CDI display during RNAV -> LOC/ILS transition

[cbretana]

I just saw a you tube video on best practices or procedural tips, for IFR Instrument Approaches, using the Garmin G1000. It mentioned, and demonstrated, how the display of the CDI on the HSI would behave when transitioning from the last leg prior to intercepting the localizer & Glide Slope signal. As you approach, buit before you are within range of the glide slope signal, the HSI displays two CDIs, one, in Magenta, which is sourced from the RNAV (GPS) data, and another, in a dashed white color, that represents the localizer signal. When the localizer signal has been identified and validated (it hears the morse code ID), the RNAM CDI goes away, and the LOC CDI goes solid and green, indicating that the CDI is now sourced from the localizer.

Does the Skyview HSI/CDI do this?
If it does not, is this feature possible/feasible with current Skyview hardware?
and if so, is it planned? and if it is not, might I suggest that it be added to the list of future upgrades?

 

[airguy]

That data would not be coming from the Skyview, it is sourced from the certified IFR navigator that feeds the CDI data to Skyview.

 

[cbretana]

There are two data sources involved, which must be compared one with the other to implement this feature. The "data" in question are the deviation data from the certified IFR navigator, and from the Localizer/ILS receiver. Skyview has access to both of these.

To clarify, I am talking about the Garmin GPS175 IFR navigator, interfaced with Skyview HDX through an ARINC-429, and an SL-30 compatible Nav Com receiver (actually, it is a Garmin GNC215), interfaced through one of the HDX serial ports.

 

[airguy]

In that particular case, no it cannot. Skyview will display information from a single outside source, screen selectable. It can follow it's own VFR gps guidance, or follow any outside device that feeds CDI guidance, but only one source at a time. In your case of a G175 navigator (which is GPS only), and the SL-30 (which is VHF only), you can manually switch between them on the screen at the appropriate point in space/time, but it will not display both of them or automatically switch between them.

 

[cbretana]

airguy,

Thanks for your response. I anticipated that it would be the case that the current capabilities of the entire Skyview system, which are of course a combination of the capabilities of the current Skyview software and the hardware are likely to be as you describe. My suspicion, which your answer does not address, is whether this inability to examine and compare two distinct sources of navigational information and modify the display of the CDI based on that comparison, is due only to the software or is a hardware limitation, an intrinsic attribute of the way the Skyview display is constructed. Clearly, the data from all navigational sources, is available to the Skyview HDX computer and the screen, as it is possible to simultaneously assign a different separate nav source to each of three distinct available navigational output tools on the HSI, (the CDI and two separate Bearing pointers.) It is only that each display element (CDI - two separate Bearing pointers), can only be "connected" to a single data source at one time.

And we know that this capability is possible, as the Garmin G1000 does provide this feature. So clearly, if it not a hardware limitation, then a software upgrade could be done that would add this capability. Other questions obviously would still need to be addressed as to the feasibility (cost/level of effort) of such a software upgrade /modification. Would it be very simple? or require a more extensive architectural change to the overall software design?

It would seem to me that the required change might simply be to add an additional display element (a second [alternate] CDI) that would appear, disappear or change color based on the data analysis/comparison/verification done in the background software routine.

In any case, once an accurate cost estimate was available, the next question would be whether the value of this feature would be worth that cost. Its absence when competing products offer the feature might play a factor...

In any event, if any Dynon technicians or the hardware/software system architects responsible for the Skyview could weigh in on these questions, I would appreciate it.

 

[tylerpattison]

I believe I understand what you are asking for: The ability for the SkyView system to monitor and automatically switch between independent (key word: independent) navigation sources when transitioning from RNAV-based navigation to localizer navigation when joining the final segment of an ILS/LOC approach.

SkyView will do what you seek if the selected navigation source driving the HSI can change itself from GPS to VLOC. For instance, on some navigators it is possible to configure their CDI mode to auto-switch from GPS to VLOC when joining a localizer on an ILS approach. If the data it is sending SkyView makes that change then SkyView will follow accordingly and transition from purple needles to green needles without pilot intervention.

SkyView can monitor independent navigation sources (e.g. a GPS175 and an SL-30) but will not switch between those sources automatically. The reason that is not possible is because the SkyView system is not a IFR navigator. It is perfectly capable of monitoring independent signals with its hardware and software, but there is not currently a way for SkyView to know (without ambiguity) that you want to do an ILS approach, nor for it to know that it's the proper time to switch sources. All it can see is that there is a navigation signal from a GPS and a navigation signal from a NAV radio. The missing "bigger-picture" knowledge is programmed into the IFR navigator. It is not practical to make assumptions about the flight plan outside the scope of the navigator and its associated flight plan. Doing this would essentially usurp the navigators authority to determine the correct navigation mode, and creates many possibilities for unintended consequences and/or pilot error.

Said in a shorter way: If you want to switch navigation sources during approaches without pilot action, you need an IFR navigator that can perform the delicate task of correctly switching sources. If you don't have that equipment you'll have to decide when to switch yourself.

A bit long-winded, but I hope that sheds light on what you were asking.

 

[cbretana]

tylerpattison,

Close, and although I am interested in that question as well, it is not exactly what I am am asking about
My question stems from the following you tube video:

In this video, during the intercept of the LOC signal, just before the LOC needle comes of the wall (around 22:20 into the video), there are two CDIs displayed, a solid line magenta one being driven by the GPS signal, based on the published ILS final approach course, and a white, dashed line one representing the actual LOC signal, (which has not come off the wall yet).

When the LOC signal comes off he wall, the LOC CDI automatically changes to the following display, with a solid green line CDI .

Is this possible in Skyview? Clearly, the data from the GPS is always available, and if the NAV/COM receiver is tuned to the appropriate frequency, The LOC navigational signal is also available. I am guessing that at the moment, the current software release of Skyview only has one available CDI object that can be bound to a data source, and that it can only be bound to one data source at a time. To do what the G1000 seems to be doing, it would have to be coded so that the one single CDI object in code had access to both the GPS and the LOC (SL30 compatible) data sources, and could display both, in different colors, or,

Skyview would have to be modified to have two CDIs (like it now has two Bearing pointers) and the when a LOC/ILS approach was loaded, it would have to initially display both of them, a magenta one bound to the GPS IFR Navigator, and a white dashed line CDI bound to the LOC signal.

Then, when the plane gets close enough to the LOC final approach course for the CDI to come "off the wall", the GPS CDI would disappear and the LOC CDI would change to a solid green line...

Would an upgrade to implement something like this require a hardware change, or just a software upgrade?

 

[rjones560]

I just saw a you tube video on best practices or procedural tips, for IFR Instrument Approaches, using the Garmin G1000. It mentioned, and demonstrated, how the display of the CDI on the HSI would behave when transitioning from the last leg prior to intercepting the localizer & Glide Slope signal. As you approach, buit before you are within range of the glide slope signal, the HSI displays two CDIs, one, in Magenta, which is sourced from the RNAV (GPS) data, and another, in a dashed white color, that represents the localizer signal. When the localizer signal has been identified and validated (it hears the morse code ID), the RNAM CDI goes away, and the LOC CDI goes solid and green, indicating that the CDI is now sourced from the localizer.

Does the Skyview HSI/CDI do this?
If it does not, is this feature possible/feasible with current Skyview hardware?
and if so, is it planned? and if it is not, might I suggest that it be added to the list of future upgrades?

Dynon does not have a IFR certified navigation system. Those of us that have Dynon equipment use a Garmin or Avadyne GPS navigator for IFR navigation.

 

[cbretana]

rjones,

Thanks for that tip. Yes, I know several individuals who have certified IFR navigators. I am, myself one of them. I have a Garmin GPS 175. But I am confused, were you intending this to address my question in some way? If so, could you elaborate? Remember I am asking about Skyview display logic/functionality during a LOC/ILS approach.

 

[rjones560]

I was replying to the wrong question by tapping on the wrong thread. Sorry about that. Dynon will not auto switch nav sources going from GPS to localizer. I only flew one jet that could do that and I did not like it. It did not always work right.

 

[cbretana]

Yes I know that that Dynon Skyview does not currently do this. Perhaps your confusion is my bad, in that I was not clear, but my question is whether this inability is the result of a hardware design issue that would require a hardware upgrade to correct, or just a failure to code this capability into the Skyview software, which would not require a hardware upgrade...

Sorry your experience with this feature in another aircraft was not a positive one, but if implemented properly, I would find this to be a workload reducer and situation awareness enhancer. It's not critical, as it is obvious when the GPS CDI comes off the wall, but that might happen before the LOC CDI even locks on. and switching the CDI to the LOC source then would be premature. Having actual LOC signal displayed on a second CDI (to visually compare with GPS CDI), would allow the pilot to monitor the LOC signal at the same time he is using the GPS to intercept the LOC/ILS final approach course, and switch to the LOC CDI only when the receiver has picked up and verified the signal.

 

[rjones560]

The problem was usually when you got a long straight in off your arrival because the runway just happened to nearly line up with your inbound heading. The system would want to go to the LOC 30 miles out or more. GPS was far more accurate that far out. What it needed to do was wait until we were close to the FAF.

 

[rjones560]

The problem was usually when you got a long straight in off your arrival because the runway just happened to nearly line up with your inbound heading. The system would want to go to the LOC 30 miles out or more. GPS was far more accurate that far out. What it needed to do was wait until we were close to the FAF.