magnetic compass

[hallschuch]

Hi Guys,
on my series 7 I find the magnetic compass is disturbed by the airframe resulting in the impression that I'm always headed west -- what solutions are out there?
thanks,
Karl

[109JB]

Never tried it but:

https://www.aircraftspruce.com/catalog/inpages/magneticcompassshield.php

[Dave S]

Karl,

I originally installed a used vertical card compass mounted in the center-top of the cockpit off the carry through tube. Swinging the compass resulted in the best setting to be at least 165 degrees off reality or worse at any direction. Worse than worthless.

Its the magnetic flux the fuselage has developed. I suspect this is hard or impossible to avoid with electric welding.

So, got some sage wisdom from John Mc Bean......who suggested I get a SIRS compass which has a far better adjustment mechanism than the previous century's VC compass; and, if it is good enough for Boeing, it could be good enough for a Kitfox.

Next - with a good compass in hand, I experimented with placement. Turned out, the center of the cockpit over the glareshield is the place that is most infected with magnetic voodoo - at least on our plane. The best place which avoided most of the voodoo was on the left corner of the glareshield and on right corner of the glareshield. I mounted the compass on the top of the glareshield just to the left of the pilot's view out the front window. That position resulted in very minimal adjustments to get the compass right; and, my correction card has correction values of 2 degrees or less all the way around.

Happy as can be with the SIRS compass.

[Dave S]

See entry #5 under "Show us your panel" for my compass placement.

[109JB]

BTW:

On my Kitfox 4 rebuild I will not even have a wet compass installed. A "magnetic direction indicator" is only required for night or IFR flight, and on top of that the "magnetic direction indicator" doesn't have to be a wet compass. Since my airplane will have a Garmin G5, I bought the GMU11 magnetometer with it and the GMU11 will satisfy the requirements for a magnetic direction indicator. Note that a GPS direction doesn't satisfy the requirements. This was verified by talking to a FSDO maintenance inspector I know.

[alexM]

91.205 still contains magnetic direction finder for day VFR

[airlina]

In this age of the ubiquitous GPS—handheld, panel-mounted, in your phone, even in your watch—the magnetic compass seems like an anachronism, a relic of a bygone era. But when the lights go out and nothing electrical works, the trusty magnetic compass will still tell you which way you are going Although a compass is not required in an Experimental airplane for day-VFR flight, some sort of “magnetic direction indicator” is required, by way of standard operating limitations, for IFR and night operations, even in an Experimental aircraft. A primary flight display connected to a magnetometer can meet the requirement, but for the highest possible level of reliability, nothing beats the old magnetic compass. The question is, what do you need to do to make one work correctly in your airplane?

From a Kitplanes article , mine was always worthless in my day VFR Kitfox so the wet compass is a decoration on my desk. Bruce N199CL

[109JB]

In night or instrument conditions I would much prefer use my watch, phone, or tablet for GPS direction over any compass. Also, many these days are going the EFIS route and many have no round gauges. In this case, if the EFIS goes out you have lost a lot more that is concerning than a compass. I was simply pointing out that if you are comfortable not having a compass, then you don't have to put one in.

[109JB]

91.205 still contains magnetic direction finder for day VFR

91.205 is for "Standard Category" airplanes. A Kitfox is not a standard category airplane.

EDIT: Here is what the Op Lims for my project airplane state:

"UNLESS EQUIPPED FOR NIGHT AND/OR INSTRUMENT FLIGHT IN ACCORDANCE WITH FAR 91.205, AND UNTIL COMPLETION OF LIMITATION NO. 2 THIS AIRCRAFT WILL BE OPERATED DAY VFR ONLY."

The operating limitations for an amateur-built airplane determine what is required for flight in this case. Nothing is prescribed in the op lims regarding instrumentation for day VFR, only for night or IFR. For example, a replica Wright Flyer would not need a compass, airspeed indicator, altimeter, etc, and many instruments on such an airplane would just be extra weight and otherwise useless.

[jiott]

In my SS7 I am using a Falcon vertical card compass, mounted high in the exact center of my panel, just under the glare shield. After tweaking with the built-in adjustments My error in any direction does not exceed 2-3 degrees.

I am not familiar with it, but I have heard that there is degaussing equipment that will remove much of the residual magnetic effects from a steel tube airframe. If you know a person or shop with this equipment it may be worth a try; can't cost too much.

[n85ae]

Trying to remember the last time I looked at my compass and cannot remember ... :)

Phone, iPad, panel mount GPS, DG ... Never look at the compass, but I have one.

Jeff

[alexM]

91.205 is for "Standard Category" airplanes. A Kitfox is not a standard category airplane.

EDIT: Here is what the Op Lims for my project airplane state:

"UNLESS EQUIPPED FOR NIGHT AND/OR INSTRUMENT FLIGHT IN ACCORDANCE WITH FAR 91.205, AND UNTIL COMPLETION OF LIMITATION NO. 2 THIS AIRCRAFT WILL BE OPERATED DAY VFR ONLY."

The operating limitations for an amateur-built airplane determine what is required for flight in this case. Nothing is prescribed in the op lims regarding instrumentation for day VFR, only for night or IFR. For example, a replica Wright Flyer would not need a compass, airspeed indicator, altimeter, etc, and many instruments on such an airplane would just be extra weight and otherwise useless.
A new part of the regulations for me. Thanks for that.

[n85ae]

I have a SIRS as well, and it has a wide range of adjustment, but lacking facilities to Degauss my airframe I never was able
to get it to where I was happy with the alignment. It is still in there, but it's good for rough cardinal headings only. Probably
on the order of +/- 20 degrees depending on heading. I use runway heading, or GPS track 99.999% of the time.

I think the SIRS is a very nice compass, more the point is that alignment in our airframe is a huge challenge. Probably if
mag heading is really important something remote mounted in the wing would be a much better solution.

I did try degaussing my airframe as much as possible with a big mag tape demagnetizer, but not sure that it really did
anything. I recall I spent a lot of time trying to get it adjusted, but in the end accepted what I worked out as "close enough"

I put mine in the MOST "voodoo infected" location, dead center in the middle of the glareshield, and this is probably why
I suffered so much. (Dave did you ever consider having an exorcism done on you plane? It just occurred to me that this
might have been a solution).

Jeff




So, got some sage wisdom from John Mc Bean......who suggested I get a SIRS compass which has a far better adjustment mechanism than the previous century's VC compass; and, if it is good enough for Boeing, it could be good enough for a Kitfox.

Next - with a good compass in hand, I experimented with placement. Turned out, the center of the cockpit over the glareshield is the place that is most infected with magnetic voodoo - at least on our plane. The best place which avoided most of the voodoo was on the left corner of the glareshield and on right corner of the glareshield. I mounted the compass on the top of the glareshield just to the left of the pilot's view out the front window. That position resulted in very minimal adjustments to get the compass right; and, my correction card has correction values of 2 degrees or less all the way around.

Happy as can be with the SIRS compass.

[Dave S]

Quote......
I put mine in the MOST "voodoo infected" location, dead center in the middle of the glareshield, and this is probably why
I suffered so much. (Dave did you ever consider having an exorcism done on you plane? It just occurred to me that this
might have been a solution).
Unquote.....

Jeff,

Originally, after chasing ghosts for so long trying to figure this out, I did consider exorcism as a possible solution! How'd you know that!

[patrick.hvac]

Paperweight or not, in Canada you must have a compass:
"a magnetic compass or a magnetic direction indicator that operates independently of the aircraft electrical generating system"
I always wondered if a battery backup G5 or something would satisfy but I have heard of no-one who has gotten away with it.

[Maverick]

Wish I had read this before buying a new compass. I couldn't get the used one I bought from the salvage company to align. Bought a new falcon from Aircraft Spruce. No better. Mounted center above panel on glare shield. I have a Garmin Area 660 that has a several hours battery so if i were to loose electrical I'd still be okay for a while, long enough to get down safely. What a waist.
Fred