Do autopilots in non-glass cockpits feed off of the gyro instruments to determine aircraft attitude, heading and rate of turn? Or do they have their own internal gyros? Since I can set the heading using the heading bug, I suppose it needs to be able to read the heading-bug offset at the very least, so there's some connection.
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$\begingroup$ Why do you think there would be difference between glass and non-glass cockpit? $\endgroup$– Jan HudecCommented Jun 25, 2014 at 16:51
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$\begingroup$ @JanHudec I clarified in a comment to Emil's answer "I deliberately made the distinction non-glass cockpit, as [in a glass cockpit] the sensors are designed to be read electronically. In a non-glass cockpit the sensors are primarily read mechanically, with the gyro physically touching some mechanism moving the 'little airplane' around. Do you have any idea how this information gets conveyed to the autopilot? Is it standardized?" $\endgroup$– falstroCommented Jun 25, 2014 at 16:57
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2 Answers
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Yes, they do. Also for glass cockpit, the autopilot uses the sensors that are used for the displays (ADC, AHRS, etc).
Here are some extracts from the FLM of the SA 365N Dolphin, describing the autopilot and coupler (I selected only parts relevant to the question):
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$\begingroup$ Hello Emil, welcome to Aviation.SE. Can you provide any reference to your answer? While I believe your answer basically is right, the answer would benefit from some background / links. $\endgroup$– DeltaLima ♦Commented Jun 25, 2014 at 11:15
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$\begingroup$ @DeltaLima: I added some extracts from the flight manual of a analog instruments helicopter with AP. Unfortunately the description in the manual is not very detailed (there are no schematics). $\endgroup$– EmilCommented Jun 25, 2014 at 11:53
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1$\begingroup$ Hi Emil! Thanks, I deliberately made the distinction non-glass cockpit, as there the sensors are designed to be read electronically. In a non-glass cockpit the sensors are primarily read mechanically, with the gyro physically touching some mechanism moving the 'little airplane' around. Do you have any idea how this information gets conveyed to the autopilot? Is it standardized? $\endgroup$– falstroCommented Jun 25, 2014 at 13:33
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2$\begingroup$ @falstro Typically there's some kind of electrical pick-up inside the gyro, connected to the same mechanism driving the display (this rather old one is a rate-of-turn indicator, and you can see the wound resistor and wiper arm on the left side of the photo -- Based on the resistance the autopilot knows what the rate-of-turn indicator is showing, and can act accordingly). Several designs exist, designed to work with different autopilots. $\endgroup$– voretaq7Commented Jun 26, 2014 at 2:05
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Typically the Turn Coordinator and DG is used. Sometimes the Attitude indicator is used as well. Of course, if NAV tracking is used the OBS or GPS has in input as well.
