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Old 12-20-2011, 07:57 PM
LifeofReiley's Avatar
LifeofReiley LifeofReiley is offline
Join Date: Jan 2005
Location: Round Rock, TX
Posts: 3,779

Originally Posted by JohnJacobsen View Post
Nobody I know that has a D-180. Looking for a steam gage Airspeed to hook up for comparison.
Stop by the airport, we can locate one you can borrow for testing. I'll email my phone #.
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Old 12-20-2011, 08:57 PM
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Tony Kirk Tony Kirk is offline
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Default Manometer Article

One of my fellow chapter members, John McAvoy, published an article in Sport Aviation about calibrating you airspeed system using a Manometer.

Here is the link to the article and materials on his webpage

Yes, his favorite building material is different than ours, but I don't hold it against him.
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Old 12-21-2011, 09:42 AM
Vac Vac is offline
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Location: Niceville, Florida
Posts: 520


Take a look at this thread: .

What you're discribing might be a static source pressure error. There's some other good info on this phenomenon (provided by Kevin Horton) in the flight test section. You'll still need manometer data, but if that shows the Dynon display to be accurate, then you'll need some flight test data. It generally takes some effort to get indicated airspeed and altitude "dialed in."

If you have any questions, you can drop a PM or e-mail.


Mike Vaccaro
RV-4 2112
Niceville, Florida

Last edited by Vac : 12-22-2011 at 09:08 AM.
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Old 12-21-2011, 10:20 AM
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jjconstant jjconstant is offline
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Location: Oakland CA
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Is your static source in the same location and using the same pop rivet head as Van supplies? Both location and shape have a strong effect on indicated airspeed. Low indicated speed implies that you may be getting pressurized air in your static source. Deploying flaps can change your static pressures at the low end if you use differing static source locations and shapes.

All best

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Old 12-21-2011, 10:30 AM
Bavafa Bavafa is offline
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Location: Sacramento, CA
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@ 35K, it seems like a big discrepancies

Is the airspeed off by a consistent amount or varies significantly?

You seem to have tested all but the instrument itself, so I would suggest to try to take that also out of the equation before messing more with the pitot/static system.

Of course, this is based on the assumption that the location of Pitot and static are on the suggested location by VANs. A quick check to make sure your pitot is not bent in a wrong angle, though doubtful since you have been checking every thing else.

Good luck
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Old 12-21-2011, 12:30 PM
WingsOnWheels WingsOnWheels is offline
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I'm not exactly close by, but I have a new airspeed indicator sitting in the box at home. If you make it up to Dallas, you are welcome to borrow it for testing. Just e-mail me if you are interested.
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Old 12-21-2011, 05:34 PM
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Walt Walt is offline
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If you get up this way to pick up the airspeed indicator in the above post, stop by and I'll throw my pitot static box on it and check it.
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
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Old 12-22-2011, 04:40 AM
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JohnJacobsen JohnJacobsen is offline
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The static is pretty close to Vans location. About half an inch forward. The air speed stays consistantly off thru the speed range.

Thanks for the offer to borrow an AS indicator in Dallas. I will see what I can get done down here first.

I have access to a pitot static test set down here.

Thank you everyone for all the suggestions and offers. Hope to have this figured out soon. This is a great community.
John Jacobsen
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Old 12-22-2011, 05:03 AM
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NickAir NickAir is offline
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Let us know what you find out. Instrument or static system.

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Old 12-22-2011, 08:00 AM
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Brantel Brantel is offline
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I went thru this as well.

Take a look at this thread:

I think like post 64 is were I found the fix....
Brantel (Brian Chesteen),
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