Inertial Navigation System INS/IRS/MEMS

Question 1

What does INS stand for?

Answer 1

Intertial Navigation Systems

Question 2

The major advantage of INS is what?

Answer 2

that it requires no external signals

Question 3

INS depends on what?

Answer 3

The laws of inertia to determine position

Question 4

Once a starting position is known, by latitude and longitude, the INS computer will:

Answer 4

determine any new position by measuring the inertial forces acting on the aircraft.

Question 5

Because a change in motion is proportional to the applied force, acceleration can be determined by:

Answer 5

measuring the external forces on the aircraft.

Question 6

We can measure the reaction force to determine the aircraft’s acceleration and therefore its acceleration and velocity.
This can be accomplished using:

Answer 6

Accelerometers

Question 7

Autonomous navigation use:

Answer 7

sensitive accelerometers

Question 8

What does LVDT stand for?

Answer 8

Linear Voltage Differential Transducer

Question 9

The LVDT is a transformer device with a core that can move:

Answer 9

in a linear direction

Question 10

If the core is in the middle - the output from S1 cancels the signal from S2. The output will be:

Answer 10

null or 0.0 VDC

Question 11

By comparing the phase of the LVDT output signal with the input:

Answer 11

the direction of the cores movement can he sensed

Question 12

What are Piezoelectric accelerometers?

Answer 12

solid state devices that use the piezoelectric effect as in quartz crystals

Question 13

The Piezoelectric accelerometer uses microscopic crystal structures that:

Answer 13

create sm voltages when stressed

Question 14

Capacitive accelerometers are designed with:

Answer 14

a tiny, nearly microscopic, capacitor with movable plates

Question 15

G-forces move the plates a small amount, changing the capacitance and capacitive reactance. The change can be:

Answer 15

sensed and used to measure acceleration

Question 16

What does MEMS stand for?

Answer 16

Micro Electro Mechanical System

Question 17

A common type of accelerometer used in autonomous navigation systems is:

Answer 17

a solid state type with a silicon inertial sensor known as a Micro- ElectroMechanical System (MEMS)

Question 18

A second type of MEMS is a:

Answer 18

Surface Acoustic Wave or SAW

Question 19

With a SAW, resonating elements are:

Answer 19

placed on a beam suspended between a frame and a mass

Question 20

Disadvantage of Solid State Accelerometers:

Answer 20

It may go into “lock-in”

Question 21

During very slow turn rates, the phase difference between the laser beams is:

Answer 21

Very small

Question 22

It is possible, in this condition (very slow turn rates), for the two laser beams to couple and:

Answer 22

“Lock in” indicating no acceleration

Question 23

FOG, works using the same principles as the LRG but is:

Answer 23

different in construction.

Question 24

What does FOG stand for?

Answer 24

Fiber-Optic Gyro

Question 25

An Inertial Navigation System: IRS, uses a combination of accelerometers and gyroscopes to determine:

Answer 25

the aircrafts attitude. It can have navigational capabilities.

Question 26

The heart of an IRS is 3 LRGs and 3 accelerometers mounted on a platform. The platform is contained in an LRU called:

Answer 26

Inertial Reference Unit (IRU)
and is mounted in the avionics/equipment bay

Question 27

The Stable Platform is sometimes called:

Answer 27

the Tilt Table

which is gimbaled and uses motors and gyro’s to maintain platform stability and alignment magnetic north as well as a local vertical

Question 28

The second type of platform is known as the:

Answer 28

Strapdown Platform
This type is directly attached to the airframe

Question 29

IRS provides information to the:
(there’s 7)

Answer 29

EFIS, FMS, INS, IFCS, weather radar, antiskid, and FDR

Question 30

The IRS can be integrated with other systems or:

Answer 30

be a standalone (independent system)

Question 31

Initialization of the system can take 10 minutes and must be:

Answer 31

accomplished before the first flight or if the aircraft is moved while the system is off.

Question 32

During initialization, the aircraft should not be:

Answer 32

moved

Question 33

To start the initialization, the crew enters what?

Answer 33

the latitude and longitude of the aircraft

Question 34

Each IRS has its own:

Answer 34

align and condition light and Mode Selection

Question 35

What is used to enter the position data?

Answer 35

the keyboard

Question 36

If the align light is flashing:

Answer 36

an error in data entry has occurred or the aircraft has been moved

Question 37

If the align light is extinguished:

Answer 37

the unit is in align mode

Question 38

Placing the mode selector in the align position does what?

Answer 38

initiates the alignment

Question 39

In attitude mode the IRS does not:

Answer 39

navigate the aircraft and only provides output information of pitch and roll attitude.

Question 40

From the Attitude Mode, the system needs to be:

Answer 40

aligned again before being used for navigation.

Question 41

From the other measurements the IRS can determine:

Answer 41

True North

Question 42

Once initialized, the IRS can be used to:

Answer 42

measure acceleration around any of the three axis precisely.

Question 43

The IRS can be combined with an:

Answer 43

Air Data Inertial Reference Unit (ADIRU)
also known as an
Air Data Inertial Reference System (ADIRS)

Question 44

ADIRUs are mounted in triplicate on:

Answer 44

transport category aircraft

Question 45

Like the air data system, the ADIRU requires:

Answer 45

ADMs (Air Data Modules) to convert air pressure to a digital signal.

Question 46

The FMS coordinates what?

Answer 46

IRS position, dependant navigation systems position and flight plans.

Question 47

You should think of the IRS as an attitude and direction indication system that has:

Answer 47

navigational capability

Question 48

What is INS?

Answer 48

a navigation system with attitude and direction capability

Often used as a synonym for IRS

Question 49

INS is ATA code:

Answer 49

34-20

34 is navigation

Question 50

Like IRS, the INS system is susceptible to:

Answer 50

Precession
(drift)

Question 51

What is integration drift?

Answer 51

the accumulation of small errors over time

Question 52

Aviation INS will drift up to:

Answer 52

1.5 kilometers per hour

Question 53

The heart of the INS is the:

Answer 53

navigation unit

Question 54

The Control Display Unit is similar to that of the:

Answer 54

FMS with data entered into a keypad

Question 55

What is Kalman Filtering?

Answer 55

a software program that takes measurements over time and estimates true values and then predicts a future value

Question 56

What is GPS aided alignment:

Answer 56

the most common form of alignment today

Question 57

What is Optical Alignment:

Answer 57

the use of a small mounted telescope known as a theodolite.
This works only on gimbaled systems, such as INS

Question 58

Gyroscope alignment only works if:

Answer 58

the aircraft is stationary. Gyrocompass alignment does not determine longitude. It is therefore not as accurate as GPS or optical alignment.

Question 59

What is Transfer Alignment:

Answer 59

If there are more than one INS in operation, the INS needing alignment can be synchronized with the aligned INS. To confirm alignment the crew may have to perform special maneuvers to verify the accuracy.