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 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.
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.
Situational awareness.
A GPS course needle. It's not the localizer needle you use to fly a LOC or LOC-BC approach. Those needles are green.
Whoa! It sounds like people are talking about two different things here. Let me see if I can clarify or maybe confuse even more
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.
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.
Which back course is that?
The point was what the arrow was called not what color it is.
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.
