Course reversal with G1000 & KAP 140

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Sandy
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Re: Course reversal with G1000 & KAP 140

Post by Sandy »

While I defer to those with far greater knowledge of the workings of autopilots, logic tells me the following. Planes turn when their ailerons are deflected, and when an autopilot is in use, the deflection of the ailerons occurs when the autopilot commands the aileron servo to move the ailerons. I suspect that the signal to the autopilot servo is limited to a deflection that will max out when the plane is turning at 3 degrees per second (“a standard rate, or two-minute, turn”), and that the autopilot includes some means, e.g., a turn coordinator, that tells the autopilot when it has maxed out the rate of turn. Other than that, the autopilot really has no clue about the position of the aircraft, but merely takes an input from some guidance system that tells the autopilot to command a left or right turn.

The MFD on the G1000, on the other hand, is a visual display device that can depict both waypoints, routes, airways, airports, and other items that can actually be used as navigation “fixes”, but it also depicts other items, e.g., rivers, towers, lakes, etc., that are not navigation fixes (absent someone entering them as a User Waypoint). Included in the “other items” category, are things like holding patterns where a course reversal may be required prior to commencing a descent. While I, personally, have always hand flown my approaches, I am now curious about whether my 2005 non-WAAS G1000 DA40 can actually enter and fly any holding pattern, as I have never tried it. That having been said, though, logic tells me that the issue of whether the plane can fly the course reversal really depends on whether the G1000 software regards the holding pattern as a series of waypoints or just simply as an “other item” to be displayed visually. From the discussion, thus far, along with logic, it should not matter whether the autopilot is a GFC700 or a KAP-140. What really matters is whether the software in the G1000 does the “visual depiction – to – waypoint” conversion so that the autopilot knows whether to command a turn. In saying the foregoing, I am simplifying things somewhat, as I recognize that the autopilot is most likely getting its left/right information from the HSI, rather than from the MFD. However, I want to raise the following as an issue that I intend to examine the next time I can go out to “test” a theory, so it is important for this discussion to think of the navigation as being depicted on the MFD.

Assuming that my logic is correct, and that the real issue is that the software in my plane simply does not include the ability to “convert” the visually depicted holding pattern into a series of navigable waypoints, I know that I can follow the procedures outlined in the KAP-140 manual, i.e., go into HDG mode upon reaching the IAF and set the heading bug to 30 degrees counterclockwise to the outbound course (assuming right turns in the holding pattern), fly for 30-45 seconds, then turn the heading bug to the inbound course while allowing the plane to make a standard rate turn inbound, at which point NAV mode can be selected on the autopilot.

On the other hand, assuming an approach speed of 90 kts, with flaps in T/O position, the same logic dictates that I could remain in NAV mode if I set a User Waypoint (WPT A) at the IAF, a second User Waypoint (WPT B) relative to the IAF with DIS equal 1 mile and RAD of 30 degrees counterclockwise to the outbound course, and a third User Waypoint (WPT C) at a DIS of 1.5 miles and a RAD of the outbound course from the IAF. If I were to then enter WPT A, WPT B, and WPT C into my FPL prior to the IAF, it seems to me that my plane will simply reach the IAF (as WPT A), then fly the course reversal back to the IAF after which it will follow the inbound approach.

Of course the location of the User Waypoints would be different (clockwise vs. counterclockwise angle) if the holding pattern requires left turns.

Comments?

Sandy
Last edited by Sandy on Wed Aug 15, 2018 2:50 pm, edited 1 time in total.
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Re: Course reversal with G1000 & KAP 140

Post by Sandy »

40flyer wrote...
Can’t figure this out. The approach I’m flying is the RNAV 28 at 6D6 with DOTIZ as IAF.
If my logic/procedures/understanding are correct (see my prior post) then WPT A would be a User Waypoint set at DOTIZ; WPT B would be a User Waypoint set at DOTIZ, DIS 1, RAD 70; and WPT C would be a User Waypoint set at DOTIZ, DIS 1.5, RAD 100. After creating and saving the User Waypoints, if you do this regularly, you can enter WPT A, WPT B, and WPT C prior to DOTIZ, then fly to WPT A (rather than DOTIZ) to start the teardrop/approach.

If you try it, let me know how it compares to the visually depicted teardrop.

Sandy
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Re: Course reversal with G1000 & KAP 140

Post by 40flyer »

Sandy, I am sure what you propose as a solution would probably work, and if you were consistently flying the same approach would be worth the time to create those user waypoints. What I still don’t understand is what the GFC 700 is responding to from the G1000 flight plan that the KAP 140 does not. And I don’t believe it has anything to do with WAAS capability. It’s a lateral issue.
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Re: Course reversal with G1000 & KAP 140

Post by Sandy »

Don, prior to actually testing my proposed approach to using the KAP140 to fly the course reversal in NAV mode, for the sake of "covering the bases" I suggested creating three new User Waypoints (WPT A, WPT B ,and WPT C), However, WPT A was merely a "renaming" of your IAF, whereby the original DOTIZ name could probably be used even though it will, again, appear in the FPL. WPT C was only created to insure that you were on the inbound leg before turning into DOTIZ, whereby WPT C might not be needed, either, as you will actually turn onto the inbound leg when you reach DOTIZ. So, depending on what flying shows me, only WPT B (DOTIZ, RAD 70, DIS 1) is really needed, so it's not a question of it really taking any time at all to follow my proposal, as WPT B is just going to be 30 degrees off from the outbound course and 1 nm from the IAF. Further, from your initial post I was under the impression that you do, actually, fly the RNAV 28 at 6D6 with DOTIZ as IAF regularly. My plane is presently getting its ADS-B installed, and, possibly, getting its backup AI replaced, so I won't be able to do anything about trying it until I get it back.

Someone in the thread mentioned using a KAP140 to fly a DME Arc approach using a KAP140 in NAV mode. I think that the way to do that would be to program a series of User Waypoints from the IAF to the IF based on an offsets from the VOR/DME with RAD of about 10 degrees each offset from the IAF and then from each succeeding User Waypoint using the DME arc radius as the DIS to the IF. Again, I don't see any reason why that won't work using the KAP140, although I always considered it to be fun to hand fly DME arcs.

Sandy
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Re: Course reversal with G1000 & KAP 140

Post by pietromarx »

Sandy - from what I can tell, your suppositions are correct. Your non-WAAS KAP-40 G1000 plane won't fly holds by itself and, yes, you can input waypoints for arcs and holds and have the airplane fly them. (An added advantage: it gives you something to do if you're ever stuck in a hold for awhile.) The WAAS versions of the G1000 correct the holds for wind, but your approach would likely do the same thing.

It is just software functionality ...
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Re: Course reversal with G1000 & KAP 140

Post by arksat »

I had been wondering why my KAP140/non-WAAS G1000 doesn't fly holding correctly :scratch: , then found this discussion thread. It clarifies my question. Thanks all!

Here's a picture of my plane flying inbound regardless of a depicted teardrop entry.
I felt bit scary when I encountered this at the first time.
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Re: Course reversal with G1000 & KAP 140

Post by midlifeflyer »

I know it's an old thread but it's the one to bring this up.

A friend recently acquired a DA40 G1000/KAP 140 to join out club's G1000/GFC700. I flew the KAP combo in the past so I've been working on a video to show the club members the difference. My experience was the same as others - no GPS. Not procedure turns. So yesterday, I go up to record. There I am, explaining how we need to change to HDG mode to fly the HILO and the AP makes the teardrop entry and turns. I'm not posting the video but I actually , "Holy crap!" when I see it turn toward the course needle.

What happened? Was there a firmware update adding GPSS to the basic NAV function? Or was it just an anomaly – basically a U-Turn due to lack of course guidance that just happened to be in the correct direction?
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Re: Course reversal with G1000 & KAP 140

Post by midlifeflyer »

midlifeflyer wrote: Sat Nov 06, 2021 1:29 pm Or was it just an anomaly – basically a U-Turn due to lack of course guidance that just happened to be in the correct direction?
Yep. I"m an idiot. I was so surprised by the turn I didn't even realize it couldn't have been a teardrop since it didn't stop turning when it hit the 30 degree outbound point. I shoulda known better - I've seen other pilots fall into that trap. At least I have a good "gotcha" for the final video!

Duh!
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Re: Course reversal with G1000 & KAP 140

Post by waynemcc999 »

midlifeflyer wrote: Sun Nov 07, 2021 9:33 am
midlifeflyer wrote: Sat Nov 06, 2021 1:29 pm Or was it just an anomaly – basically a U-Turn due to lack of course guidance that just happened to be in the correct direction?
Yep. I"m an idiot. I was so surprised by the turn I didn't even realize it couldn't have been a teardrop since it didn't stop turning when it hit the 30 degree outbound point. I shoulda known better - I've seen other pilots fall into that trap. At least I have a good "gotcha" for the final video!

Duh!
Mark, waitin' for that video! :P
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Re: Course reversal with G1000 & KAP 140

Post by midlifeflyer »

It will be a while, Wayne.
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