A - INS/IRS (08-06-18) Flashcards
How does an INS work?
It comprises a platform with 3 accelerometers and 3 gyros all aligned perpendicular to each other with one N/S
The gyro systems provide information on angular deviations which get sent to motors will allow the platform to continually keep itself aligned with north.
It then uses an initial fed position to calculate new positions with measured accelerations and calculated velocities
What is inertial drift?
Where accelerometer imperfections cause calculated position to diverge from actual position
What is the sole purpose of INS?
To provide nav capability
What would be the purpose of equipping an aircraft with multiple INSs?
To enable cross comparison and redundancy
What is the purpose of STBY mode on the INS?
Bringing the gyros up to speed.
How does an INS know if it is not properly aligned with north?
The N/S accelerometer will read an acceleration which is due to earth rate, when stationary.
the reading should be zero so it can rotate and seek zero to align with north.
What is the initial alignment process for an INS?
The system is powered up and caged
The system levels itself with the horizontal
The system the undergoes gyrocompassing to seek north alignment
When is initial alignement more difficult and why?
At high latitude due to less topple occuring at high latitudes
However if aligned at lower latitudes then high latitude travel is possible.
What is a bounded error?
an error which has a value that doesn’t change
What is an unbounded error?
an error which has a value that changes over time
In terms of latitude and longitude, what errors can an INS detect?
errors of latitude.
What is the schuler period?
84.4minutes
What inertial system corrections are required for an INS?
Coriolis effect
Centripetal acceleration
Schuler oscillation
What is the accuracy of an INS system?
1.5nm per hour
What is a wander azimuth system?
a system which calculate position from heading and speed over the poles due to the INS not being able to align with true north
