D – accelerometers, and laser gyros, mounted in the direction of the aircraft axis <-- Correct


Arrow What does the sensor of an INS/IRS measure?

a) Velocity
b) Precession
c) Horizontal Earth Rate
d) Acceleration <-- Correct


Arrow The platform of an inertial navigation system (INS) is maintained at right angles to the local vertical by applying corrections for the effects of:

a) aircraft manoeuvres, earth rotation, transport wander and coriolis <-- Correct
b) gyroscopic inertia, earth rotation and real drift
c) vertical velocities, earth precession, centrifugal forces and transport drift
d) movement in the yawing plane, secondary precession and pendulous oscillation


Arrow An INS platform is kept at right angles to local gravity by applying corrections for the effects of:

i. Aircraft manoeuvres
ii. Earth rotation
iii. Transport wander
iv. Coriolis
v. Gyroscopic inertia

a) i, iii and v
b) ii, iii and v
c) ii, iv and v
d) ii, iii and iv <-- Correct

Just rule out v i.e. Gyroscopic inertia.


Arrow The term drift refers to the wander of the axis of a gyro in:

a) the vertical and horizontal plane
b) the vertical plane
c) the horizontal plane <-- Correct
d) any plane


Arrow What additional information is required to be input to an Inertial Navigation System (INS) in order to obtain an W/V readout?

a) Mach Number
b) IAS
c) Altitude and OAT
d) TAS <-- Correct


Arrow The purpose of the TAS input, from the air data computer, to the Inertial Navigation System is for:

a) position update in Attitude mode
b) the calculation of wind velocity <-- Correct
c) position update in Navigation mode
d) the calculation of drift


Arrow In an IRS:

a) the accelerometers are strapped down but the platform is gyro stabilised
b) the platform is strapped down but the accelerometers are gyro-stabilised
c) accelerometers and platform are both gyro-stabilised
d) accelerometers and platform are both strapped down <-- Correct


Arrow Some inertial reference systems are known as strapdown. This means:

a) the system is mounted on a stabilised platform
b) the system is mounted and fixed to the aircraft structure <-- Correct
c) the accelerometers are fixed bu the gyros are stabilised
d) the gyros are fixed but the accelerometers are stabilised


Arrow Some inertial reference and navigation systems are known as strapdown. This means that:

a) only the gyros and not the accelerometers, become part of the units fixture to the aircraft structure
b) gyros, and accelerometers are mounted on a stabilised platform in the aircraft
c) gyros and accelerometers need satellite information input to obtain a vertical reference
d) the gyroscopes and accelerometers become part of the units fixture to the aircraft structure <-- Correct


Arrow In order to maintain an accurate vertical using a pendulous sytem, an aircraft inertial platform incorporates a device:

a) without damping and a period of 84.4 min
b) with damping and a period of 84.4 min <-- Correct
c) without damping and a period of 84.4 sec
d) with damping and a period of 84.4 sec


Arrow Within the platform levelling loop of an earth-vertical referenced INS:

a) The levelling signals are unbounded, with a period of 84.4 seconds
b) The levelling signals are bounded with a period of 84.4 minutes <-- Correct
c) The levelling signals are unbounded, with a period of 84.4 minutes
d) The levelling signals are bounded, with a period of 84.4 seconds


Arrow In a ring laser gyro, the purpose of the dither motor is to:

a) enhance the accuracy of the gyro at all rotational rates
b) overcome laser lock <-- Correct
c) compensate for transport wander
d) stabilise the laser frequencies


Arrow One of the errors inherent in a ring laser gyroscope occurs at low input rotation rates tending towards zero when a phenomenon known as lock-in is experienced. What is the name of the technique, effected by means of a piezo- electric motor, that is used to correct this error?

a) Dither <-- Correct
b) Cavity rotation
c) Zero drop
d) Beam lock


Arrow In an Inertial Navigation System, what is the output of the first stage North/South integrator?

a) Groundspeed
b) Latitude
c) Velocity along the local meridian <-- Correct
d) Change of latitude


Arrow The resultant of the first integration of the output from the east/west accelerometer of an inertial navigation system (INS) in NAV MODE is:

a) velocity along the local parallel of latitude <-- Correct
b) change of longitude
c) vehicle longitude
d) departure


Arrow Double integration of the output from the east/west accelerometer of an inertial navigation system (INS) in the NAV MODE give:

a) distance north/south
b) vehicle longitude
c) distance east/west <-- Correct
d) velocity east/west


Arrow On an INS, what is the output of the E/W second-stage integrator?

a) Velocity N/S
b) Distance N/S
c) Distance E/W <-- Correct
d) Velocity E/W


Arrow What is the name given to an Inertial Reference System (IRS) which has the gyros and accelerometers as part of the units fixture to the aircraft structure?

a) Solid state
b) Rigid
c) Strapdown <-- Correct
d) Ring laser


Arrow IRS differs from INS in that it:

a) has a longer spin-up time and is not affected by vertical accelerations due to gravity
b) has a shorter spin-up time and suffers from laser lock <-- Correct
c) does not need to correct for coriolis and central acceleration
d) does not experience Schuler errors as accelerometers are strapped down and are not rotated by a V/R feedback loop


Arrow A laser reference system (IRS), as compared to a gyro reference system (INS):

a) is not strapped down and is adversely affected by g-forces
b) is strapped down and is not adversely affected by g-forces <-- Correct
c) the platform is strapped down but the accelerometers are not
d) the accelerometers are strapped down but the platform is not


Arrow Which of the following lists, which compares an Inertial Reference System that utilises Ring Laser Gyroscopes (RLG) instead of conventional gyroscopes, is completely correct?

a) The platform iskept stable relative to the earth mathematically rather than mechanically but it has a longer spin up time
b) It does not suffer from lock in error and it is insensitive to gravitational (g) forces
c) There is little or no spin up time and it does not suffer from lock in error
d) There is little or no spin up time and it is insensitive to gravitational (g) forces <-- Correct


Arrow Which of the following statements concerning the aircraft positions indicated on a triple fit Inertial Navigation System (INS)/Inertial Reference System (IRS) on the CDU is correct?

a) The positions will only differ if one of the systems has been decoupled because of a detected malfunction
b) The positions will be the same because they are an average of three difference positions
c) The positions are likely to differ because they are calculated from different sources <-- Correct
d) The positions will only differ if an error has been made when inputting the present position at the departure airport


Arrow After alignment, is it possible to update IRS positions?

a) Yes by operation of the TO/GA switch, the runway threshold co- ordinates are inserted into the IRS
b) No <-- Correct
c) Yes, the pilots can insert updates
d) Yes, the process is automatic in flight from the DMEs

FMC position is updated not the IRS position


Arrow When and where are IRS positions updated?

a) During all phases of flight
b) Only on the ground during the alignment procedure <-- Correct
c) When the FMS is in IRS ONLY NAV operation
d) When the VHF Nav Radios are selected to AUTO


Arrow Which of the following statements concerning the position indicated on the Inertial Reference System (IRS) display is correct?

a) It is updated when go-around is selected on take-off
b) It is constantly updated from information obtained by the FMC
c) It is not updated once the IRS mode is set to NAV <-- Correct
d) The positions from the two IRSs are compared to obtain a best position which is displayed on the IRS


Arrow Alignment of INS and IRS equipments can take place in which of the following modes?

a) ATT and ALIGN
b) NAV and ALIGN <-- Correct
c) ALIGN and ATT
d) NAV and ATT


Arrow Which of the following statements concerning the loss of alignment by an Inertial Reference System (IRS) in flight is correct?

a) It is not usable in any mode and must be shut down for the rest of the flight
b) The IRS has to be coupled to the remaining serviceable system and a realignment carried out in flight
c) The mode selector has to be rotated to ATT then back through ALIGN to NAV in order to obtain an in-flight realignment
d) The navigation mode, including present position and ground speed outputs, in inoperative for the remainder of the flight <-- Correct


Arrow Which of the following statements is correct concerning gyro-compassing of an inertial navigation system (INS)?

a) Gyro-compassing of an INS is possible in flight because it can differentiate between movement induced and misalignment induced accelerations

b) Gyro-compassing of an INS is not possible in flight because it cannot differentiate between movement induced and misalignment induced accelerations<--Correct

c) Gyro-compassing of an INS is possible in flight because it cannot differentiate between movement induced and misalignment induced accelerations

d) Gyro-compassing of an INS is not possible in flight because it can differentiate between movement induced and misalignment induced accelerations


Arrow The full alignment of the stable platform on an Inertial Navigation System: "is only possible on the ground when the aircraft is at a complete stop"


Arrow The alignment time, at mid-latitudes, for an Inertial Reference System using laser ring gyros is approximately:

a) 5 min
b) 20 min
c) 2 min
d) 10 min <-- Correct


Arrow A pilot accidently turning OFF the INS in flight, and then turns it back ON a few moments later. Following this incident:

a) everything returns to normal and is usable
b) no useful information can be obtained from the INS
c) it can only be used for attitude reference <-- Correct
d) the INS is usable in NAV MODE after a position update


Arrow The data that needs to be inserted into an Inertial Reference System in order to enable the system to make a successful alignment for navigation is:

a) airport ICAO identifier
b) aircraft heading
c) the position of an in-range DME
d) aircraft position in latitude and longitude <-- Correct


Arrow The drift of the azimuth gyro on an inertial unit induces an error in the position given by this unit. T being the elapsed time. The total error is:

a) sinusoidal
b) proportional to the square of time, t?
c) proportional to t/2
d) proportional to t <-- Correct


Arrow The azimuth gyro of an inertial unit has a drift of 0.01o/hr. After a flight of 12 hrs with a ground speed of 500 kt, the error on the aeroplane position is approximately:

a) 6 NM
b) 1 NM
c) 12 NM <-- Marked Correct
d) 60 NM

See the discussion here (http://www.atpforum.eu/showthread.php?t=9445)


Arrow Comparing the Present Position display on the Boeing 737-400 FMC, you note that there is a 10-mile difference between the left IRS and the right IRS positions. This means that:

a) One system is in IRS ONLY NAV operation and the other has the VHF Nay Radios selected to AUTO
b) No special significance this is normal
c) At least one of the IRS is drifting <-- Correct
d) One position has been computer generated from radio nay positions whilst the other is raw IRS


Arrow An aircraft equipped with an Inertial Navigation System (INS) flies with INS 1 coupled with autopilot 1. Both inertial navigation systems are navigating from waypoint A to B. The inertial systems Central Display Units (CDU) shows:

-XTK on INS 1 = 0 –XTK on INS 2 = 8L (XTK = cross track)

From this information it can be deduced that:

a) the autopilot is unserviceable in NAV mode
b) only inertial navigation system No. 2 is drifting
c) only inertial navigation system No. 1 is drifting
d) at least one of the inertial navigation systems is drifting <-- Correct


Arrow ATT Mode of the Inertial Reference System (IRS) is a back-up mode providing:

a) only attitude and heading information <-- Correct
b) only attitude information
c) navigation information
d) altitude, heading and position information


Arrow What are the positions (in the order left to right) on the Boeing 737-400 IRS MSU mode selector?

d) OFF ALIGN NAV ATT <-- Correct


Arrow With reference to an inertial navigation system (INS) the initial great circle track between computer inserted waypoints will be displayed when the control display unit (CDU) is selected to:

a) TK/GS
b) HDG/DA
c) DSRTK/STS <-- Correct
d) XTK/TKE


Arrow Aircraft position determined by radio navigation in an FMC is derived from:

a) VOR/DME
b) DME ranges and/or VOR/ADF bearings
c) VOR/ADF
d) DME only <-- Marked Correct

In a non-GPS FMS, ground based radio navaids provide the inputs for FMS calculated position fixes. These are DME-DME, VOR-DME and VOR-VOR in order of priority


Arrow Waypoints can be entered in an INS memory in different formats. In which of the following formats can waypoints be entered into all INSs?

a) Bearing and distance
b) Geographic co-ordinates <-- Correct
c) Hexadecimal
d) By waypoints name


Arrow When is the last point at which an INS or IRS may be selected to NAV mode?

a) After passengers and freight are aboard
b) Immediately prior to push back or taxi from the gate <-- Correct
c) At the holding point
b) On operation of the TOGA switch when opening the throttles for the take- off


Arrow Which of the following statements concernikng the operation of an Inertial Navigation System (INS)/Inertial Reference System (IRS) is correct?

a) NAV mode must be selected prior to movement of the aircraft off the gate <-- Correct
b) NAV mode must be selected on the runway just prior to take-off
c) NAV mode must be selected prior to the loading of passengers and/or freight
d) NAV mode must be selected when the alignment procedure is commenced
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