In article et, Bill Daniels wrote:

Every figured what you would do if
the wet compass goes TA while you are in the soup and all you have is a
manually set DG? Been there.

Declare an emergency and request a no-gyro approach. If I'm out
of radar coverage, then I guess I'd just start compensating for drift
as though there were wind, even though it's really precession error.
That would get kind of difficult eventually, so I might be tempted to
reset it based on what I thought the winds really were when I appeared
to be tracking a course accurately. It probably wouldn't be any
worse afterwards....

Did you have some suggestions in mind when you asked the
question? If so, I for one would like to hear them.

Regards,

Mike