INERTIAL NAVIGATION SYSTEM

#1. INS errors are classified as “Bounded errors” and “Unbounded errors”.

• AAn “Unbounded error” is an error that increases with time, an example being the distance gone error due to a ground speed error.
• BAn “Unbounded error” is an error that increases with time, an example being an increasing ground speed error due to the platform not being levelled correctly.
• CA “Bounded error” is an error that is subject to sudden unpredictable random changes. Most notable during pitching manoeuvres and when raising or lowering flap and U/C.
• DA “Bounded error” is an error that is “tied” to the real wander rates of the gyros on the platform.

#2. Two checks that can be carried out to check that two selected sequential waypoints have been entered correctly are:

• Aselect DSR.TK/STS and check that the status is less than 4; select DIS/TIME and check that the time agrees with the flight plan time.
• Bselect DIS/TIME and check that the distance agrees with the distance on the flight plan; then check that the time agrees with the flight plan time for the leg
• Cselect DIS/TIME and check that the distance agrees with the distance on the flight plan; select DSR.TK/STS and check that the track agrees with the flight plan track for the leg.
• Dselect DIS/TIME and check that the distance agrees with the distance on the flight plan; select HDG/DA and check that the heading agrees with the flight plan heading for the leg.

#3. In an INS the E/W accelerations are converted into an E/W speed (kt) at the first stage of integration and into E/W distance gone (nm) at the second stage of integration. This gives:

• Adeparture which is multiplied by Cosine of the present latitude of obtain d'long (min) which is used to automatically up-date the present longitude.
• Bd'long (min) which is used to automatically up-date the present longitude.
• Cdeparture which is multiplied by Secant of the present latitude to obtain d'long (min) which is used to automatically up-date the present longitude.
• Ddeparture which is multiplied by Sine of the present latitude to obtain d'long (min) which is used to automatically up-date the present longitude.