DGs and Autopilots

Doug wrote:


Having said that, I would urge you to consider an autopilot that does
not use a DG. STEC makes them. They work very well. The big advantage
is if you loose vacuum, your all electric autopilot continues to work.
Big safety factor in IMC.

I know what you're saying, and I agree. Our current ARC AP model, and the
STEC model under consideration, are both rate-based. The DG is merely
providing HEADING information (ie. the setting of the bug).

- Andrew

Andrew,

The DG is merely
providing HEADING information (ie. the setting of the bug).


And that is autopilot specific. We had to get a certain model of
Sigmatek DG for it to work with the STEC-50. Also, we now switched to
another model, which also delivers bootstrap heading info like a remote
compass would. We need that for the WX-500 we installed.

--
Thomas Borchert (EDDH)

Thomas Borchert wrote:

Andrew,

The DG is merely
providing HEADING information (ie. the setting of the bug).


And that is autopilot specific.

Apparently.

We had to get a certain model of
Sigmatek DG for it to work with the STEC-50.

I was told by a person that installs STECs for us that the STEC can be
"configured" to work with different DGs. He didn't say "all different",
though. We're upgrading from ARC units: Navomatic 300As. According to
him, we merely specify this when we purchase a new STEC.

Also, we now switched to
another model, which also delivers bootstrap heading info like a remote
compass would. We need that for the WX-500 we installed.

Ah, this is something I didn't understand. What is "bootstrap heading
info", and how does the WX-500 (whatever that is {8^) use it? We've a
strikefinder in our aircraft. Does that mean we need "bootstrap heading
info"?

- Andrew

Andrew,

Ah, this is something I didn't understand. What is "bootstrap heading
info", and how does the WX-500 (whatever that is {8^) use it? We've a
strikefinder in our aircraft. Does that mean we need "bootstrap heading
info"?


Depends on the model of Strikefinder. In order for the the Strikefinder to
orient its display correctly in relation to where the aircreaft's nose is
pointing, it needs some kind of heading info. The WX-500 (remote
"Strikefinder" with no display, working with Garmin 430 and other
displays) uses the heading info from a "bootstrap compass" as it is
normally found in HSI installations. This compass sends out a compass
signal to auto-align the HSI. It can also be used to align the
Strikefinder displays. Even if the WX-500 is displaying on a GPS, it
cannot use GPS derived heading signals to align itself - the reason being
that the GPS doesn't know your heading, only your track.

If you don't already have an HSI, installing one (including the bootstrap
compass) is really expensive. The "cheap way" to get a bootstrap signal
without actually having a bootstrap compass is to have a DG with a
bootstrap signal output (as made by Sigmatek). Of course, that signal is
not derived from a compass but rather from the manual setting of the DG -
if you don't align it with the compass manually and it precesses out of
the real heading, so will the bootstrap signal.

Hope I'm clear ;-)

--
Thomas Borchert (EDDH)

Thomas Borchert wrote:

Hope I'm clear ;-)

Very! I appreciate the explanation.

- Andrew