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Issue with Direct To distance count down

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oskrypuch View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oskrypuch Quote  Post ReplyReply Direct Link To This Post Posted: 16 Feb 2015 at 7:10pm
Teeth6,

Let's say you had planned a direct to route/track, due east, to a certain airport.

You then flew off the track to the north, and are now offset by 10nm to the north from the original track.

As you now turn, and continue to fly due east, that Along Track Normal (ATN) point continues to countdown to 0, as it nears that original destination.

When directly north of the destination, the ATN point will be at the destination, and the distance will correctly show zero. But, you will still be 10nm north of the destination.

If you then reselect direct to that original airport, presuming you want to go there, the distance will then change to show 10nm.

* Orest

(BTW Steve, great post above)




Edited by oskrypuch - 16 Feb 2015 at 7:43pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TogaDriver Quote  Post ReplyReply Direct Link To This Post Posted: 16 Feb 2015 at 7:23pm
I "think" if you parallel the plan course back toward the waypoint but, being parallel, though never intersecting, your track angle error becomes zero and cos(zero)=1 so it starts counting down 1:1 with your parallel travel until you can look 10 miles off your right wing at the waypoint and wave.

Yeah, weird.  I'm thinking of ATN as a little red ball in the magenta track that gets yanked along by a string tied to your airplane, but cannot leave the track.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote brou0040 Quote  Post ReplyReply Direct Link To This Post Posted: 16 Feb 2015 at 8:55pm
Originally posted by AviJake AviJake wrote:

For example, if we didn't design it this way, what distance would you present in the To Waypoint distance field when flying a DME arc as part of an approach?  Etc, etc, etc.

Thank you very much for this response.  I think this is very informative to understand what the system is doing.

How would have I done it to include distance to the waypoint along a DME arc?

I would have made it so it calculated the distance along the arc from current position to the waypoint (what it does currently if on the magenta line).  If you are off the magenta line, it would calculate the distance to intercept the magenta line, then fly along it to the waypoint.  You almost have this currently if you'd just add the distance from the current position to the red dot to the calculation.  I'd think you'd do it a bit more elegant such as calculating the button hook distance to turn to an intercept and the turn from the intercept back onto the desired course.

If you are off the magenta line while dodging storms and when it's most critical to have good information, you do not have a data block that will provide useful information.  From how you are using this calculation, I'll go out on a limb and assume that this is the calculation you are using for fuel range as well.  We all plan for fuel reserves, but we all know that the unknown is how much are we going to get vectored off course and how that will affect our fuel range.  We've just seen how the distance to waypoint will provide non-useful data (even though as designed, I don't know if it can be argued that it is still useful when vectored off course) and direct to data does not account for turns or returning to the intended flight path.  To me the most useful data would be the distance (and time) to intercept the magenta line then flying the flight plan from there.  I don't see it as being that difficult to create straight forward intercept to calculate the missing information.

Away from how I would have done it.  I would suggest adding some of these figures to the pilots guide to capture this information in the formal reference material.  I'd also suggest doing something as a reminder to pilots that this scenario is occurring.  Maybe when the present position is a certain distance away from the course line, you could change the color of the time and distance in the datablock to red and add the red dot to the display similar to what you did in the .pdf.  I think this would be a subtle reminder that you are not flying as the IFD is expecting you to and that calculated data is going to be affected.

Again, thanks for the explanation, you did a very good job of illustrating and annotating the scenario.


Edited by brou0040 - 16 Feb 2015 at 8:59pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pburger Quote  Post ReplyReply Direct Link To This Post Posted: 17 Feb 2015 at 12:33am
Steve,

I appreciate the explanation.  I viewed the pdf file, and it explains exactly what I surmised and observed.  While I don't like the design, and I still believe the "TO Waypoint" datablock will present very confusing and non-intuitive information in certain situations, I will not belabor the point any further.  I look forward to the addition of the "Active Waypoint Direct Info" datablock (AWDI).  I will put that one in the upper right corner just as soon as it becomes available. 



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Post Options Post Options   Thanks (0) Thanks(0)   Quote teeth6 Quote  Post ReplyReply Direct Link To This Post Posted: 17 Feb 2015 at 7:19am
Thanks for the detailed explanation with the PDF to illustrate.   That makes it very understandable.  I also will look forward to the release of the Direct To which will be released in the future.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bellanca1730a Quote  Post ReplyReply Direct Link To This Post Posted: 17 Feb 2015 at 8:16am
I admit that my limited FMS experience leaves me with a bit of a learning curve here, so forgive the rookie question -- but what is the real utility of the ATN distance? I looked over the slide presentation and re-read the explanations above, but must be too steeped in direct-to-waypoint tradition to wrap my head around it.


Edited by bellanca1730a - 17 Feb 2015 at 8:19am
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Post Options Post Options   Thanks (1) Thanks(1)   Quote 94S Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 2015 at 3:08pm
Ditto bellanca1730a.

I understand the math behind ATN, but fail to see the utility of it.  I can think of many reasons why one might be flying off of the flight plan.  Where, the TO Waypoint distance, as designed, would be confusing because it's not intuitive.  Some scenarios would be; ATC vectors, diverting around weather, dealing with an emergency, going to look at that thing over there, etc.  One particular use I have for direct distance and bearing is situational awareness at my home airport.  I select "Direct To" before departing to go out in the practice area where I monitor the CTAF for other traffic coming and going.  The direct bearing and distance to the airport help me understand my relationship to other traffic in the area as well as make position reports to same.
The architecture of FMS might assume that you will always be on the magenta line where this won't be an issue, but if it simply showed direct bearing and distance to the waypoint it would be correct and intuitive when you are on the magenta line and when you are not.  I don't see the value in knowing the distance your perpendicular intercept to the magenta line is from a way point.  I want to know how far away my airplane is from a waypoint, on or off the magenta line.  I understand that you are adding a couple of new data blocks that will provide the direct to information, but I am really puzzled why your keeping the original ATN logic.  It seems to me that it could bite somebody already task saturated by the weather, atc, or other extenuating circumstance, not by leading them astray, but by taking valuable mental resources off the primary task of flying the airplane to try to understand why the "number" is not doing what it is intuitively supposed to do.
I think pburger has brought up an issue that requires more attention than just saying "it works the way we want it to".
Sincerely,
David
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oskrypuch Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 2015 at 3:35pm
Quote  I select "Direct To" before departing to go out in the practice area where I monitor the CTAF for other traffic coming and going.  The direct bearing and distance to the airport help me understand my relationship to other traffic in the area as well as make position reports to same. 

There are two great datablocks, which I use all the time, one shows just the distance to your destination, the other the distance, bearing, etc. They will do a better job of giving you that information, you could additionally create a user waypoint at the practice area, and set that as part of the plan, returning to homebase.


As I understand it ATN logic is always required to keep track of where you are relative to the flight plan you set out, for sequencing in particular. Think of DME arcs or procedure turns. So it will always be used internally.

With additional information datablocks added, you can have it both ways. There will be no reason you have to keep the original ATN related TO waypoint block.

That said, now that I'm getting used to the current setup of the (only) TO waypoint datablock, I kind of like it. It adds another data point to SA.

* Orest



Edited by oskrypuch - 18 Feb 2015 at 3:50pm
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Post Options Post Options   Thanks (1) Thanks(1)   Quote 94S Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 2015 at 5:14pm
Well ok, if it is needed internally for the program logic, keep it internal. I see no use for knowing the distance my perpendicular intercept of the magenta line is from a waypoint.  Even on a DME arc, DME arcs are flown with the DME and a VOR, not the IFD (I believe any approach that has a DME arc is "GPS Overlay Not Authorized", which the IFD will tell you when you select it).  The distance (or time) around the arc is of no use.  The distance from and degrees flown around the VOR are.  And has been discussed up-thread, the distance around a holding pattern is similarly not useful, the distance from the fix that defines the hold is (The time to the fix may be beneficial if departing the hold at a particular time, but I would think this could be displayed without the ATN distance and bearing info).  And if I am flying off my route, what use is it to know when my perpendicular intercept is going to cross the waypoint since I am not going to cross the waypoint?

The point of my previous post is not just that the information currently presented is not useful, it could be dangerous.  I am an engineer, and like to keep things simple (KISS - keep it stupid simple), which for the most part the IFD is wonderful at.  But this particular piece of it, I think strays from that philosophy.  I know there will be options to do away with the "ATN TO" information when I set up my IFD and that I'm really not going to fly by the "ATN TO" information, but what about those who haven't followed this thread and don't know about the subtle but significant difference in the two?  And what about those who have, and who in the heat of the moment in an emergency forget the difference, lose their SA because of the confusing information, and possibly their chances at a successful outcome?
It would make more sense to have the Direct To info be the basic configuration and the ATN To information optional for those that want it, instead of the other way around.

Just my 2 cents.
David
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bellanca1730a Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 2015 at 5:55pm
To be clear, I was just hoping to better understand the utility of ATN and assuming that someone with more FMS experience would be able to weigh in and explain.

Orest, as a primer, perhaps you might expound on "Think of DME arcs or procedure turns."
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Victor Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 2015 at 6:42pm
Originally posted by 94S 94S wrote:

The distance (or time) around the arc is of no use.


Not true. As one example, it is very useful when determining your descent profile. We always use it during an arc approach and upon conducting other approaches in the airline industry regularly. You just need to know how to use it and I applaud Avidyne for including it in the IFD. In my opinion, it is a great bit of inclusion. Having said that we also can see our direct to distance on the flight plan page if needed.

Please try to refrain from using emotional words like, 'it could be dangerous'. Any instrument or avionics equipment in an aircraft is dangerous if the user does not know the correct method as to how to use it or interpret the information provided.

Victor
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Edited by Victor - 18 Feb 2015 at 6:56pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote brou0040 Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 2015 at 10:20pm
Originally posted by Victor Victor wrote:

Please try to refrain from using emotional words like, 'it could be dangerous'. Any instrument or avionics equipment in an aircraft is dangerous if the user does not know the correct method as to how to use it or interpret the information provided.

I'd equally say please don't shoot down others concerns.  I wouldn't say this is emotional.  When you read this thread, do you get the perception that most people understood how ATN was being implemented in the system, what it meant, how to use that information, when the measurement will give you a non-intuitive answer, etc?  I agree that it is dangerous because it is misleading unless you have a greater understanding of the system than the baseline documentation provides.

I do like knowing the time and distance along the flight path, but I fail to see the value of ATN beyond sequencing the waypoints.  I still argue that it would be more useful to have a measurement based on getting back to the flight path and then along the flight path because that is a realistic estimate of the time to get to where I'm going.  Even with the planned datablocks, this data is still not available when off the flight path because only ATN is being calculated that includes the flight path, but the ATN measurement without recapturing the flight path gives me zero useful information.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Victor Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 12:49am
Originally posted by brou0040 brou0040 wrote:

I'd equally say please don't shoot down others concerns.


I apologise to anyone who interprets my post as shooting down others concerns. That certainly is not my intent. (Problem with emails and forums)

As well as ourselves, there are potential buyers out there accessing these forums to help decide whether to purchase an IFD or a Garmin or BK. I think we are doing this great and very capable unit a big disservice by using words in our posts like 'dangerous' when we know otherwise. Some features of the IFD are misunderstood, but it is not dangerous.

We all have differing opinions in our preferences. That is fine and respected by all of us and importantly Avidyne, who are endeavouring to rectify concerns raised. Re this particular matter, I am happy with the unit the way it displays distances. However, other poster's concerns have been acknowledged by Steve with a future rectification. We can't ask for more than that.

Victor
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MysticCobra Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 7:05am
Originally posted by 94S 94S wrote:

Even on a DME arc, DME arcs are flown with the DME and a VOR, not the IFD (I believe any approach that has a DME arc is "GPS Overlay Not Authorized", which the IFD will tell you when you select it).  
This is not true, so not a good argument for this debate.  Certified GPS systems have been approved substitutes for DME since 1999.  It is fully legal to fly DME arcs via certified GPS.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pburger Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 7:26am
I said I wasn't going to belabor the point, but here I go.

Victor,

You say your intent is not to shoot down others' concerns, but that is exactly what you are doing when you say that "we know otherwise".  No, WE don't. Let's agree to disagree.  I used the word dangerous on my Feb 15 post, and David used it again yesterday, on Feb 19.  Steve and you both are on record as disagreeing with that characterization.  That's fine.  We can have different opinions.  I respect yours, and I believe you should respect ours.  I stand by my opinion as stated on Feb 15: 

"I believe that this presentation in the TO Waypoint datablock is dangerous and should be modified somehow to present better, less confusing information when off course.  I really don't want someone to hit a mountain."

I also think David's recent posts describe the concern much better than I have.

This forum has been a free and open forum with complete transparency up until now, and I applaud Avidyne for that.  That was a gutsy move, and I think it was the correct one.  With all the transparency, it's still been a big love fest for the IFD-540, and that's understandable because it is a great unit.  As I have said before, I want to sing its praises and I will be the biggest salesperson/advocate for the box because it is a great unit, and because I want it to be a success so that it will retain its value over the years.  However, that doesn't mean I'm going in the tank for Avidyne for something that I think is a bad feature.

I'm happy Avidyne will be adding a few more datablock options which will add some more useful information to my screen, but I must admit I was surprised that no change will be made to the existing TO Waypoint block.  I do think this will turn out to be a thorn in Avidyne's side, but I might be wrong.  The datablock in question shows a waypoint name, Dtk, and Dist, and ETE. To the uninitiated, "Dist" would imply "distance to the waypoint", and "ETE" would imply "estimated time enroute" to the waypoint.  However, these two fields are not what they seem to be if you are off course.  In fact, you have to read a two-page PowerPoint presentation to understand what these two fields mean.  It's not intuitive, and I still have yet to hear how the data is useful -- it really has more to do with what is going on inside the box's calculations than with where the airplane is right now.  I can just hear a lot of people telling their non-initiated friends, "oh that's just how Avidyne does it", or "well, it's not really the actual distance to the waypoint...", and other such excuses.  This confusing off-course presentation may be infrequent enough so that this doesn't become a big issue, but time will tell.  




Edited by pburger - 19 Feb 2015 at 7:28am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SB Jim Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 9:02am
Hi Jake,

How can the ATN distance make any sense (as calculated) if the pilot flies (or is vectored) further off track?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SB Jim Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 9:10am
PS. I'm in year 11 of flying behind a GNS 480, the first WAAS FMS type GPS/NAV/COM for general aviation.

I don't recall ever seeing ATN distance. But I've used the direct to distance on every flight and I find it incredibly useful.

If I can permanently hide the ATN datablock I am likely to do so when my 540 arrives. While it may make sense in an Engineering discipline I'm having a hard time wrapping my head around the usefulness of a distance measuring device that counts down as I get further from my To waypoint.

At that time the ATN figure is theoretical, innacurate and meaningless; it's only valid if one is precisely on course.

With the significant amount of radar vectoring we get out here on the west coast that data block would be useless.

Regards,

Jim
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Victor Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 9:20am
Originally posted by pburger pburger wrote:

when you say that "we knowĀ otherwise"


I don't mind a robust discussion, but I will not tolerate being deliberately misquoted.

Your comment about uninitiated saying that is just how Avidyne does it is equally as assinine. FMS units have been installed in jets and heavy turboprops throughout the world for many years. I fly professionally and have thousands of hours behind different manufacturer FMS's including Universal, Honeywell and Thales. I can tell you the info that is the subject of this discussion that is displayed on those units and the IFD is no different. You don't hear about hundreds of jets and turboprops slamming into mountains around the world because the crews aren't familiar with their FMS.

We are very fortunate to have Avidyne design such a unit for us in the GA sector. By all means bring matters to their attention that are of concern, which are being addressed, but it is also encumbent upon you as a user to learn how to operate and understand its logic properly.

If that is too much for you then ditch your IFD and go back to using a Garmin 100.

Victor
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Edited by Victor - 19 Feb 2015 at 9:33am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bellanca1730a Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 9:44am
Originally posted by Victor Victor wrote:

.... As one example, it is very useful when determining your descent profile. We always use it during an arc approach and upon conducting other approaches in the airline industry regularly. ....

Victor
Mooney M20J


How does one extract the utility of this ATN tool beyond the one example that Victor gave of determining descent profile on a DME-arc approach?

It's a real question. I'm looking for real answers. I'm not looking to make a point. I just want to learn something to help maximize my use of the equipment.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote brou0040 Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 10:33am
Originally posted by Victor Victor wrote:

Originally posted by pburger pburger wrote:

when you say that "we know otherwise"


I don't mind a robust discussion, but I will not tolerate being deliberately misquoted.

Your comment about uninitiated saying that is just how Avidyne does it is equally as assinine. FMS units have been installed in jets and heavy turboprops throughout the world for many years. I fly professionally and have thousands of hours behind different manufacturer FMS's including Universal, Honeywell and Thales. I can tell you the info that is the subject of this discussion that is displayed on those units and the IFD is no different. You don't hear about hundreds of jets and turboprops slamming into mountains around the world because the crews aren't familiar with their FMS.

We are very fortunate to have Avidyne design such a unit for us in the GA sector. By all means bring matters to their attention that are of concern, which are being addressed, but it is also encumbent upon you as a user to learn how to operate and understand its logic properly.

If that is too much for you then ditch your IFD and go back to using a Garmin 100.

Victor
Mooney M20J


I can appreciate Avidyne trying to bring new technology to the GA world, but please acknowledge the target market of this unit.  Most of us are not professional jet pilots with the associated training that comes with that job.  This unit was advertised as being extremely user friendly, not requiring an ATP and FMS dedicated training courses.

It is also not fair to say it is encumbent on the user to learn about ATN because ATN is NOT in any training material.  Do you expect new users to read through every forum post and let them decide for themselves what posts they should learn and which are people posting who misunderstand the equipment?  Nobody should be learning to fly from these forums.  They can come to ask questions, but this should not be the official library of non-intuitive features of the unit.

I think pburger's post was right on and I agree with the non-initiated comment.  If someone were to ask me about that block, I would say I don't understand it's value and that it can give misleading information when you are off course - don't use it.  People may blame me for speaking out of line for Avidyne, but that is currently my opinion.

Since my unit is FINALLY being installed after numerous delays, I have an interest in not turning new customers away as well, but one of the great things about Avidyne is the transparency and ability to debate and potentially impact the design of the box.  I think people reading these posts when tied with responsive posts by Avidyne goes a long way for positive advertisement - beyond any negative exposure by debating the issue in the first place.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 94S Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 10:34am
Ok, ok!  I stand corrected on my comments about DME arcs.  However, the fact that GPS can be used to replace the DME for "measuring the distance to the fix that defines the arc" while flying the DME arc, and the fact that knowing the distance around and arc is useful for descent planning does not negate the fact that the presentation of ATN data in the TO Waypoint block is only valid when you are on the magenta line.  Direct To data will be valid at all times.  I think it is very short sited of Avidyne to assume that we, the end users will always be flying on the planned (or as modified) track.  Mr. Burger has already demonstrated that off track flying does happen, and I thank him for bringing this to everyone's attention.  I was initially hopeful that Avidyne was going to change things to present the direct to data instead of the ATN data.  I'm a bit disappointed that their response was to provide a slide show that explained why the information displayed is not what one would expect and provide a couple of new optional data blocks that provide the information, but only after the user configures the unit accordingly. I'm thankful that the data blocks are being provided, but disappointed that they are not in the base "out of the box" configuration.  There must be away that the unit can display direct-to data on straight segments and curved-to (which I'll lump together with direct-to from here on) data on curved segments, without presenting the ATN data.  Like I've said before, the distance my perpendicular intercept to the magenta line is from the waypoint is of no use to me.

I can see the day long after this thread has gone quiet (or maybe even before) when, if things are left as they are or will be after 10.1.0.0, that someone posts that they were "...out flying the other day and the information in TO Waypoint datablock was giving incorrect information" and this discussion will start all over again.  Because as it is, the base configuration is not intuitive when you are off the track.  I know Avidyne will be adding datablocks that will give the intuitive direct-to information, but my hope is that they will swap the priority of the information and make the direct-to information the base configuration and the ATN info optional so that the unit is as intuitive out of the box as it can be.

I too very much appreciate this forum and Avidyne's willingness to let it all hang out.  I have learned a lot about IFD from the forum, and hope that I can contribute to it as well.  I too think the IFD is a amazing product and sing its praises to my fellow pilots, and I haven't even flown with one yet.  I think the real power of this forum is our ability to share experiences with Avidyne and each other to try to help IFD be the absolute best it can be.  And to that end, I would expect and appreciate that anyone who discovers something potentially "dangerous" or otherwise not ideal to share that info so we may all learn from it.  That is part of the transparency of the forum.  I would also think that most potential customers who research the forum for info on IFD would be glad to see how concerns of users are voiced and addressed.  Kudos to Avidyne for this. 

I would hope that others will chime in on this issue, which ever side your on, so Avidyne can weigh the importance of it and act accordingly.  If I'm only one of a few who wants the direct-to info, I will configure my IFD (hopefully someday to be IFDs) accordingly and fly on.

Sincerely,
David
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pburger Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 11:25am
Victor,

I didn't want to get into a personal debate, but apparently that is where we have landed.  You implied that I misquoted you.  Here is the full sentence from which I took the quote.  This was from your post on this very thread on February 18, at 11:49pm.  I'm not sure how I misquoted you, deliberately or otherwise. 

Originally posted by Victor Victor wrote:

I think we are doing this great and very capable unit a big disservice by using words in our posts like 'dangerous' when we know otherwise.  


I believe my comments were clear that I believe there is confusing information shown when off course, and I stand by that belief.  On the other hand, you are "happy with the unit the way it displays distances."  That's okay with me.  We are all entitled to our opinions.  Can we just leave it at that?

pburger
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AviJake Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 11:53am
The topic is timely indeed - I'm sitting in a FAA sponsored session on Human Factors in aviation displays and distraction is a hot topic here. We take this very seriously and note that while we have no desire to stifle free speech and expression of your concerns, please act as responsibly as you can on this forum when it comes to declaring something as "dangerous".

That is a phrase that is seized upon in our litigious society and twisted into all sorts of perverse and inappropriate uses.

For this particular topic, and the unit in general, we and the FAA have combined thousands of hours into determining the units to be safe.

As to the specific question about how ATN makes any sense as you get farther off trackā€¦ The answer is, of course, that it doesn't. But there's a rhetorical corollary to that. As you get farther off track, how does the flight plan make any sense? You might as well not have one. Everything the FMS does is based on the existence of the flight plan and the assumption that there's actually an intent to fly that.

I think that this whole issue started because the pilot used a technique that works for a GNS430 and that same technique doesn't work on an IFD540. It's not that the Garmin shows the remaining distance to the active waypoint. It's just that the data shown on the Garmin for this particular scenario is what the user wanted. Our data isn't wrong, it's just different than the Garmin. Garmin has no more idea of what the pilot's intent is than we do. He's entered a flight plan and is not flying it. So what's the remaining distance to the active waypoint? Who knows? There is no way to know whether the intent is to fly direct to that waypoint or whether the intent is to fly 10 mile S-turns. Or maybe, as in this case, there is no intent whatsoever to fly to that waypoint. You could just as easily make the case for displaying dashes for the distance to go.

Nevertheless, it seems like everyone is used to seeing distance/bearing direct-to the active waypoint. We get that. It's a useful piece of information to have. So, in the short term, we're adding the new datablocks. We have related considerations to take into account like if someone was looking at that datablock and then switched over to look at the active leg stats on the plan page, they wouldn't match.

In the long term, we can look across the board to determine how to handle all of this. As I said above, the flight plan is what the FMS uses to establish the intent of the pilot. All of the time and fuel predictions are based on that intent. Thus, the existence of the along track information that we are showing. So the real question is what should the FMS assume when the aircraft is significantly off of that path and what measurement is used to establish whether you're significantly off path. When the aircraft is significantly off path, should the FMS assume that the intent is to rejoin the active leg or should it assume that the intent is to fly direct to the active waypoint? In the case that started all of this, neither of those is true. So, what would we compute for remaining distance (which directly affects ETE and fuel burn)?

So, there's much more to consider than just what distance should be shown in a datablock. We'll noodle on it for a while and see if we can come up with a comprehensive solution.
Steve Jacobson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TogaDriver Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 12:17pm
Steve,  thanks for the response.  Since only ATC and the pilot know the intent of their current deviation from a flight plan, I suggest you give the pilot some control over toggling ATN/Direct calculation via an LSK or similar option that is immediately available to the pilot without a lot of messing around.  On the upcoming 440 you will have limited screen real estate.  Maybe just post a notice in the data block that you've gone on VECTORS instead of the standard calculation method.

I've spent 30+ minutes getting vectored all around NorCal airspace even on IFR plans during a busy push - that's a long time to be off the flight plan.  Even with the Garmin I did a good bit of D->,Ent,Ent.

Steve, since you have more time than the rest of us combined with these IFDs, how do you handle extended vectors that take you off plan?  How do you determine, and report, your location when VFR to an airport environment and the runway changed such that you had to maneuver.  

If you have some good tricks we'd love to use them while we wait for the update. Thanks!


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Post Options Post Options   Thanks (0) Thanks(0)   Quote AviJake Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 1:04pm
No magical tricks here. I typically use one of three basic techniques:

1. I use Destination Direct Info block which has the snap vector to my destination. Seems most helpful when flying a radar pattern or terminal area vectoring and want to maintain snap vector SA to the landing patch;
2. I use the range ring on moving map to provide close enough distance;
3. I keep the FMS flight plan representative of the route I'm trying to fly.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SB Jim Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 1:54pm

Most of my instrument flying is in California.

Of course it's very busy out here. As a result radar vectors are the norm, not the exception. I can't remember the last time I flew an instrument approach as published, with or without procedure turns.

On a simple IFR trip to Palm Springs (a 1 hour flight or less) I received four significant reroutes, one of which took me backwards towards Fillmore VOR after I had been cleared direct to Van Nuys.

I think my record for being vectored back and forth across an ILS approach course is 4 times on a single approach (into Oakland, weather was worse than forecast, busy).

Flying off flight plan is simply how they get us all from A to B with all the traffic.

Perhaps the simple answer is to compute ATN as you have done until such time as the aircraft is clearly off course, then compute distance to the waypoint shown as "To" in the flight plan.

If anyone's fuel planning is so tight that can't make a course reversal they have other problems they need to solve.

I'm glad this forum exists, that would've been a "what is that box doing now?" moment had it happened in my cockpit.

<g>

Jim

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Post Options Post Options   Thanks (0) Thanks(0)   Quote NZFlyer Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 2:40pm
Flying the Litton 72 many years ago I seem to remember it had a function called 'remote range', which was instantaneous present position, range and bearing to a waypoint. This was very useful for spacial orientation around weather and when being vectored in the terminal area etc.
If a similar function was used as an IFD Data Block it would be like Destination Direct, but more flexible in that any waypoint could be selected as the subject. Could this be a solution to those wanting more pertinent information when off flight plan?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AviJake Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 2:44pm
I think so. We're trying to create another datablock that allows you to create that kind of datablock for any waypoint, whether it is part of the flight plan or not.
Steve Jacobson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote teeth6 Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 3:20pm
Steve,

That would be awesome.  When I had dual 430s, I had them setup to crossfill in ONLY 1 direction so I could use my bottom 430 for the "what if" scenario.  I could enter direct to any waypoint to get bearing and distance direct without affecting my original flightplan.  Since the 540s crossfill in both directions, that was no longer possible but having the ability to have a datablock for ANY waypoint would be very useful.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AviJake Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 3:23pm
roger
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 94S Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 4:26pm
Steve,

Thanks for the response.  I'm glad to hear this issue is still being discussed on your end.

As you talked about in your 10:53am post today, there is no way of knowing why a pilot has left the planed route.  Or if, how or when he/she might rejoin the route.  That's why in my simple way of looking at things it seems the most appropriate way to display the TO Waypoint data is with the direct-to info for the next down-plan waypoint.  If you're on the course it's correct.  If you're off the course, it's correct.  Simple.  As for the FMS calculations of distance, time and fuel; again using the direct-to info for the next down-plan waypoint followed by the along-track distances for subsequent down-plan waypoints gives the unit the information it needs to do the calculations.  Just as I would if I was doing it with my map, plotter and E6B.  If the pilot is flying to one side, perpendicular to or away from the next down-plan way point, base the calculations on the "if the pilot turns to the waypoint now" scenario.  That is about all you can do, because as you said you can't predict if, how or when they might.  But displaying information that indicates that the aircraft is AT the waypoint, when it is NOT, is confusing to put it lightly.

I am all for having the option to select ATN info for those that want it.  It was mentioned up-thread about using a LSK to select between ATN and Direct-To.  I would offer another idea, tapping (or double tapping maybe more appropriate to avoid accidental selection) of the TO Waypoint datablock to "flip" it from one to the other.  Not sure if that fits into IFD's architecture or not, but thought I'd through it out there.

I understand that the beauty of the FMS is getting from point A to B along the planned route and most people will do just that, but human nature is in play here and we will not always do what we planned.  I think making the unit as human proof as humanly possible is in everyone's best interest, Avidyne's and ours.  The heavy iron airline folks might understand and appreciate the ATN philosophy, but it is my understanding that your target customer is GA.  Nowhere in my GA flight training have I even heard the term "Along Track Normal".  IFD is huge step forward for GA, but in regards to this particular aspect, baby steps may be in order.

Sincerely,
David
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AviJake Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 4:29pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gring Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 4:47pm
All this discussion is interesting, but in practice (and I think I've flown behind an IFD540 longer than any non Avidyne employee) it isn't an issue.  I've used offset tracks, I've been vectored, I've used the FMS flight plan, I've been Direct To, I've created a user waypoint, and none of what has been discussed has ever been an issue in determining where I am relative to a waypoint.  The IFD 540 has so many different ways to maintain SA and of the options Steve mentions above, I primarily use the range rings for distance calculations when flying off route.

I've said it before, if you want an evolution of technology, then be prepared to accept an evolution of process and procedure too.

The only thing I miss is the time/distance on a procedure turn/hold from the waypoint which was displayed in both time and distance on a 430 default nav page.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MysticCobra Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 5:13pm
Originally posted by 94S 94S wrote:

As you talked about in your 10:53am post today, there is no way of knowing why a pilot has left the planed route.  Or if, how or when he/she might rejoin the route.  That's why in my simple way of looking at things it seems the most appropriate way to display the TO Waypoint data is with the direct-to info for the next down-plan waypoint.  If you're on the course it's correct.  If you're off the course, it's correct.  Simple.  

Except, that's not true.  If you're flying a DME arc, the distance along the arc to the next waypoint and the straight-line distance to the next waypoint are not the same.  If you're flying a course reversal, the along-track distance is not the same as the direct-to distance (to the next waypoint).

As Steve has explained, it's not so simple.  If it were, there would never have been a need for this discussion.


Edited by MysticCobra - 19 Feb 2015 at 5:14pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 94S Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2015 at 5:52pm
Yes, but I'm sure that the IFD has a computer in it capable of calculating the actual curve distance to the down-path waypoints from the actual airplane position in both those scenarios, whether on or off the planned course.  And in reality, by the time you're in those phases of an instrument approach, you'd better be pretty close to on the planned course.
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