Emergency compass

bobmrg

bobmrg

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Bob Gardner
It might be old news to most of you, but it is news to me. The iPhone default compass app indicates direction relative to true north. I searched for iphone + compass and found a free app that lets you choose between true and magnetic. Display is like a pocket compass from back in the day, but it sure doesn't jiggle around as much as a wet compass.

Bob Gardner
 
On the iPhone if you go to settings there's an option to use true North or not, no?
 
A backup radio would be better than a backup compass.
 
I've wondered.

Does a solid-state magnetometer (like your phone) suffer the same errors as a traditional compass? Like lead/lag and such.
 
CTLSi said:
A backup radio would be better than a backup compass.
Click to expand...

Why don't you man up and answer this question - are your posts serious or are you a troll? If no answer, we can assume troll. Because it's hard to believe anyone who is serious could continue to say such impossibly stupid things on the subject of flying.
 
bobmrg said:
It might be old news to most of you, but it is news to me. The iPhone default compass app indicates direction relative to true north. I searched for iphone + compass and found a free app that lets you choose between true and magnetic. Display is like a pocket compass from back in the day, but it sure doesn't jiggle around as much as a wet compass.

Bob Gardner
Click to expand...

I knew this Bob, but it is always a good reminder. Never used it in the plane as my GPSs work fine. ;)
 
JeffDG said:
I've wondered.

Does a solid-state magnetometer (like your phone) suffer the same errors as a traditional compass? Like lead/lag and such.
Click to expand...

I think it does since it is working off the magnetic field. I think there are adjustments you can make for deviations, but I don't know for sure. I have droids now. I kicked the iWhatever habit.
 
RoscoeT said:
Why don't you man up and answer this question - are your posts serious or are you a troll? If no answer, we can assume troll. Because it's hard to believe anyone who is serious could continue to say such impossibly stupid things on the subject of flying.
Click to expand...

Whoa, RT! Take it easy now. :dunno:
 
Geico266 said:
I think it does since it is working off the magnetic field. I think there are adjustments you can make for deviations, but I don't know for sure. I have droids now. I kicked the iWhatever habit.
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Deviation, absolutely.

However, lead/lag are based upon physical properties of the compass, along with magnetic dip. Those should not exist in a solid-state magnetometer.
 
Geico266 said:
Whoa, RT! Take it easy now. :dunno:
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Maybe I should, but have you been paying attention to the junk this dude has so arrogantly been writing ever since he joined the forum? It's just hard to believe...even by internet standards. And he shows no sign of improvement or humility.
 
The Iphone's compass would be a fine backup, but if you already have a GPS nav app like Foreflight, you already have the functionality of the internal magnetometer.
 
RoscoeT said:
Maybe I should, but have you been paying attention to the junk this dude has so arrogantly been writing ever since he joined the forum? It's just hard to believe...even by internet standards. And he shows no sign of improvement or humility.
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Agreed.
 
I just fly around until I see the moss on a tree or which way an old tall chimney is tilting. (They tilt south in the N hemisphere)

Never been lost, although, sometimes I haven't known where I was.
 
bobmrg said:
It might be old news to most of you, but it is news to me. The iPhone default compass app indicates direction relative to true north. I searched for iphone + compass and found a free app that lets you choose between true and magnetic. Display is like a pocket compass from back in the day, but it sure doesn't jiggle around as much as a wet compass.

Bob Gardner
Click to expand...

Where are you going to hold the iPhone while using it as a compass? How will you know how much local disruption is impacting its compass? Lay it on a kneeboard with a steel spring clip or other magnetic material and it will be GIGO.

No thanks, that is pretty far down on my list of backup devices.
 
Jeff Oslick said:
Where are you going to hold the iPhone while using it as a compass? How will you know how much local disruption is impacting its compass? Lay it on a kneeboard with a steel spring clip or other magnetic material and it will be GIGO.

No thanks, that is pretty far down on my list of backup devices.
Click to expand...

Helps to actually try it before dismissing it:

I've had no problem using an iPhone's compass in an airplane - or anywhere in my home - or in my car. The difference between the whiskey compass was not large - certainly less than the amount of wiggle you observe in a whiskey compass in mildly turbulent air.

By the way - the chip that measures the ambient magnetic field vector in an iPhone or iPad (and probably all mobile devices using that or similar chips) yields a 3 dimensional vector. As a result, on the iPhone and iPad at least, they've programmed it so that the main relative axis (for purposes of display) points to the top or back of the device, so you can hold the iPhone upright or even upside down and see which way the device's back or top is facing. Flip it upside down and see what happens.
 
Jim Logajan said:
Helps to actually try it before dismissing it:
Click to expand...

A standard binder clip will drag the compass in my Samsung S4 off by 40 degrees, and the same binder clip will drag my Nexus 7 off by 20 degrees. YMMV with an iPhone, but I doubt it.
 
I would rather see FF use mag heading + planned TAS + GPS track to estimate a wind vector.

Sac Arrow said:
The Iphone's compass would be a fine backup, but if you already have a GPS nav app like Foreflight, you already have the functionality of the internal magnetometer.
Click to expand...
 
JeffDG said:
I've wondered.

Does a solid-state magnetometer (like your phone) suffer the same errors as a traditional compass? Like lead/lag and such.
Click to expand...
Lead / lag are due to the fact that in an aircraft you bank to make a turn and the compass banks with the airframe so you end up mixing some of the vertical component of the magnetic field with the horizontal component. If you hold your phone so that it stays flat with respect to the horizon, you will eliminate the lead / lag. If it just has accelerometers to determine "up" it will have the same problem as the whiskey compass. If it has gyros to provide the horizontal reference, then it could be compensated to avoid the lead / lag.
 
I've tried a few compass aps for my droid and can't find one that has less than a 45* error. Maybe it's the otter box that it's in. :dunno:
 
I said that it was new to me, right? Even the iPhone is new to me.

Bob
 
jordane93 said:
Is this something I can get on the Ipad?
Click to expand...

My gen 1 iPad has something for heading compasss information. It changes the sky view for constellations as you look and turn around facing different parts on the horizon.
 
I've never had a wet compass fail in flight. If flying a small airplane VFR I hardly see that as an "emergency". Even IFR if the wet compass fails unless you have a really bad precessing DG it's hardly an emergency.

YMMV
 
RoscoeT said:
Why don't you man up and answer this question - are your posts serious or are you a troll? If no answer, we can assume troll. Because it's hard to believe anyone who is serious could continue to say such impossibly stupid things on the subject of flying.
Click to expand...

Depends on the radio...I have a handheld that I can tune and track to the VOR's....Depending on the situation I might prefer one of these radios to a compass.
 
I think the smart thing to do, if you intend to use it, is to test it first. Trying holding it on your lap or the yoke mount or whatever and see what it reads. Do some circles and power changes. Move around. See how it reacts now so the first time isn't while you're lost.

As far as the smart devices go, all the aviation apps, even the free ones, can provide your GPS based mag heading. So the internal compass isn't needed.
 
Pedals2Paddles said:
As far as the smart devices go, all the aviation apps, even the free ones, can provide your GPS based mag heading.
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Nitpick: the GPS devices can only provide info on track, not heading...about the only time it would be important is knowing where to look out the window for a landmark or airport...
 
Clark1961 said:
Nitpick: the GPS devices can only provide info on track, not heading...about the only time it would be important is knowing where to look out the window for a landmark or airport...
Click to expand...

You're right. Wrong wording.
 
RotorAndWing said:
I've never had a wet compass fail in flight. If flying a small airplane VFR I hardly see that as an "emergency". Even IFR if the wet compass fails unless you have a really bad precessing DG it's hardly an emergency.

YMMV
Click to expand...

I've seen two fail... one drained all its liquid out onto the top of the panel. Another detached itself from the panel when I rotated and ended up lost in the bank checks in the back.
 
Speed said:
I've seen two fail... one drained all its liquid out onto the top of the panel. Another detached itself from the panel when I rotated and ended up lost in the bank checks in the back.
Click to expand...

Even with fluid loss the compass will still work. As for your other, well, short of crawling through check bags.......;)
 
Speed said:
I've seen two fail... one drained all its liquid out onto the top of the panel. Another detached itself from the panel when I rotated and ended up lost in the bank checks in the back.
Click to expand...

I had a compass compensator end up under a front seat on departure after a shop swung the compass...

thunk...what was that?! oh...no bueno
 
I've found the compass on my Samsung S4 to be very accurate, however sometimes it must be initialized first by moving the phone through a couple figure 8s.
 
Pedals2Paddles said:
I think the smart thing to do, if you intend to use it, is to test it first. Trying holding it on your lap or the yoke mount or whatever and see what it reads. Do some circles and power changes. Move around. See how it reacts now so the first time isn't while you're lost.

As far as the smart devices go, all the aviation apps, even the free ones, can provide your GPS based mag heading. So the internal compass isn't needed.
Click to expand...

No GPS, alone, will give heading.
 
I must be missing something, but I thought the "backup compass" was that funny thing with the numbers on it floating in the kerosene above the instrument panel.

The primary compass is the DG. Not all airplanes have them, but most do. When that goes TU, you fly the mag compass. When Hell freezes over and that goes TU as well, you use landmarks on the ground.

I've definitely had multiple DG failures. But a mag compass failure? Only if it leaks and no one pays attention. Which is problematic from a 91.205 standpoint.

Note that mounting your iPad so that the mag compass doesn't work makes your airplane unairworthy.

Not all those tablet magnetometers work worth a damn, especially around electronic equipment (sometimes, it would seem, even the tablet itself). Never bet your life on untested equipment, or you may lose the bet.
 
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I've had a wet compass tumble and lock up in the Pitts. But it takes more of a beating than a compass in a Cessna. ;)
 
MAKG1 said:
Not all those tablet magnetometers work worth a damn, especially around electronic equipment (sometimes, it would seem, even the tablet itself). Never bet your life on untested equipment, or you may lose the bet.
Click to expand...

Magnetic field distortion should affect a traditional compass in the same way that the magnetometers in a tablet should be affected. Unless you think they are somehow different in that the measure different forms of magnetic fields!?

I think that the same caveats apply to use of any compass - keep it as far as possible from ferrous or other metal alloys that may distort magnetic fields. The one nice advantage of, say, an iPhone is that you can hold it vertically to get a steady reading - something you can't do with a traditional compass. Obviously the latter needs no power.

As to untested equipment - it should not take that long to check the operation of a compass in a cockpit or on the hiking trail. I found it works best to simply hold an iPhone in my hand maybe a foot or two away.
 
Jim Logajan said:
Magnetic field distortion should affect a traditional compass in the same way that the magnetometers in a tablet should be affected. Unless you think they are somehow different in that the measure different forms of magnetic fields!?
Click to expand...

No. Flux gate magnetometers are subject to EMI that permanent magnets are not.

Your whiskey compass won't give a damn about RF in the cockpit. Your tablet will. There is a reason such magnetometers, when installed in an aircraft by someone who knows what they are doing, aren't anywhere near the avionics. Typically in the tailcone or a wingtip, occasionally on the roof. Never in or near the panel.

Jim Logajan said:
to untested equipment - it should not take that long to check the operation of a compass in a cockpit or on the hiking trail. I found it works best to simply hold an iPhone in my hand maybe a foot or two away
Click to expand...

You carry your avionics stack on the hiking trail?

Change conditions of the "test" from reality, and you don't have a test. And at a minimum, you'll need a transit/orienteering compass and the skills to use it accurately to make your test.
 
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