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Static Ports...

Piper J3

Piper J3

Well Known Member
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.
 
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Piper J3 said:
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.
Click to expand...

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.
 
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.
 
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...
 
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...
 
Do you think size of hole maters?
Click to expand...
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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Just one word can have a big influence of meaning.....

Mich48041 said:
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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I think he meant to say "not" (at least that is what the correct statement is)
 
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.
 
Piper J3 said:
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.
Click to expand...

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.
 
Piper J3 said:
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.
Click to expand...

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/revisions/RV-12/User_Manuals/PAP-R8.3.pdf
 
BigJohn said:
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.
Click to expand...

I would confirm that the static/pito lines are connected to the correct ports on the Adahrs.
 
Curious if the plane ever had an initial or subsequent 24 month pitot static check?

I met at least one RV-12 builder who had signed this off himself, rather than having a test with a properly calibrated test set by a repair station.

Carl
 
newamiga said:
Curious if the plane ever had an initial or subsequent 24 month pitot static check?

I met at least one RV-12 builder who had signed this off himself, rather than having a test with a properly calibrated test set by a repair station.

Carl
Click to expand...

I don't think you need to have this done for a VFR only RV-12....which most are except those few putting in the waas or a NAV.....

"§91.411 Altimeter system and altitude reporting equipment tests and inspections.

(a) No person may operate an airplane, or helicopter, in controlled airspace under IFR unless—"


....what am I missing?

You do need to do the transponder check (make sure you change the settings from "auto" in Skyview), and every once and a while I'll ask ATC for an altitude and airspeed check....feel good self-calibration.
 
To get back to the original topic........

....... were you able to get to the bottom of the airspeed issue? Did clening out the static ports make a difference?
 
I opened the static ports and still did not fix high IAS readings. D-180 is currently sent to Dynon for repair. Dynon says airspeed transducer failed.
 
Still have very high IAS...

Synopsis from my posts above?. I bought a flying RV-12 with Dynon D180. I have units set for statute (fpm, mph). The airspeed indicator consistently shows IAS as 60 mph too high. In level cruise flight I show 180mph and I?m indicating about 125 mph on final approach. In addition, the White Arc for Vfe is set at 150 mph. I did some troubleshooting and found the original builder forgot to open the static port rivets on each side of the fuselage. I drilled this out and verified the ports were open and connected to the static tubing. This didn?t make any difference and IAS reading sere still in the range of 60 mph too high. I have set zero pressure value and this too didn?t make any difference.

Recent information? Three weeks ago I sent the D180 unit to Dynon telling them IAS was reading ~ 60 mph too high. Dynon replaced the airspeed sensor and returned the unit to me. I installed the unit today and still have IAS reading 60 mph too high.

So here?s my thoughts?

1) Perhaps Dynon didn?t repair and completely check out the unit and returned it to me with same problem, or maybe a scaling factor is wrong in the software.

2) Maybe somehow I?m getting over-pressurization in the pitot line. Maybe a hole in the tubing where it runs inside the engine cowl. The cowling most likely is at higher pressure.

3) Maybe too much vacuum created in the static line. I could disconnect the static line from the back of the D-180 for a test.

4) Maybe having Vfe white arc set at 150 mph is causing some interaction. Tomorrow I will configure airspeed color thresholds per D180 Installation Guide and RV-12 POH.

If anyone has any ideas on how to troubleshoot this problem I?d appreciate hearing.

Piper J3
 
Check the pitot - static for leaks per page G5-1 of the PAP as suggested by Cactuspilot in post 10 above. Van's documentation tells how to easily do it.
 
Problem Fixed

Problem turned out to be human error - mine. I had IAS units set to kilometers/hour instead of mph. Works fine now. Time to eat some humble pie... :eek:
 
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