12.38.8(a) . acceleration error;
Aircraft accelerates on westerly heading
CG of the magnet system will lie slightly to the N of the point of suspension
During acceleration the inertia causes the CG to lag behind and it’s offest from the point of suspension sets up a turning moment which rotates the compass system
If viewed from above this rotation will be clockwise
When accelerating on magnetic N or S – no error
When accelerating on E or W headings the compass shows an apparent turn to the S
When decelerating on E or W headings compass shows an apparent turn to the N
12.38.8. State the effects of:
12.38.6(c) . define residual dip.
A simple bar magnet suspended from its centre of gravity will align itself horizontally with the earths lines of magnetic force
Also will take up another angle in the vertical plane
This is the magnetic Dip
The Dip happens because the centres of attraction for the earths magnetism at the poles lie deep below the surfce.
The lines of magnetic force do not parallel the earths surface
Dip is greatest at or near 90 degrees above the N and S poles and zero at or near the equator
Compensated for by being constructed with its centre of gravity (CG) well below its pivot point
In S Hemisphere the CG of the compass system is always offset slightly to the N of the pivot point
Residual dip ………
12.38.6(b) . state how it is compensated for;
A simple bar magnet suspended from its centre of gravity will align itself horizontally with the earths lines of magnetic force
Also will take up another angle in the vertical plane
This is the magnetic Dip
The Dip happens because the centres of attraction for the earths magnetism at the poles lie deep below the surfce.
The lines of magnetic force do not parallel the earths surface
Dip is greatest at or near 90 degrees above the N and S poles and zero at or near the equator
Compensated for by being constructed with its centre of gravity (CG) well below its pivot point
In S Hemisphere the CG of the compass system is always offset slightly to the N of the pivot point
Residual dip ………
12.38.6(a) . describe what it is;
A simple bar magnet suspended from its centre of gravity will align itself horizontally with the earths lines of magnetic force
Also will take up another angle in the vertical plane
This is the magnetic Dip
The Dip happens because the centres of attraction for the earths magnetism at the poles lie deep below the surfce.
The lines of magnetic force do not parallel the earths surface
Dip is greatest at or near 90 degrees above the N and S poles and zero at or near the equator
Compensated for by being constructed with its centre of gravity (CG) well below its pivot point
In S Hemisphere the CG of the compass system is always offset slightly to the N of the pivot point
Residual dip ………
12.38.6. With respect to magnetic dip:
12.38.4(c) . the functions of the fluid in the compass bowl.
– Supports some of the weight
– decreases the friction on the pivot
– dampens / decreases the oscillations of the magnet and float during flight
12.38.4(b) . define lubber line;
Direct reading compass is filoled with a liquid in which a float supporting a bar magnet is pivoted
Attached to the pivot assembly is a sompass magnet / card unit
– graduated in degrees
This can be read by the pilot against a reference marker which is known as the lubber line
– lubber line attached to the bowl of the compass
–
12.38.4(a) . describe the construction of a present-day direct-reading compass;