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#11
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Compass Questions ?
Dallas wrote in
- september.org: Bob wrote: Regarding the compass heading that shows in the glass displays: The heading information from the PFD comes from a directional gyro. The directional gyro's drift is constantly corrected (slaved) by a magnetic compass located in the tailcone on the airplane. The output of this compass is electrically "enhanced" and amplified through a "flux gate". Bottom line: A very accurate, stable, compass reading that never needs adjustment. And to expand on that a bit... https://en.wikipedia.org/wiki/Attitu...ference_system Brian -- http://www.earthwaves.org/forum/index.php - Earth Sciences discussion http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism Sed quis custodiet ipsos Custodes? |
#12
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Compass Questions ?
Oh my, a reasonable question, attracting answers over the next two days,
of which just one had it right - and that referred to the AHRS attitude heading system. What used to be an expensive collection of gyros and accelerometers is now commercially available (for model aircraft and drones) for $20 on up. Glass cockpits can often select heading in TRUE or MAG form. For those of us flying on the cheap, a moving map application like APIC from Approach Systems (an update costs $10) loaded on a personal assistant like the HP IQue which cost around $300 when new uses its internal GPS to provide a track made good (over the ground) which can be presented as Mag or True. It is convenient to set the direction indicator to the MAG track indicated, though this ignores the difference between Heading and Track - the former being needed to make good the latter, despite a crosswind. Sincerely Brian W On 7/13/2015 5:36 PM, Bob wrote: Hello, Not a Pilot, but always interested in the engineering aspects. This question came up, and I realize that I am not sure of a correct answer. Regarding the compass heading that shows in the glass displays: How is it derived ? GPS ? If not GPS, what ? Is it then Magnetic or True ? Does the Pilot have to correct for variation/declination changes during a flight ? Does aviation use True or Magnetic when discussing or flying ? etc. ? Thanks, Bob |
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