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Skyview Screen Shutter Flutter

todehnal

Well Known Member
I call it "Shutter Flutter" because it reminds me of some old film strip movies where your eye catches the frames advance which gave them a flutter effect. At cruise I can detect a very slight screen flutter on my Skyview. It is more noticeable in the background on the primary display area, and it appears to be cycling somewhere in the 8 Hz area. Interestingly, I don't see it at idle. I have watched some of the in flight training videos that Kirk from Dynon made and noted that there was no flutter, of course he is not flying an RV-12. So, I thought that it may be unique to my installation, but I just viewed a youtube video of a Skyview display in a flying RV-12 and I noticed similar flutter. It is not a serious distraction, but I sure would like to identify the cause. Now I am thinking that this may be common to the RV-12. Is anyone else experiencing this, or do I have a unique problem?

Thanks.........Tom
 
I've got almost 300 hrs on my -12 and I haven't noticed anything like that. I'll specifically look for it next time out ...
 
I have never seen this, even in an RV-12 with Skyview. I wonder if it is voltage/installation related.
 
Just going to throw this out there .. random thought .. are you perhaps viewing through polarized sunglasses? They can cause the effect you are describing on some displays.
 
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How's your interior painted? Could it be a strobing effect caused by sunlight either passing through or reflecting off of your prop, then reflecting off the interior paint?

Alternatively, it's not too much of a stretch to imagine a vibration issue with the backlight driver board.
 
This is a very subtle shutter effect. It is not even particularly annoying, other than concern as to what is causing it. I only detect it by fixing my view on the horizon line on the display, but it is there. I don't wear polarized glasses,and it is not a reflection from anything that I can detect. On my next flight I will see if I can determine more accurately the RPM range where it becomes apparent and report back. As always I greatly appreciate the input from you guys.

Tom
 
FWIW I have seen a few unusual screen behaviours on the D-100 series that were caused by bad grounds to EMS sensors. However, they were isolated to specific section of the screen. What you described sound more like what you would see on your computer screen at home if you set the refresh rate below 60mhz (which can be very annoying).

If not already, I would check with Dynon. Unless it's a know software or hardware issue they will most likely tell you to check all connections.

Let us know what you find out.
 
To see if its noise on the incoming power, just turn off the master and let the Dynon run off of the backup battery. If the problem goes away, you know where to look next. If not, call Dynon for further ideas.
 
Do Not turn master switch off with engine running unless a real emergency. See RV12 POH.
Date: 06/14/16 Revision:5
GENERAL
This section covers the recommended procedures to follow during emergency and adverse flight conditions. As it is not possible to define every type of emergency that may occur, it is the pilot?s responsibility to use sound judgment based on personal experience and knowledge of the aircraft to determine the best course of action.
It is considered mandatory that the pilot be familiar with this entire manual, in particular, the ?Emergency Procedures? section prior to flight.
W ARNING
Do not turn off the Master switch with the engine running
except in an EMERGENCY situation.
Running the engine with the Master Switch off may damage the voltage regulato
 
Post Test Flight Update

OK, a post test flight update. First of all, it was not the best day for a comfortable test flight so I cut it short, but I was able to do a little. The shutter flutter is not there at idle, in fact, anything below 5000 rpm and the screen is on solid. At about 5000 rpm and above it become subtly visible, but it never is particularly annoying, or distracting. I would just like to identify the cause. I couldn't tell if there was any shutter frequency difference between 5000, and 5500. On my next flight I will pull the 5 amp Skyview fuse, and see what happens. I didn't do it on this last flight because I wasn't sure if the fuse also interrupted the battery backup, or not. I first want to check the schematic to verify before doing that. I don't like experimenting without having a reasonable expectation. I do find the RPM sensitivity to be interesting, albeit not real informative to this novice. But with my tenacity, and tapping into the vast talent in the group, I am confident in a positive cause and fix outcome

More to come.........Tom
 
2nd Update

Today's flight was a great time to pull the EFIS fuse, and to take note of any changes in my screen shutter flutter. The screen dimmed slightly, as would be expected while running on the backup battery. My little girl gave me a warning call, but the shutter effect continued. Not sure what that rules out, but anything over 5000 RPM still produces a slight screen shutter effect, with a frequency of somewhere around 5 cycles per second. Any other ideas would be greatly appreciated...............Tom
 
Take a 10 second as clear as possible video with your phone and email it to Dynon tech support. See what they think. You may have to send it back. Do you have the latest software update installed?
 
I still would suspect a beat between the prop blades modulating sunlight, and LCD backlight.

At 5000 to 5500 engine RPM your prop is turning at 2057-ish to about 2263 RPM, or about 68 to 75 blades per second passing in front of your field of view. I think that's probably within the range required to create a strobe effect with the dimmer for an LCD screen backlight - depending on exactly how the engine is running and the dimmer switching rate. I don't know for sure what the Dynon display uses, but a few CCFL driver data sheets I looked at typically showed PWM rates in the 250 - 350 Hz range, depending on the model. LEDs I'm not sure, I've seen numbers like 400 Hz but I'm sure that's not carved in stone.

It would be interesting to check it at a low sun angle to see if flying into, away from, or perpendicular to the sun makes a difference. It would also be interesting to see if changing the screen brightness made the flicker more or less pronounced. Another test would be to very slowly reduce throttle and see if the strobe effect slows and stops.
 
I have also seen this effect on some of my flights. When I notice it next time I'll try to write down some parameters.
 
While at Oshkosh I had the opportunity to chat with one pf the Dynon tech gurus about the slight screen flutter at high RPM. He was very specific in stating the there was nothing in the Skyview that could cause this condition. He said that the condition as stated was most likely being generated by the tach signal and that the filtering was done in the EMS. His suspicion was a bad filter capacitor in the EMS box. So, I will be sending it in for rework. Thanks for all of your thoughts..........Tom
 
VR

I suspect the VR whenever weird things begin to happen. Have you purchased a replacement VR to carry with you just in case? We seem to have an airframe good for many years, an engine good for 2000 hrs and a VR set up good for?
 
I still have the original regulator, and my voltage has not varied. From day one I get 13.8 volts which shows up slightly above idle. Also, I just completed another backup battery test and passed. The Dynon tech was pretty certain about the source of the interference coming from the tach input to the EMS module, which makes sense if you consider that it only shows above 5000 rpm. Also, lets not forget that even when I pulled the fuse, which isolated the charging circuit and ran it strictly on the back up battery, the condition did not change.
 
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