How can a compass suddenly go out by 20 degrees?

[Bob Chilcoat]

Recently one of my partners reported that the compass (standard whiskey
compass, not a vertical card) on our Archer was reading 20-25 degrees off of
runway heading at departure. Today a new partner was up with an instructor
for his sign off and reported the same thing. I hadn't noticed, but we seem
to have a definite problem. Nothing has changed in the plane for a long
time. We recently replaced the old Garmin GPS with a Lowrance AirMap 300
(which has its antenna on the top of the glare shield near the compass), but
the first incident was before that substitution was made. Any idea how
something like this can happen?

--
Bob (Chief Pilot, White Knuckle Airways)

[Jay Smith]

Bob Chilcoat wrote:
> Recently one of my partners reported that the compass (standard whiskey
> compass, not a vertical card) on our Archer was reading 20-25 degrees off of
> runway heading at departure. Today a new partner was up with an instructor
> for his sign off and reported the same thing. I hadn't noticed, but we seem
> to have a definite problem. Nothing has changed in the plane for a long
> time. We recently replaced the old Garmin GPS with a Lowrance AirMap 300
> (which has its antenna on the top of the glare shield near the compass), but
> the first incident was before that substitution was made. Any idea how
> something like this can happen?


Move the antenna and you will observe the compass swing. Although the
antenna cable is theoretically shielded (?), the leakage of the electric
field affects the adjacent magnetic field, thereby affecting the
magnetic compass.

[Don Tuite]

On Sun, 15 Feb 2004 05:08:30 GMT, Jay Smith >
wrote:

>Bob Chilcoat wrote:
>> Recently one of my partners reported that the compass (standard whiskey
>> compass, not a vertical card) on our Archer was reading 20-25 degrees off of
>> runway heading at departure. Today a new partner was up with an instructor
>> for his sign off and reported the same thing. I hadn't noticed, but we seem
>> to have a definite problem. Nothing has changed in the plane for a long
>> time. We recently replaced the old Garmin GPS with a Lowrance AirMap 300
>> (which has its antenna on the top of the glare shield near the compass), but
>> the first incident was before that substitution was made. Any idea how
>> something like this can happen?
>
>
>Move the antenna and you will observe the compass swing. Although the
>antenna cable is theoretically shielded (?), the leakage of the electric
>field affects the adjacent magnetic field, thereby affecting the
>magnetic compass.

Doubtful. No DC. A screwdriver in the glove box is more likely.

Don

[Mark Mallory]

Bob Chilcoat wrote:

> Recently one of my partners reported that the compass (standard whiskey
> compass, not a vertical card) on our Archer was reading 20-25 degrees off of
> runway heading at departure. Today a new partner was up with an instructor
> for his sign off and reported the same thing. I hadn't noticed, but we seem
> to have a definite problem. Nothing has changed in the plane for a long
> time. We recently replaced the old Garmin GPS with a Lowrance AirMap 300
> (which has its antenna on the top of the glare shield near the compass), but
> the first incident was before that substitution was made. Any idea how
> something like this can happen?


I had a problem with the Airpath compass in my '182, which at first seemed very
similar to what you describe. Turns out it wasn't a magnetic-field-related
problem; rather, the compass was simply "sticking". The compass has a flexible
diaphragm at the rear of the housing to allow for fluid expansion; the diaphragm
is separated from the main volume of the housing by a thin (non-magnetic) metal
plate. Apparently, pressure changes had caused the diaphragm to force the plate
forward, such that it would occasionally come in contact with the compass card,
causing the card to stick. The sticking would only happen on certain headings
with certain pitch attitudes; it worked fine most of the time.

I replaced the original compass with the same model Airpath, but after about two
years the replacement compass developed the same problem! I finally replaced IT
with one of these:

http://www.vargaair.com/navigator.htm

which works great (looks cool at night too.)

Mark/C182L

[Roy Smith]

In article >,
"Bob Chilcoat" > wrote:

> Recently one of my partners reported that the compass (standard whiskey
> compass, not a vertical card) on our Archer was reading 20-25 degrees off of
> runway heading at departure. Today a new partner was up with an instructor
> for his sign off and reported the same thing. I hadn't noticed, but we seem
> to have a definite problem. Nothing has changed in the plane for a long
> time. We recently replaced the old Garmin GPS with a Lowrance AirMap 300
> (which has its antenna on the top of the glare shield near the compass), but
> the first incident was before that substitution was made. Any idea how
> something like this can happen?
>
> --
> Bob (Chief Pilot, White Knuckle Airways)
>
>
>

There are two basic possibilities:

1) Something is wrong with the compass. Things that can go wrong with
compasses include leaking fluid, worn or damaged bearings, or somebody
twiddling with the conmpensation magnets.

2) Something changed in the environment the compass operates in. The
aircraft has its own magnetic field. What the compass senses is the
(vector) sum of the Earth's field and the aircraft's field (this is what
the compensating magnets compensate for). If you've had equipment
installed or removed, or wires re-routed, this could cause the problem.

Note that "installed" doesn't mean it's got to be bolted in. If it's in
the plane, it'll affect things. Maybe your partner is carrying
something in his flight bag that might affect things?

[rip]

Actually, I think most GPS antennae do receive DC through the coax to
power the preamplifier in the antenna.

Rip

Don Tuite wrote:
> On Sun, 15 Feb 2004 05:08:30 GMT, Jay Smith >
> wrote:
>
>
>>Bob Chilcoat wrote:
>>
>>>Recently one of my partners reported that the compass (standard whiskey
>>>compass, not a vertical card) on our Archer was reading 20-25 degrees off of
>>>runway heading at departure. Today a new partner was up with an instructor
>>>for his sign off and reported the same thing. I hadn't noticed, but we seem
>>>to have a definite problem. Nothing has changed in the plane for a long
>>>time. We recently replaced the old Garmin GPS with a Lowrance AirMap 300
>>>(which has its antenna on the top of the glare shield near the compass), but
>>>the first incident was before that substitution was made. Any idea how
>>>something like this can happen?
>>
>>
>>Move the antenna and you will observe the compass swing. Although the
>>antenna cable is theoretically shielded (?), the leakage of the electric
>>field affects the adjacent magnetic field, thereby affecting the
>>magnetic compass.
>
>
> Doubtful. No DC. A screwdriver in the glove box is more likely.
>
> Don

[Dave Stadt]

"rip" > wrote in message
. com...
> Actually, I think most GPS antennae do receive DC through the coax to
> power the preamplifier in the antenna.
>
> Rip

You are correct. My Garmins do exacly that.


> Don Tuite wrote:
> > On Sun, 15 Feb 2004 05:08:30 GMT, Jay Smith >
> > wrote:
> >
> >
> >>Bob Chilcoat wrote:
> >>
> >>>Recently one of my partners reported that the compass (standard whiskey
> >>>compass, not a vertical card) on our Archer was reading 20-25 degrees
off of
> >>>runway heading at departure. Today a new partner was up with an
instructor
> >>>for his sign off and reported the same thing. I hadn't noticed, but we
seem
> >>>to have a definite problem. Nothing has changed in the plane for a
long
> >>>time. We recently replaced the old Garmin GPS with a Lowrance AirMap
300
> >>>(which has its antenna on the top of the glare shield near the
compass), but
> >>>the first incident was before that substitution was made. Any idea how
> >>>something like this can happen?
> >>
> >>
> >>Move the antenna and you will observe the compass swing. Although the
> >>antenna cable is theoretically shielded (?), the leakage of the electric
> >>field affects the adjacent magnetic field, thereby affecting the
> >>magnetic compass.
> >
> >
> > Doubtful. No DC. A screwdriver in the glove box is more likely.
> >
> > Don
>

[RJ]

Bob,

This happens with precision when I turn on the airconditioning in my
Bonanza. (It's described in the POH.) While I realize you're probably
not running AC in the winter, it does show how equipment can affect
the compass. Have you noticed a difference with and without the master
turned on?

Rob


Mark Mallory > wrote in message >...
> Bob Chilcoat wrote:
>
> > Recently one of my partners reported that the compass (standard whiskey
> > compass, not a vertical card) on our Archer was reading 20-25 degrees off of
> > runway heading at departure. Today a new partner was up with an instructor
> > for his sign off and reported the same thing. I hadn't noticed, but we seem
> > to have a definite problem. Nothing has changed in the plane for a long
> > time. We recently replaced the old Garmin GPS with a Lowrance AirMap 300
> > (which has its antenna on the top of the glare shield near the compass), but
> > the first incident was before that substitution was made. Any idea how
> > something like this can happen?
>
>
> I had a problem with the Airpath compass in my '182, which at first seemed very
> similar to what you describe. Turns out it wasn't a magnetic-field-related
> problem; rather, the compass was simply "sticking". The compass has a flexible
> diaphragm at the rear of the housing to allow for fluid expansion; the diaphragm
> is separated from the main volume of the housing by a thin (non-magnetic) metal
> plate. Apparently, pressure changes had caused the diaphragm to force the plate
> forward, such that it would occasionally come in contact with the compass card,
> causing the card to stick. The sticking would only happen on certain headings
> with certain pitch attitudes; it worked fine most of the time.
>
> I replaced the original compass with the same model Airpath, but after about two
> years the replacement compass developed the same problem! I finally replaced IT
> with one of these:
>
> http://www.vargaair.com/navigator.htm
>
> which works great (looks cool at night too.)
>
> Mark/C182L

[Jim Weir]

Oh, fer corn sake. Not likely. The cable isn't theoretically shielded, it is
shielded. The leakage of the electric field? You mean the e-field of the
sub-microvolt GPS signal or the e-field of the three or four milliamps into the
antenna amplifier? Not likely. Not through a tinned copper braid shield.

More likely that the antenna has a steel mounting plate. Move the antenna or
remove the mounting plate.

Jim



Jay Smith >
shared these priceless pearls of wisdom:


->
->Move the antenna and you will observe the compass swing. Although the
->antenna cable is theoretically shielded (?), the leakage of the electric
->field affects the adjacent magnetic field, thereby affecting the
->magnetic compass.





Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[Don Tuite]

Ok. But he should check the glovebox anyway.

Don

On Sun, 15 Feb 2004 14:56:03 GMT, rip >
wrote:

>Actually, I think most GPS antennae do receive DC through the coax to
>power the preamplifier in the antenna.
>
>Rip
>
>Don Tuite wrote:
>> On Sun, 15 Feb 2004 05:08:30 GMT, Jay Smith >
>> wrote:
>>
>>
>>>Bob Chilcoat wrote:
>>>
>>>>Recently one of my partners reported that the compass (standard whiskey
>>>>compass, not a vertical card) on our Archer was reading 20-25 degrees off of
>>>>runway heading at departure. Today a new partner was up with an instructor
>>>>for his sign off and reported the same thing. I hadn't noticed, but we seem
>>>>to have a definite problem. Nothing has changed in the plane for a long
>>>>time. We recently replaced the old Garmin GPS with a Lowrance AirMap 300
>>>>(which has its antenna on the top of the glare shield near the compass), but
>>>>the first incident was before that substitution was made. Any idea how
>>>>something like this can happen?
>>>
>>>
>>>Move the antenna and you will observe the compass swing. Although the
>>>antenna cable is theoretically shielded (?), the leakage of the electric
>>>field affects the adjacent magnetic field, thereby affecting the
>>>magnetic compass.
>>
>>
>> Doubtful. No DC. A screwdriver in the glove box is more likely.
>>
>> Don

[Dennis O'Connor]

Sounds like something steel was introduced and has now become magnetized...
denny
"Roy Smith" > wrote in message
...
> In article >,
> "Bob Chilcoat" > wrote:
>
> > Recently one of my partners reported that the compass (standard whiskey
> > compass, not a vertical card) on our Archer was reading 20-25 degrees
off of
> > runway heading at departure. Today a new partner was up with an
instructor
> > for his sign off and reported the same thing. I hadn't noticed, but we
seem
> > to have a definite problem. Nothing has changed in the plane for a long
> > time. We recently replaced the old Garmin GPS with a Lowrance AirMap
300
> > (which has its antenna on the top of the glare shield near the compass),
but
> > the first incident was before that substitution was made. Any idea how
> > something like this can happen?
> >
> > --
> > Bob (Chief Pilot, White Knuckle Airways)
> >
> >
> >
>
> There are two basic possibilities:
>
> 1) Something is wrong with the compass. Things that can go wrong with
> compasses include leaking fluid, worn or damaged bearings, or somebody
> twiddling with the conmpensation magnets.
>
> 2) Something changed in the environment the compass operates in. The
> aircraft has its own magnetic field. What the compass senses is the
> (vector) sum of the Earth's field and the aircraft's field (this is what
> the compensating magnets compensate for). If you've had equipment
> installed or removed, or wires re-routed, this could cause the problem.
>
> Note that "installed" doesn't mean it's got to be bolted in. If it's in
> the plane, it'll affect things. Maybe your partner is carrying
> something in his flight bag that might affect things?

[[email protected]]

Bob Chilcoat > wrote:
: Recently one of my partners reported that the compass (standard whiskey
: compass, not a vertical card) on our Archer was reading 20-25 degrees off of
: runway heading at departure. Today a new partner was up with an instructor
: for his sign off and reported the same thing. I hadn't noticed, but we seem
: to have a definite problem. Nothing has changed in the plane for a long
: time. We recently replaced the old Garmin GPS with a Lowrance AirMap 300
: (which has its antenna on the top of the glare shield near the compass), but
: the first incident was before that substitution was made. Any idea how
: something like this can happen?

: --
: Bob (Chief Pilot, White Knuckle Airways)

I had a compass problem that ended up coming from the coaxial cable going to the
GPS antenna. The RG-142B coax has a copper-clad steel center conductors and running it
up the center pillar in my Cherokee caused the compass to have an error. If you swapped
your GPS's, this could have happened.

It doesn't have to be a magnet in the area to cause problems... just some magnetic
material (like unmagnetized iron/sheet metal/etc). Might also check any bracketry or
screws that may have been replaced. I know the stock compass mounting screws are usually
brass for that reason.

Basically, if it's not just a broken compass but is truly magnetic
interference, you need to find out *absolutely everything* that changed between when it
worked an when it was off. Even stupid little things can cause the error.

-Cory




--
************************************************** ***********************
* The prime directive of Linux: *
* - learn what you don't know, *
* - teach what you do. *
* (Just my 20 USm$) *
************************************************** ***********************

[Brian Cox]

I used to own a 1969 Mooney M-20C Ranger. I know your's isn't a
Mooney, but I can tell you of similar problems and how I was able to
fix them. Perhaps you might benefit from my experience. Mooneys have
a steel cage with non-stressed aluminum over the cockpit forward, and
use monocoque aluminum construction aft of the cabin. The wet
compass, an Airpath, worked just fine for at least the first year that
I owned the airplane (1996-1997). After a time, it would exhibit up
to 40 degree errors, and this was an intermittent problem.
I researched the problem and found that one way to fix the
problem was to degauss the steel cage. Seems that there are a lot of
ground loops in the plane, as most systems just use the aluminum as
ground. The currents can eventually cause the steel cage to be
magnetized. Or so it is said. I got lots of advice on how to do it.
One of the better Mooney shops can rent out a de-gausser.
Alternately, I heard that they are available at a local TV repair shop
(although I doubt that many folks get TVs repaired any more). The
device, as I understand it, wraps around the steel tube. The operator
presses a button, holds it down, then removes the device from the
aircraft before letting go of the button. I heard that it was
sufficient to wrap it around the post in the center of the windshield.
Now for the confusing part. I had advice all over the map. One
shop said that the procedure described above was all I had to do.
Another said that I had to remove all electrical equipment from the
panel before doing the process. That is, take out all radios, and all
instruments. Even the ammeter and fuel gauges, etc. For anyone who
has worked on a Mooney panel, this is a very daunting task. Since I
couldn't get consensus, and didn't know if the procedure would even
work, I continued investigation.
Since the problem was intermittent, I asked the folks flying the
plane what the conditions were. Here in Colorado, we have a pretty
dry climate. It seemed that the problem was worse if there was
precipitation, even if just misty or foggy. That led me to suspect
P-static. I drove all around my home field and looked at the Mooneys
taht were tied down. None of them had static wicks, and neither did
mine. All the other brands of aircraft had at least a few.
I decided to spend about ~$300 on a static wick kit. This
included 15 wicks (three each for ailerons, elevators and rudder), and
the threaded attachments that rivet to the control surfaces. It also
included all of the STC paperwork. The wicks themselves were the
solid jet style and were about 3" long. After installing them, the
compass problem went away.
Just my experience. It may not apply to your situation, but you
may have a look at the static wicks on your plane to see if they are
in OK condition. I also have owned a Cessna single, a T207. It had
about 3-5 static wicks, the flexible rope style. I now have a 310
with a few of the rope style. I haven't seen any effects of P-static
on either of these planes, and have flown a lot more in instrument and
skuddy conditions.

Hope this is helpful,
Brian Cox

[Jim Weir]

I've got a stupid question. Why would somebody use silver-plated copper coated
steel coax with teflon dielectric at about a buck a foot RG-142 when any decent
active antenna will drive 50' of nickel a foot and no magnetic errors RG-174?

Jim



shared these priceless pearls of wisdom:

-> I had a compass problem that ended up coming from the coaxial cable
going to the
->GPS antenna. The RG-142B coax has a copper-clad steel center conductors and
running it
->up the center pillar in my Cherokee caused the compass to have an error.



Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[G.R. Patterson III]

Jim Weir wrote:
>
> I've got a stupid question. Why would somebody use silver-plated copper coated
> steel coax with teflon dielectric at about a buck a foot RG-142 when any decent
> active antenna will drive 50' of nickel a foot and no magnetic errors RG-174?

Jim, dontcha know? If it costs more, it's gotta be better. :-)

George Patterson
A diplomat is a person who can tell you to go to hell in such a way that
you look forward to the trip.

[[email protected]]

Two words:

Installation manual.


That's the last time I'll follow one of those. Oh wait... DOH! :)

-Cory

Jim Weir
> wrote:
: I've got a stupid question. Why would somebody use silver-plated copper coated
: steel coax with teflon dielectric at about a buck a foot RG-142 when any decent
: active antenna will drive 50' of nickel a foot and no magnetic errors RG-174?

: Jim


:
: shared these priceless pearls of wisdom:

: -> I had a compass problem that ended up coming from the coaxial cable
: going to the
: ->GPS antenna. The RG-142B coax has a copper-clad steel center conductors and
: running it
: ->up the center pillar in my Cherokee caused the compass to have an error.



: Jim Weir (A&P/IA, CFI, & other good alphabet soup)
: VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
: http://www.rst-engr.com

--
************************************************** ***********************
* The prime directive of Linux: *
* - learn what you don't know, *
* - teach what you do. *
* (Just my 20 USm$) *
************************************************** ***********************

[Javier Henderson]

Jim Weir > writes:

> I've got a stupid question. Why would somebody use silver-plated copper coated
> steel coax with teflon dielectric at about a buck a foot RG-142 when any decent
> active antenna will drive 50' of nickel a foot and no magnetic errors RG-174?

Same reason people will buy this:

http://www.stereotimes.com/cables071003.shtm

-jav

[Roy Smith]

In article >,
Javier Henderson > wrote:

> Jim Weir > writes:
>
> > I've got a stupid question. Why would somebody use silver-plated copper
> > coated
> > steel coax with teflon dielectric at about a buck a foot RG-142 when any
> > decent
> > active antenna will drive 50' of nickel a foot and no magnetic errors
> > RG-174?
>
> Same reason people will buy this:
>
> http://www.stereotimes.com/cables071003.shtm
>
> -jav

That's hilarious. I assume this is for real? People really do buy
these things? I was waiting for the part where they said they're
lovingly assembled by virgins and all the welds are x-rayed.

[Dennis O'Connor]

uhhh, are any of those virgins looking for a new challenge?
denny

"Roy Smith" > wrote in message > > I was waiting for the part
where they said they're
> lovingly assembled by virgins and all the welds are x-rayed.

[Jay Somerset]

On 16 Feb 2004 17:26:24 -0800, Javier Henderson > wrote:

> Jim Weir > writes:
>
> > I've got a stupid question. Why would somebody use silver-plated copper coated
> > steel coax with teflon dielectric at about a buck a foot RG-142 when any decent
> > active antenna will drive 50' of nickel a foot and no magnetic errors RG-174?
>
> Same reason people will buy this:
>
> http://www.stereotimes.com/cables071003.shtm

This article is reminiscent of the "blue windshield corner lights cut
headlight glare," or "new gizmo increases gas mileage 500% -- for only
$19.95," and similar automotive nonsense addvertisements )


>
> -jav

[Bob Chilcoat]

Thanks for all the suggestions. I went out today and looked at the plane
myself (I had only heard about this via a couple of my partners. Turns out
that someone had riveted a compensation magnet to the windshield post behind
the compass, with a really crumby bracket made from very thin aluminum
sheet. Somehow this had been bent a few tenths out of line, probably by
someone parking their headset on the glare shield. It was obvious that it
was out of position, because you could see where it had originally been by
paint marks. When I pushed it back to near the original position, the
compass swung back to near the correct reading. Unfortunately, now that the
bracket is bent, it will not go back to the original position without being
removed and straightened. Since I don't want to drill out the rivet in 25
degree weather, I duct taped it back into position and will fix it properly
when spring finally gets here. Actually, I think I'll try and swing the
compass without it first, and see if it's really necessary at all.

Next question, can a non-A&P owner swing a compass, or must I have a real
mechanic do it?

BTW, the GPS antenna and cable has no effect on the compass at all, even
when right next to it with the GPS on. I knew the antenna was OK, because
the compass problem was reported before I changed to the glareshield-mounted
AirMap antenna.

Bob (Chief Pilot, White Knuckle Airways)

"Bob Chilcoat" > wrote in message
...
> Recently one of my partners reported that the compass (standard whiskey
> compass, not a vertical card) on our Archer was reading 20-25 degrees off
of
> runway heading at departure. Today a new partner was up with an
instructor
> for his sign off and reported the same thing. I hadn't noticed, but we
seem
> to have a definite problem. Nothing has changed in the plane for a long
> time. We recently replaced the old Garmin GPS with a Lowrance AirMap 300
> (which has its antenna on the top of the glare shield near the compass),
but
> the first incident was before that substitution was made. Any idea how
> something like this can happen?
>
> --
> Bob (Chief Pilot, White Knuckle Airways)
>
>
>

[Tina Marie]

In article >, Bob Chilcoat wrote:
> Recently one of my partners reported that the compass (standard whiskey
> compass, not a vertical card) on our Archer was reading 20-25 degrees off of
> runway heading at departure. Today a new partner was up with an instructor

I see you've already found the problem, but the local soaring club's
Grob has problems with the front-seat compass, and it turned out to be
related to a weld on the cabin-air vent. The mechanic managed to magnatize
it when he was welding it, and the compass swings 20-30 degrees off,
depending on the position of the cabin air vent!

So I'd check things that had been welded on recently.

Tina Marie

[G.R. Patterson III]

Bob Chilcoat wrote:
>
> Next question, can a non-A&P owner swing a compass, or must I have a real
> mechanic do it?

You cannot legally adjust the compass unless you belong to Ron Natalie's church. :-)
You can't make up a new official compass card. You *can*, however, swing the
plane through the compass points and find out how bad the situation actually is.
I have also heard of people making up their own unofficial compass card while
leaving the official one in the plane.

George Patterson
A diplomat is a person who can tell you to go to hell in such a way that
you look forward to the trip.

[James M. Knox]

"G.R. Patterson III" > wrote in
:

> You cannot legally adjust the compass unless you belong to Ron
> Natalie's church. :-)

This is, unfortunately, true. Some FSDO's will tell you that even your
A&P/IA can't do it.

> You can't make up a new official compass card.

This one is more controversial. I've heard your view. I've also heard
some folks whom I would consider very knowledgable say that you can.
[Barry Schiff has a section of a WWoF tape showing how.] Have you ever
seen anything official (and John Lynch doesn't count <G>), either way?

Yes, it's not listed in 43.13, but then since you aren't repairing
anything, it wouldn't need to be.

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

[John Galban]

"G.R. Patterson III" > wrote in message >...
>
> You cannot legally adjust the compass unless you belong to Ron Natalie's church. :-)


Hmmm... My compass has a little light inside. Now that light's
wire runs down behind the panel and into the bus. Coincidentally, the
landing light circuit is also on the same bus. Anyone for
troubleshooting a pesky landing light problem?

John Galban=====>N4BQ (PA28-180)

[Fly]

Sacramento Sky Ranch rents out a degausser.
kent Felkins





>
> I see you've already found the problem, but the local soaring club's
> Grob has problems with the front-seat compass, and it turned out to be
> related to a weld on the cabin-air vent. The mechanic managed to
magnatize
> it when he was welding it, and the compass swings 20-30 degrees off,
> depending on the position of the cabin air vent!
>
> So I'd check things that had been welded on recently.
>
> Tina Marie