Need help! Magnetic Compass Errors!

[kha0z]

Hello all, I'm still very unsure about the magnetic compass errors. Mainly the Northerly Turning Error and the Acceleration Error. I been researching on them on google, and I still don't understand what they mean! If someone is free, please post a very simplified and easy to understand guide about the errors.

From what I know about Northerly Turning Error, If the plane is heading to the North, If you make a turn to East or West, there will be something wrong with the Magnetic Compass? What is it..?

Then for the Acceleration Error, If the plane were to accelerate to East or West, the magnetic compass will show a false turn to the North but if the plane decelerates, it will show a false turn to the South. But how does the magnetic compass even do that ? Thanks a lot!

Hope someone can clarify..

[BT]

The magnet likes to stay aligned with the north pole
So if heading north and you turn either to the E or W, the magnet resists
the turn and will initially indicate that you have turned the other way.
If you are heading other than north, the magnet will rush to get to north
and will accelerate towards north, giving the impression that the turn rate
is faster than actual.
So if you are heading S, E or W and make a turn, it will initially indicate
the proper direction of turn.

"kha0z" > wrote in message
...
>
> Hello all, I'm still very unsure about the magnetic compass errors.
> Mainly the Northerly Turning Error and the Acceleration Error. I been
> researching on them on google, and I still don't understand what they
> mean! If someone is free, please post a very simplified and easy to
> understand guide about the errors.
>
> From what I know about Northerly Turning Error, If the plane is heading
> to the North, If you make a turn to East or West, there will be
> something wrong with the Magnetic Compass? What is it..?
>
> Then for the Acceleration Error, If the plane were to accelerate to
> East or West, the magnetic compass will show a false turn to the North
> but if the plane decelerates, it will show a false turn to the South.
> But how does the magnetic compass even do that ? Thanks a lot!
>
> Hope someone can clarify..
>
>
>
>
> --
> kha0z

[Karl-Heinz Künzel]

kha0z schrieb:
> Hello all, I'm still very unsure about the magnetic compass errors.
> Mainly the Northerly Turning Error and the Acceleration Error. I been
> researching on them on google, and I still don't understand what they
> mean! If someone is free, please post a very simplified and easy to
> understand guide about the errors.
>
> From what I know about Northerly Turning Error, If the plane is heading
> to the North, If you make a turn to East or West, there will be
> something wrong with the Magnetic Compass? What is it..?
>
> Then for the Acceleration Error, If the plane were to accelerate to
> East or West, the magnetic compass will show a false turn to the North
> but if the plane decelerates, it will show a false turn to the South.
> But how does the magnetic compass even do that ? Thanks a lot!
>
> Hope someone can clarify..
>
>
>
>

http://en.wikipedia.org/wiki/Aircraft_compass_turns

KH

[Capt. Geoffrey Thorpe]

"Tman" > wrote in message
...
> Ever try _PARTIAL_ panel flight without visual reference?

Nope

> I mean no gyros at all, only the mag compass and pitot/static
> instruments.
> Fortunately, it would take a crazy failure mode to put one into this
> predicament -- but it could happen -- think about the effects of a
> firewall-forward fire that destroys the master switch and the vacuum pump
> plumbing.

It has happened.

Plus not all aircraft have gyros to begin with.

>
> Anyways it is real tough, but possible -- just keep saying ANDS and South
> leads North lags, etc to yourself!


The experts suggest that it is best to just point south wher the compass at
least swings in the right directon when you turn. How you manage to get
pointed south to begin with is left as an excercise for the reader.

Other things I have heard of:

Benign spiral - some aircraft can be left to their own devices - just hang
out flaps, gear, whatever you have and let go. Most authorities recommend
trying it in visual conditions in your particular aircraft first.

Spin. And hope there is enough visual altitude under the clouds.

GPS heading - works if your airspeed is high compared to wind speed.
Doesn't work, for example, in a sailplane flying in wave where the ground
speed can be near zero.

Fly straight down (or thereabouts). Heard of a guy that did this in a twin
(a spin was not an option in this aircraft). Gear out, flaps down, props
flat. Bent the airplane, but it remained in one piece. I also personally
know another guy who did this in an acro biplane - no damage in this case.

By guess and by gosh - chances are you will end up in the good old
"graveyard spiral". So when speed, noise, and G's start building try to
stop the turn with a random application of alieron - if you guess right,
things quiet down. If it gets worse, you guessed wrong - try the other way.
I read an account of someone who got out of the soup this way.

But as I understand it, most likely you will end up dead (at least in real
life - I find thing a lot easier when playing a computer game)

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

[Stefan]

BT schrieb:

> The magnet likes to stay aligned with the north pole
> So if heading north and you turn either to the E or W, the magnet resists
> the turn
....

Hilarious!

[Stefan]

Karl-Heinz Künzel schrieb:

> http://en.wikipedia.org/wiki/Aircraft_compass_turns

Did you read this article? It explains exactly nothing.

[Stefan]

Due to the construvtion principle, a whisky compass tilts when
accelerated. The result is that the vertical component of the earth's
magnetic will turn it.

[[email protected]]

On Jan 1, 9:46*am, Stefan > wrote:
> Karl-Heinz Künzel schrieb:
>
> >http://en.wikipedia.org/wiki/Aircraft_compass_turns
>
> Did you read this article? It explains exactly nothing.

A better one:
http://pilotsweb.com/navigate/compass.htm

And a better layout of the magnetic lines of force that cause compass
errors:
http://www.geology.ohio-state.edu/~vonfrese/gs100/lect25/xfig25_14.jpg

Because the lines of force are not parallel to the earth's surface
except near the equator, anytime we tip a magnetic compass's card its
magnet will want to point downward toward the earth's core. If its
level it's pretty accurate. So in turns or during acceleration or
deceleration, the card tips and the magnet points elsewhere than where
we'd like it.

Dan

[[email protected]]

On Jan 1, 11:18*am, wrote:
> On Jan 1, 9:46*am, Stefan > wrote:
>
> > Karl-Heinz Künzel schrieb:
>
> > >http://en.wikipedia.org/wiki/Aircraft_compass_turns
>
> > Did you read this article? It explains exactly nothing.
>
> * A better one:http://pilotsweb.com/navigate/compass.htm
>
> And a better layout of the magnetic lines of force that cause compass
> errors:http://www.geology.ohio-state.edu/~vonfrese/gs100/lect25/xfig25_14..jpg
>
> Because the lines of force are not parallel to the earth's surface
> except near the equator, anytime we tip a magnetic compass's card its
> magnet will want to point downward toward the earth's core. If its
> level it's pretty accurate. So in turns or during acceleration or
> deceleration, the card tips and the magnet points elsewhere than where
> we'd like it.
>
> * * * * *Dan

I should have added that at high latitudes, where the dip is
severe, the compass is not accurate and isn't used. In northern Canada
we have the Area of Compass Unreliability; see
http://gsc.nrcan.gc.ca/geomag/field/compass_e.php

In this area pilots may use the sun's true bearing tables, which give
a direction based on an accurate time. Of course, most rely on GPS...

Dan

[Capt. Geoffrey Thorpe]

"kha0z" > wrote in message
...
>
> Hello all, I'm still very unsure about the magnetic compass errors.
> Mainly the Northerly Turning Error and the Acceleration Error. I been
> researching on them on google, and I still don't understand what they
> mean! If someone is free, please post a very simplified and easy to
> understand guide about the errors.
>
> From what I know about Northerly Turning Error, If the plane is heading
> to the North, If you make a turn to East or West, there will be
> something wrong with the Magnetic Compass? What is it..?
>
> Then for the Acceleration Error, If the plane were to accelerate to
> East or West, the magnetic compass will show a false turn to the North
> but if the plane decelerates, it will show a false turn to the South.
> But how does the magnetic compass even do that ? Thanks a lot!
>
> Hope someone can clarify..
>

Simple answer (what you need to know when flying)-
If you are straight and not accelerating/decelerating - look at the
magnetic compass to determine your heading.

Otherwise, do not look at the magnetic compass.

Why?


The reason being is that the magnetic field is at an angle to the surface
of the earth. The compass does it's best to line up with the direction of
the magnetic field. When the plane of the compass is parallel to the
surface of the earth, it lines up with just the horizontal component of the
magnetic field. when you tip the compass (in a turn or due to acceleration)
it lines up along that tilted plane which brings in errors due to the
angled field.




Mount a compass on it's side and point it north/south and it will indicate
an angle in the same ball park as your latitude.



--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

[Tman[_2_]]

Ever try _PARTIAL_ panel flight without visual reference?
I mean no gyros at all, only the mag compass and pitot/static instruments.
Fortunately, it would take a crazy failure mode to put one into this
predicament -- but it could happen -- think about the effects of a
firewall-forward fire that destroys the master switch and the vacuum
pump plumbing.

Anyways it is real tough, but possible -- just keep saying ANDS and
South leads North lags, etc to yourself!


T



Capt. Geoffrey Thorpe wrote:

>
> Simple answer (what you need to know when flying)-
> If you are straight and not accelerating/decelerating - look at the
> magnetic compass to determine your heading.
>
> Otherwise, do not look at the magnetic compass.
>

>
>
>

[Mxsmanic]

"Capt. Geoffrey Thorpe" <The Sea Hawk @See My Sig.com> writes:

> Simple answer (what you need to know when flying)-
> If you are straight and not accelerating/decelerating - look at the
> magnetic compass to determine your heading.
>
> Otherwise, do not look at the magnetic compass.
>
> Why?
>
>
> The reason being is that the magnetic field is at an angle to the surface
> of the earth. The compass does it's best to line up with the direction of
> the magnetic field. When the plane of the compass is parallel to the
> surface of the earth, it lines up with just the horizontal component of the
> magnetic field. when you tip the compass (in a turn or due to acceleration)
> it lines up along that tilted plane which brings in errors due to the
> angled field.
>
>
>
>
> Mount a compass on it's side and point it north/south and it will indicate
> an angle in the same ball park as your latitude.

One of the clearest explanations I've seen. Excellent!

[kha0z]

Ok I understand much better now. Thanks a lot BT and Dan for the good answers. And thanks guys, for giving a reply too :D

[Tman[_2_]]

Great ideas!

Never heard of some of these... I am going to try the "fly the GPS
heading" and the "benign spiral"....


T


Capt. Geoffrey Thorpe wrote:
> "Tman" > wrote in message
> ...
>> Ever try _PARTIAL_ panel flight without visual reference?
>
> Nope
>
>> I mean no gyros at all, only the mag compass and pitot/static
>> instruments.
>> Fortunately, it would take a crazy failure mode to put one into this
>> predicament -- but it could happen -- think about the effects of a
>> firewall-forward fire that destroys the master switch and the vacuum
>> pump plumbing.
>
> It has happened.
>
> Plus not all aircraft have gyros to begin with.
>
>>
>> Anyways it is real tough, but possible -- just keep saying ANDS and
>> South leads North lags, etc to yourself!
>
>
> The experts suggest that it is best to just point south wher the compass
> at least swings in the right directon when you turn. How you manage to
> get pointed south to begin with is left as an excercise for the reader.
>
> Other things I have heard of:
>
> Benign spiral - some aircraft can be left to their own devices - just
> hang out flaps, gear, whatever you have and let go. Most authorities
> recommend trying it in visual conditions in your particular aircraft first.
>
> Spin. And hope there is enough visual altitude under the clouds.
>
> GPS heading - works if your airspeed is high compared to wind speed.
> Doesn't work, for example, in a sailplane flying in wave where the
> ground speed can be near zero.
>
> Fly straight down (or thereabouts). Heard of a guy that did this in a
> twin (a spin was not an option in this aircraft). Gear out, flaps down,
> props flat. Bent the airplane, but it remained in one piece. I also
> personally know another guy who did this in an acro biplane - no damage
> in this case.
>
> By guess and by gosh - chances are you will end up in the good old
> "graveyard spiral". So when speed, noise, and G's start building try to
> stop the turn with a random application of alieron - if you guess right,
> things quiet down. If it gets worse, you guessed wrong - try the other
> way. I read an account of someone who got out of the soup this way.
>
> But as I understand it, most likely you will end up dead (at least in
> real life - I find thing a lot easier when playing a computer game)
>

[Tman[_2_]]

Capt. Geoffrey Thorpe wrote:
> "Tman" > wrote in message
> ...
>> Ever try _PARTIAL_ panel flight without visual reference?
>
> Nope
>
>> I mean no gyros at all, only the mag compass and pitot/static
>> instruments.
>> Fortunately, it would take a crazy failure mode to put one into this
>> predicament -- but it could happen -- think about the effects of a
>> firewall-forward fire that destroys the master switch and the vacuum
>> pump plumbing.
>
> It has happened.
>
> Plus not all aircraft have gyros to begin with.
>
>>
>> Anyways it is real tough, but possible -- just keep saying ANDS and
>> South leads North lags, etc to yourself!
>
>
> The experts suggest that it is best to just point south wher the compass
> at least swings in the right directon when you turn. How you manage to
> get pointed south to begin with is left as an excercise for the reader.
>
> Other things I have heard of:
>
> Benign spiral - some aircraft can be left to their own devices - just
> hang out flaps, gear, whatever you have and let go. Most authorities
> recommend trying it in visual conditions in your particular aircraft first.
>
> Spin. And hope there is enough visual altitude under the clouds.
>
> GPS heading - works if your airspeed is high compared to wind speed.
> Doesn't work, for example, in a sailplane flying in wave where the
> ground speed can be near zero.
>
> Fly straight down (or thereabouts). Heard of a guy that did this in a
> twin (a spin was not an option in this aircraft). Gear out, flaps down,
> props flat. Bent the airplane, but it remained in one piece. I also
> personally know another guy who did this in an acro biplane - no damage
> in this case.
>
> By guess and by gosh - chances are you will end up in the good old
> "graveyard spiral". So when speed, noise, and G's start building try to
> stop the turn with a random application of alieron - if you guess right,
> things quiet down. If it gets worse, you guessed wrong - try the other
> way. I read an account of someone who got out of the soup this way.
>
> But as I understand it, most likely you will end up dead (at least in
> real life - I find thing a lot easier when playing a computer game)
>