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  #1  
Old 10-23-2015, 05:32 PM
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Piper J3 Piper J3 is offline
 
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Default Very High IAS Readings Dynon D180...

I just bought a flying RV-12 and the airspeed is erratic and reading way too high. I did the zero adjustment for IAS in the Dynon D-180 and it didn't help. Now I'm thinking the static ports are blocked. I cut a small length of .032 safety wire to investigate the static openings and it indeed appears they are block. Possibly blocked when painted. Can someone tell me the correct drill size for both static ports on the RV-12 so I can check and open if necessary? I searched the drawings and don't see any reference to static port opening.

Last edited by Piper J3 : 11-14-2015 at 05:24 PM.
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  #2  
Old 10-23-2015, 06:38 PM
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Phantom30 Phantom30 is offline
 
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Quote:
Originally Posted by Piper J3 View Post
I just bought a flying RV-12 and the airspeed is erratic and reading way too high. I did the zero adjustment for IAS in the Dynon D-180 and it didn't help. Now I'm thinking the static ports are blocked. I cut a small length of .032 safety wire to investigate the static openings and it indeed appears they are block. Possibly blocked when painted. Can someone tell me the correct drill size for both static ports on the RV-12 so I can check and open if necessary? I searched the drawings and don't see any reference to static port opening.
They are rivets, that have had the mandels removed (I believe that is what they called)....use a 1/16" or smaller....don 't penetrate much more than 1/8"...should do it.
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  #3  
Old 10-23-2015, 08:16 PM
RFSchaller RFSchaller is offline
 
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If you think he static ports are blocked try the Production Acceptance Procedure of blocking one and drawing a vacuum on the other to see what happens.
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  #4  
Old 10-23-2015, 08:26 PM
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Piper J3 Piper J3 is offline
 
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What I did try was disconnecting the static tubing from the D-180 and blowing thru the tube. Tremendous restriction, so I think both ports are closed off. One has paint over the opening for sure. Do you think size of hole maters? I'll start with small drill and back flush the lines with compressed air to remove chips. Tomorrow's project...
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Old 10-23-2015, 08:32 PM
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Tony_T Tony_T is offline
 
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Don't use a lot of pressure to back flush the static lines or you'll blow the tubing off the rivets.

Seen it happen...
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  #6  
Old 10-23-2015, 09:23 PM
Mich48041 Mich48041 is online now
 
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Quote:
Do you think size of hole maters?
There is very little air flow through the static ports and tubing. So the size does NOT affect the instruments. However, smaller ports and tubing could get plugged up easier.
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Last edited by Mich48041 : 10-25-2015 at 06:13 PM.
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  #7  
Old 10-24-2015, 10:15 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Default Just one word can have a big influence of meaning.....

Quote:
Originally Posted by Mich48041 View Post
There is very little air flow through the static ports and tubing. So the size does not affect the instruments. However, smaller ports and tubing could get plugged up easier.
I think he meant to say "not" (at least that is what the correct statement is)
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  #8  
Old 10-24-2015, 08:18 PM
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Piper J3 Piper J3 is offline
 
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Per my original post... Today I found that the two static ports were never installed correctly. The head of the blind rivet should have been driven out with a punch at assembly. The builder did not do this - why I don not know. So I drilled out the remaining steel nail head and now the ports are unobstructed. Raining so no test flight for a couple of days. Still need to do the zero calibration. I'm confident that this should fix abnormally high IAS on the Dynon D-180.
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  #9  
Old 10-25-2015, 06:24 AM
BigJohn BigJohn is offline
 
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Quote:
Originally Posted by Piper J3 View Post
Per my original post... Today I found that the two static ports were never installed correctly. The head of the blind rivet should have been driven out with a punch at assembly. The builder did not do this - why I don not know. So I drilled out the remaining steel nail head and now the ports are unobstructed. Raining so no test flight for a couple of days. Still need to do the zero calibration. I'm confident that this should fix abnormally high IAS on the Dynon D-180.
Hopefully this will correct your bad readings, but I have lingering doubts. Ever since your original post I've been wondering about your theory that plugged static ports are causing HIGH airspeed readings. Normally, plugged static causes LOW airspeed indications. When you flew how were the altitude readings? If the static line was plugged the altimeter would not have read correcly. Considering that mistakes were made such as not removing the mandrels and painting over the holes, I would be concerned about other areas of construction as well.
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  #10  
Old 10-25-2015, 11:01 AM
cactusman cactusman is offline
 
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Quote:
Originally Posted by Piper J3 View Post
Per my original post... Today I found that the two static ports were never installed correctly. The head of the blind rivet should have been driven out with a punch at assembly. The builder did not do this - why I don not know. So I drilled out the remaining steel nail head and now the ports are unobstructed. Raining so no test flight for a couple of days. Still need to do the zero calibration. I'm confident that this should fix abnormally high IAS on the Dynon D-180.
There is a leak down test for both the pitot and static that requires a large syringe and some modeling clay in the PAP....

You can download it here: (sect G5)

https://www.vansaircraft.com/pdf/rev...s/PAP-R8.3.pdf
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