Old-school Ball Magnetic Compass Question

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trimtab

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A three axis magnetometer can do the job with some big assumptions and some semitechnical filtering. But inertial measurement is so much better...why not use it? MTBF's of many, many years, etc. Laser ring interferometry (laser gyro) can last for many decades...no moving parts. Lots of options for attitude aside from mechanical angular momentum sensors (gyros).

For position, there are a lot of options as well. During the day, solar information can be used with accurate clocks to determine location to hundreds of yards without haze or perhaps a mile in haze and clouds with projects that are executed by amateurs. Without clouds, during the day and at night, celestial nav can locate to less than a mile with reasonable time accuracy. No GPS or ground stations required. Topographic location can yield position to within meters. But ground or satellite stations allow far higher accuracy and precision, so why not use them?
 

speedracer

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Magnetic compasses don’t move with the aircraft. Remember your ground school lessons about the half-dozen compass errors to be aware of?
  • Variation.
  • Deviation.
  • Magnetic Dip.
  • Oscillation.
  • Northerly Turning Error (part of magnetic dip)
  • Acceleration/Deceleration Errors (part of magnetic dip)
I just use the compass on my iPhone.
 

Richard Roller

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The key phrase is "self-erecting". Without a self-erecting mechanism, when power is applied to the AI, it will spin up in whatever attitude it was when it shut down. It needs something to provide a level reference as it spins up.

Ron Wanttaja
Very true. In the old 180 cessna I flew occasionally it had an old air corp style horizon. You had to manually cage the gyro on start up. We used to amuse ourselves in flight by entering a steep turn, cage the gyro and then level out. Then we'd wait and see how long the passengers took to notice it showing a 45° bank.
 

Dan Thomas

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Trust me, I'm learning. Not being cheap, just trying to find affordable on a disability income. If that affordable instrument isn't gyroscopic, but works well, then I won't be complaining.
You have to determine whether you NEED that gyro. It's only necessary for flight in IMC, and even then it's only helpful if you've had the IFR training. In most airplanes it's a totally unnecessary expense, and lots of weight, once you include the also-IFR-necessary heading indicator, vacuum pump, vacuum regulator, electric turn coordinator, pitot heat, alternate static source, VSI, and at least two NAV radios suitable and calibrated for enabling an IFR approach at your destination and alternate. Often also required is a transponder and encoder. More periodic calibration requirements.
 

Jimboagogo

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For many years , I've had the thought that a Magnetic Ball compass could be marked for more functionality...
Artificial Horizon
Slip, Turn and Bank Indicator

View attachment 120244

Any thoughts/ideas on such a device?
Flying mag once proposed a cat and a duck. When the wx turned too crappy and you knew no sensible duck would be in the air, throw your duck out the window and follow it down. You can always reference gravity with the cat because cats always land on their feet. Just keep dropping the cat and know that its feet will always point perpendicular to the horizon. Best of luck! Don't lose sight of the duck.
 

Pops

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Dropping cat from the airplane--- Told a story on this site one time about my old friend Sam having to stuff a tom cat out the left vent window of his Piper Tri-pacer when he was hired by an old rich widow to fly her tom cat from WV to WY. Sam said it was devil of a job to get the cat out the window.
 

Wanttaja

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Dropping cat from the airplane--- Told a story on this site one time about my old friend Sam having to stuff a tom cat out the left vent window of his Piper Tri-pacer when he was hired by an old rich widow to fly her tom cat from WV to WY. Sam said it was devil of a job to get the cat out the window.
Got a buddy that said he and some airport buddies rigged up a parachute for the airport cat and took it out to skydive. Ended up with his arm sticking straight out the window with the cat wrapped in a death-grip around it.

Ron Wanttaja
 

speedracer

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Got a buddy that said he and some airport buddies rigged up a parachute for the airport cat and took it out to skydive. Ended up with his arm sticking straight out the window with the cat wrapped in a death-grip around it.

Ron Wanttaja
In the 80's I built a hang glider for the cat. I was in the back yard test flying it with a 10 pound weight and It flew pretty good. My wife, being a mind reader, came outside and said "If you put my cat in that I'll leave you!" End of story since I'm still married.
 

Pops

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In the 80's I built a hang glider for the cat. I was in the back yard test flying it with a 10 pound weight and It flew pretty good. My wife, being a mind reader, came outside and said "If you put my cat in that I'll leave you!" End of story since I'm still married.
So that is how you get to be single again. Do you have to help in the packing ?
 

jedi

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Why be proficient with a compass. You will know when you have to shoot an ILS approach down minimums after a vacuum pump failure with no vacuum gyros. Electric T&B or Turn Coordinator only. I prefer the T&B.

As a student pilot, my instructor told me if I got caught above a cloud layer, trim for approach speed and decent on a 180 degree heading, sit on your hands, and keep the heading with the rudder until you break out the bottom. Compass is most sensitive at the 180 degree heading.
You had a good CFI. Every pilot should know this but most do not. I try to spread the word but it is hard to teach those who already know it all.
 

Topaz

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How about a light weight LIDAR setup? I know of a project...
Or, and I'm just spit-balling here, confine your ultralight flights to days when you're assured of clear weather. (/snark off)

Learn about aviation weather - the study is far less expensive and far more effective than any instrument listed in this thread (except a mag compass, which has been demonstrated not to be suitable for your purpose). You can learn aviation weather and get all the accurate forecasts you want, for your area, for a tiny fraction of the cost of any artificial-horizon technology you might find, not counting the training necessary to make that tech useful for your purpose. And a knowledgeable eye and brain will do something no instrument technology ever could: Keep you on the ground and out of of the crud in the first place.

Understand that I'm not taking a shot at you, but you seem to be looking for a technological solution to something that, for an ultralight, is really a pilot-knowledge problem.
 

jedi

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Have you ever been an instructor? The degrees of turn have nothing to do with it. The attitude indicator has no sense of direction. The forces on the airplane in flight have everything to do with it. The gyro case, inside the instrument, remains upright in the turn, and its pendulum vanes are pulled outward by the centrifugal force of the turn and confuse the instrument if the turn is maintained long enough. Ordinary turning won't do it. Not enough time.
Yes, and I do not profess to know it all and that is why I said, "If i remember correctly....."

The older versions of the Instrument FlyingHandbook((FAA H--8083-15B) had more details on the operation of the self-erecting mechanism and the errors. If you need more information I can see if I can find my old copy that gave more detail on the errors. You could with your background study the system and see for yourself why the error cancels out in a 360 degree turn. If you want to check it out in flight you need a fast airplane. It is difficult to see the error in any turn slower than 350 knots.



Page 5-19 The Attitude Indicator
"There is also a possibility of a small bank angle
and pitch error after a 180° turn. These inherent errors are
small and correct themselves within a minute or so after
returning to straight-and-level flight."

Dan,

I would like to hear your comments on the following. Are you currently teaching as a CFII?
Pops said:
Why be proficient with a compass. You will know when you have to shoot an ILS approach down minimums after a vacuum pump failure with no vacuum gyros. Electric T&B or Turn Coordinator only. I prefer the T&B.

As a student pilot, my instructor told me if I got caught above a cloud layer, trim for approach speed and decent on a 180 degree heading, sit on your hands, and keep the heading with the rudder until you break out the bottom. Compass is most sensitive at the 180 degree heading.
You had a good CFI. Every pilot should know this but most do not. I try to spread the word but it is hard to teach those who already know it all.
 

jedi

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Trust me, I'm learning. Not being cheap, just trying to find affordable on a disability income. If that affordable instrument isn't gyroscopic, but works well, then I won't be complaining. If I happen to accidentally kill myself, I still won't be complaining.

Thing is, some of what I'm learning could be applied at far lower cost than the gyroscopic gauge(s). I may not be a genius in all matters, but I am smart enough to recognise potentially useful information. I also have access to an engineer with mechanical, electronics and programming skills.

I ask for help when I should and am truly grateful for it.

At the moment, I am learning both new and old technologies in order to have a concept to at least present to my friend.
Post #33 and #54 will tell you how to use the whiskey compass to save yourself if you can understand it, master it, know it's limitations and can make it work.

Why be proficient with a compass. You will know when you have to shoot an ILS approach down minimums after a vacuum pump failure with no vacuum gyros. Electric T&B or Turn Coordinator only. I prefer the T&B.

As a student pilot, my instructor told me if I got caught above a cloud layer, trim for approach speed and decent on a 180 degree heading, sit on your hands, and keep the heading with the rudder until you break out the bottom. Compass is most sensitive at the 180 degree heading.

You had a good CFI. Every pilot should know this but most do not. I try to spread the word but it is hard to teach those who already know it all.
 
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J.L. Frusha

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Or, and I'm just spit-balling here, confine your ultralight flights to days when you're assured of clear weather. (/snark off)

Learn about aviation weather - the study is far less expensive and far more effective than any instrument listed in this thread (except a mag compass, which has been demonstrated not to be suitable for your purpose). You can learn aviation weather and get all the accurate forecasts you want, for your area, for a tiny fraction of the cost of any artificial-horizon technology you might find, not counting the training necessary to make that tech useful for your purpose. And a knowledgeable eye and brain will do something no instrument technology ever could: Keep you on the ground and out of of the crud in the first place.

Understand that I'm not taking a shot at you, but you seem to be looking for a technological solution to something that, for an ultralight, is really a pilot-knowledge problem.
Weather prediction is tricky enough subject that some of the best are wrong only 20% of the time. I've been driving by a decent weather service, in a downpour, when they announced there would be no rain. Being friends with the fella, I called him and suggested he look out the window...

In a way, you're both correct and incorrect. I'm looking for a solution to problems I've encountered, regardless, and, yes I HAVE had aviation weather. Been a while and I could use a refresher course, but no prediction is ever 100% accurate. Pop-up storms happen.

Getting down safely is more the issue. Losing track of time happens to the best, which I most certainly am not, so being prepared to land in the dark can also be an issue.
 

Topaz

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Weather prediction is tricky enough subject that some of the best are wrong only 20% of the time. I've been driving by a decent weather service, in a downpour, when they announced there would be no rain. Being friends with the fella, I called him and suggested he look out the window...

In a way, you're both correct and incorrect. I'm looking for a solution to problems I've encountered, regardless, and, yes I HAVE had aviation weather. Been a while and I could use a refresher course, but no prediction is ever 100% accurate. Pop-up storms happen.

Getting down safely is more the issue. Losing track of time happens to the best, which I most certainly am not, so being prepared to land in the dark can also be an issue.
Nope, no prediction is 100% accurate. So, let me ask the obvious question then: Why would you be flying on a day when there's any question of the weather going sour? If there's a reasonable chance the weather's going to turn bad, why are you even taking off in an ultralight? And when you take off on a good day, you're continuing to keep your eyes on the weather in-flight, right? Watching what's going on around you? That's part of being a pilot, too. You don't just take the forecast as gospel.

... Losing track of time happens to the best, which I most certainly am not, so being prepared to land in the dark can also be an issue.
No. If you're SO "losing track of time" that you can't tell the sun is going down, your situational awareness isn't in a place where you're safe to fly. And it's not like you're going to be up there for hours and hours after takeoff - you don't have the fuel. To land in darkness, you'll have to have taken off less than an hour before sunset, and why did you do that? You've got all the world's knowledge available right there on your cell phone before you take off - including the time of local sunset. There's no excuse not to know what it's going to be that day.

An ultralight is a fair-weather, daytime, local flying machine. There's no place you have to go with one, no reason to have to fly at all. If you really want to fly "whenever," maybe it's time for a PPL with an instrument rating, and the training that comes with it.
 

J.L. Frusha

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Nope, no prediction is 100% accurate. So, let me ask the obvious question then: Why would you be flying on a day when there's any question of the weather going sour? If there's a reasonable chance the weather's going to turn bad, why are you even taking off in an ultralight? And when you take off on a good day, you're continuing to keep your eyes on the weather in-flight, right? Watching what's going on around you? That's part of being a pilot, too. You don't just take the forecast as gospel.



No. If you're SO "losing track of time" that you can't tell the sun is going down, your situational awareness isn't in a place where you're safe to fly. And it's not like you're going to be up there for hours and hours after takeoff - you don't have the fuel. To land in darkness, you'll have to have taken off less than an hour before sunset, and why did you do that? You've got all the world's knowledge available right there on your cell phone before you take off - including the time of local sunset. There's no excuse not to know what it's going to be that day.

An ultralight is a fair-weather, daytime, local flying machine. There's no place you have to go with one, no reason to have to fly at all. If you really want to fly "whenever," maybe it's time for a PPL with an instrument rating, and the training that comes with it.
So, a pleasure craft, according to you is local flight only. If you're enjoying the ride you have to be stressed-out about everything every second of the flight and so forth. Yet people have made incredible journeys in ultralights without following your advice.

Uhmm... Sailplanes don't necessarily have ANY fuel, yet they commonly do cross-country flights using thermals. Many ultralights are capable of the same feats.

An ultralight is INTENDED for fair weather and daytime, as stated NO weather prediction is 100% accurate. **** happens and Mother Nature is NOT at our command.

Have you considered that there might be REASONS that I AM NOT throwing money at a Private Pilot's License and Instrument Rating?

Ultralight flight is considered a 'poor man's' way to fly. I guess, for you, that has changed.

However, if you happen to have a spare $150k, instead of a homebuilt ultralight I might possibly be able to afford something more expensive and the additional schooling... By the way, there are also additional registrations and fees I do not have the funds for. That would be part of your added expenses, as well.

(/snark-on) In the meantime, I am looking for a solution and you don't seem to have one... (/snark-off)
 
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