Learning Magnetic compass

RalphInCA

RalphInCA

Cleared for Takeoff
Joined
Jun 1, 2014
Messages
1,391
Location
McMinnville, OR
Display Name
RalphInCA
Home Airfield
KMMV
I'm having a heck of a time remembering all I need to know about Mag compass turning errors.

I have read about OSUN and ANDS, and I sort of comprehend, but is there is an easy to use chart or diagram summarizes all I need to know as I continue to prepare for my IR?
 
I use the above mentioned acronyms and I also read about compass errors in the PHAK. They give nice illustrations and explanations.
 
MauleSkinner said:
Find somebody that knows the foam coffee cup demonstration.
Click to expand...

I used an ashtray. It proved the theory by demonstration, but didn't help with rote nemorry for test. Stick with ANDS and (my other uncommon one).
 
Cover up your DG and do some compass turns. OSUN is a lot more obvious that way.

Make it a game to turn from north to south and back again, and roll out on heading.
 
Picture the magnetic fields dipping into the earth, and then your compass banking or pitching (due to acceleration), and you should be able to form a mental picture of the compass response. It is far easier than memorizing some acronyms and trying to remember what each letter stands for.


RalphInCA said:
I'm having a heck of a time remembering all I need to know about Mag compass turning errors.

I have read about OSUN and ANDS, and I sort of comprehend, but is there is an easy to use chart or diagram summarizes all I need to know as I continue to prepare for my IR?
Click to expand...
 
sarangan said:
Picture the magnetic fields dipping into the earth, and then your compass banking or pitching (due to acceleration), and you should be able to form a mental picture of the compass response. It is far easier than memorizing some acronyms and trying to remember what each letter stands for.
Click to expand...

Agreed. This is one concept where the moving airplane really is the best classroom. It makes so much sense when you see the compass doing funky things.

Now don't ask me to say that with respect to NDBs. :wink2:
 
MauleSkinner said:
Find somebody that knows the foam coffee cup demonstration.
Click to expand...

RalphInCA said:
What is this, pray tell? :confused:
Click to expand...

Ralph, here’s my version of the foam coffee cup.

First, jam a pencil through a cup and pretend that the pointy end is the north-seeking part of the compass needle:

Compass_Cup.jpg


Next, write the N, S, E, and W cardinal directions on the cup, along with the intermediate 30 degree numbers and ten degree tic marks, remembering everything is opposite of normal because the compass card is magnetically, albeit imperfectly held to north and the plane rotates around it.

Next, facing north and holding you compass cup in front of you, with the pencil tip pointing northward and with the big N on the eraser side facing you, bank your imaginary plane (and actual cup) and start curving off toward the west or the east.

Think about the north pole tugging on that pencil tip as the compass card housing is tilted and the plane is rotating around it as it moves from (or through) north.

Then try it while facing your "plane" to the south, with the pencil tip aimed right at your eye. Don't trip.

As you continue looking like a crazy person, flying around your living room with your compass cup, it will all start to make sense. :goofy:
 
Last edited:
DONT DO IT! ITS A PRANK!!!
I tried this once. Coffee went everywhere.
 
SixPapaCharlie said:
DONT DO IT! ITS A PRANK!!!
I tried this once. Coffee went everywhere.
Click to expand...

6PC, I believe eetrojan forgot to mention that this exercise is only to be performed while flying inverted. That should come around the third lesson.
 
[email protected] said:
First, jam a pencil through a cup and pretend that the pointy end is the north-seeking part of the compass needle:

Compass_Cup.jpg


Next, write the N, S, E, and W cardinal directions on the cup, along with the intermediate 30 degree numbers and ten degree tic marks, remembering everything is opposite of normal because the compass card is magnetically, albeit imperfectly held to north and the plane rotates around it.

Next, facing north and holding you compass cup in front of you, with the pencil tip pointing northward and with the big N on the eraser side facing you, bank your imaginary plane (and actual cup) and start curving off toward the west or the east.

Think about the north pole tugging on that pencil tip as the compass card housing is tilted and the plane is rotating around it as it moves from (or through) north.

Then try it while facing your "plane" to the south, with the pencil tip aimed right at your eye. Don't trip.

As you continue looking like a crazy person, flying around your living room with your compass cup, it will all start to make sense. :goofy:
Click to expand...
Step 7: Before you do step 1, drink all the coffee in the cup.
 
Reminiscing...

I taught ground school at Burnside Ott.

The chief instructor (Al Johnson?) had built a compass simulator that was really quite clever.

It was a little airplane on a gimbal with a compass card. It had an elastic string orienting the compass card to "North" on the platform below. When you banked the plane, the downward pull of the elastic would clearly show how compass errors worked.

Might have been a one-off - Google is not coming up with anything similar.

Does anyone else remember a device like this?
 
Long ago in a universe far away I was enrolled in the Multi-engine+Insturment course at Ft Rucker, AL flying Baron B55s and my flying mate was a member of the Ethiopian Airforce in the states for this training.

He had several thousand hours flying VFR only and was very experienced with flying using the mag compass.

He was used to flying near the equator and had a hell of a time trying to figure out why the mag compass did not just point where he wanted to go at 30* North Latitude.
 
FastEddieB said:
Reminiscing...

I taught ground school at Burnside Ott.

The chief instructor (Al Johnson?) had built a compass simulator that was really quite clever.

It was a little airplane on a gimbal with a compass card. It had an elastic string orienting the compass card to "North" on the platform below. When you banked the plane, the downward pull of the elastic would clearly show how compass errors worked.

Might have been a one-off - Google is not coming up with anything similar.

Does anyone else remember a device like this?
Click to expand...

What about <AS A TRAINING AID> using an inexpensive marine wet compass, mounted to a board, with a protractor and plumb bob to give you angle of bank info? Has anyone tried something like that?
 
Last edited:
wilkersk said:
What about <AS A TRAINING AID> using an inexpensive marine wet compass, mounted to a board, with a protractor and plumb bob to give you angle of bank info? Has anyone tried something like that?
Click to expand...

The problem is you need the centrifugal force to go along with the bank angle and the acceleration inertia for the errors to show up...you'd probably be flinging the training aid around fast enough to not be able to see it.:eek:
 
You must log in or register to reply here.
Back
Top