---------------------------------------------------------- RV8-List Digest Archive --- Total Messages Posted Tue 12/27/11: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:04 AM - Re: RV-List: Dynon Skyview Airspeed Calibration... (Carl Froehlich) 2. 09:16 PM - Re: Dynon Skyview Airspeed Calibration... (Matt Dralle) 3. 10:33 PM - Dynon Skyview vs. GRT HX EFIS... (Matt Dralle) ________________________________ Message 1 _____________________________________ Time: 08:04:18 AM PST US From: "Carl Froehlich" Subject: RV8-List: RE: RV-List: Dynon Skyview Airspeed Calibration... A few of thoughts. 1. It is an easy set up to verify IAS reads properly. Attached photos are the rig I used. I also attached the scale to translate inches to knots. There are various placed to find the test rig on the web. You need not take the airspeed indicator out of the plane, just attached the tube to the pitot and seal with electrical tape. In the attached rig photo, the pressure source attaches to the tube that is hanging free on the left. I found an old blood pressure bulb for this. 2. For my 8A, I initially used a pitot tube that included the static port. It word well except for high pitch angles. At high angles the static port started to get ram air. The result was I could have "0" IAS in power on stalls but still be flying. 3. When I took the plane down for paint, I installed two of the Cleveland tool static ports in the standard fuselage locations. These are flush ports. I found this induced a static error. I did a simple fix by drilling a 1/16 inch hole in the center of a 3/16 round head rivet, cut the rivet head off and then epoxied the rivet head over the static port. I used a toothpick to hold the rivet head in place while the epoxy set, and to keep the epoxy out the hole. This fix solved the static problem. Photo attached. 4. On the RV-10, I used the same rivet but did not use the Cleveland ports. I drilled the 1/16" hole all the way thought the head and rivet shank. I epoxied the rivet to the fuselage, adding a 1/8" thick, 1/2" diameter aluminum ring (3/16 hole drilled in the middle) backer to the inside of the fuselage to add strength. The static line then gets epoxied over the rivet shank. Once you verify the IAS is correct, but you still have a problem with TAS reading high, recommend you talk a look at where you mounted the Dynon OAT probe. If you have it in a place that is typically hotter than outside or getting a lot of prop wash (increases temperature), TAS will read high. Carl -----Original Message----- From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matronics.com] On Behalf Of Linn Walters Sent: Monday, December 26, 2011 11:01 PM Subject: Re: RV-List: Dynon Skyview Airspeed Calibration... --> RV-List message posted by: Linn Walters I think you're on the right track ..... airspeed is the measurement of the difference in pressure between the pitot and static. So, it appears (to me anyway) that the static pressure is in a lower pressure area than it 'should be'. You should have two static ports, one on each side of the fuselage about 1/2 way between wing trailing edge and horizontal stab leading edge. This should be the area of least disturbed air going by. Having the ports on each side balances the pressures caused by slipping and sliding. The port should stick out a little to get out of the laminar air flow along the fuselage. Since there's no airflow in either the pitot or static lines, a restricter won't have any effect. The angle of the pitot to relative airflow will have some effect on the airspeed reading too. One of our RV-4 pilots (he bought it, not built it) was complaining about inaccurate airspeed and we found the single static port above and forward of the wing leading edge on the left fuselage side. It's a 'washer' about 1" dia and 1/16" thick with a small hole in the center. It's located right where prop wash will really hit it with turbulent air. He plans on moving it and installing two ports as above. Linn On 12/26/2011 10:39 PM, Matt Dralle wrote: > --> RV-List message posted by: Matt Dralle > > Dear Listers, > > I've been flying the new 10" Dynon Skyview in the RV-6 for a few weeks now and it seems like the airspeed is reading maybe 10mph fast. The GS always reads 10mph or more slower than the True airspeed, no matter which way I fly with respect to the current wind. Looking through the configuration options on the Skyview, I'm not seeing parameters to calibrate the airspeed. If the airspeed were *slow* compared to the GS, I could envision making adjustments to the Pitot tube to get it in better alignment with slipstream. But *fast* is a head scratcher. If there's no electronic configuration parameters to adjust, what do you do? Are there Pitot line "attenuators" like for RF in coax? ;-) > > Matt > > - > Matt "Red Dawg" Dralle > > RV-8 #82880 N998RV "Ruby Vixen" > http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log > http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log > http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel > Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap... > > RV-6 #20916 N360EM "The Flyer" > http://www.mattsrv6.com - Matt's RV-6 Revitalization Log > Status: 42+ Hours Since Purchase - Upgrades Complete; Now In Full Flyer Mode > > ________________________________ Message 2 _____________________________________ Time: 09:16:58 PM PST US From: Matt Dralle Subject: RV8-List: Re: Dynon Skyview Airspeed Calibration... At 07:40 PM 12/26/2011 Monday, Matt Dralle wrote: >Dear Listers, > >I've been flying the new 10" Dynon Skyview in the RV-6 for a few weeks now and it seems like the airspeed is reading maybe 10mph fast. The GS always reads 10mph or more slower than the True airspeed, no matter which way I fly with respect to the current wind. Looking through the configuration options on the Skyview, I'm not seeing parameters to calibrate the airspeed. If the airspeed were *slow* compared to the GS, I could envision making adjustments to the Pitot tube to get it in better alignment with slipstream. But *fast* is a head scratcher. If there's no electronic configuration parameters to adjust, what do you do? Are there Pitot line "attenuators" like for RF in coax? ;-) > >Matt Listers, Thank you for all the great suggestions on resolving this airspeed issue! I took a look at the static ports on the RV-6 today and found that they are done using a flush head screw with a hole drilled in the center on either side of the fuselage. They do *not* protrude from the side of the plane at all. They are totally flush (see attached picture). Just for fun, I whipped up a couple of quick test deals using a 3/16" washer and some electrical tape. I poked a 1/16" hole in the center of the tape and then put the washer centered over the static ports on both sides of the fuselage (see attached pictures). Then, I went flying on this beautiful December 27 day in California! I didn't have time to do any real scientific multi-leg testing, but I was amazed that the True Airspeed is now falling in a much more believable range compared to the GPS-derived ground speed. On one cross-country leg, I had an exactly 90 degree crosswind component and the True Airspeed and GPS Ground Speed were tracking exactly the same. Yahoo! Obviously I need to do some additional, more scientific measurements and probably come up with a slightly more "permanent" washer arrangement, but the early returns are very promising! :-) Thanks again for all the great feedback! Matt - Matt "Red Dawg" Dralle RV-8 #82880 N998RV "Ruby Vixen" http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap... RV-6 #20916 N360EM "The Flyer" http://www.mattsrv6.com - Matt's RV-6 Revitalization Log Status: 42+ Hours Since Purchase - Upgrades Complete; Now In Full Flyer Mode ________________________________ Message 3 _____________________________________ Time: 10:33:03 PM PST US From: Matt Dralle Subject: RV8-List: Dynon Skyview vs. GRT HX EFIS... >At 09:47 PM 12/27/2011 Tuesday, you wrote: >I have looked at the Dynon stuff up at Arlington Air Show the past two years >and really like the looks of them. They added autopilot and said last year >that they were about to announce communications added to their system. A >single 10" screen to do everything would be pretty easy to install learn to >operate. Mostly Dynon looks best in the magazines. I guess you get used to >any of them or they would not all still be in business. >Pete I have a Dynon 10" Skyview in the RV-6: http://www.mattsrv6.com/users/display_log.php?user=MattsRV6&project 43&category=0&log=138164&row=45 http://www.mattsrv6.com/users/display_log.php?user=MattsRV6&project 43&category=0&log=138163&row=46 and a triple GRT HX setup in the RV-8: http://www.mattsrv8.com/users/display_log.php?user=MattsRV8&project=638&category=2973&log'376&row=134 http://www.mattsrv8.com/users/display_log.php?user=MattsRV8&project=638&category=2973&log'375&row=135 I've flown the GRT HX setup about 170 hours and the Dynon Skyview system about 45 hours now. Which do I prefer? That's a tough call. There are parts about each system that I like a lot... The installation and configuration of the Dynon is easier. Instructions are also better. The network cable interconnect system that Dynon uses (I think it is just RS485, but it works well) is also a no-brainer to install. Their display (PFD/Engine/Map) are definitely very pretty and demo well. The GRT is a little harder to get installed, the manual is a little sketchy in places and there are a LOT of configuration options that can seem daunting at first. BUT, there is power and utility in those options. If you use them to your advantage, you can probably do more, better on the GRT compared to the Dynon. The displays on the GRT don't have the "3D-y", "Windows-y" look to them. BUT, I think I'm preferring that at this point. Doing a scan on the GRT looking for something out of the ordinary is quicker and more accurate. I also like the PFD layout and operation on the GRT better. It feels more "accurate" and "believable" to me for some reason. I never quite "trust" what I'm seeing on the Dynon for some reason and I don't know why. Maybe I just need more time on the Dynon. So, the Dynon has it for Installation and Configuation, but the GRT has it for Operation and Presentation as far as I'm concerned. If I was building a new plane, I think that I would probably go with the GRT. But its a close race. I really like the Dynon system too. I guess I'm saying if you're in the market for a full-featured EFIS system, give GRT and Dynon both very close look before you make your selection. In my opinion, it comes down to personal preferences in a few select areas on which way to go. Both systems are top notch. BTW, Dynon's autopilot add-on for the Skyview which I have in the RV-6 works well. Its a good autopilot that does the job. The servos are the same as with the TruTrak system. In the RV-8, I have the TruTrak Digiflight II VSGV system. The TruTrak is a smoother, more accurate autopilot in my opinion, and I would go that route again. But, it also costs quite a bit more than just adding servos to the Dynon or GRT. $.02 - Matt "Red Dawg" Dralle RV-8 #82880 N998RV "Ruby Vixen" http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap... 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