Inertial Navigation Systems Flashcards
How many accelerometers are in an INS?
2, one facing N-S, one facing E-W
What 3 laws does an INS work off?
Newtons 3 laws, if you know 2 factors, you know the other (Speed Distance Time triangle)
Why is the initial position in the INS required to be accurate?
Because the system applies acceleration, bearing, and velocity changes from this position. Therefore if this position is wrong, the system will be wrong until updated in the air.
Does gravity have an effect on the INS?
If it wasn’t for the gyroscopes installed, then yes! But overall no
What is earth rate compensation?
Because we want the accelerometers to be horizontal to the earth, they need to be tipped at a rate proportional to the earth’s rotation.
Is latitude or longitude being compensated for with earth rate?
Latitude. Maximum at the equator.
What is transport rate?
Compensation longitudinally in order to keep the accelerometer horizontal to the earth. It is based off velocity.
Is the INS aligned to true north or magnetic north?
True north
What is the disadvantage of a north-pointing INS system?
Can’t be used in polar regions, need to have a wander azimuth inertial system
In a wander azimuth inertial system, how are the accelerometers angled?
EW and NS, but with a wander angle.
Up to what radial error rate can an INS/IRS experience before being considered unserviceable
3+3t nm (t=number of hours of operation)
What is the maximum time you can navigate with a single IRS/INS?
10hrs since last alignment, must have backup. 3hrs nav in CTA, and 5hrs in oceanic areas
What is the maximum time you can navigate with two or more IRS/INS?
5hrs CTA, 12hrs OCTA or oceanic. Must be aligned within 10hrs
When can an IRS/INS be manually updated?
Overhead a VOR, within 25nm of a VOR/DME, or a visual fix <5000ftAGL
When can an IRS/INS be automatically updated?
within 140nm of a DME, or 200nm or two DMEs (DME/DME fix), <25nm from a VOR/DME
