Backup Mag Compass

KALEWIS · #1 03-19-2015, 07:17 PM

Looking for another modification to do. Considering a panel mount compass like this one

http://www.aircraftspruce.com/catalo...h_compass1.php

Would interference be an issue if mounted in the panel with all the other electronic gizmos ?

Looking to do airspeed and altimeter too. Eventually.

Bill_H · #2 03-19-2015, 08:52 PM

Regarding "looking for a project" - sure, why not? I'd prefer a vertical card compass though.

But regarding actually having a backup, I would consider something else entirely. Any smartphone has a compass app. But better than that, Foreflight or something similar on your smartphone gives you independent backup for nav, course, speed, altitude, etc - all GPS based but that's good enough.

If your ADAHRS fails (thus losing mag compass) the GPS still gives you course, heading etc. on the map. So what is this mag compass actually "backing up?" Would you pull out your "backup paper chart" and actually start flying by this thing rather than GPS? Or if the GPS and ADAHRS both fail, would having just a compass and a paper chart really be anywhere near as good as the smartphone app?

I would much prefer something like those headrests in the modification thread as a project, than backup steam gauges.

KALEWIS · #3 03-19-2015, 09:07 PM

My concern with the iPhone/iPad compass using foreflight is the lack of cell signal to drive the phone GPS. A standalone GPS source like a bad elf or Garmin glo would solve that, but having a panel compass takes out all electronic failure scenarios.

sblack · #4 03-20-2015, 05:59 AM

You don't need a cell signal for the ipad gps to work.

N130WN · #5 03-20-2015, 07:13 AM

The iCompass works in airplane mode.

If equipped, the internal GPS works without cellular input. Check the last graphic here:

http://ipadpilotnews.com/2013/09/how...g-preflight-2/

KALEWIS · #6 03-20-2015, 08:03 AM

I'm looking at a situation with no electronic devices at all. Highly unlikely, but does stand to reason that it's a possibility. A panel mounted compass is cheaper than an iPad with a years subscription to fore flight.

It does worry me how reliant we are to mobile devices ........ Cue rise of the machines ..... What happened to looking out the window ?

Plus my original question had nothing to do with iPads and iPhones I could care less what they can or can't do, it was if the electronics already in the panel would interfere with a compass....

aturner · #7 03-20-2015, 08:16 AM

Quote:

Originally Posted by KALEWIS

Looking for another modification to do. Considering a panel mount compass like this one

http://www.aircraftspruce.com/catalo...h_compass1.php

Would interference be an issue if mounted in the panel with all the other electronic gizmos ?

Looking to do airspeed and altimeter too. Eventually.

I put that very compass into my panel, it is the only device in my panel that is not a computer networked whiz bang electronic gizmo. Figured it would be good to have one stone age instrument, if only for sentimental reasons. I mounted it top left corner, next to one of the three G3X screen, and it is surprisingly accurate, once I swung it. Try to keep it away from wiring, and it should work OK.

Dgamble · #8 03-20-2015, 08:18 AM

Quote:

Originally Posted by KALEWIS

if the electronics already in the panel would interfere with a compass....

They do, and that is why the compass will have adjustment screws to get it as close as possible and a compensation chart to account for anything that can't be handled with the adjustments. There's nothing all that exotic behind the panel of a -12 as compared to any other GA plane, so I would think the adjustment range would work as well as with any other "legacy" plane.

jimgreen · #9 03-20-2015, 08:25 AM

I have a similar compass mounted in my panel. Had to fiddle with it to find a good position, but was able to correct it to within 2 degrees. Transmitting deflects it temporarily.
The worst effect is from the joystick in my case. Mounting low on the panel wasn't an option.
Each panel is going to be different, but it is easy to power up and move it around for the best spot. Electrics on/off only makes 3 degrees difference on mine.

KALEWIS · #10 03-20-2015, 08:35 AM

Thanks for all the real world experience answers..... It seems it can be done with minimal hassle!