Magnetic Compass

[alaskabearhawk]

You would be better off just getting one off ebay. Postage alone would be around $32 round-trip. Plus I'm not too keen on loaning out tools. Best intentions and all, compost does happen and it usually happens at inopportune times.

[JimParker256]

svyolo wrote "I just can't imagine a scenario other than WW3, or a gigantic hack attack that leaves me with nothing more than a whiskey compass."

And I doubt I would have a critical need to go flying in either of those scenarios... LOL

A lot of people swear by their SIRS compass. I've had incredibly good performance from Precision Vertical Card compasses in my last 3 airplanes (including the tube-and-fabric '65 Citabria I'm flying now). Most of the people who report problems with these devices are not using the correct mount for their airplane, or the "cushions" in the mount are totally worn out. (Although one airplane did require the optional "compass compensator" (ACS part number 10-07900), because there was so much residual magnetism in the frame.)

But I expect to just use the remote magnetometer with EFIS to meet the requirement.

[svyolo]

It looks to me the top of the windshield has the least metal proximity, followed by the top of the instrument panel.It is close. Every tube and fabric airplane has one somewhere. It is obviously doable.

I know you are required to have some magnetic reference by regulation. I just can't imagine a scenario other than WW3, or a gigantic hack attack that leaves me with nothing more than a whiskey compass.

[zkelley2]

I think the best location for a wet compass would be top of the windscreen, centered. Get it farther away from anything electric in the panel, and farther from the engine.

It's not the panel that is the issue. The steel frame is ferrous and even somewhat magnetic in areas. Putting a compass near the v brace makes it point at one of the tubes.

From doing some reading on other forums on this, it appears you can degaus a metal frame but it will just remagnatize with flight after so many hours.

[svyolo]

I think the best location for a wet compass would be top of the windscreen, centered. Get it farther away from anything electric in the panel, and farther from the engine.

[zkelley2]

Zkelly, have you measured your Mag Flux number yet? My "Mag Flux" number when I put my phone on top of the instrument panel was 43. That is about what the number was when I was walking out to the workshop. I'm not worrying any more about this and will install the classic whiskey compass there.

Using the iPhone app to obtain a quantifiable number to the magnetic issue sure removes the hocus-pocus element for me. If I cant measure it or I choose not to then its luck if it works, and a mystery if it doesn't. A Mysterious problem can suck enthusiasm out of me for the project. A man has got to know his limitations.

Nah, I decided it's more trouble than worth.

[svyolo]

I don't remember being taught the use, correction, or anything else in any commercial aircraft. Maybe in 95-96 when I was an FE on a 727 I had to know something.

I guess if you have an old school DG that you need to reslave, a wet compass has a use. Other than that, knowing your course is much more useful. If you know your course, even if it comes off a phone, you have better navigation than a wet compass.

A couple of years ago they installed some com equipment on our 737's that were causing dual FMC (old school IFR navigator) failures. All of our flights were overwater/class II (no radio navaids available)/ETOPS. But we had a wet compass. But we also had 2 IPADS. We never even glanced at the compass. It was a bit annoying, but kind of a no brainer. Heading select and keep yourself on the magenta line on the IPAD.

[zkelley2]

Honestly I dont even know.

What I'm trying to do is have backups for ifr.

In instrument training compass turns worked great.

[jaredyates]

What does the correction card look like on the Boeing? On the Embraer card it's up to 30 degrees on some headings. Between the airframe errors, the dip errors, the lag, the traditional compass is not something that seems useful to me. But in preparing for instrument flight, your comfort is what matters, not anyone else's of course.

[whee]

Maybe consider a Sirs compass. That’s what I would put in if I had needed to. The EFIS magnetometer meets the requirement so you’ll only need one it you want one.

I haven’t navigated off a compass or really even looked at one in forever. I actually don’t even know if my EFIS heading is accurate. Guess I should check that. Avare on my Samsung tablet works good though😉

[Bcone1381]

I wonder what Mag Flux number would if I placed it on the top of my instrument panel where the compass be installed? I wonder what I need to provide an accurate compass reading.

Zkelly, have you measured your Mag Flux number yet? My "Mag Flux" number when I put my phone on top of the instrument panel was 43. That is about what the number was when I was walking out to the workshop. I'm not worrying any more about this and will install the classic whiskey compass there.

Using the iPhone app to obtain a quantifiable number to the magnetic issue sure removes the hocus-pocus element for me. If I cant measure it or I choose not to then its luck if it works, and a mystery if it doesn't. A Mysterious problem can suck enthusiasm out of me for the project. A man has got to know his limitations.

[zkelley2]

I have an EFIS that's going in, I was just thinking for a backup for IFR. Seems imprudent to have a compass that is tied to the EFIS as a sole compass for IFR flight.

I mean we have 6 screens on the Boeing, but we have a fluid compass.

Might be overkill though. Reading 91.205 again, it looks like the EFIS remote magnetometer meets the reg for VFR day/night and IFR.

[Chris In Milwaukee]

Yep, a good option if you’re using glass.

[Chris In Milwaukee]

I'm unclear on this, I'm thinking an EFIS that uses a magnetometer fills the requirement. If that is true, then a wet compass is optional as a backup.

You’re right. OP didn’t mention an EFIS or similar; said there was an empty panel. Just have to have a magnetic heading source.

[Bdflies]

Having read, what I thought was the applicable regs, I was left a bit unclear about the requirement for a wet compass. I asked my DAR if I was required to install such, considering that 3 GPS receivers reside in my panel. He laughed and pulled his phone out. "This thing will get me anywhere I need to go!" was his reply. The G5 battery is supposed to last 4 hours. Don't get me wrong, though. I have no aversion to a nice old fashioned compass and I do use one very regularly. I just didn't feel the need to have one, in the Patrol and haven't felt lacking.

Bill