Chapter 18A - Inertial Navigation Flashcards
INS measures?
Track and Groundspeed
Is INS self contained?
Yes
Any inertial system must be given a _____ on which it will base all its calculations
- starting reference point
INS requires no external information except? and from what?
TAS from the ADC
INS follows what?
Great Circles
Commonly the alignment of accelerometers is _____ or Longitudinal axis and _____ or Lateral axis.
- North/South
- East/West
If acceleration is measured, integration with respect to time will provide? Is this first or second stage integration?
Velocity
First stage integration
A integration with respect to time will give _____, or distance travelled in a particular direction. Is this first or second stage integration?
- displacement,
Second stage integration
What two things do you need to initially put into an INS?
Position, Speed
What navigation capabilities does an INS give you?
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
Accelerometer uses a?
Repulsive magnet - bigger the displacement bigger the repulsive force
INS Panels – Mode Select Unit (MSU), STBY is?
System powers up, gyros are brought to speed and temperature. The aircraft can be moved.
In EASA you have to be ___ to do an alignment?
Stationary
INS Panels – Mode Select Unit (MSU), ALIGN is?
The system levels and aligns the platform. Once complete, the READY NAV light goes on. The aircraft must be stationary during the alignment process.
in an INS alignment the accelerometers do?
Levelling
In INS alignment, what is caging?
Gimbals are driven to 900 to one another, voltage applied to heat oil, gyros brought up to speed.
How long does alignment take on an INS?
17 Minutes
How long does caging take on an INS alignment?
3 Minutes
How long does levelling take on an INS alignment?
3 Minutes
How long does gyrocompassing take on INS alignment?
11 minutes
An INS does not calculate?
Longitude
With longitude:
Two repeated crew inputs different from the stored value?
The system accepts the new value.
With latitude:
Two repeated crew inputs different from the calculated value?
The system does not complete alignment.
An INS does not compute its?
Longitude - you have to input it
An INS consists of?
- A platform
- a standalone computer (navigation information)
In ATT mode what information do you get?
Attitude reference still available, attitude reference for AI and Autopilot - System cannot be aligned in flight (navigation ability lost)
Two types of errors with an INS?
Bounded and unbounded errors
What is the typical error for an INS?
1 - 2 Nm/hr (can wonder off)
The INS positional error of 1 – 2 NM/hr is dependent on factors affecting the accuracy of the platform, such as:
- The gyro drift rate
- Accelerometer bias
- Misalignment of the platform
- Computational errors
The Inertial Navigation System + Air Data Computer = ?
Air Data Inertial Reference Unit (ADIRU)
The INS needs the ____ from the ADC in order to calculate the wind information.
TAS
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.
Fly By associated with the __ mode?
Auto
Fly over assciated with the ____ mode?
Manual
What is the cross track position and tracking error?
