Magnetic compass

[tazin river]

Need to replace the windshield mounted magnetic compass as the bracket wore off on my Cessna 180. Are those vertical magnetic compass any good? Are they panel mounted?

Thanks

[twotter]

Personally I don't like them. More moving parts means more chance for something to go wrong. And no, they aren't panel mounted, they need to go right back in the windshield area. Buy a normal compass and save the extra $100 for fuel...

[SuperchargedRS]

I've flown quite a few planes with them, I like them, they respond 50% like a DG 50% compass (if that makes sense), the big perk is they arnt as twitchy and are easier to read. I also have yet to see a busted one and at right around 200-300 bucks for a lit TSOed unit how can you complain! FYI they sell panel or windshield mounted ones.

http://www.cumulus-soaring.com/precision.htm

[twotter]

Let's be real, in today's world of GPS, not many people really even look at a compass so in all reality, the first time you are going to realize that your compass is out is when the Engineer tells you about it after your annual. So why would you spend extra money on it? Anybody who tells you they rely on their magnetic compass is not realistic in today's environment..

[twotter]

BTW, $250 installed and swung with a correction card from my shop.

[CID]

I generally ignore twotters musing but I feel it appropriate to write something when he gives bad and/or dangerous advise.

First let's discuss the general statement that "not many people really even look at a compass". I assume he means the standby compass but I don't want to put words in his mouth.

Second, based on the regulations, that little unappreciated compass hanging on the windscreen is required equipment for IFR flight. Good pilots, many of whom I know, regularly check the accuracy of the standby compass during flights.

Third, and perhaps most important, it's not completely unheard of that compass being the only source of heading in an airplane after certain failures.

It's a huge mistake to take the installation and availability of the standby compass so lightly.

Cheers

[burhead1]

I generally ignore twotters musing but I feel it appropriate to write something when he gives bad and/or dangerous advise.

First let's discuss the general statement that "not many people really even look at a compass". I assume he means the standby compass but I don't want to put words in his mouth.

Second, based on the regulations, that little unappreciated compass hanging on the windscreen is required equipment for IFR flight. Good pilots, many of whom I know, regularly check the accuracy of the standby compass during flights.

Third, and perhaps most important, it's not completely unheard of that compass being the only source of heading in an airplane after certain failures.

It's a huge mistake to take the installation and availability of the standby compass so lightly.

Cheers

+1

also how did "as the bracket wore off"

Always carry a basic compass as a backup and a wrist watch.

[robertsailor1]

A compass is all I have for direction, old idea but works fine. Served us well in bringing the little Bipe home..almost 3000 miles, well that and charts. The vertical one is pretty cool.

[SeptRepair]

CID, when you swing the compass annually how much do you charge? When you fill out the correction card how accurate is it? Or in other words how anal are you in ensuring the accuracy of the compass is within 1 or 2 degrees?

[azimuthaviation]

BTW, $250 installed and swung with a correction card from my shop.

Given your previous statement on your opinion of the value of a compass, if it was me, I would rather pay someone who actually gives a shit about the job theyre doing to do it. Tends to produce a better final product I have noticed.

[CID]

SeptRepair, I'm not sure what your question is trying to achieve. Are you suggesting that the compass readings have to be within 1 degree of the actual magnetic heading? Or that the compass correction card doesn't need to be reasonably accurate? I don't understand what you're asking.

[SeptRepair]

Not suggesting anything. Asked a simple question. How much do you charge for a compass swing on lets say a C-172 and what do YOU consider to be an acceptable deviation recorded on the compass correction card?

[azimuthaviation]

According to AC 43.13 it needs to be accurate to +/- ten degrees at every thirty degree test point starting from 0. The Canadian regs do not specify any other tolerances (although some nation's regulatory bodies do). Other than that it would be what the airframe manufacturer specifies, which I dont recall any being as low as one or two degrees. The slaved compass system however has tolerances as low as a degree.

[CID]

OK. Keep in mind I haven't touched a 172 in years but typically for a C172 it would take between 1 and 2 hours by the time it was done and the paperwork was finished. That includes an index swing, the correction swing and the recording swing.

Of course that depends on how far you have to move the airplane to a suitable area.

Your question about accuracy has little to do with how "anal" a person is. The standards contain the answer. Compensated readings can not be more than 10 degrees from the indicated heading. If they are, you need to figure out what the interference problem is and fix that first.

I sometimes chuckle when I see compass correction cards that say "+1" or "-1". How exactly people can someone discriminate 1 degree on a scale with 5 degree increments is beyond me. Normal instrumentation standards will tell you that you shouldn't discriminate more than half the scale increment so in this case, 2.5 degrees. That can be awkward to document so it's acceptable to round up or down to 2 or 3 degrees.

It's not really a cause for concern however. The standby compass scale uses the same increments as the main compass cards. It's not a matter of the thing being more accurate or less accurate than the main gyro stabilized compass. It's a matter of having a reasonably accurate heading source when other systems fail.

For example, when the left and right main compasses have a 30 degree split, which one is correct? Check your standby compass and see.

Or when all the EFIS tubes go blank on your Kingair, how do you maintain the vectors to the nearest airport?

http://findarticles.com/p/articles/mi_m ... n19332287/

Unfortunately this dude threw away the whiskey compass.

P.S.: The standards for maximum deviation is derived from the certification standards. Check CAR 523.1327 for little airplanes and 525.1327 for transport category and 527/529 for rotorcraft. It reads almost identically to the corresponding FAR standards.

[Cat Driver]

There is a vast spread between regulations and airmanship when it comes to flying an airplane.

Personally I fly either VFR or IFR.

I never mix the two.

If I ever got myself into a situation either VFR or IFR where I had to rely on a magnetic compass to find a safe landing area I would never ever fly again because I would know my thought process was finally affected by old age to a degree that I can no longer think properly..

[burhead1]

There is a vast spread between regulations and airmanship when it comes to flying an airplane.

Personally I fly either VFR or IFR.

I never mix the two.

If I ever got myself into a situation either VFR or IFR where I had to rely on a magnetic compass to find a safe landing area I would never ever fly again because I would know my thought process was finally affected by old age to a degree that I can no longer think properly..

If you could only remember where you left the keys to the plane you might have that opportunity.

[Cat Driver]

What makes it even worse is the key to my neighbors wife's chastity belt is on the same ring.

[dstechnical]

could someone out there tell me if a gps could be used instead of a master compass for doing a compass swing

[CID]

GPS doesn't know your heading. It knows your track along the ground. Furthermore it can't establish that track unless you're moving. So unless you have a very large area with no magnetic interference that you can taxi around in relatively long straight lines in, no.

[straightpilot]

unless you have a very large area with no magnetic interference that you can taxi around in relatively long straight lines in

That's exactly how the manufacturer of the vertical card compass say to swing them. The instructions say to carefully set the heading indicator - a runway is a good reference, if there's an approach they will be surveyed to one degree - and then in flight, do a rate one turn to a heading of north, and to swing the vertical card compass in cruise, in flight.

Back to your regularly scheduled ridiculing and personal attacks.

[twotter]

What Azimuthaviation and CID don't realise it that I really do give a shit and know more about compasses than either of them.

Have they ever thought to research what the manufacturer of the compass says regarding the swing? This will supersede AC43, but I'm sure that was just an oversight to reference it. Right?

As for CID and his drivel,

here is what he says..

"I generally ignore twotters musing but I feel it appropriate to write something when he gives bad and/or dangerous advise.

First let's discuss the general statement that "not many people really even look at a compass". I assume he means the standby compass but I don't want to put words in his mouth.

Second, based on the regulations, that little unappreciated compass hanging on the windscreen is required equipment for IFR flight. Good pilots, many of whom I know, regularly check the accuracy of the standby compass during flights.

Third, and perhaps most important, it's not completely unheard of that compass being the only source of heading in an airplane after certain failures.

It's a huge mistake to take the installation and availability of the standby compass so lightly."

Now first let's get it straight that I have more time at the top of a loop than CID has total time in an airplane. That should let you know where that is coming from. He is not a pilot and therefore not qualified to comment.

As for Azumutaviation..

Here is what she says,

"Given your previous statement on your opinion of the value of a compass, if it was me, I would rather pay someone who actually gives a shit about the job theyre doing to do it. Tends to produce a better final product I have noticed."

When I swing a compass IAW the manufacturers instructions (not AC43), I actually do it properly and with care. You are a very arrogant person to assume otherwise. Let me know what shop you own and I'll bring one of my airplanes there and see how it goes!! Even though I do think the compass is not that important in most airplanes I still do my job properly and if you would like to say I don't I'd like to have a face to face with you.
EDITED

Cheers

[CID]

EDITED

[twotter]

EDITED



As for the compass, in these days of the wonderful technology that we have people tend to not even look at it, that does not mean you don't need one but just that it's no where near as important as it once was. In most cases, as I mentioned, a professional pilot will almost never even look at one. To be ridiculed for this shows the lack of experience of those doing the ridiculing.

I will bet you Azimuth and CID have never even checked with Airpath on what the manufacturer says for how to swing their compasses.. Anyhow for all of you, here we go..

Written by Administrator
Thursday, 16 October 2008
AIRPATH INSTRUMENT COMPANY
13150 Taussig Road
Bridgeton, Missouri 63044
Tel: 314-739-8117
Fax: 314-739-1564
airpathcompass.com
COMPENSATING INSTRUCTIONS FOR AIRPATH COMPASSES

Before attempting to compensate compass, every effort should be made to place the aircraft in simulated flight conditions. Check to see that doors are closed, flaps are in retracted position, throttles set at cruise position, engine(s) operating, and aircraft in a level attitude. All electrical switches, generators, radios, etc., should be in the position they will normally be for navigation flight.

COMPENSATION

1. Set adjustment screws of compensator on zero. Zero position of adjustment screw is obtained by lining up the dot on the screw with the dot on the compensator frame.
2. Head aircraft on magnetic North heading. Adjust N-S adjustment screw until compass reads exactly North.
3. Head aircraft on magnetic East heading. Adjust E-W adjustment screw until compass reads exactly East.
4. Head aircraft on magnetic South heading. Note the resulting South error. Adjust the N-S adjusting screw until one-half of this error is removed.
5. Head aircraft on magnetic West heading. Note the resulting West error. Adjust the E-W adjusting screw until one-half of this error is removed.
6. Head aircraft in successive magnetic 30-degree headings and record all errors on the deviation card furnished with the compass.
For satisfactory results, all extraneous magnetism causing over 30-35 degree compass errors should be removed from the aircraft, or the compass should be relocated to a position where uncompensated error does not exceed 30-35 degrees. Use a brass or other non-ferrous material screwdriver when making compensator adjustments.

Best results can be obtained in actual flight compensation by following the procedure outlined below:

A. Set directional gyro from a sectional line or runway. (Allow for magnetic variation to ensure gyro corresponds to magnetic heading)
B. Follow procedures 1 through 6 above.
C. Re-check directional gyro occasionally for possible precession, and allow for such precession error in recording results on magnetic compass deviation card.
NOTE: If aircraft is equipped, GPS can be used (allow for deviation) to establish reference headings for compass compensation. This technique will eliminate possible errors caused by gyro precession.

For any questions please contact Airpath Instrument Company at the address or phone numbers listed above.

COMMON COMPENSATION PROBLEMS

Any time there is a maintenance or repair to your aircraft, it is recommended that the compass be compensated. This is particularly true if there is work associated with the removal of old and/or installation of new equipment in the instrument panel. New radios and relocation of speakers or intercoms could affect the compensation required. New hardware (i.e. screws, nuts, etc.) installed during maintenance can sometimes be the cause of excessive errors if the hardware is steel or magnetic.

Loose electrical grounds, lighting, or extended periods of parking in North-South alignment on the ramp can lead to the magnetization of the airframe itself. This is often evidenced by excessive uncompensated compass error (more than 30-35 degrees). Engine mounts on single engine aircraft and center windshield posts becoming magnetized can lead to compensation problems. demagnetizing (degaussing) the airframe component or relocating the compass will solve this problem.

Remember that every aircraft is different. Following the set-up procedures outlined above prior to compensation is important. As stated, in-flight compensation will achieve the best results. Landing gear position can sometimes affect deviation. Other factors to consider are: yoke position, cruise configuration, pilot heat, and de-icing equipment (particularly windshield anti-ice).

Operators should consider removing any jewelry while compensating compasses. Such things as watches, rings, and eyeglasses can affect the amount of compensation required. If above method does not give satisfactory results, determine the amount of uncompensated error by aligning the reference dots on the compensator adjustment screws and frame or by removing the compensator assembly from the compass. If the uncompensated error is in excess of 30-35 degrees, troubleshoot for magnetization of aircraft components or excessive electrical interference.

Last Updated ( Thursday, 18 December 2008 )

This will be a real surprise for all these "EXPERTS" who don't have a real M licence!!!

Sorry to screw all you rip off avionics shops who charge a ridiculous amount of money to swing a compass..

[sky's the limit]

I have edited this thread for personal attacks and potential outing of poster's identification. If it cannot be kept clean and civil I will lock the topic and issue time-out's to both posters engaged in this garbage. There is a good opportunity to pass knowledge along here, let's take it.

stl

[avyonx]

Don't forget the new regs about compass swings having to be done at an AMO.....Specialized Maintenance and all...