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#21
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Compass swinging?
Stache wrote: Roy Smith wrote: I've got AC 43.13-1B, which describes the procedure to swing a compass. What I can't find is the bureaucratic stuff -- who can do it (any pilot?), and what paperwork follow-up is required (airframe logbook entry, or is just making the new compass card sufficient?). Recently the compass rose has come up office conversation and who, when, how, and what type of compass survey should be accomplished. I can assure everyone reading this not all airport have a surveyed compass rose (calibrated). Many airports have compass roses that may not be accurate due to underground pipes or other metal objects that will affect the accuracy of the survey. The FAA has published a document FAA No. 405, Standards for Aeronautical Surveys and Related Products that explains why and how a compass rose should be surveyed. Next who can perform the calibration to your onboard compass installed in your aircraft? Only a Repair station with the proper ratings with the proper training, current manuals available, and proper tooling. This is where it may get sticky for some. FAR 65 Subpart D for Mechanics does NOT allow Airframe rated mechanic to calibrate compasses. Only a repair station with the proper rating can perform this task. FAR 65.81(a) excluded airframe mechanics form performing maintenance, major repairs to, and major alterations of, propellers, and any repair to, or alterations of instruments. FAR 1.1 under maintenance explains calibrations are considered a repair. So this just leaves repair stations to adjust your compass. Needless to say a pilot cannot perform this task as it is not considered preventive maintenance. AC 43.13-1B does explain how to perform a compass swing and is acceptable data however the compass rose has to be surveyed to make it legal. The repair station will make an airframe record entry stated what data the followed such as AC 43.13-1B, chapter 1, section 3. FAR 23.1327 explain the installed compass has to be accurate and all compasses are classified as instruments. Bottom line is the compass rose has to be surveyed (check with your local airport) and a repair station has to perform the compass swing and make a airframe record entry. Stache When we discussed this topic on another web page I posted this question to the FAA , and here is the answer I got from them. An A&P mechanic is authorized to approve an aircraft for return to service after performing a compass swing. Adjustment of the readily available compensating adjustments of a wet compass are included in the procedures described in AC 43.13-1B Chapter 12, Section 3. While the FAA believes that the calibration and repair of all instruments should be classified as appliance major repairs, which an A&P mechanic is not authorized to approve and return to service (see 14 CFR §65.85(a)), calibration procedures normally require the instrument case to be opened, special skill and knowledge, and the use of test equipment. Calibration does not include those adjustments of instruments and equipment which are accomplished using readily accessible simple adjusting means that do not have an appreciable effect on the airworthiness of the instrument. Swinging a compass, adjusting the compensators to minimize error, and preparation of a compass correction card is typically considered minor airframe maintenance. Charles Fellows Federal Aviation Administration General Aviation & Avionics Branch, AFS-350 Phone (202) 267-3922 Fax (202) 267-5115 I hope this clearifies the question of who can swing a compass Tom Downey A&P-IA |
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Compass swinging?
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#23
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Compass swinging?
M wrote: RST Engineering wrote: C'mon Roy, you've been around airplanes long enough to know the real answer -- "Why that compass card has been in the airplane since I bought it." Same reaction here. Doesn't everyone here have at least two GPS's onboard that show a ground track bearing 10 times better than the compass? No, and you won't either next time your alternator decides to go south. Dan |
#24
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Compass swinging?
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#25
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Compass swinging?
wrote in message ps.com... M wrote: RST Engineering wrote: C'mon Roy, you've been around airplanes long enough to know the real answer -- "Why that compass card has been in the airplane since I bought it." Same reaction here. Doesn't everyone here have at least two GPS's onboard that show a ground track bearing 10 times better than the compass? No, and you won't either next time your alternator decides to go south. Gee, Dan! Do you sleep in a house? You know, you'd be squashed like a bug when your roof collapses! -- Matt --------------------- Matthew W. Barrow Site-Fill Homes, LLC. Montrose, CO (MTJ) |
#26
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Compass swinging?
Matt Barrow wrote: wrote in message ps.com... M wrote: RST Engineering wrote: C'mon Roy, you've been around airplanes long enough to know the real answer -- "Why that compass card has been in the airplane since I bought it." Same reaction here. Doesn't everyone here have at least two GPS's onboard that show a ground track bearing 10 times better than the compass? No, and you won't either next time your alternator decides to go south. Gee, Dan! Do you sleep in a house? You know, you'd be squashed like a bug when your roof collapses! Don't be dumb. The magnetic compass is legally required because it operates independently of any electrical supply, unlike any other navigational doodad you might have. And in some areas we fly here in Canada, the mag compass has saved a lot of lives when the rest of the goodies failed. An accurate compass and a pilot able to use it is absolutely necessary for finding the way home when other stuff quits, especially the GPS. There are no other navaids in much of this country. When the visiblility is low, you can miss your airport by a mile or two and never see it. A one-degree error on a 60-mile track is a mile off course, so we teach some of our navigation exercises in an airplane with nothing more than a compass. We have had alternator failures several times over the years, even with carrying out the 500-hour alternator inspections. On the other hand, the compass is mostly useless in the far North due to magnetic dip. Up there pilots sometimes keep the "sun's true bearing" tables aboard. Dan |
#27
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Compass swinging?
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#28
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Compass swinging?
On Mon, 18 Dec 2006 11:48:14 -0500, B A R R Y
wrote: wrote: No, and you won't either next time your alternator decides to go south. Alternator? We don't need no steenkin' alternator! Both the avaiation GPS on my panel, and the portable hiking unit in my bag have alkaline power. The hiking unit even has a magnetic compass and barometric altimeter. I also have spare alkalines in my bag and flashlights. G And when the GPS signal goes out? It's happened twice. OTOH we're near the bottom of the solar cycle. BUT OT OH there was a major class 9 coronal mass ejection a week or so ago which fortunately missed us. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com |
#29
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Compass swinging?
wrote in message oups.com... Matt Barrow wrote: wrote in message ps.com... M wrote: RST Engineering wrote: C'mon Roy, you've been around airplanes long enough to know the real answer -- "Why that compass card has been in the airplane since I bought it." Same reaction here. Doesn't everyone here have at least two GPS's onboard that show a ground track bearing 10 times better than the compass? No, and you won't either next time your alternator decides to go south. Gee, Dan! Do you sleep in a house? You know, you'd be squashed like a bug when your roof collapses! Don't be dumb. Well bless my stars (as my grandfather used to say), that's a great CYA! The magnetic compass is legally required because it operates independently of any electrical supply, unlike any other navigational doodad you might have. Duh! And in some areas we fly here in Canada, the mag compass has saved a lot of lives when the rest of the goodies failed. And how many died because they navigated by compass alone and got hopelessly lost or ran into something...like a mountain? |
#30
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Compass swinging?
Matt Barrow wrote: wrote in message And how many died because they navigated by compass alone and got hopelessly lost or ran into something...like a mountain? People who run into mountains aren't using their eyes, much less the compass. That's what VFR minima are for. Anyone in the mountains in low viz is likely to die and it's not the compass' (or the government's) fault. IFR minima require a flight altitude 2000' above the peaks. As I said befo Your fancy electronics (and gyros, too) can die from any number of diseases, leaving you with only your magnetic compass, and if it isn't accurate (and you don't have your VNC handy and know exactly where you are) you might regret it. At least the mag compass will continue to work much more reliably than the electronics. ELTs are another item often ignored, and we've heard the stories of the guys down in the bush, watching the search planes fly over looking for that needle in the haystack while they think about their ELT with the long-expired battery. They've just bought the farm for the price of an ELT battery and recertification. The diaries they leave behind are sad. Dan |
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