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Synthetic Vision on IFR Approach

avrojockey

Well Known Member
Patron
Anyone else not care for the synthetic vision will shooting approaches to minimums?

When it's smooth it works great with the FPV on the runway, but if there's the slightest turbulence and associated yawing (no YD in my ship) the terrain in the synthetic vision is distracting at the frame rates of the GDU370. Of course, the closer you get to the ground the worse it is.

Weather ended up below minimums yesterday (1300 RVR not forecast :() and had to divert and wife pick us up.
 
I don't know what you are using, but I have a Garmin stack, often have to fly approaches to minimums, flying the LPV is like being on rails, if I didn't disconnect the auto pilot, the mains would touch the 1,000' mark (refrigerators). I used to teach "glass" school at the airline, pilots were resistant for a few days, then you couldn't get them to return to the old steam gauges for anything. Once you have the "gains" on the autopilot or EFIS tweaked, it should work as advertised. I suggest reading the F______G manual in the setup section!
Once dialed in, after a few approaches, you will learn to love it!

DAR Gary
 
I gotta admit that I've never paid too much attention to the synthetic vision on the G3X when shooting an approach, other than glancing at the runway alignment, but that's mostly in smooth air. But I've never flown a coupled approach either, I suppose it would be much more distracting if you're just monitoring on a coupled approach. I'm just trying to keep up when hand flying in turbulence.
 
I gotta admit that I've never paid too much attention to the synthetic vision on the G3X when shooting an approach, other than glancing at the runway alignment, but that's mostly in smooth air. But I've never flown a coupled approach either, I suppose it would be much more distracting if you're just monitoring on a coupled approach. I'm just trying to keep up when hand flying in turbulence.

These are all hand flow, I don't seem to have the Vertical Speed Gain and Vertical Accel Gain dial in enough to trust it during approach. It likes to chase the GS when coupled. I'm all ears if anyone has some tips outside what is in the installation manual to get that set up.

Yesterday we had to divert because the RVR was 1300 and got to minimums and saw nothing...nada. Ended up in KMTW with low ceilings but decent vis and a bit a wind to keep the fog at bay that was starting to effect everywhere else.

This is not a matter of being able to execute the approach or skill...it has to do with background scenery, at low screen Hz, swaying back and forth with the yawing motion in turbulence. I didn't care for it, and will do some practice without the synthetic vision and see if it makes a difference. I absolutely love the syn vision when it is smooth...it is fantastic!

Does anyone know if the G3X Touch screens have a better refresh rate?

Maybe it was just the circumstance...I was also flying from the right seat and not shot an approach from over there in awhile. I had a newly instrument rated pilot in the left seat, try to get some quality actual time. The weather went south pretty fast (not forecast) and decided the situation was not build for learning experiences, so I decided to fly.

Here was our flight from MSN to ATW and divert to MTW -
https://flightaware.com/live/flight/N904DC/history/20211224/2015Z/KMSN/KMTW I really want to go to GRB or OSH but they were going the way of ATW pretty fast. It did end up being a good learning experience for my left-seater, but not in the way I was hoping.

Here's what the weather was doing in ATW yesterday...you can see it dropped close to minimums after our departure from MSN and went below minimums right after we checked on with approach (only a 25 minute flight with tailwind)
https://www.aviationweather.gov/metar/data?ids=KATW&format=raw&hours=36&taf=off&layout=on

Maybe it's just me, but I hope the newer generations of the G3X are better. BTW I have everything Garmin and I'm definitely a Garmin Fanboy
 
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Tim,
You really need to talk to Stein for the “Cliff Notes” version of setting up your autopilot. They are worth the money.
 
I use my G3X setup for RNAV approaches in to work, and often the return back home, for my daily commute. I’ve done just over a thousand instrument approaches with this system now and value it’s accuracy and usability very much.

On several occasions, I have let the AP fly it to the runway just to see it work; the centerline has always been between the mains, which is more than I can say for the human pilot who does all the other landings.

And now that Garmin has made the transition from VNAV to GP seamless, it literally is, well, seamless.

I’d suggest that if you’re not solidly holding the “purple line", maybe you have a bit much gain and are hunting. I do agree the AP can't eliminate all of the effects of turbulence, but neither can my hand on the stick. Overall, I think it performs very well.

More specific to the use of SV itself, I enjoy having the synthetic overlay for comparison to view out the windshield.
 
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Sorry guys...I'm doing a poor job of explaining the issue. There is no problem with the guidance the G3X/GPS175 is giving my on the approach. It is dead on..fantastic! The pilot, far from perfect, but as a CFII and 121 instructing experience knows when he's screwing up. The approach was great...except for the weather.

The issue is with the background terrain graphics moving side-to-side (yaw) in turbulence. It's worse the closer you get to the ground, because, as with real life, motion displayed is more pronounced the closer you get to the ground. I have to consciously block it out...I don't think that's a good thing form a human factors standpoint

Football analogy...Let's say you're kicking a field goal. You have the goal/uprights (ie. the FD/CRS/GP), and the background - the stands full of people (synthetic terrain). Now imaging aiming for the uprights with all the people and the stadium moving side-to-side. The goal isn't moving, it's perfectly displayed, but the background movement creates a distraction at best and possibly the perception of goal movement. I'm trying to identify if there's a systemic threat that needs addressing or if it's just me.

The whole issue is compounded by the refresh rate of the classic G3X screen. It's normally fine but seems poor in this circumstance. Think movie at 24fps instead of TV at 30 fps...not really and issue, but enough to distract and sometimes jumpy.

Please do not discount this a pilot performance issue. There are example's of accidents related to limitations in instrument systems, such as speed precession in Attitude Indicators. I'm curious if there's more to this, more than just a great system that otherwise greatly enhances safety.
 
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SV ? Not a big fan! But today’s technology is wonderful.

When I practice ILS approaches (my 430s are non-was) I always do at least two approaches. The first one “coupled” and the second “uncoupled.”

My GRT EX has a ten mile range SV and frankly I find it more distracting than useful. It’s not the refresh rate either. I guess I’m old school in that I prefer “needles” over their “flight director” guidance for the PDF screen and map mode for the MFD screen. That’s not to say the FD guidance lags or anything like that; it’s just that I feel like I’m in “chase mode” as opposed to a “proactive flight mode” when I’m using the FD.

The SV function on the GRT EX has a “white horizon line” that is displayed when SV is selected and that horizon line is different from where the terrain and sky come together on the PDF screen when at altitude (often 3+ degrees) - which I frankly find extremely distracting. It less distracting at typical approach altitudes but the difference is still annoying.

It boils down to what flight system read out gives you the ability to fly a consistent stabilized approach. I will say my autopilot coupled approach needs some tweaking because there does appear to be some lag. I’ve also noticed the auto trim will sometimes lag too much (aircraft gets nose high during configuration and airspeed changes) which indicates (to me) the auto trim speed rate is probably set too slow.

Now SAP (synthetic approach) is something else! On the GRT EX there is a synthetic approach function which will compute a 3 degree straight-in approach approach into any database runway. While it doesn’t provide a guaranteed obstacle obstruction approach it is great for RNAV approach backup or flying into a new airport environment. Coupled to the autopilot it’s really sweet because it allows the pilot to catch a lot of “peeks” while monitoring the aircraft’s approach.

Getting back to the subject of this thread I am not a fan of SV “unless” I’m scud running - which frankly I wouldn’t trust any SV system for obstruction avoidance. Like I said - I’m old school.
 
The issue is with the background terrain graphics moving side-to-side (yaw) in turbulence. It's worse the closer you get to the ground, because, as with real life, motion displayed is more pronounced the closer you get to the ground. I have to consciously block it out...I don't think that's a good thing from a human factors standpoint

Hi Tim,

You may already know this, but synthetic vision is heading aligned (aligned with the aircraft nose), not GPS track aligned. Synthetic vision is meant to mimic the view out the aircraft windshield (not aircraft track). If your aircraft is yawing in turbulence, the synthetic vision view will also be moving (yawing) to match the nose of the aircraft.

Heading aligned synthetic vision is actually required behavior for certified systems offering this feature. When you break out of the clouds, the airport environment and runway position/alignment shown on the PFD should match what you see out the window. Not sure why this would be poor human factors.

The whole issue is compounded by the refresh rate of the classic G3X screen. It's normally fine but seems poor in this circumstance. Think movie at 24fps instead of TV at 30 fps...not really and issue, but enough to distract and sometimes jumpy.

The G3X Touch GDU 4XX displays are much faster than the older G3X GDU 37X displays, including display refresh rate.

Steve
 
Hi Tim,

You may already know this, but synthetic vision is heading aligned (aligned with the aircraft nose), not GPS track aligned. Synthetic vision is meant to mimic the view out the aircraft windshield (not aircraft track). If your aircraft is yawing in turbulence, the synthetic vision view will also be moving (yawing) to match the nose of the aircraft.

Heading aligned synthetic vision is actually required behavior for certified systems offering this feature. When you break out of the clouds, the airport environment and runway position/alignment shown on the PFD should match what you see out the window. Not sure why this would be poor human factors.



The G3X Touch GDU 4XX displays are much faster than the older G3X GDU 37X displays, including display refresh rate.

Steve

Makes total sense this the expected behavior. I’m glad to here the 47X is improved. It’s not distracting enough warrant an upgrade but if I have GDU go out then I most certainly will.
 
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