Need help! Magnetic Compass Errors!

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.

"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!

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

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)

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)