Autopilot

CurrentSea

CurrentSea

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Running from block island to Montauk.
Locked on auto at 245 deg and 27mph.
I saw display suddenly jump to a reading of 283 and boat went into a sharp port turn.

What would make this happen? It's like it suddenly ran over a magnet and lost the true reading Worked fine before and after that.

Very odd and scary.
 
I'm no expert in marine but in aircraft you would have corrupted data from the heading sensor. Either the sensor itself is bad, or it is being corrupted at the plugs. Find the plug(s) from the sensor to the AP and clean them with contact cleaner. Check the sensor placement to insure nothing is in its field of sense. Failing that, replace bad sensor.
 
In that area the military may have messed with GPS practicing sub avoidance.
 
"I saw display suddenly jump to a reading of 283 and boat went into a sharp port turn."

Poor plug connections at the course computer or the compass.
Intermittent signal on the computer circuit board.
Power fluctuations to the computer or GPS driver.
Larger metal objects or tools with motors being moved or stored near the course computer.

Did it come back on its own or did you have to switch it to 'off'.
Were you able to switch it back on with no issues shortly thereafter?
 
I would hope people don't feed GPS to their autopilot, that is dumb as hell. I set my autopilot course from my paper chart, check GPS for agreement, if they agree then go. If no agreement find which one is wrong and set the autopilot, keep WATCH and go. Any other way is not safe.
 
quote:
Originally posted by JimPend

I would hope people don't feed GPS to their autopilot, that is dumb as hell. I set my autopilot course from my paper chart, check GPS for agreement, if they agree then go. If no agreement find which one is wrong and set the autopilot, keep WATCH and go. Any other way is not safe.

Click to expand...


Strongly, emphatically diaagree with that for my use .

...Some... newer APs will overcome varying drift and set (cross track error) when in Auto mode using the heading sensor, but most APs in present use do not.

So best bet for straightest most efficient navigational route held over ground is using Nav mode to a carefully reviewed GPS WP or route.

I've had AP on my boats since about 1986 and love their beneficial convenience, definitely including the very helpful NAV mode.
 
It drifted back on its own after I went to standby mode.
I don't use ap to follow a route. I use it only when on a long run with a straight course.
So I set a heading and nothing more.
As far fetched as that sounds there are subs in the area as they do practice in block island sound.
I will check connections. It was fine after that. I also don't think it adjust more than 10 degrees at a time so not concerned with a major course correction keeling my boat. My thought is interference with something like my cell phone. I do notice it will cause my gauges to read wrong and I have a habit of keeping it on the dash when running.
 
Are far fetched as it may seem a few years ago I was in the same area and this appeared out of no where I watched it surface in front of me and I had no idea what was happening. It was quickly flanked by to patrol boats.
Sub1_zpsc154a77a.jpg
 
You do not need GPS for 'auto' but you do need it to 'track'.
Clearly Currentsea was utilizing auto as a heading control only.

"I set my autopilot course from my paper chart"
In this case the autopilot will only be able to point your bow in the correct direction at the time. With a larger cross current that direction will change increasing its offset from your original attempting to reach that same point.

Audrey II - I have seen that a few times now but not out near BI sound. It is always in the same place and it appears that place is where you picture was taken. Approaching the Thames river where electric boat reside a bit further inland in where we have seen the subs surface. Interestingly they surface well out into the sound but when you look at a chart in then makes perfect sense. If you carefully look at the depths approaching the Thames you can see that they surface when they 'run out of water' which for a sub that is 50-60' tall is not nearly what we deal with. Other than that they appear to remain submerged for most all of the time they are in the immediate areas.

Currentsea - If you play around with the connectors or circuit board edges whatever you do don't apply WD-40 or anything similar to the boards,edges or even get it close to these items.

FWIW - a majority of the time I set the autopilot to Track and expect the tracking to0 be exactly on my planned and loaded route. Watching the GPS and zooming in on the screen will confirm the route as well as a paper on hand for a confirm. This method assures me I am not a victim of cross track error and makes it much less likely that I will make an approach to a planned passageway from a potentially more dangerous angle - such as Watch hill or Mystic river.

Hope this helps
 
There was no current and it was flat. I doubt there was a 38 degree cross track.
And it clearly changed my course beyond where my bow was pointed as I could see Montauk lighthouse and suddenly I was heading port of it when my bow was pointed starboard.
 
not far fetched. that is the transit choke point for Groton sub yard. Have seen them surfacing right at the BI, Montauk Pt. line multiple times.
 
When a cell phone vibrates it puts out a magnetic field. I've had too many hotel room keys erased by putting them in my pocket with the cell. Could easily be the cause if the phone is on the dash and the heading sensor is below it.
 
I agree. Gonna keep cell phone in pocket when ap is engaged and see if that makes a difference.
 
You could always experiment by having someone aboard call you with the phone near the compass and see what happens. There are probably any number of things that can generate a field. For example, the auto pilot pump motor, a radio, the cell phone, who knows what else. I did have an issue with ours in the Bahamas and it turned out to be a bad connection between two modules of the AP.
The AP went into a mode where it only turned in one direction. I could not adjust the course in the other. Eventually I had the AP out of the electronics locker and it started working. I narrowed it down to a cable, looked it all over and it was fine. I put some GOOP on the connector when it was in a "good position" and let it dry.
It's been fine since.
 
quote:
Originally posted by CurrentSea

Mine is under my dash.

Click to expand...


That location seems as one that could potentially have the most negative influences on the heading sensor, and ones which would change as various electrical items were turned on or off. It might even be near the AP pump as that turns on and off in either flow direction to maintain the course.

It's darn hard to find a good protected area for the rate or fluxgate compass on most boats, and it's probably wise to perform recalibration when possible influences are added or removed or anything seems amiss .

I kind of like the submarine theory though...

FWIW- I'd note, however , I've never noticed any aberrant effect on my AP as I have cruised close to large weather and other buoys.
 
"FWIW- I'd note, however , I've never noticed any aberrant effect on my AP as I have cruised close to large weather and other buoys."

If only our attack submarines were so easily detected...
 
My wife stored some extra metal parts near the flux gate compass. As long as I was on GPS track, no problem. When I went to the flux gate compass, wham, a hard left turn. I cannot tell you how much time it took to locate problem. So far the flux capacitor has not affected our speed yet:)

Ron
 
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