Question about compass

[speedbird1]

Does anyone know if you still need a regular compass if you have the HDX and the D10A? I figure that due to them both being independent and having battery backup it is no longer needed.

 

[Raymo]

If you have an AD-AHRS, you have a magnetic compass. If you have a backup AD-AHRS, you have a backup magnetic compass, as well.

 

[Brent Dana]

Wondered the same thing! Asked, and answere.

 

[maartenversteeg]

In my past plane case, the FSDO (MIDO) inspected my plane that didn't have an additional whiskey compass (so only a single Dynon compass that I was willing to defend as being a VFR required magnetic compass) and accepted this setup as satisfying the rules. I had heard stories (possibly 10 years old) that stated that there were FSDOs and DARs that were not satisfied with this. Maybe nowadays, with many more electronic displays, this is much less of an issue/question.

 

[kellym]

In my past plane case, the FSDO (MIDO) inspected my plane that didn't have an additional whiskey compass (so only a single Dynon compass that I was willing to defend as being a VFR required magnetic compass) and accepted this setup as satisfying the rules. I had heard stories (possibly 10 years old) that stated that there were FSDOs and DARs that were not satisfied with this. Maybe nowadays, with many more electronic displays, this is much less of an issue/question.

IIRC there was a time, way back that the regs said you needed a compass. Today's regs say you have to have a magnetic direction indicator, which covers most any form of magnetometer, whether built into ADAHRS or separate.

 

[WorkingWarbirds]

We deleted on our Bonanza install based on the current regulations. FAA has certified light sports with MEL that do not include a wet compass, so I think thats pretty definitive.

 

[n363rv]

This simple question seems to really confuse the IA that have to sign off on the install. 91.205 seems to spell this out clearly... Ha! At lease I think so, but a lot of folks think that if there are electrons required than you must have the non-stabilized whiskey compass. That is not the case.
If you take a look at the circular https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC 23.1311-1C.pdf and do a search for "8.6 Display of Direction (Heading or Track)." as well as "8.7 Display of Altitude, Airspeed, and Magnetic Compass Information."
This last part essentially says that you need an backup to your primary display. Most of us satisfy this with another electronic display by dynon, grt or garmin... not an old crappy non-stabilized whisky compass. You also must have an alternate power supply in case the main electrical system craps out. Dynon provides us with a battery in Skyview and D10A to do this. Finally, do a look up on the Cessna Skycatcher... a beguiled aircraft certified with a G300 that did not come with a old fashioned compass.

 

[Corefile]

If you have an AD-AHRS, you have a magnetic compass. If you have a backup AD-AHRS, you have a backup magnetic compass, as well.

My understanding was that the HDX was not certified with the backup ADAHRS - can install it on experimental but the STC does not support a backup one for the HDX? Or are we talking about something else ?

 

[Spert]

My understanding was that the HDX was not certified with the backup ADAHRS - can install it on experimental but the STC does not support a backup one for the HDX? Or are we talking about something else ?

The D10A should count on the certified version.

 

[Corefile]

Does this change if one is planning to go IFR in the future?

 

[Brent Dana]

On the dynon system, you have to have the d10a. That is your secondary. It is complete by itself, ifr, whatever.! D10a is total separate system from the hdx. It is standalone.

 

[chriscalandro]

In the certified installation the heading indicator on the D10 should be off.

 

[Spert]

In the certified installation the heading indicator on the D10 should be off.

The HSI mode is not available in the certified configuration, but the heading display in the EFIS mode should still work.

 

[chriscalandro]

The HSI mode is not available in the certified configuration, but the heading display in the EFIS mode should still work.

When I put my airplane together the heading was waaayyy off from interference.
I was told it is not supposed to be enabled for this reason and the remote magnetometer unit is not possible in the certified installation.

if yours isn’t up to 40 degrees off like mine was I don’t see why you shouldn’t use it.

This was just my experience and interaction.

 

[Spert]

When I put my airplane together the heading was waaayyy off from interference.
I was told it is not supposed to be enabled for this reason and the remote magnetometer unit is not possible in the certified installation.

if yours isn’t up to 40 degrees off like mine was I don’t see why you shouldn’t use it.

This was just my experience and interaction.

I will be displeased if it’s off by that much, but I can only speak in hypotheticals at this point. I will let you know what I see when I shift from book learning to actual observation after I pick it up next week.

 

[lavallejd]

In the certified installation the heading indicator on the D10 should be off.

Good point. And when everything goes down hill, the old whiskey compass becomes your best friend. My shop enabled the heading for the D10 but I always go back to old habits... compare everything to the wet compass. Always.