Magnetic deviation with G5 HSI

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Seth.A

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Seth.A
Basic flight planning question with a magnetic compass vs a G5 HSI. I know we need to factor in magnetic deviation as outlined on the compass card, but how does that work if the plane is equipped with a G5. It doesn't seem to make sense that the magnetometer would have the same error as the magnetic compass since they aren't in the same place.

Is the G5 simply calibrated to match the error from the magnetic compass? calibrated to eliminate the error from deviation entirely? Is the deviation different and if so where would I expect to find that info?

Thanks
 
When we installed a G5 w/ magnetometer, I was told "this thing has no deviation error".
 
Seth.A said:
Basic flight planning question with a magnetic compass vs a G5 HSI. I know we need to factor in magnetic deviation as outlined on the compass card, but how does that work if the plane is equipped with a G5. It doesn't seem to make sense that the magnetometer would have the same error as the magnetic compass since they aren't in the same place.

Is the G5 simply calibrated to match the error from the magnetic compass? calibrated to eliminate the error from deviation entirely? Is the deviation different and if so where would I expect to find that info?

Thanks
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Should behave and read exactly like a magnetic compass. It won't, but it should. Both the magnetic compass and the G5 should be calibrated to read nearly the same on a compass rose. If different, should have a correction card.
 
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The magnetometer is usually placed far enough out on the wing where there should be no interference.
 
If the G5 suffered from deviation it would have its own deviation card.
 
Line up on the runway and if the G5 reads the same as the big numbers in front of you, its accurate!
 
The G5 is not a “magnetic direction indicator” that requires a deviation card, it’s some form of AHRS, which according to the Advanced Avionics Handbook “contains not only the sensors used to measure attitude and heading, but also a computer that accepts sensor inputs and performs calculations.”

Essentially the deviation card is “built into” the G5 system. They take it out on a compass rose and tell it “This is north, this is south, this is east, this is west,” etc., and the hardware/software makes the appropriate adjustments.
 
Seth.A said:
Basic flight planning question with a magnetic compass vs a G5 HSI. I know we need to factor in magnetic deviation as outlined on the compass card, but how does that work if the plane is equipped with a G5. It doesn't seem to make sense that the magnetometer would have the same error as the magnetic compass since they aren't in the same place.

Is the G5 simply calibrated to match the error from the magnetic compass? calibrated to eliminate the error from deviation entirely? Is the deviation different and if so where would I expect to find that info?

Thanks
Click to expand...

My understanding is that the deviation is already built into the G5 as a correction table.
 
MauleSkinner said:
The G5 is not a “magnetic direction indicator”
Click to expand...

Can you explain more about this? My understanding was that the sensor the G5 uses to measure heading was a magnetometer, which according to wikipedia is a device that measures magnetic field. Is that different than a "magnetic direction indicator"?

Sorry for my ignorance. I totally get how deviation can be corrected for in software, but I'm not sure how a device that indicates direction based on magnetic field is not a magnetic direction indicator. I sense there's a reg i'm not familiar with that specifically defines "magnetic direction indicator".
 
Seth.A said:
Can you explain more about this? My understanding was that the sensor the G5 uses to measure heading was a magnetometer, which according to wikipedia is a device that measures magnetic field. Is that different than a "magnetic direction indicator"?

Sorry for my ignorance. I totally get how deviation can be corrected for in software, but I'm not sure how a device that indicates direction based on magnetic field is not a magnetic direction indicator. I sense there's a reg i'm not familiar with that specifically defines "magnetic direction indicator".
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It’s not a “magnetic direction indicator” as used in 91.205 and other places in FAA regs referring to a simple compass that requires a deviation card.
 
My new install has dual G5s with a GMU 11 magnetometer mounted in the tail section away from any interference (tested for compliance before install). The plane was taxied, turned in circles, and the G5s calibrated. It gives me mag heading as accurate or better than I can read the compass.


Sent from my iPhone using Tapatalk Pro
 
Joe_B1 said:
Line up on the runway and if the G5 reads the same as the big numbers in front of you, its accurate!
Click to expand...
Those numbers can be off by five degrees, sometimes more if the runway hasn't been surveyed in years and the variation has changed enough.
 
The magnetometer senses magnetic direction and it also uses the earth's lines of magnetic flux to sense attitude.
 
Variation correction is via a database that is updated from time to time.

Deviation correction is done at the install to 'calibrate' the system to the aircraft.
 
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