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  #21  
Old 12-22-2011, 01:15 PM
Slagergren Slagergren is offline
 
Join Date: Jan 2007
Location: Litchfield, MN
Posts: 61
Default Low airspeed problem

I had/ possibly still have a similar problem with my D180/ RV7 airspeed inidicated lower by 6-10 mph than what should have been. I have Dynon's older pitot/ AOA probe which has much larger vent opening and possibly different plumbing inside. I ended up piling up the paint just in front of the stock Van's static ports to get the speed corrected at least at my crusie speed however its not a linear correction. I was going to suggesat trying one of Dynon's new AOA/Pitot probes and I see you tried a different probe. Also I built my own water manometer and was able to bench check somewhat the D180 was calibrated. I posted some pictures of the whole probe on this site about 3 months ago.

Steve
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  #22  
Old 12-22-2011, 01:22 PM
Slagergren Slagergren is offline
 
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Location: Litchfield, MN
Posts: 61
Default D180 static calibatrion

The D180 has a speed calibration which is as I understand it a simple zeroing of the pressure sensor used on the static side only. There is no calibration to actually add some correction factor to the ram air pressure sensor.

Steve
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  #23  
Old 12-22-2011, 04:31 PM
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JohnJacobsen JohnJacobsen is offline
 
Join Date: Jan 2005
Location: Taylor, TX
Posts: 98
Default

Brantel
That was one of the many posts I had read . Tried it, had no effect
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  #24  
Old 01-15-2012, 01:10 PM
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JohnJacobsen JohnJacobsen is offline
 
Join Date: Jan 2005
Location: Taylor, TX
Posts: 98
Default Update

Well I flew with another airspeed indicator installed along with Dynon. Airspeed is the same on both, so its not the Dynon.
Guess I will go back and look at static ports and pitot tube placement.
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RV7 Flying "Aluminum Falcon"
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  #25  
Old 01-15-2012, 01:59 PM
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schristo@mac.com schristo@mac.com is offline
 
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Location: WA
Posts: 995
Default you have a leak...

Sure sounds like you have a leak in the pitot system...
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  #26  
Old 01-15-2012, 03:03 PM
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NickAir NickAir is offline
 
Join Date: Nov 2008
Location: McMinnville, Oregon: HOME of the SPRUCE GOOSE
Posts: 540
Default

Try checking your system from the pitot. If you don't have the tools for this you can have a shop do a simple static system test which will confirm if a leak exists. The leak can then be traced and repaired.

I did this once and found I had two problems:
1) A slight leak at the hose on Pitot connection.
2) A bad ASI.

Frustrating I know, although you are almost to a resolution. Hang in there.
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Last edited by NickAir : 01-15-2012 at 03:06 PM. Reason: word correction
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  #27  
Old 01-15-2012, 03:33 PM
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RV10inOz RV10inOz is offline
 
Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,308
Default

Static error is a most likely cause, many of us are victims here.

But.........nick now you think it is correct, but I have seen one guy who had the AOA tube and pitot tube crossed over. The both sorta work but the AoA calibration never works so that was how I found his problem.

Triple check you have the right tube in the right port.
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  #28  
Old 01-15-2012, 03:44 PM
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NickAir NickAir is offline
 
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Location: McMinnville, Oregon: HOME of the SPRUCE GOOSE
Posts: 540
Default

Quite possible that plumbing is misapplied. Good point.
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Tailwinds...

Simplicity is the ultimate sophistication.
Leonardo Da Vinci

Working on a RV-4
Citabria 7GCBC
Cessna 180, sold
RV7 I0-360 C/S, Slider, AP, Glass, etc. sold.
RV6 O-320 F/P, Slider, AP, Steam, etc., sold
Citabria 7KCAB rental
Piper Cherokee, sold
Sparrowhawk, sold

Proud -VAF- Supporter - Exempt, Dues Paid Anyway.
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  #29  
Old 01-15-2012, 04:06 PM
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JohnJacobsen JohnJacobsen is offline
 
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Location: Taylor, TX
Posts: 98
Default AOA

I have checked that AOA and pitot are in the correct ports. But believe me I will double check that .
Almost positive it isnt a leak. I had Barfield pitot static tester hooked to it with spot on AS and Alt and no leaks. But will check it again.
Thinking of adding another washer under the static.

P.S. Thanks for all the suggestions.
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RV7 Flying "Aluminum Falcon"
Zenith CH750 (Scratch building) SOLD
Locost 7 (Lotus 7 replica)
Taylor TX

Youtube channel: http://www.youtube.com/user/johnjaco...e=results_main

Last edited by JohnJacobsen : 01-15-2012 at 04:07 PM. Reason: Thanks
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  #30  
Old 01-15-2012, 05:20 PM
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N941WR N941WR is offline
 
Join Date: Jan 2005
Location: SC
Posts: 12,884
Default

Quote:
Originally Posted by JohnJacobsen View Post
I have checked that AOA and pitot are in the correct ports. But believe me I will double check that .
Almost positive it isnt a leak. I had Barfield pitot static tester hooked to it with spot on AS and Alt and no leaks. But will check it again.
Thinking of adding another washer under the static.

P.S. Thanks for all the suggestions.
I went through the same thing earlier this year and my issue was a leak at the pitot tube connection.

Crossing the AoA and AS lines will give you a zero airspeed indication. Been there, done that.

I have a steam gauge AS indicator along with my Dynon and they both indicated the same AS. When I tried flying with either the round gauge or the Dynon, the airspeed indications were the same as when both were connected.

I wound up replacing both the AoA and airspeed lines from the pitot tube to the instrument panel. It was a pain but that was when I found the leak at the pitot. The black lines were replaced with AN fittings.
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