Chapter 18A - Inertial Navigation

Question 1

INS measures?

Answer 1

Track and Groundspeed

Question 2

Is INS self contained?

Answer 2

Yes

Question 3

Any inertial system must be given a _____ on which it will base all its calculations

Answer 3

• starting reference point

Question 4

INS requires no external information except? and from what?

Answer 4

TAS from the ADC

Question 5

INS follows what?

Answer 5

Great Circles

Question 6

Commonly the alignment of accelerometers is _____ or Longitudinal axis and _____ or Lateral axis.

Answer 6

• North/South
• East/West

Question 7

If acceleration is measured, integration with respect to time will provide? Is this first or second stage integration?

Answer 7

Velocity

First stage integration

Question 8

A integration with respect to time will give _____, or distance travelled in a particular direction. Is this first or second stage integration?

Answer 8

• displacement,

Second stage integration

Question 9

What two things do you need to initially put into an INS?

Answer 9

Position, Speed

Question 10

What navigation capabilities does an INS give you?

Answer 10

Position (latitude & longitude)
Heading/drift
Track/groundspeed
Waypoint navigation
Planned track
Distance and time to go
Cross track error
Track angle error

Can also provide:

Roll and Pitch

Question 11

Accelerometer uses a?

Answer 11

Repulsive magnet - bigger the displacement bigger the repulsive force

Question 12

INS Panels – Mode Select Unit (MSU), STBY is?

Answer 12

System powers up, gyros are brought to speed and temperature. The aircraft can be moved.

Question 13

In EASA you have to be ___ to do an alignment?

Answer 13

Stationary

Question 14

INS Panels – Mode Select Unit (MSU), ALIGN is?

Answer 14

The system levels and aligns the platform. Once complete, the READY NAV light goes on. The aircraft must be stationary during the alignment process.

Question 15

in an INS alignment the accelerometers do?

Answer 15

Levelling

Question 16

In INS alignment, what is caging?

Answer 16

Gimbals are driven to 900 to one another, voltage applied to heat oil, gyros brought up to speed.

Question 17

How long does alignment take on an INS?

Answer 17

17 Minutes

Question 18

How long does caging take on an INS alignment?

Answer 18

3 Minutes

Question 19

How long does levelling take on an INS alignment?

Answer 19

3 Minutes

Question 20

How long does gyrocompassing take on INS alignment?

Answer 20

11 minutes

Question 21

An INS does not calculate?

Answer 21

Longitude

Question 22

With longitude:

Two repeated crew inputs different from the stored value?

Answer 22

The system accepts the new value.

Question 23

With latitude:

Two repeated crew inputs different from the calculated value?

Answer 23

The system does not complete alignment.

Question 24

An INS does not compute its?

Answer 24

Longitude - you have to input it

Question 25

An INS consists of?

Answer 25

• A platform
• a standalone computer (navigation information)

Question 26

In ATT mode what information do you get?

Answer 26

Attitude reference still available, attitude reference for AI and Autopilot - System cannot be aligned in flight (navigation ability lost)

Question 27

Two types of errors with an INS?

Answer 27

Bounded and unbounded errors

Question 28

What is the typical error for an INS?

Answer 28

1 - 2 Nm/hr (can wonder off)

Question 29

The INS positional error of 1 – 2 NM/hr is dependent on factors affecting the accuracy of the platform, such as:

Answer 29

• The gyro drift rate
• Accelerometer bias
• Misalignment of the platform
• Computational errors

Question 30

The Inertial Navigation System + Air Data Computer = ?

Answer 30

Air Data Inertial Reference Unit (ADIRU)

Question 31

The INS needs the ____ from the ADC in order to calculate the wind information.

Answer 31

TAS

Question 32

After first integration, the speeds are
measured along E/W (known as U)
and N/S (known as V).

Adding the speeds as vectors gives
us a resultant ground speed…

…and a track as the resultant speed
will have an angle clockwise from
north.

Answer 32

Question 33

Fly By associated with the __ mode?

Answer 33

Auto

Question 34

Fly over assciated with the ____ mode?

Answer 34

Manual

Question 35

What is the cross track position and tracking error?

Answer 35