What are the differences between an OBS, a CDI, and a Heading Selector?

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What are the differences between a Heading indicator and an OBS?All of them use VORs.There are 4 different versions of the same instrument.The most advanced of the 4 is the HSI.

The heading indicator is a mechanical instrument that helps with the use of the magnetic compass.Straight flight and precision turns to headings are difficult in turbulent air because of the many errors in the magnetic compass.The forces that make the magnetic compass difficult to read do not affect a heading indicator.

Heading Indicators are not related toVOR.They can be used when the compass reading is not straight and level flight.They need to be aligned with the compass periodically.

A course deviation indicator is an instrument used in aircraft navigation to determine an aircraft's position in relation to a course.If the location of the aircraft is left, the needle will go to the right.

The knob on the CDI is not its own instrument.You can use the knob to select the course you want to track from a VOR ground station.Only a single needle is required when tracking a radial because you only track left/right deviation.You need to track the glide slope for an approach in order to show vertical deviation on a CDI.The left/right deviation from the runway is tracked by the CDI when on an instrument approach.

Is a Heading Indicator in one unit?Left right deviation is provided along with glide slope information as well as heading indication in turns.If the HSI's are coupled to auto pilots, they may allow course selection via a heading knob.The sum of the counter parts is more advanced than the HSI, but it is difficult to read for a new pilot.

A Very High Frequency omnidirectional radio fix is used in these 3 things.AVOR.A VOR may have different symbols on the map.