Compass swing

[piecrust]

Just read manual and can't see anywhere that warns about magnetic interference. I have it mounted with airgizmos docking station.

 

Has anyone removed the speaker out of a Garman aera 500 series?

 

 

[piecrust]

http://www.recreationalflying.com/threads/gps-and-permanent-compass-problem.37514/

 

Ok

 

 

[planesmaker]

Didn't think about that, they are steel with steel nuts under the dash. Nice jab by the way, remember reading the write up a few years ago.

Thanks. Change the screws to brass and probably fix the problem. Unless something else is also interfering. Tom

 

 

[Mark11]

My compass is out too and I bet nearly every silva compass is aswell

 

Spent a lot of time observing its reading against the GPS whilst flying on the weekend as I'm about to start Cross country endorsement training.

 

Found it varied from 15 degrees W to 15 degrees E depending on direction of travel. That means there is two directions where it is completely accurate.

 

It's a sine curve error - which im told is normal

 

I thought mine was just bad because I dropped it a couple of times - but because it's an equal error both ways I don't think so anymore

 

Now I need to make a chart for the errors so I can correct for it...

 

 

[Mike Borgelt]

My compass is out too and I bet nearly every silva compass is aswellSpent a lot of time observing its reading against the GPS whilst flying on the weekend as I'm about to start Cross country endorsement training.

 

Found it varied from 15 degrees W to 15 degrees E depending on direction of travel. That means there is two directions where it is completely accurate.

 

It's a sine curve error - which im told is normal

 

I thought mine was just bad because I dropped it a couple of times - but because it's an equal error both ways I don't think so anymore

 

Now I need to make a chart for the errors so I can correct for it...

You DO know that a GPS gives ground TRACK and a compass shows HEADING? They aren't the same?

 

If there is wind there will be two times where the track and heading are identical - when you are flying directly up or down wind. The rest of the time track and heading will be different - yes it is a sine curve error.

 

I DO hope your cross country endorsement includes some basic navigation theory.

 

 

[Guest Andys@coffs]

Also compass shows magnetic bearing, GPS generally show true bearings (mag var adjusted) so another delta to consider....

 

 

[OZJohn]

Depending where you are there is about 11 degrees difference between magnetic and true north.

 

 

[Guernsey]

Does your gps have a speaker? Some Garmin ones do???!!If it does and it's within a metre of the compass you'll have compass issues, any other instruments with speakers same thing.....Garmin should know better!! Speaker = bloody big magnet

 

Andy

I've always told my wife not to speak when I'm flying....never had any problems with my compass

 

Alan.

 

 

[Garfly]

Hi Andy,

 

You wrote in #31 above that "GPS generally show true bearings (mag var adjusted)"

 

I'd always assumed that the default on GPS devices (portables, at least) was Magnetic heading (variation automatically accounted for) and that you needed to go into the menus to set True if you wanted it. I just checked on a couple of older Garmins that I have hanging about and that does seem to be the case. Maybe it's changed more recently or maybe I misunderstood your drift. This is the relevant bit of the user manual for the GPS12.

 

 

(By the way, if we planned to fly from Esperance to Carnarvon, the point would be moot. ;-)

 

 

[Mark11]

My gps provides both !!

 

Hence why I was checking

 

 

[Mark11]

You DO know that a GPS gives ground TRACK and a compass shows HEADING? They aren't the same?If there is wind there will be two times where the track and heading are identical - when you are flying directly up or down wind. The rest of the time track and heading will be different - yes it is a sine curve error.

I DO hope your cross country endorsement includes some basic navigation theory.

You do know that GPS provides both

 

I've done the theory - thanks

 

 

[DWF]

.......By the way, if we planned to fly from Esperance to Carnarvon, the point would be moot. ;-)

The VARIATION would not be a problem as you would be flying along the agonic line - the line of NO or zero magnetic variation. But it changes depending on where you are which is I guess why they call it variation.

 

The DEVIATION of your compass could still be a problem and would have to be accounted for.

 

 

 

DWF

 

 

[Garfly]

DWF, that is True.

 

Which brings us back to the original post. ;-)

 

 

[Garfly]

Hi Mark,

 

I believe that the best way to check your compass against your gps is to fly a square course and to note the differing readings on each of the four directions. This is the only way to cancel out the wind drift factor, that is, the difference between where you're pointing and where you're going - on each leg (assuming the wind remains constant over the course). The problem is a gps never knows (or cares) which way it's actually pointing, whereas that's the only thing a compass knows - or is supposed to know! - which brings us back to the original post. ;-)

 

 

[Mark11]

Hi Mark,I believe that the best way to check your compass against your gps is to fly a square course and to note the differing readings on each of the four directions. This is the only way to cancel out the wind drift factor, that is, the difference between where you're pointing and where you're going - on each leg (assuming the wind remains constant over the course). The problem is a gps never knows (or cares) which way it's actually pointing, whereas that's the only thing a compass knows - or is supposed to know! - which brings us back to the original post. ;-)

I'm doing ground calibration in the middle of the field away from metal

 

 

[Garfly]

Sounds a lot easier. ;-)

 

Hell, we're still having so much trouble with that thousand year old technology - especially in our magnetically polluted cockpits. One wonders why we bother. Especially when the modern alternative is sooooo accurate and sooooo reliable and - especially in your well ventilated office - soooo much easier than wrangling large paper sheets to keep on track. Anyway, I suppose it's useful to learn nav in the style of the pioneers - and ded reckoning can be a lot of fun - but in any case, soon you won't be forced to tangle with that troublesome lodestone. (Except to stay legal until the laws finally catch up.)

 

 

[piecrust]

E

 

Sounds a lot easier. ;-)Hell, we're still having so much trouble with that thousand year old technology - especially in our magnetically polluted cockpits. One wonders why we bother. Especially when the modern alternative is sooooo accurate and sooooo reliable and - especially in your well ventilated office - soooo much easier than wrangling large paper sheets to keep on track. Anyway, I suppose it's useful to learn nav in the style of the pioneers - and ded reckoning can be a lot of fun - but in any case, soon you won't be forced to tangle with that troublesome lodestone. (Except to stay legal until the laws finally catch up.)

Exactly, I would much rather have as much information as possible rather than the bare minimum. So do I live with 30 deg out or throw out the gps

 

 

[Old Koreelah]

...I suppose it's useful to learn nav in the style of the pioneers - and ded reckoning can be a lot of fun - but in any case, soon you won't be forced to tangle with that troublesome lodestone. (Except to stay legal until the laws finally catch up.)

Even though my compass can be up to 30 degrees out, I don't foresee the day they'll be left out of aircraft.

 

When-not if- electronics Nav systems fail, you'll be thankful for that lodestone.

 

 

[spacesailor]

Hi,

 

You do realize there's more ships sunk do to the "lodestone" compass than anything else.

 

For the weight of the compass you can have multiple backup GPS gadgets, the men who went to the moon had two HP 41 calculators in their pockets, and they didn't miss their target.

 

spacesailor

 

 

[Garfly]

True, OldK, new fangled technologies fail us as much as the ancient ones.

 

(Though most of us seem to carry about 5 levels of back up these days.)

 

Still, it seems to me the best use of heading info these days (as opposed to track info) is in working out winds aloft.

 

I don't mean by way of E6B and lots of mental figurin' out.

 

Now it's all electronic compasses feeding heading to EFIS boxes and, voila!

 

Real time winds aloft. (at least in theory).

 

With all the other info the EFIS has on hand (track, GS, OAT and air data) all it needs is 'heading' to continuously calculate W/V.

 

And that is useful as you poke around the sky looking for the optimal level.

 

But, otherwise, I can't see much use in knowing where we're pointed when we know perfectly well where we're going and how long it'll take.

 

 

[Old Koreelah]

Hi,You do realize there's more ships sunk do to the "lodestone" compass than anything else.

For the weight of the compass you can have multiple backup GPS gadgets, the men who went to the moon had two HP 41 calculators in their pockets, and they didn't miss their target.

 

spacesailor

Perhaps true, Spacey, but I'd still rather have a "stone axe" compass than a plethora of useless gadgets when the satellite system fails.

 

 

[spacesailor]

OLDK,

 

The Hp 41 that the astronauts used, wasn't a GPS dependent but could still put you on to the Rumb-line, or do the ded-reckoning and lots of other nav calculations.

 

The big snag here is getting the N type batteries. the keypad doesn't have an equal sign, the input makes that key obsolete.

 

spacesailor

 

 

[Guest Andys@coffs]

Reverse Polish Notation..... Back when memory and CPU grunt was thin on the ground.

 

On my iPad I press the button down until the machine speaks to me and ask it to "solve xxxxx" where xxxx is whatever mathematical issue I'm needing an answer for.....it tells me the answer I need.....unless the maths operator can be confused for something else......cosine 45 was easy sine 45 was always sign 45 and it had trouble with that......

 

But I digress

 

 

[spacesailor]

Hi Andy s

 

That's right "Reverse Polish Notation", don't know why it didn't catch on as it seems very "Logical"

 

Just like "Esperanto" very logical ( but not practical).

 

spacesailor

 

oops I digress

 

 

[pmccarthy]

I used RPN as an engineer for forty years, now frustrated by the conventional calculator in my phone and iPad. There is probably an RPN app but I haven't looked.