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12-20-2011, 06:16 PM
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Join Date: Jan 2005
Location: Taylor, TX
Posts: 98
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Low air speed
I could use a little help on this one. My air speed has been reading low since first flight. I am indicating a stall of 35 knots, the airspeed is consistantly off thru the whole speed range. Rv-7 equiped with Dynon D-180, Dyon pitot, safe air static.
Pitot static tested ok, air damns in front of static no effect, static vented to cabin slight change, new static and pitot lines no effect, drilled out safe air ports and installed rivet (like vans ports) no effect, added washer under static port (rivet) no effect, different pitot tube no effect.
Have not compared to another airspeed indicator as I only have one. Seems to me that the D-180 is off, but Dynon tells me that since it passed the pitot static test that it was probably ok.
If anyone has any suggestions for me I would appreciate it.
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12-20-2011, 06:24 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,884
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I would go back and check your entire pitot system again.
Mine was reading low, and like you, my stall was at 35 MPH. I replaced the entire pitot and AoA lines, from the D100 back to the Dynon pitot tube. Found a pretty good leak at the connection to the pitot tube. Problem solved.
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Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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12-20-2011, 06:29 PM
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Join Date: Jan 2005
Location: Taylor, TX
Posts: 98
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I've already replaced the lines, both pitot and static. As well as passing a pitot static test with a Barfield pitot static tester.
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12-20-2011, 06:38 PM
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Join Date: Jan 2005
Location: Ontario, Canada
Posts: 1,603
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set your altimeter to field elevation and then do a low pass (100) over the runway and note the altimeter setting. You will have to eyeball the 100 feet but if the altimeter is reading something much different then the 100 feet plus field elevation then you have a static error.
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Tom Martin RV1 pilot 4.6hours!
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EVO F1 Rocket 1000 hours,
2010 SARL Rocket 100 race, average speed of 238.6 knots/274.6mph
RV4, RV7, RV10, two HRIIs and five F1 Rockets
RV14 Tail dragger
Fairlea Field
St.Thomas, Ontario Canada, CYQS
fairleafield@gmail.com
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12-20-2011, 07:35 PM
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Join Date: Nov 2006
Location: Boise, ID
Posts: 1,095
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Already replaced the lines and checked the static system for leaks? My next guess would be the instrument. Fortunately for you, Dynon has (I think) the ability to calibrate your airspeed and altimeter.
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Sonny W
Boise, Idaho
RV-7A Flying!
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12-20-2011, 07:46 PM
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Join Date: Jan 2005
Location: St. Paul, MN.
Posts: 4,838
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Any other RVers in the area with a similar Dynon instrument you could swap out for a quick check?
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Bob Collins
Working on RV-12iS avionics
N612EF Builder log (EAA Builder log)
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St. Paul, MN.
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12-20-2011, 07:48 PM
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Join Date: Jun 2005
Location: West Coast
Posts: 2,571
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Did you try the recalibration function on the Dynon?
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The information that I post is just that; information and my own personal experiences. You need to weigh out the pros and cons and make up your own mind/decisions. The pictures posted may not show the final stage or configuration. Build at your own risk. Further more, these are my opinions and not those of Van's Aircraft.
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12-20-2011, 07:49 PM
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Join Date: Jan 2005
Location: Taylor, TX
Posts: 98
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Nobody I know that has a D-180. Looking for a steam gage Airspeed to hook up for comparison.
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12-20-2011, 07:51 PM
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Join Date: Jan 2005
Location: Taylor, TX
Posts: 98
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Yeah tried recalibration
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12-20-2011, 07:53 PM
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Join Date: Dec 2009
Location: Bismarck, ND
Posts: 212
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Quote:
Originally Posted by JohnJacobsen
Have not compared to another airspeed indicator as I only have one. Seems to me that the D-180 is off, but Dynon tells me that since it passed the pitot static test that it was probably ok.
If anyone has any suggestions for me I would appreciate it.
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airpeed calibration is not part of the static system test, however the Barfield test box is capable of airpeed testing. my skyview and D6 were spot on.
you might consider using a homemade water manometer to check your airpeed and plumbing. search for other threads on airspeed, you'll find more info.
__________________
Larry Buller
RV7A slow build, Tip up, IO360 200hp, Catto 3 blade, Dynon Skyview, arinc 429, ems, SV transponder, Garmin GNS430w, Aera 560, Dynon D6.
FLYING!
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