Regarding the magnetic compass, note that its usefulness is not limited to
those "catastrophic blackout" emergency-landing scenarios that some of the
posts here suggest. It may be simpler events such as an in-flight restart
of
the FMS, or a handheld GPS falling on the floor in a small aircraft. In
such
cases the magnetic compass helps against straying off course until the
problem is fixed.


Hi Snowbird,

I realize that, in placing this comment here, I am indeed preaching to the
choir; but feel compelled, for the benefit of any newbies reading still
this, to add that the most common use of the magnetic compass in more fully
equipped aircraft is to correct the DG as is precesses or to verify that a
slaved DG or HSI is properly correcting for precession. I was taught to
perform this task as part of the cruise checklist at 15 minute intervals.

Best regards, and thanks for an interesting and iformative series of posts.

Peter