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Electronic heading indicator

Ron B.

Well Known Member
First time going through final inspection without a whisky compass ( assisting a friend). Does a Garmin G3X require a compass swing and placard for correcting for deviations as would a whisky compass?
 
No. It does require a magnetometer calibration, though.

(details of how to do it are in the installation manual; It only takes ten minutes, just follow the prompts on the PFD in setup mode)

- mark
 
No. It does require a magnetometer calibration, though.

(details of how to do it are in the installation manual; It only takes ten minutes, just follow the prompts on the PFD in setup mode)

- mark

Sorry - this information is not correct in the Canadian context.

If you are relying on the heading indication of an electronic flight instrument as your primary compass indication, it MUST be calibrated and a compass correction card MUST be posted in the cockpit. It also must be recalibrated on an annual basis.

Additionally, the electronic compass must be capable of functioning independent of the aircraft electrical system - in the case of an EFIS with magnetic heading sensing, the EFIS and magnetometer must be powered by an alternate power source such that magnetic heading information will be available to the pilot in the event of an aircraft electrical system fire.

From a logic standpoint, we know we have had since the beginning of time the requirement for a whiskey compass. We know the whiskey compass functions in the absence of aircraft electrical power. The requirement for the ability to navigate using magnetic heading has not changed, despite the advent of EFIS gear. If we're using an EFIS as our compass it needs to provide the same capabilities as the whiskey compass it replaces. This includes verification of its operation and calibration of its errors as part of the aircraft's approved maintenance schedule.

Spend some time on the MD-RA website - you'll find in the guidance to builders that this requirement is very clearly addressed.
 
Sorry - this information is not correct in the Canadian context.

If you are relying on the heading indication of an electronic flight instrument as your primary compass indication, it MUST be calibrated and a compass correction card MUST be posted in the cockpit. It also must be recalibrated on an annual basis.

Additionally, the electronic compass must be capable of functioning independent of the aircraft electrical system - in the case of an EFIS with magnetic heading sensing, the EFIS and magnetometer must be powered by an alternate power source such that magnetic heading information will be available to the pilot in the event of an aircraft electrical system fire.

From a logic standpoint, we know we have had since the beginning of time the requirement for a whiskey compass. We know the whiskey compass functions in the absence of aircraft electrical power. The requirement for the ability to navigate using magnetic heading has not changed, despite the advent of EFIS gear. If we're using an EFIS as our compass it needs to provide the same capabilities as the whiskey compass it replaces. This includes verification of its operation and calibration of its errors as part of the aircraft's approved maintenance schedule.

Spend some time on the MD-RA website - you'll find in the guidance to builders that this requirement is very clearly addressed.

The same applies to type certificated aircraft in the USA. To make sure it is followed Garmin and others make the requirement for a whiskey compass part of their STC instructions and must be complied with. Those STC instructions are the final authority over any ambiguous FARs. Experimental in USA no. Since there is no STC instructions as there is no TC for the airplane.
 
C-18

If you haven't already, refer to document C-18 of the MD-RA.
All requirements and definitions concerning compass and magnetic sensor/magnetometer are there.
 
If you haven't already, refer to document C-18 of the MD-RA.
All requirements and definitions concerning compass and magnetic sensor/magnetometer are there.

All I see on C-18 is related to magnetic compass. We will preform a magnetometer swing tomorrow to make sure we have everything.
 
...it MUST be calibrated and a compass correction card MUST be posted in the cockpit. It also must be recalibrated on an annual basis.

If your airport doesn't have a compass rose and you do a calibration, will the required compass card show zero deviation on every heading?
 
If your airport doesn't have a compass rose and you do a calibration, will the required compass card show zero deviation on every heading?

Yes, I have a compass card showing 0 degree correction for every heading
 
Compass Swing

Someone will have to explain the purpose of "swinging" a magnetometer.

A whiskey compass can be adjusted, a magnetometer cannot.
 
Someone will have to explain the purpose of "swinging" a magnetometer.

A whiskey compass can be adjusted, a magnetometer cannot.

"swingng" a magnetometer is actually "calibrating it". The digital sensor corrects airframe errors during calibration. The display instrument, whether large glass panel or small EFIS/PFD will direct the pilot step by step during calibration from a setup mode. Usually it has you start on a cardinal heading and then have the pilot or technician taxi in a circle at a slow speed with instruction to stop every dozen or so degrees for a short time and then request more turn followed by another stop. And so on. During this process the system is correcting heading for the specific airframe with the engine running. Once done it is very accurate and dependable. If the system cannot calibrate itself to within tolerance it will set a "fail" code instead of a "successful" code in the calibration. Without a successful calibration procedure the features dependent on magnetometer such as heading, wind direction and speed and autopilot heading bug will not work. The need for proper calibration prior to getting heading information and the tight tolerance on a modern magnetometer can make a correction card obsolete (but still required if by reg hence the 0/0/0/0 type correction). Enough magnetic correction to mention on a paper card is to much for a digital magnetometer to accept and thus provide heading to the pilot or systems. If the magnetometer fails the calibration test the installer will have to re-locate the magnetometer to an area on the airframe with less magnetic field interference. A compass rose isn't really necessary to calibrate a magnetometer since the system calls out the turns and stops to the pilot during set up.
 
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Magnetic Direction Indicator

All I see on C-18 is related to magnetic compass.


I respectfully disagree...
Screen shots of poages 2 and 3 of document C-18 talking specifically about magnetic direction indicators.
 

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Magnetic indicator

There are several types of magnetic indicators.

- Whiskey Compass.
- An old style mecanical KI 525A HSI with an external magnetometer.
- EFIS HSI with a magnetometer with built in electronic calibration.

Only the Whiskey compass requires a compass correction card.
This is the only compass that needs manual compensation in terms
of the direction of flight.
 
Only the Whiskey compass requires a compass correction card.
Not true in Canada, which is what this sub-forum is concerned with. In Canada, the regulations lag the technology, and even though your correction card will show 0/0/0/0 when complete, one must be displayed.
 
I guess I could use my calibrated remote magnometer equipped D10a to swing my whiskey compass and have the compass correction card apply to it.

Would I have to also display a 0/0/0 correction card for the Dynon?
 
I respectfully disagree...
Screen shots of poages 2 and 3 of document C-18 talking specifically about magnetic direction indicators.

Thanks , I could not find those documents on the MD-RA site.
Got the compass swing completed today.
 
CAR standard 625 ap C

Please check this link.
Standard 625 Appendix C: Out of Phase Tasks and Equipment Maintenance Requirements - Canadian Aviation Regulations (CARs)

10. Non-stabilized Magnetic Direction Indicators (MDIs).
(a) Except as provided in (b) and (c), non-stabilized magnetic direction indicators shall be calibrated, and a dated correction card installed for each indicator, at at intervals not exceeding 12 months;

Where doubt exists as to the compliance requirements in respect of a specific aircraft installation, the owner can contact the nearest Transport Canada district or regional office for assistance.

https://tc.canada.ca/en/corporate-s...quirements-canadian-aviation-regulations-cars

https://www.md-ra.com/docs/GUIDE_TO_OUT_OF_PHASE_ITEMS.pdf

As I understand It, there is NO requirement for a compass card/ compass swing for other than a Whiskey compass.

I got my PPL in Dawson Creek many years ago.
 
Calibration

"swingng" a magnetometer is actually "calibrating it". The digital sensor corrects airframe errors during calibration. The display instrument, whether large glass panel or small EFIS/PFD will direct the pilot step by step during calibration from a setup mode. Usually it has you start on a cardinal heading and then have the pilot or technician taxi in a circle at a slow speed with instruction to stop every dozen or so degrees for a short time and then request more turn followed by another stop. And so on. During this process the system is correcting heading for the specific airframe with the engine running. Once done it is very accurate and dependable. If the system cannot calibrate itself to within tolerance it will set a "fail" code instead of a "successful" code in the calibration. Without a successful calibration procedure the features dependent on magnetometer such as heading, wind direction and speed and autopilot heading bug will not work. The need for proper calibration prior to getting heading information and the tight tolerance on a modern magnetometer can make a correction card obsolete (but still required if by reg hence the 0/0/0/0 type correction). Enough magnetic correction to mention on a paper card is to much for a digital magnetometer to accept and thus provide heading to the pilot or systems. If the magnetometer fails the calibration test the installer will have to re-locate the magnetometer to an area on the airframe with less magnetic field interference. A compass rose isn't really necessary to calibrate a magnetometer since the system calls out the turns and stops to the pilot during set up.
Jim

I understand the calibration process. I did it on my G3X. It is the swinging I don’t understand. Swinging refers to a whisky compass. Not a magnetometer. I have yet to see a magnetometer with a 0/0/0/0 compass card.
 
I guess I could use my calibrated remote magnometer equipped D10a to swing my whiskey compass and have the compass correction card apply to it.

Would I have to also display a 0/0/0 correction card for the Dynon?

A couple of thoughts here...
1) not sure where the 0/0/0 idea is coming from. We are allowed to have errors as large as 10 degrees, or larger than 10 degrees if caused by operation of electrical equipment such as windshield heaters - just note what causes the exceedance of the 10 degree limit

2) do not for a moment believe your Dynon will be perfectly calibrated to zero degrees of error on every heading. Magnetometers generally are pretty good but also generally still cannot correct for all errors.

3) Calibration of a compass requires a "known good" reference. That reference can be a compass rose which is properly maintained (many at airports have not been corrected for the drifting magnetic poles in many years thus they contain a "built in" error). Another reference is a calibrated master compass. A third reference more commonly available to us is a cross-check of heading indication versus GPS-derived ground track while taxiing (NOT while flying, thanks to wind!). It's difficult using this method to calibrate headings every 30 degrees unless the airport has a large flat surface suitable for stable taxiing in multiple directions.

Coming back to the CARs requirements, if an aircraft has a whiskey compass, that compass can be calibrated and a calibration card posted in the cockpit. Great - no problems there.

Where it gets a little more tricky is when we have opted to use an EFIS and have no whiskey compass. That's when we have to meet the guidance outlined in the excellent MD-RA C-18 document. And the kicker is that, if you have multiple EFIS systems using multiple magnetometers, each of them must be calibrated and a calibration card posted in the cockpit.

Interestingly, I have dual magnetometers literally stacked one atop the other in precisely the same orientation and, of course, in the same magnetic interference environment. These two magnetometers produce surprisingly-different results after following the manufacturer's calibration procedures. The manufacturer hasn't yet been able to explain to me why there may be as much as 7 degrees difference between these two sensors. That's just the way they are. Luckily I have a whiskey compass which is calibrated and for which a calibration card is posted in the cockpit.

Technically speaking, Transport Canada, if they ramp check, can snag an aircraft where its compass calibration card is missing any vital information including the signature, date and license number of the person certifying the compass calibration data. That piece of paper is tiny, so write the excess information on the back side!
 
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