Roy Smith wrote On 12/03/05 12:09,:
In article ,
john smith wrote:


LASER ring gyros are certainly small enough, I don't know how much they
cost. If the US military can put them in artillery shells, they should
be available for light GA inertial nav systems.


Googling for LRG prices surprisingly came up with mostly a blank, but I did
come up with one doc
(http://www.armadilloaerospace.com/n....ws?news_id=140)
that hints at a "6 figure price" for them. That same doc, however, talks
about commercially available Fiber Optic Gyros (which I don't know much
about) in the $1500-$2500 price range. There is an old adage, "Sooner or
later, anything made from silicon will cost $5", so I can only assume that
the days of affordable solid state gyros for GA are not too far off.

What do things like the Garmin G-1000 use?

Those are non-TSO FOGS. The current crop of "gyros" used on the electronic
displays aren't actually gyros at all. They are rate of turn accellerometers.
Turns out accellerometers are dirt cheap, that IS a product that can be
made (literally) on a silicon chip. They are not as accurate, but some
genius figgured out how to tie them to GPS position to correct their
long term drift. So, in roundabout answer to this roundabout thread, they
rely on GPS, and so negate the original idea of this thread about inertial
NAV as a backup to GPS.

By the way. Don't expect FOGs to be cheap, or small anytime soon. These are
precision wound spools of optical fibre connected to lasers. Turns out there
is a minimum "bend radius" for the spool that works out to 3" or so in
diameter, which means don't expect to see it show up in a 3" instrument
package anytime soon.

As for traditional ring gyros, you are now talking precision mirrors set up
on a rigid mechanical frame with accuracy that would do a space mission
proud. I.e., forgedda 'bout it.