The Comair crash reminds me...

Because it is in flight and has had a total electrical
failure, all I have to navigate with is my wrist watch and
the magnetic compass. In that case, I want the compass to
be the most accurate as possible. When the radios work, I
can use the VOR/GPS and even radar vectors, when all that is
dead, the compass will get you there IF it is accurate. A
10 degree error will but you off course 10 miles every 60
[57.3] miles you fly. If visibility is 5 miles an
inaccurate compass will leave you lost at sea. Maybe you
will find the coastline of the continent, but if you're hope
is land fall on an island, you need an accurate compass.



"Matt Whiting" wrote in message
...
| Jim Macklin wrote:
| The slaved compass is corrected so as many errors
| (deviation) are corrected and variation is also
corrected as
| much as possible too, so the slaved compass may be
reading
| different from the whiskey compass unless you apply the
| compass correction card FOR-Steer to get a more accurate
| setting for the HI. But the whiskey compass is not
supposed
| to have any error greater than 10 on any heading. Often
the
| compass is swung with the electrical and radios running.
It
| seems that swinging the compass should be done with the
| electrical system dead and the radios off, that is when
I'd
| want the most accurate magnetic compass.
|
| Why do you want your compass to be most accurate when your
airplane
| isn't being used?
|
| Matt