?roll steering

[jaba-who]

Just a question to bring myself up to the latest.

I have a D 180, AP 74 connected to a Garmin 296. One roll servo (SV32 in my Jabiru 430.)

The GPS Nav is working well with the AP following the route beautifully till it crosses over a waypoint and then it turns and hunts to find the track crosses over it and hunts again etc. Same if I engage the Nav mode while not actually on the track. It turns abruptly, crosses the track then recrosses etc till finally on track.

From my reading it seems (maybe I have it wrong) that the mode needed to have the AP/GPS anticipate and smoothly turn onto the new track is "Roll Steering" and seems to require something called ARINC. All the sites I have read say the Garmin 430 has this capacity but I have also read sites which say you can get an ARINC adapter for other GPS's including a 496.

My quesions:
Do I have it correct regarding the need for Roll Steering and ARINC capable GPS to get the whole system to anticipate ans smooth roll onto new tracks?

Is there an adapter which will work with a 296 or is that too old technology?

Jaba-Who

 

[DBRV10]

I was not aware the roll steering output was available from the GX96 series. Maybe it is but over serial I don't think so.

It is true the G430/530 series over ARINC429 does work very nicely, especially when doing RNAV's

 

[dynonsupport]

Only the 430 and 480 (maybe the GX-60?) output roll steering. There are no portables that output roll steering.

If you really want it, the only way to get it is to move to a panel mounted, IFR legal GPS.

 

[Brantel]

Most panel mounted GPS's with ARINC ports support GPSS or GPS steering. They do not always have to be IFR certified.

The GX series Garmins in their later firmware did support GPSS over serial but this was a very unique set of labels that Garmin added to the data stream and as far as I know, they were the only ones to do this.

TruTrak and S-Tec support this weird GPSS on the GX series with some of their autopilot models.

Even without a GPSS enabled GPS, the autopilot should rejoin the course after crossing a waypoint without excessive hunting. I would work on the gain settings to see if you can smooth that out.

 

[PhantomPholly]

Too, in order for the Dynon firstgen units to receive ARINC, it is necessary to have an HS-34.

Since you are using the autopilot hooked to a strictly VFR GPS (and thus one presumes are NOT flying IFR), you might be happier simply using the course select knob to dial in a course, adjusting it a degree or two if it isn't lined up with the magenta line. That will prevent the "course hunting" associated with that combination of autopilot/gps.

 

[jaba-who]

Phantom.

I'm not sure I follow what you mean. Basically the AP setup is working in Nav mode from the GPS while I am on the track. It is not hunting but gives an nice smooth following of te track.

The problem arises when I get to a waypoint where the course changes direction. The AP/GPS takes me directly overhead the waypoint then it realizes it off track and turns me back to towards the new track. But it then crosses the new track and then works out it is off track and turns again.
It eventually does get onto track but at the expense of a lot of turns and time just after each waypoint.

Same thing if I engage Nav mode while not on course. It gets there eventually but after a lot of extra work.

I guess it's not a real disaster since I am able to hand fly each bend but it would be nice to have it all taken care of.

Jaba-who

 

[jakej]

Jaba-who

What is happening is 'normal' however the amount of 'hunting' can be mitigated by changing the gain setting - applies to most autopilots when using only a serial datastream, not Arinc or GPSS.

HTH

Jake J

OZ

 

[jaba-who]

Hi Jake,

Yeah I understand. What I really would like is steeringing onto the new track PRIOR to reaching the waypoint - say 1/2 a mile or something so it just turns and smooths onto the new track. I am not that keen on changing the gain to have it turn abruptly after crossing the waypoint onto new track - that would by necessity, mean big abrupt attitude changes.
I would rather hand fly a smooth change of direction if those mentioned were my only two options.

If someone knows a way to have the AP and my G296 anticipate the track and turn toward it prior to actually hitting the exact waypoint I am all ears. Otherwise I'll probably leave it as is and hand fly the bends.

Therest of the time it is great so I don't want to stuff up that.

Jaba-Who

 

[Brantel]

Adjust the max bank angle, turn rate limit and gain to get this worked out without scaring you on the turns.  You should be able to find a happy medium that stops all that hunting.

There is no way to get turn anticipation on any handheld made to date.

The only way to get that is to use a GPS that has ARINC outputs and that supports GPSS.  That means a panel mount GPS and an HS34 for the Dynon.

 

[jaba-who]

I have been discussing it with a couple of the guys at our aero club tonight and they both have G296's and "EZ pilot" autopilots and they both have the set up on theirs (apparently an easy menu button press sets it on into "Anticipate Mode") and were surprised it wasn't available on the Dynon.

From what they were saying it's an inherent capability of the A/P rather than relying on some specific output of the GPS. Maybe Dynon can sneak a look at EZ pilot and steal their idea.

Jaba-Who

 

[Brantel]

There is no Anticipate mode on the EZ pilot. There is an Intercept mode which basically is heading hold @ 25° from the course until .5 miles from the course then it joins the course.

All this does is automatically limit the angle at which you can join a course to prevent a steep turn from being required to get on course.

 

[PhantomPholly]

Phantom.

I'm not sure I follow what you mean.  Basically the AP setup is working in Nav mode from the GPS while I am on the track. It is not hunting but gives an nice smooth following of te track.

The problem arises when I get to a waypoint where the course changes direction.  The AP/GPS takes me directly overhead the waypoint then it realizes it off track and turns me back to towards the new track.  But it then crosses the new track and then works out it is off track and turns again.
It eventually does get onto track but at the expense of a lot of turns and time just after each waypoint.

Same thing if I engage Nav mode while not on course. It gets there eventually but after a lot of extra work.

I guess it's not a real disaster since I am able to hand fly each bend but it would be nice to have it all taken care of.

Jaba-who

Perhaps I'm not describing it well.

On most APs, there is a mode you can engage which simply flies the course you select (ignores any flight plan active in the GPS).

As you see the next turn approaching, you can simply change the selected course to fly so that it initiates a turn before the new flight plan course intercept.  In other words, YOU do the course anticipation.

None of the hand-helds output steering information in the serial stream, and most don't output the "next course" information.  They only output "current leg" information - that is why the autopilot overflys and then corrects.