Does the EFIS use a magetometer?

[Chris in Marshfield]

Hi all,

Does the EFIS use a magnetometer to determine heading, or is it all inertial? I read through the manual and it described the process of aligning the DG to the aircraft's magnetic compass occasionally, just as it would be done with traditional instrumentation. I didn't see any evidence of a magnetometer in the installation docs, so I presumed that this is probably the case.

This assumes, of course, that there is no GPS signal available from which to derive a ground track.

Thanks and best regards,
Chris

[TrutrakTech]

Chris,

You've got it correct. No magnetometer. It uses GPS track when available, otherwise it's in a "free gyro" mode. Thanks!

[rshannon]

Did the Digi II use a magnetometer in the past? If so, at what S/N was it discontinued?

Ron

[TrutrakTech]

Hi Ron,

It did use a magnetometer in the past and no longer does. I don't have the exact serial number on record as it wasn't a completely black and white change to the new style. If you engage your DII with the GPS turned off and it shows Bank Angle 0.0, it has no magnetometer. Conversely, if you see HDG XXX in the top left (X's are numbers), and SEL XXX in the bottom left, it has a magnetometer.

Thanks!

[rckol]

Question:

How do I comply with a ATC direction to "fly heading xxx" if there is no magnetic reference?

Thanks

[PhantomPholly]

Did the Digi II use a magnetometer in the past? If so, at what S/N was it discontinued?

Ron

The reliability of it depended on the installation. In my case, it happens to work wonderfully - but for many people the surrounding electronics cause errors. They offered me the "upgrade," but since mine tracks mag just fine I actually installed a switch to purposely disconnect it from my GPS in case I want to fly a mag heading...

:D

[TrutrakTech]

Question:

How do I comply with a ATC direction to "fly heading xxx" if there is no magnetic reference?

Thanks

Simple answer, fly ground track. ATC doesn't care and many of them are now using ground track anyway. If you're not flying the direction they want, they'll turn you. It's pretty simple and FAR more reliable than wind affected magnetic heading. :)

Ask an ATC some time. I'm pretty good friends with one that works at a large center, ground track is A-OK with him.

[rckol]

IFR just ran an article on this subject in the July 2010 issue (which included a picture and mention of the Trutrak EFIS), based on their discussions with "a wide sampling of controllers".

To condense their two page article into 2 sentences: It is normally not a problem with the controllers if you fly track instead of heading. The exceptions are situations where you are in line of traffic being vectored, such as departure from a large metro airport.

Other suggestions were to get an OK from ATC for flying a track, or figure your own track based on the wind correction to get to the track ATC is trying to put you on.