Issue with Direct To distance count down

Thanks, I'm pretty sure the different update rate explains what I observed.

An explanation will have to wait another day or two.   No ability to get to lab and check out today due to snowstorm.

If I remember correctly, nav was working just fine.  The airplane knew where it was, however the guidance stopped working.  The distance to the next waypoint didn't update and so the datablock froze.

Edited by tony - 02 Feb 2015 at 2:53pm

That's interesting, Royski.

....not sure you understand the issue/concern??  Seriously?

1. If currently on the courseline, then it will show the distance to the current waypoint from present position ALONG THE PLOTTED COURSELINE (magenta line).
2. If currently off of the courseline, then it will show the distance to the current waypoint from the nearest intercept point of the courseline ALONG THE PLOTTED COURSELINE (magenta line).

1. TO Waypoint identifier
2. bearing to TO Waypoint from present position and
3. distance (in NM) to TO Waypoint from present position. 

(3 lines)

The above datablock would be similar to the "Destination Direct Info" datablock, but would use the TO Waypoint instead of the Destination.  You might use a color other than magenta to differentiate it from the standard "TO Waypoint" datablock.

Now, THAT would be some useful information, especially if I was off of the courseline.

Edited by pburger - 02 Feb 2015 at 6:50am

I'll pipe in to address those questions on Monday - I'm not able to do the appropriate level of homework on this until Monday, presuming the weather permits travel.

I've been waiting to see this post updated.  This seems like a primary navigation issue that should be a very high priority, yet it's been silent for over a month - disappointing, not even a status of we're still working it.

Edited by brou0040 - 01 Feb 2015 at 11:50am

I just saw this video.  It jibs with some weird behavior I noticed recently with my newly installed IFD540.  I noted this incorrect distance also populates my Aspen's next waypoint data block too.  In the soup I'm trained to use the Aspen info as primary.

I think you guys are confusing the distance to go with the distance to the airport.  Its different.  As we start to move into the Next Gen environment, someday we will have to be ready to do time nav.  This FMS was built around DO-236.  It's not a Garmin.  Its much more sophisticated.

In reply to brou0040 post above, It seems to me that pburger's and teeth6's situations are very related.  When pburger entered the "Direct To" into the IFD it computed the magenta line and distance, just like it would for the hold in teeth6's scenario.  The problem arose when pburger didn't fly the magenta line as the IFD expected he would.  It would be interesting to experiment with teeth6's hold by entering it in the IFD and then not flying it as shown to see how the IFD would handle that.  It seems to me that the "Direct To" algorithm should repeatedly recalculate the direct to solution from the aircraft's current position rather than just calculating the solution once when the "Direct To" function is activated.  Even if you overfly the direct to destination, it should continue to recalculate the solution until told otherwise.

I agree with teeth6 that the straight-line distance to the fix is important as I am putting an IFD 540 in a round dial airplane with a less than stellar auto-pilot.  The along-path distance would also be useful, but for the reasons teeth6 gave, the straight-line seems more important.

David

I've changed the title of the post to be a little more descriptive of the squawk.

Something does appear to be not-quite-right and we're actively looking at it some more in the lab right now.  Will post an update when I have something.

This is probably not totally related to your issue but when you first hit direct to it gave you the distance along the magenta line (not the point to point) as you already said.  I agree this is confusing especially when wanting to know exactly how far you are from the airport.  Along these same lines, I saw a similar issue when I was in a hold with 5 miles legs after a missed approach.  I had intended to fly outbound 5 miles and then start my turn inbound to the fix when the 540 said I was 5 miles from XYZ.  As I passed XYZ to start my outbound leg it said I was 15 miles from it and then starting counting DOWN so (as in the case above on this thread) the further I flew from XYZ, the distance got less.  I am not sure I really like the logic in the box on this one but the explanation from Avidyne was:
That datablock shows remaining leg distance.  A hold is considered a single leg that looks a lot like a racetrack, so the leg distance represents an entire lap and the remaining distance counts down until you cross the hold fix.  If you continue in the hold, then the distance will jump back up when you cross the fix and then start counting down again.
The start of the issue here (with the magenta line and the turn back) sounds similar to what I saw.

That's great data, I assume its repeatable since you had the camera all set up to capture it. 

To me it looks like nav was working fine.  You had altitude, heading, and ground speed; but guidance pewked. If you notice in your video, when TS07 was the nearest airport and you continued to fly away, the distance was correctly updated until another airport became closer to your position.   So when guidance pewked the 540 stopped figuring out where to go. 

I wonder what would of happened if you selected a direct to, to a different destination, let the IFD figure out new guidance, and then did another direct to TS07.  I'll bet you that would have probably worked.  I'm guessing that the guidance CSCI didn't like that you selected a direct to from the origin. 

This is normal stuff for a new FMS.  We are fortunate to have a forum like this to get the data back to the design team, and management willing to fix it.  This is going to be an awesome product. 

https://www.youtube.com/watch?v=ayCOKFZcuQk&feature=player_embedded

Okay, here's the video:

One theory --

Edited by pburger - 22 Dec 2014 at 2:39pm

Steve,

I had just departed my home airport (TS07) for a lunch run to 11R which is out to the west.  A buddy called me up on the radio and asked if I could go to 1500' and 10 miles and call him from that spot so that he could adjust the sensitivity of our pilot-controlled-lighting.  No problem.  At that time I was on a Direct-to flight plan to 11R.

Edited by AviJake - 23 Dec 2014 at 12:17pm