Q1. To obtain heading information from a gyro-stabilised platform, the gyros should be?
1 degree of freedom and a horizontal axis.
Q2. The vertical reference unit of a three axis data generator is equipped with a gyro with?
2 degrees of freedom and a vertical spin axis.
Q3. The fundamental difference between INS and IRS is that?
The IRS is a strap down system with 3 accelerometers mounted at 90° to each other.
Q4. Where would a rate integrating gyro be used? 1. inertial attitude unit 2. autopilot system 3. stabilizer servomechanism system 4. inertial navigation unit 5. rate of turn indicator
1,4
Q5. A rate integrating gyro is used in?
Inertial navigation system.
Q6. An INS with the accelerometers aligned N/S and NAV is limited to use at latitudes below about 82°. This is because?
The functions of secant latitude and tangent latitude used in certain corrections in the computer start to approach infinity and the computer cannot handle the rapid changes involved. (in simple word sec of latitude with approach infinity )
Q7. While inertial platform system is operating on board an aircraft, it is necessary to use a device with the following characteristics, in order to keep the vertical line with the pendulous system?
With damping and a period of about 84 minutes.
Q8. An inertial navigation system’s control and display unit indicate a position of 48°10.9’N 000°12.2’W on a ramp position 46°07.5’N 000°05.1’E. What is the radial error rate if it has been in NAV mode for 8 hours and 20 minutes?
1.37 Nm/hr.
Q9. INS errors are classified as “bounded errors” and “unbounded errors”.
An “unbounded error” is an error that increases with time, an example being the distance gone error due to a ground speed error.
Q10. The computer of a north referenced Inertial Navigation System (INS) in flight, provides compensation for:
earth rotation, transport wander, coriolis
Q11. The position accuracy of an RLG (Ring LASER Gyro) INS is?
2 nm/hr.
Q12. The errors of an INS fall into three categories?
Bounded, unbounded and inherent.
Q13. The product of the first integration of the E/W acceleration sensed by an INS system is?
Speed along the local parallel. flying E-W , means flying along parallel of latitude
Q14. When using an INS platform Coriolis affects?
Both a, and b.
Q15. In an INS a TAS (from ADC) input is?
Required in order to provide a wind velocity read out.
Q16. Alignment of a RLG INS takes?
Less than 10 minutes.
Q17. In an IRS system?
Both the platform and accelerometers are strapped down.
Q18. In order to align a strap-down inertial unit, it is required to insert the local geographical coordinates. This is necessary to?
Position the computing trihedron with reference to the earth.
Q19. During initial alignment the IRS must be given coordinates to?
Establish the trihedral with reference to the earth.
Q20. When initial position is put into an INS system?
It rejects initial latitude errors, but accepts initial longitude errors.
Q21. The correct latitude must be put into INS?
Because small latitude errors will not be detected but will cause unbounded errors during the subsequent flight.
Q22. Why must latitude and longitude be inserted into an IRS?
To determine the aircraft position relative to the earth.
Q23. When an IRS is first switched on it must be aligned in order to?
Calculate the computed trihedron.
Q24. The selection on an IRS mode panel are used in the following order?
OFF;STBY;ALIGN;NAV;ATT.
Q25. Setting zero cost index on an FMS gives?
Best range.
Q26. A cost index is?
An FMS input code telling the FMS the required balance between optimizing fuel costs and sector time.
Q27. At the second stage of integration E/W speed is converted into E/W distance gone. To convert this departure into the change of longitude it has to:
be multiplied by secant of the latitude
Q28. In an INS the E/W accelerations are converted into an E/W speed (kt) at the first stage… and into E/W distance gone (NM) at the second stage. This gives:
departure which is multiplied by secant of the present latitude to obtain d’long (min) which is used to automatically update the present longitude
Q29. With reference to Inertial Navigation Systems, the functions of the integrators are: I. at the second stage of integration to suppress unbounded errors (when in the NAV mode) II. at the first stage of integration to convert acceleration, with respect to time, into speed, (when in NAV mode) III. at the second stage of integration to convert speed, with respect to time, into distance gone, (when in the NAV mode) IV. to align the platform (when in the level and align modes)
only (ii) and (iii) of the above statements are true
Q30. During initialization of an INS the aircraft must not be moved until:
the green “ready NAV” light has been illuminated and the mode selector switch has been set to the “NAV” position
Q31. In an INS which is Schuler tuned, the largest unbounded errors are?
Due to the real wander of the platform gyroscopes.
Q32. Dither is used in a laser gyro in order to:
break the frequency lock which would prevent small rotational rates from being sensed by the gyro
Q33. A ring laser gyro consists of:
a laser split into two beams
Q34. The triangular cavity in a RLG is filled with which combination of gasses?
Helium and neon.