VAF Forums

VAF Forums (https://vansairforce.net/community/index.php)
-   RV General Discussion/News (https://vansairforce.net/community/forumdisplay.php?f=2)
-   -   Low air speed (https://vansairforce.net/community/showthread.php?t=80254)

Slagergren 12-22-2011 01:15 PM

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

Slagergren 12-22-2011 01:22 PM

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

JohnJacobsen 12-22-2011 04:31 PM

Brantel
That was one of the many posts I had read :) . Tried it, had no effect :(

JohnJacobsen 01-15-2012 01:10 PM

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. :confused:

schristo@mac.com 01-15-2012 01:59 PM

you have a leak...
 
Sure sounds like you have a leak in the pitot system...

NickAir 01-15-2012 03:03 PM

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.

RV10inOz 01-15-2012 03:33 PM

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.

NickAir 01-15-2012 03:44 PM

Quite possible that plumbing is misapplied. Good point.

JohnJacobsen 01-15-2012 04:06 PM

AOA
 
I have checked that AOA and pitot are in the correct ports. But believe me I will double check that :p .
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. :)

N941WR 01-15-2012 05:20 PM

Quote:

Originally Posted by JohnJacobsen (Post 617887)
I have checked that AOA and pitot are in the correct ports. But believe me I will double check that :p .
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.


All times are GMT -6. The time now is 12:43 PM.