Inertial Navigation | Strapdown

Question 1

A ___ ___ system is strapped to the aircraft structure

Answer 1

Strapdown

Question 2

A strapdown system has no gimbals, because it uses ___ ___ gyros

Answer 2

ring laser

Question 3

The outputs of a strapdown is ___ sensitive rather than displacement sensitive

Answer 3

rate

Question 4

The ___ system follows the airframe, and its alignment to True North is calculated

Answer 4

strapdown

Question 5

A strapdown system has (no) moving parts and its stable platform is maintained ____

Answer 5

no mathematically

Question 6

A strapdown system has a ___ degree of accuracy and reliability

Answer 6

higher

Question 7

A strapdown IRS contains:

• ___ ADIRUs
• Display Unit
• Mode Selector Unit

Answer 7

two

Question 8

The inertial reference in the ADIRU senses and computes ___ accelerations and turning rates around each axis

Answer 8

linear

Question 9

In a strapdown system, rotation about an axis can be sensed with ___ or ___

Answer 9

fibre optic or ring laser gyros

Question 10

A strapdown systems aligns ___ than a stable platform

Answer 10

faster

Question 11

From its direction and magnitude, the position of ___ ___ can be sensed and the latitude can be estimated

Answer 11

True North

Question 12

You need to position the computer trihedron with reference to ___

Answer 12

Earth

Question 13

Without Earth Rate compensation, the system would think it was upside down after ___ hours at the Equator

Answer 13

12

Question 14

If you input the wrong lattiude, the Earth rate calculations will be wrong and you won’t be able to align to True North correctly, the ___ lights will be flashing

Answer 14

ALIGN

Question 15

You can get away with switching straight to NAV when between __N and __S

Answer 15

70 70

Question 16

Alignment might take _ minutes at the Equator

Answer 16

5

Question 17

Alignment might take __ minutes at 70N

Answer 17

10

Question 18

Alignment might take __ minutes at 70-80N

Answer 18

17

Question 19

Fast realignment can be done by switching to ___ and entering the gate position. Then reselect ___ once the ALIGN lights extinguish.

Answer 19

ALIGN NAV

Question 20

In NAV mode, the gyros measured the Earth’s movement with respect to ___, and your movement with respect to the Earth, in the form of ___ ___

Answer 20

space, Transport Rate

Question 21

Gyro autocal measures the position error after the flight and estimates the ___ ___ that would have caused it

Answer 21

gyro errors

Question 22

Accelerometer autocal picks up lateral bias errors found during ___, because movement is mostly forward

Answer 22

taxi

Question 23

A strapdown system can suffer from ___ ___ errors, caused by imperfect mirrors

Answer 23

lock in

Question 24

Lock in error can be reduced by ___

Answer 24

Wobbling, or vibrating with the dither motor and spring.

Question 25

A strapdown system requires Schuler tuning as a result of ___ ___

Answer 25

platform oscillations

Question 26

One of the largest errors in the system is ___ ___, at around ___ degrees per hour

Answer 26

Real Wander, 0.01

Question 27

During the initial levelling, errors can include:

Answer 27

• Accelerometer misaligned
• Velocity error unbounded
• Distance error unbounded

Question 28

The list of errors from which a strapdown system suffers are:

Answer 28

• Schuler Tuning
• Levelling and Azimuth
• Initial levelling
• Accelerometer
• Earth Shape
• Altitude
• Coriolis
• Centripetal Acceleration

Question 29

When dividing the distance off by the time that the system has been in NAV mode, the maximum accepted error is _nm/hour

Answer 29

1

Question 30

The output of an IRS includes:

Answer 30

Ground Speed

Question 31

Sustained oscillations in a RLG is initially caused by ___

Answer 31

Gas inside the triangular cavity being ionised by the voltage, causing helium atoms to collide with and transfer energy to the neon atoms

Question 32

A strapdown system requires at least _ laser gyros and _ accelerometers

Answer 32

3 3