Inertial Navigation | Schuler Tuning

Question 1

With the INS not moving, it assumes that it is ___. This is a form of error and must be removed from the calculations to ensure that it actually measures __

Answer 1

falling towards the centre of the Earth, zero

Question 2

The time taken to go from one extreme to the other is the Schuler period of __ minutes

Answer 2

84.4

Question 3

A system with an identical period would indicate the local ___, regardless of any acceleration of a vehicle carrying it

Answer 3

vertical

Question 4

An INS platform behaves just like an Earth pendulum in that, when it is disturbed, it takes ___ minutes to settle down again.

Answer 4

84.4

Question 5

The ___ wobbles, rather than the INS even though it appears to when seen relative to the Earth

Answer 5

Earth

Question 6

The relationship between a circle’s angle in radians and its circumference is ___

Answer 6

1/R

Question 7

Multiplying 1/R by V gives the angular velocity over a surface distance, or the ___ ___, which is used to torque the gyro and make the platform precess at the same rate that it is being moved over the Earth’s surface

Answer 7

transport rate

Question 8

Schuler tuning prevents the accumulation of errors which would be caused by ___ ___ and treating ___ as an acceleration

Answer 8

platform tilt, gravity

Question 9

Schuler tuning will not compensate for errors from the precession of the ___ ___

Answer 9

steering gyro

Question 10

Schuler tuning provides an dampened closed-loop corrective action to stop tilt errors, oscillating around a zero value over __ minutes

Answer 10

84.4

Question 11

The Schuler tuned platform maximises its error at ___ and ___ minutes through each cycle

Answer 11

21.1 63.3

Question 12

The magnitude of the maximum error depends on the size of the disturbance that caused it, but the mean error remains at ____

Answer 12

zero

Question 13

Any errors in the output of the accelerometers caused by Schuler tuning is ___

Answer 13

bounded

Question 14

The output of the ___ indicator will be bounded

Answer 14

first

Question 15

___ ___ systems are considered to be Schuler tuned, and to suffer similar bounded errors

Answer 15

Strapped down

Question 16

You cannot use the system until the platform is levelled and the system is aligned with __ __, called ___

Answer 16

True North, gyrocompassing

Question 17

Gyrcompassing is completed by motoring the level platform until there is no topple output from the ___ gyro

Answer 17

East

Question 18

After having been gyrocompassed, the topple output of the North Gyroshoule equal the ___ ___, which is __ x ___

Answer 18

Earth Rate 15 x Cos( Latitude )

Question 19

Gyrocompassing is ____ at high latitudes as a result of the high torque rates

Answer 19

impossible

Question 20

With coarse levelling, the __ and ___ gimbals are driven until they are at __ degrees to each other.

Answer 20

pitch roll 90

Question 21

The platform is levelled to __ degrees against the aircraft frame or gravity, using the horizontal accelerometers or gravity switches

Answer 21

10

Question 22

Coarse azimuth is achieved by turning the platform in azimuth until the heading output agrees with the ___ ___ ___ ___

Answer 22

aircraft best known heading

Question 23

Coarse azimuth is followed by ___ levelling, which is done by motoring the platform until no acceleration from gravity is sensed by the _ and _ accelerometers

Answer 23

fine x y

Question 24

___ levelling uses the accelerometer null technique, with the aircraft stationary there shuold be no output from the horizontal accelerometers if the platform is level

Answer 24

Fine

Question 25

It takes around __ minutes overall for a stable platform

Answer 25

17

Question 26

When flying over the ___, the workaround is to keep the platform level, but not worry about aligning it to North, just detect how far out of alignment it is and include that in future calculations. In such situations, the accelerometers are offset by a ___ ___

Answer 26

Poles wander angle

Question 27

An alternative to levelling and aligning gyros, is to figure out ___

Answer 27

how far out of alignment they are to begin with, and monitor the changes

Question 28

If there is excessive movement during alignment, the ___ annunciator will flash and the fault indicator will come on. In such a situation, you should switch the Mode Select switch off for at least _ absconds, then back to ___

Answer 28

ALIGN 3 ALIGN

Question 29

The ____ light will flash if you do not enter the present position within the normal alignment time.

Answer 29

ALIGN

Question 30

Once aligned, the platform will be ___, pointing along ___ ___, and then you can switch back to NAV mode

Answer 30

level True North

Question 31

___ errors are constant over time, such as ___/___ that start off at a fixed rate

Answer 31

Bounded, track/groundspeed

Question 32

____ errors can develop over time

Answer 32

Unbounded

Question 33

Some errors can be calculated and corrected for, these include ___

Answer 33

Earth rate, transport wander, Coriolis Effect, centripetal acceleration

Question 34

Schuler corrections can be applied to compensate for ___ ___

Answer 34

Transport Rate

Question 35

___ ___ is compensated for on the ground, but can occur in turbulence

Answer 35

Real wander