I mounted my standby compass at the very front of the overhead panel
where it meets the windscreen. This avoids most stray electric currents
and does not obstruct vision. As it is a standby it doesn't matter so
much that it is not so easy to include in the scan. However
conventional compasses in that position suffer from paralllax error and
in any case small conventional compasses are often difficult to read
due to turbulence. For these reasons I used a digital fluxgate compass
which I use as a reference to set my DI. As it happens it is also
possible to use a fluxgate drive for a uEncoder so I have another
fluxgate mounted in the rear fuselage. There are sometimes a few
degrees difference between the two so I use an average when setting the
DI. Another advantage is that swinging fluxgate compasses is far easier
and quicker than the convention type.
As most of us use GPS's it is possible to treat the DI as a back up
and fly GPS track. An updated DI will then give an idea of drift and
can be applied should the GPS fail.
Nigel Charles
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