The Comair crash reminds me...

"Bob Moore" wrote in message
. 122...
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,

SAY WHAT!!!! How does one fly an ATC assigned heading if VAR
has been 'corrected' out?

Probably the same way you do it when there's a wind. ATC assigns you a
heading. If that doesn't provide the track they want, they assign a new
one, adjusting for the error in the track.

They don't care what your heading indicator is telling you. They care that
you follow it consistently.

(Note: I don't actually know anything about how a slaved compass is
corrected...seems to me that variation and local deviation (that is, not due
to the aircraft installation itself) are not things one could usefully build
into a slaved compass. But assuming the slaved compass IS correcting for
all manner of things, there's no reason to believe it would cause a problem
with ATC).

Pete

The flux valve is usually located well away from steel and
electrical components, so it avoids many deviation errors.
It also is designed to be more accurate and reduce turning
errors sent to the indicator.


"Peter Duniho" wrote in
message ...
| "Bob Moore" wrote in message
| . 122...
| 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,
|
| SAY WHAT!!!! How does one fly an ATC assigned heading
if VAR
| has been 'corrected' out?
|
| Probably the same way you do it when there's a wind. ATC
assigns you a
| heading. If that doesn't provide the track they want,
they assign a new
| one, adjusting for the error in the track.
|
| They don't care what your heading indicator is telling
you. They care that
| you follow it consistently.
|
| (Note: I don't actually know anything about how a slaved
compass is
| corrected...seems to me that variation and local deviation
(that is, not due
| to the aircraft installation itself) are not things one
could usefully build
| into a slaved compass. But assuming the slaved compass IS
correcting for
| all manner of things, there's no reason to believe it
would cause a problem
| with ATC).
|
| Pete
|
|

"Jim Macklin" wrote in message
news:_lOIg.6238$SZ3.83@dukeread04...
The flux valve is usually located well away from steel and
electrical components, so it avoids many deviation errors.
It also is designed to be more accurate and reduce turning
errors sent to the indicator.

But there's no way, absent some sort of absolute position information (eg
GPS) and a detailed database, to ascertain deviation due to local geology or
other external magnetic interference, nor due to magnetic variation (which
was Bob's point).

Of course, my point is that correcting those errors isn't relevant to ATC.
They don't care if your compass is actually right or not. They just care
that you can hold it to a specific heading. But I think it's fair to
comment on the statement that "the slaved compass is corrected so
as...variation is also corrected". That's clearly just not true, at least
in most installations (I suppose there's at least one GPS-based slaved
compass setup in which it is corrected...never say never...but generally,
this isn't used)

Pete