KAP140 coupled approach question

[Marc_CYBW]

Agreed.

I've had the same vectoring problem a few times, once on a renewal IFR flight test! <grrr>

One always has the be ready to turn off George and fly the plane.

[Tim H]

Make sure the heading bug is aligned with (or very near) the localizer course otherwise the KAP-140 may not capture the localizer.

[Artiom]

Why would activating ILS approach in G1000 matter? It matters for LPV approach but I believe ILS is different. In case of ILS approach LOC1 provides both vertical and lateral guidance to both the pilot and (I assume) AP. So I set localizer frequency and identified it and switched to LOC1 using CDI soft button on G1000. Both lateral and GS were 2-3 dots off when I switched to APR mode. Isn't it enough for AP to follow the glide slope? As I understand APR mode is more precise version of NAV plus vertical guidance.

Thinking about it now, I agree with you - activating the approach (or even loading one, for that matter) should not be required for the AP to fly a coupled approach. I just never use it that way, but no reason it shouldn't work. I still believe that the AP will not intercept the GP/GS when in SUSP mode, though, so that may have been your problem.

I double checked G1000 Pilots Guide and they are talking about SUSP only in context of missed approach when automatic waypoint sequencing is suspended. Not sure why SUSP may happen while receiving vectors to final. After thinking about it more I believe it shouldn't matter to AP. Not auto-sequencing waypoints should not affect AP's ability to capture GS. As I understand it AP using raw localizer input in this case.
But I'll certainly keep an eye on SUSP next time.

[Artiom]

The reason to activate the approach is to have the missed procedure ready to go. On the missed switch to GPS and NAV.

Good point. However I believe loading approach should be enough. GNS430 auto-sequencing approach and suspends upon arrival at MAP. Doesn't G1000 behaves the same way?

[Artiom]

The KAP140 is funny in how it will capture/couple and ILS. You must be close to, but not on, the LOC and must have an intercept angle that is about 30 degrees. If intercept angle is too shallow you will be too close to the LOC and it will not capture. On many occasions I have had ATC turn me too close to the LOC and I would not caputre an "activated" approach. While this is not supposed to happen with the KAP140, it does. Be prepared to hand fly the approach and turn off the KAP140 if that LOC isn't captured when you expect it to be so. If the LOC is not captured, the glide slope will not capture either.

Does that mean if I switch to APR mode when I'm already established on localizer KAP140 will not capture GS?

[carym]

Does that mean if I switch to APR mode when I'm already established on localizer KAP140 will not capture GS?

Yes, that is what happens for me. If localizer does not capture, then neither does the glide slope.

[gandalfim]

Another thing to keep in mind is to notify ATC you're on a coupled approach. That will require that they vector you two miles beyond the approach gate. (the approach gate is 1 mile outside the FAF.) This will give you and the AP more time/space to slide in under the glideslope and begin the descent. They should never vector you to the FAF unless you ask. That's too close.
From the ATC manual:

5-9-1. VECTORS TO FINAL APPROACH COURSE
Except as provided in para 7-4-2, Vectors for Visual Approach, vector arriving aircraft to intercept the final approach course:
a. At least 2 miles outside the approach gate unless one of the following exists:
1. When the reported ceiling is at least 500 feet above the MVA/MIA and the visibility is at least 3 miles (report may be a PIREP if no weather is reported for the airport), aircraft may be vectored to intercept the final approach course closer than 2 miles outside the approach gate but no closer than the approach gate.
2. If specifically requested by the pilot, aircraft may be vectored to intercept the final approach course inside the approach gate but no closer than the final approach fix.
EXCEPTION. Conditions 1 and 2 above do not apply to RNAV aircraft being vectored for a GPS or RNAV approach.
b. For a precision approach, at an altitude not above the glideslope/glidepath or below the minimum glideslope intercept altitude specified on the approach procedure chart.
c. For a nonprecision approach, at an altitude which will allow descent in accordance with the published procedure.
NOTE-
A pilot request for an “evaluation approach,” or a “coupled approach,” or use of a similar term, indicates the pilot desires the application of subparas a and b.

[Artiom]

On the flight yesterday KAP140 behaved weird on descends. I was cruising at 6,500', set altitude 4,500' and VS -400ft/min.The plane started descending but actual VS was jumping between +150 to -900. Same happened later on approach when I tried to set next stepdown altitude. Climbs and level flight worked just fine.
Should I notify maintenance or this is know problem?

[Rick]

On the flight yesterday KAP140 behaved weird on descends. I was cruising at 6,500', set altitude 4,500' and VS -400ft/min.The plane started descending but actual VS was jumping between +150 to -900. Same happened later on approach when I tried to set next stepdown altitude. Climbs and level flight worked just fine.
Should I notify maintenance or this is know problem?

Was it wandering back and forth betweeh 150 and 900 fpm, sort of bobing up and down? If so, this could be the porpoising issue others have complained about in this forum with the KAP140. I have experienced this in both my previous KAP140-equipped DA40's before. I would hit the CWS button and hold the rate of climb/descent steady for a few seconds, then release CWS and often that would "cure" it - for a while at least. In my case, it would happen on climbs and in level flight, too - but just sometimes... As I recall, theories ranged from moisture in the air to plugged static ports, but no definitive solution was ever found that I can remember.

[Marc_CYBW]

This is a known problem on the DA40 and is caused by an eddy that forms behind the pitot/static "tube" at certain angles of attack.

Another pilot on our field had the same problem. He had "the fix" and solved the problem.

We finally agreed to implement "the fix" which consists of installing a pair of static ports that replace the static port on the pitot tube. Parts include two static ports (port and starboard just behind the canopy, and lines to the G1000 sensors).

Since then, not even a hint of a problem.