On Sat, 15 May 2004 12:33:25 GMT, "Roger Long"
om wrote:

A recent compass swing on our plane has turned up some opinions about
magnetic compasses that are surprising to me..

A club member has asked me why we spent money to have a 14 degree error
removed from our compass since it is just a back up instrument if everything
else quits. He just sets the DG to the runway heading on takeoff and uses
that. A couple of 360 in our 172 to look at something on the ground will
put our DG 15 -20 degrees off and it drifts about that much each hour. That
doesn't seem to concern him.

An A&P I asked in another forum said he hopes his customers don't expect him
to get the compass closer than about 10 degrees. Our shop says 10 degrees
is what is allowed.


the australian standard is 5 degrees maximum error with an annual
compass swing.
most compasses will be well within that.

most common problem is a leaking diaphragm followed by some wear on
the spindle. both are easily repaired by someone knowledgable.

yes it does matter. when you need it most is a situation where you
cant recognise a damn thing below and will need to fly a known bearing
until something that you do recognise comes into view.

they are pretty reliable in a pinch since the earth's magnetic field
doesnt have an off switch :-)

Stealth Pilot