MBDiagMan
Final Approach
In the case of flying a backcourse with either of these navigators, what will the navigator, if anything, bring to the party? Surely it won’t reverse the CDI to make it the same as flying a LOC or could I be that lucky?
420/430W and a Backcourse?
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What kind of CDI? If you have a G5 HSI it will do it automatically.
MBDiagMan
Final Approach
A CDI in both planes with vertical guidance on the WAAS unit and no vertical guidance on the 420 non WAAS.
Your response brings another question to my mind. Although I wouldn’t use it except in an extreme emergency, I wonder if the HSI in Foreflight synthetic vision would work the same way you describe?
Your response brings another question to my mind. Although I wouldn’t use it except in an extreme emergency, I wonder if the HSI in Foreflight synthetic vision would work the same way you describe?
Actually, an HSI or its electronic equivalent doesn't have to "do" anything to handle back courses. It's not the "course" that's the problem with the apparent needle sensing, but the pilot's point of view.
But if you don't reverse the needle you have to reverse sense, right. When I do a BC with my 530 and G5 the G5 already has the needle reversed and I fly it like a front course.
An HSI like the G5 does not reverse the needle. It just turns it upside down so it looks reversed to you.
I guess I don't understand the nuance. The arrow is pointing down. How is that not reversed?
The needle is oriented to the course. The nuance is that the G5 didn't reverse the needle, your view of the needle is reversed. If you were flying a perpendicular course, then the needle would be moving up and down instead of side-to-side. I suppose that, in a way, the G5 unlocks how you see the needle. You could crane your neck looking at a conventional CDI to get the same effect.
I suppose it's also possible we're both saying the same thing, but from different perspectives...
... but mine's better.
luvflyin
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It sounds like with the G5 installation, it might be the G5 that's doing the work to give 'normal sensing.' Is this true? I'm wondering about the OP question.
"In the case of flying a backcourse with either of these navigators, what will the navigator, if anything, bring to the party? Surely it won’t reverse the CDI to make it the same as flying a LOC or could I be that lucky?"
"In the case of flying a backcourse with either of these navigators, what will the navigator, if anything, bring to the party? Surely it won’t reverse the CDI to make it the same as flying a LOC or could I be that lucky?"
chemgeek
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chemgeek
Won't a GPS navigator in VLOC mode just drive a traditional CDI just like any other VOR/LOC receiver? If you have an HSI like a G5 you get a more intuitive display of your position relative to the desired track. In GPS mode the CDI will always sense "normally" for the selected leg.
I think some of the confusion might be because the SL30 (on which the GNS VLOC radios are based) does have a BC mode, which can reverse the CDI needle.
luvflyin
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Does the 'box', the 420/430, do that internally? Literally send out a 'reversed' signal to the CDI/HSI or whatever other things there are, if any, that your looking at for your 'needles.' Seems like that could be a problem if your CDI/HSI or whatever has it's own 'reversing' function. If there are any, I dunno for sure. But it seems I've seen some that do.
I'm probably using the wrong term. What do you call the purple arrow thingy? When I load a BC the G5 automatically puts that opposite the course. So when established it is pointing down instead of up.The needle is oriented to the course. The nuance is that the G5 didn't reverse the needle, your view of the needle is reversed. If you were flying a perpendicular course, then the needle would be moving up and down instead of side-to-side. I suppose that, in a way, the G5 unlocks how you see the needle. You could crane your neck looking at a conventional CDI to get the same effect.
I suppose it's also possible we're both saying the same thing, but from different perspectives...
... but mine's better.
This isn’t a G5 thing, it is an HSI thing. If you’re flying a backcourse with an HSI and invert the course needle it will be “normal sensing” on all of them.
So in the case of the G5 or G500 or G1000, etc. when you load a backcourse approach the needle is automatically inverted rather than you having to manually do it.
It sounds like the OP has a DG and a separate indicator. If you’re using a separate indicator you can spin the OBS knob to whatever you want and it won’t change the indication. As far as I know, the G430/530 will not reverse the indication on those. It has been a long time since I’ve flown instruments in an airplane with a 430 and a separate indicator though so I’m willing to be proven wrong.
midlifeflyer
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Situational awareness.
midlifeflyer
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A GPS course needle. It's not the localizer needle you use to fly a LOC or LOC-BC approach. Those needles are green.
midlifeflyer
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Whoa! It sounds like people are talking about two different things here. Let me see if I can clarify or maybe confuse even more
1. a localizer-based approach is flown with the localizer needle primary.
2.A GPS course is a GPS course is a GPS course. Always "to" something. It's always normal sensing. So if you are following a GPS needle instead of the LOC, there's no translating going on. It's a GPS course, not a localizer course, so reverse sensing is not an issue whether you are using a stand-alone CDI or a HSI. (I won't get into the issue whether or not yo are allowed to substitute GPS for a LOC).
3. A HSI - no matter whether associated with a digital PFD or or completely old school - operatives differently than a stand-alone CDI. With a HSI, there is no reverse sensing issue. You set the course to the LOC front course. The head of the needle points in the opposite direction, but the needle senses normally. Needle left, turn left; needle right, turn rit.
luvflyin
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Whoa! It sounds like people are talking about two different things here. Let me see if I can clarify or maybe confuse even more
1. a localizer-based approach is flown with the localizer needle primary.
2.A GPS course is a GPS course is a GPS course. Always "to" something. It's always normal sensing. So if you are following a GPS needle instead of the LOC, there's no translating going on. It's a GPS course, not a localizer course, so reverse sensing is not an issue whether you are using a stand-alone CDI or a HSI. (I won't get into the issue whether or not yo are allowed to substitute GPS for a LOC).
3. A HSI - no matter whether associated with a digital PFD or or completely old school - operatives differently than a stand-alone CDI. With a HSI, there is no reverse sensing issue. You set the course to the LOC front course. The head of the needle points in the opposite direction, but the needle senses normally. Needle left, turn left; needle right, turn rit.
Gotcha. What I'm still not completely sure about is what was said above in post #11. "I think some of the confusion might be because the SL30 (on which the GNS VLOC radios are based) does have a BC mode, which can reverse the CDI needle." Will an SL30 or any other NAV or NAV/COM, including those that are in a GPS box(VLOC) that has the NAV function, ever literally send out a reversed signal?
midlifeflyer
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Beats me. Autopilots generally have a BC or "REV" mode. I guess there's no reason why a NAV box couldn't. Whether it has been done or the post is actually talking about "ink needles" rather than green, I don't know. One of the few remaining LOC BC courses is nearby and I haven't bothered, but I know it gets used for instrument training in aircraft with GNS and GTN and I haven't heard anything suggesting they are getting "fixed" localizer signal to a separate CDI.
midlifeflyer
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Which back course is that?
But what are you sighing about? You asked about the "purple" thingy and that yu owere probably using the wrong terminology.
The point was what the arrow was called not what color it is.
midlifeflyer
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To help (or not). Here is the difference between conventional navaid course needles (commonly, "green needles") and GPS course needles (commonly, "pink needles") with a LOC-BC loaded. For reference, this is the LOC-BC runway 22 at Fayetteville, NC (KFAY). Same approach, same location on the approach, same heading. The one and only difference is whether the CDI is set to GPS or to VLOC. The pics are from a GDU 1060 PFD connected with a GTN750Xi GPS unit. In both cases, there is no reverse sensing. If the airplane were left of course, the needles would be to the right in both cases
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I believe it's called the "course pointer". It points to the selected course, which on the G5 is only selectable when using VLOC sources. For GPS sources, the G5 automagically gets/sets the course from the flightplan. I believe the G5 can also get/set the course pointer for VLOC sources if VLOC navigation is part of your GPS flight plan (I know this is true for the G1000), so the course pointer selection is mainly there in case you don't bother to load your VLOC stuff into the GPS flightplan.
Old school HSI, you'd have to manually set the course pointer to match the GPS flight plan. Or if you don't care about wind correction, just keep setting it to be vertical.
luvflyin
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Ah. That seems to the answer the question. If you select it, it outputs a reversed signal. Thx