Magnetic Compass Attributes & Errors

Magnet Compass  - Errors

Magnetic North  - Earth  North and South Pole
True North  - on Sectional Charts  - have isogonic lines to add or subtract for Magnet North


Navigate off a chart designed which is based on True North and a Magnetic Compass

1. Variation - Angular difference is True and Magnetic North is know as Variation and it changes geographically. East is Least (subtract)  Isogonic line on Sectional Chart - Depicts the Variation 
2. Deviation -  Electrical Electronic system in aircraft  -  Error written on compass card and affix to front face of magnetic card. 
3. DIP Errors - Not impacted on Straight and level unaccelerated flight.
1. Turning - Accelerating or Decelerating  Magnet on the Card Tries to align on the Lines of flux of the earth between the north and south pole. 
1. Cause a downwards deflection or dip of the compass card. 
2. in a turn the compass card dips to the low side of the turn giving an incorrect Turn indication.  Most apparent on North and South heading
3. Turn from a Heading of North it will give an indication of a turn in the opposite direction 
4. Turning from heading South the direction of turn indicated is correct - The rate of turn is faster than the actual turn   (UNOS - Undershoot North Overshoot South)
1. North: Lags   - Roll out about 30 deg before actual heading anticipate lag
2. South : Leads - Roll out about 30deg more that desire heading to correct for lead.
4. Acceleration and Deceleration Error
1. Cause by inertia of the compass card  - If the airplane accelerates, on a heading of east, the inertia of the weight holds the compass card back causing the card to rotate to the North  . It stabilized and card swings to correct east indication.
2. When flying East and decelerate , inertia cause the card to move ahead and rotate towards south until the speed stabilized. 
3. Same thing happened when heading west 
4. ANDS - Accelerates North Decelerate South 

                          Section 7 of  Pilot Handbook of Aeronautical Knowledge

 
  (True Virgins Make Dark Company +w -e)

T   - True
V   - Variation
M  - Magnetic
D   - Deviation
C   - 

+W 
-E  



T   - True  45 deg
V   - Variation
M  - Magnetic
D   - Deviation
C   - 

+W 
-E