Garmin 430W autopilot operation
Glasair470
Garmin talking to our STEC autopilot using its ARINC 429 roll steering
commands through the STEC GPSS interface. In the old 430 non-WAAS
unit, even if you selected an ILS approach on the Garmin and loaded
it, you would get roll steering commands down to the ground out of the
Garmin. Of course, you are using the VLOC receiver and the ground
stations for the approach but the autopilot would still fly the
magenta line on the screen that was provided "for guidance". I now
notice on the WAAS'd unit we got back that the roll steering commands
only seem to be provided until we get to the ILS final approach fix,
and then the STEC starts flashing to indicate that there is no more
roll steering. It drops out at the FAF.
We have to revert to HEADING mode if we still want to use the
autopilot on the approach or maybe NAV mode and track the localizer
needle, although I cut those wires figuring that roll steering is so
good I would never again want to track needles.
If we are flying a GPS or an RNAV approach on the 430W it does give
the roll steering signals all the way down to the ground or out to the
holding fix on the missed approach and will even fly the holding
pattern.
Anyone else can confirm this? I called Garmin technical support and
the guy really couldn't get what I was talking about. He was under
the impression that we should not be getting ANY roll steering on an
ILS approach but that was not the case with the 430 and semi-not the
case with the 430W.
Is this a deliberate feature programmed into the software to insure
that you are not flying the "guidance only" course line on an ILS
approach?
John Collins
only seem to be provided until we get to the ILS final approach fix, and
then the STEC starts flashing to indicate that there is no more roll
steering. It drops out at the FAF."
You correctly described the way the 430W works on an ILS approach. You
probably don't have an autopilot that will fly the GS. If you did, you
would most likely want to switch the 430W to VLOC and use Nav (or Appr)
depending on the autopilot manufacturer. Roll steering is available after
the MAP when the CDI switch is changed to GPS, so you can fly the missed
approach using roll steering.
One other caveat, if the GPSS is hooked up according to the STC for the
430W, when you switch the CDI to VLOC, the GPSS is disabled, which will
prevent the GPSS from following the roll steering when you switch the CDI to
VLOC.
--
Regards,
John D. Collins
4317 Old Saybrook Ct
Charlotte, NC 28211
(704) 364-3696 Tel/Fax
(704) 576-3561 Cell
johnc...@carolina.rr.com
"Glasair470" <gla...@cox.net> wrote in message
news:bbe5ced4-d697-45a5...@d21g2000prf.googlegroups.com...
Bill Zaleski
<johnc...@carolina.rr.com> wrote:
>Someone wrote: "I now notice on the WAAS'd unit we got back that the roll
>steering commands
>only seem to be provided until we get to the ILS final approach fix, and
>then the STEC starts flashing to indicate that there is no more roll
>steering. It drops out at the FAF."
>
>You correctly described the way the 430W works on an ILS approach. You
>probably don't have an autopilot that will fly the GS. If you did, you
>would most likely want to switch the 430W to VLOC and use Nav (or Appr)
>depending on the autopilot manufacturer. Roll steering is available after
>the MAP when the CDI switch is changed to GPS, so you can fly the missed
>approach using roll steering.
>
>One other caveat, if the GPSS is hooked up according to the STC for the
>430W, when you switch the CDI to VLOC, the GPSS is disabled, which will
>prevent the GPSS from following the roll steering when you switch the CDI to
>VLOC.
I have extensive experience with the above problem. The same thing
happens to one of my students units with the same equipment. Roll
steering cannot also provide vertical guidance to an autopilot at the
same time. You will have to be in NAV (APPR) mode if you need to do
an LPV approach and have the AP follow the GS needle. Roll steering
cannot be invoked at the same time. Letting the autopilot follow the
analog needles is pretty lame with roll steering potentially
available, but for now, as far as I can see, you can't have both at
the same time.
Harvey Spencer
flew 2 ILS approaches since I had the unit WAAS'd but
was familiar enough with the operation of the 430 before it got WAAS'd and
realized that at the FAF roll steering goes away with the
430W. I don't have GS coupling on my STEC so I have never had to worry
about that problem. It is incredible that with roll steering you
have to resort to the analog "fly the needles" with the autopilot.
Concerning the STC implications of the hookup of my Garmin to the autopilot
I chose to NOT hook it up according to the STC for the
430W, so GPSS is NOT disabled when the CDI is switched to VLOC. It is
because my autopilot flies like a pro with roll steering but
in NAV mode and following the needle, it S-turns like a drunken sailor.
To have GPSS roll steering active all the time, it just involves not hooking
up the inhibit wire on the autopilot
to the VLOC active line from the Garmin. If you hook up that line, then
when you switch the Garmin to VLOC it grounds that inhibit line which tells
the autopilot to forget about using roll steering.
I know that in my plane, roll steering is always following the magenta line,
because that is how I hooked it up. Pretty easy to remember. There are
actually very few times when my flight plan does not match where
I am going using the VLOC, so the magenta line is for all intents and
purposes the same as the VLOC radial or the LOC.
"Glasair470" <gla...@cox.net> wrote in message
news:bbe5ced4-d697-45a5...@d21g2000prf.googlegroups.com...
Thomas Borchert
> I chose to NOT hook it up according to the STC for the
> 430W, so GPSS is NOT disabled when the CDI is switched to VLOC.
Not many of us have that option. You're flying an experimental.
> It is
> because my autopilot flies like a pro with roll steering but
> in NAV mode and following the needle, it S-turns like a drunken sailor.
Not many of us have that problem. You're flying an experimental.
<gd&r>
What I'm trying to say is: If the S-TEC installation is properly done in
an aircraft it is designed for, it will follow the localizer in approach
mode just fine - and it'll be the legal way to fly that approach.
--
Thomas Borchert (EDDH)
John Collins
I have advised owners of certified aircraft that the GPSS inhibit not be
connected to the VLOC annunciator signal. To be legal, you would need a
field approval. So far, those who have had this done have not had
difficulty in obtaining a field approval for the change. Not all GPSS units
have an inhibit capability, such as the Century unit and the DAC unit, and
the Icarus Sam unit has a configuration setting that allows the pilot to
override it.
Regarding whether or not it is legal to steer the autopilot using the GPSS
when conducting an ILS approach or whether you must use the analog inputs to
the autopilot, IMHO either is OK, so long as the GPS outputs steering
information (as is the case in the GNS430 but is not the case in the
GNS430W). Regardless of how the autopilot is determining the course, the
pilot is required to be displaying the ILS localizer and GS on the CDI or
HSI, and must use the CDI or HSI to determine if corrections need to be made
or not. So if the autopilot is not doing an adequate job, the pilot must
take remedial action.
If you own an autopilot that has GS capture and tracking, it is a moot
point, because the GS tracking only works with the analog data. The way I
typically fly the full ILS approach with my 60-2 and GNS530W is to use GPSS
until I join the final approach course inbound, and then just press the Nav
button on the autopilot. From this point on, the autopilot follows the
analog localizer indications and the GS.
--
Regards,
John D. Collins
4317 Old Saybrook Ct
Charlotte, NC 28211
(704) 364-3696 Tel/Fax
(704) 576-3561 Cell
johnc...@carolina.rr.com
"Thomas Borchert" <borcher...@hotmail.com> wrote in message
news:VA.0000779...@hotmail.com...
John Collins
You wrote: "Letting the autopilot follow the analog needles is pretty lame
with roll steering potentially
available, but for now, as far as I can see, you can't have both at the same
time."
I agree, but the legacy autopilots did not anticipate using digital inputs
(GPSS) with the exception of the S-tec 55X and the Bendix King
KAP-140/KFC-225, and even the autopilots that had lateral digital control
built in, predated vertical digital control. In fact most autopilots that
use GPSS are "faked" into believing that they are in heading mode and that
the pilot is commanding the turns with the heading bug.
The new "all digital" autopilots such as the Garmin 700 don't have the
issue.
Regards,
John D. Collins
4317 Old Saybrook Ct
Charlotte, NC 28211
(704) 364-3696 Tel/Fax
(704) 576-3561 Cell
johnc...@carolina.rr.com
"Bill Zaleski" <w...@instrumentratings.com> wrote in message
news:f7rqo3dfqsje94uc7...@4ax.com...
Thomas Borchert
> So far, those who have had this done have not had
> difficulty in obtaining a field approval for the change.
Very interesting, thanks! Our EASA is not that flexible, I'm afraid.
> Regardless of how the autopilot is determining the course, the
> pilot is required to be displaying the ILS localizer and GS on the CDI or
> HSI, and must use the CDI or HSI to determine if corrections need to be made
> or not.
Agree. Would you agree that a properly set-up S-TEC should be able to follow a
localizer without too much weaving about?
--
Thomas Borchert (EDDH)
John Collins
You wrote: "Would you agree that a properly set-up S-tec should be able to
follow a localizer without too much weaving about?"
Yes, with the exception of strong crosswinds. The S-tec has to figure out a
correction based on drifting off, re-intercepting, estimating the WCA,
drifting off again and repeating the process. Sometimes it can't settle out
over the distance of 7 or 8 NM while tracking the localizer, especially if
the winds are different closer to the ground. That is one distinct
advantage of roll steering, as the GPS can detect any difference between the
DTK and the TK and apply a roll correction within a second, long before the
localizer needle has shown even the slightest deviation.
If there was a way for my old autopilot to use digital roll steering and
digital vertical guidance, I am sure it would be much more precise. Alas, I
will just press the Nav button when I join the final approach course, no big
deal.
--
Regards,
John D. Collins
4317 Old Saybrook Ct
Charlotte, NC 28211
(704) 364-3696 Tel/Fax
(704) 576-3561 Cell
johnc...@carolina.rr.com
"Thomas Borchert" <borcher...@hotmail.com> wrote in message
news:VA.0000779...@hotmail.com...
Glasair470
better job of flying the analog needle output. I have worked on the
sensitivity tailoring by hanging internal resistors under the
direction of the technical service personnel at STEC and can only get
it a little better than when I started. Also, tinkered with the roll
centering that is a user adjustment (hidden under a panel screw) to
try and null that out as best as possible. The Glasair just has too
much roll sensitivity to do a very good job with this particular
autopilot in NAV mode, but in roll steering mode where, yes, it is
"faked" into thinking it is in an everchanging HDG mode, it works
great.
I also agree with the poster that you can drive the autopilot any way
you want when doing an approach using terrestrial nav aids and as long
as you are watching the appropriate needles it is legal. One way is
to just put it in HDG mode and keep tweaking the heading bug. I guess
that is a "brain-driven" coupled approach. It doesn't matter where
the autopilot gets its intellengence from as long as the aircraft is
flying on the right path.
Peter Clark
<borcher...@hotmail.com> wrote:
>Agree. Would you agree that a properly set-up S-TEC should be able to follow a
>localizer without too much weaving about?
Mine do. Check main aircraft rigging and cable tensions, upper end of
the limit seems to ork best, autopilot servo brible cable tensions,
and the servo start voltages are within spec. There can be a feedback
loop when one or more of the above is wrong, the computer thinks it
needs a correction, starts it, but due to slow or damped response
because of one of the items above being wrong it doesn't stop on time,
starts a correction back the other way, but lag due to start voltage
and/or having to take up the control slack makes it overcorrect the
other way, ever increasing oscilations.....
John Collins
Besides cable tensions another biggie is a startup voltage for the servo is
too high.
--
Regards,
John D. Collins
4317 Old Saybrook Ct
Charlotte, NC 28211
(704) 364-3696 Tel/Fax
(704) 576-3561 Cell
johnc...@carolina.rr.com
"Peter Clark" <Inva...@NotIn.YourLifetime.com.hatespam> wrote in message
news:on0to3lo36m4bp6gq...@4ax.com...
Peter Clark
<johnc...@carolina.rr.com> wrote:
>Peter,
>
>Besides cable tensions another biggie is a startup voltage for the servo is
>too high.
Yea, I had start voltage listed in the things to check ;)
Ron Natalie
When you're converging on the final course you need to
go into regular NAV+APR+ALT mode.