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bench testing static and pitot ports (Read 417 times)
Apr 16th, 2018 at 8:26am

gianmarko   Offline
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Hi
i am rebuidlng my panel and i am installing a D10A i had on another a/c

i am testing the pitot and static lines, pitot tests goes ok, i pressurize the line and i see a speed increase according to pressure applied

i tried to test the static port but applying positive or negative pressure the ASI also shows speed, and the pressure  and altitude indicated slowly equalizes wiith ambient and retuns to zero. this happens also with a direct connection to the EFIS so is not a leakage in the lines.

is this normal behaviour for the static port or is there a problem with the EFIS?

thanks
 
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Reply #1 - Apr 16th, 2018 at 5:21pm

Dynon Support   Offline
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Airspeed will change with a change in the static pressure.

The instrument should meet FAR static leakage requirements. It depends on what "slowly equalizes" means. What is slowly? And how are you pressurizing the static line? Everything will leak eventually.

So your question becomes "is the equipment and static system within FAR requirements?" and depends on whether your test equipment is calibrated and accurate, and to what pressure you are subjecting it.
 

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Reply #2 - Apr 16th, 2018 at 11:38pm

gianmarko   Offline
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Hi

this is a homebuilt airplane so i am using homebuilt equipment

i am pressurizing the system using a hand piston, and connecting in parallel a standard altimeter and electronic altimeter to monitor pressure variations

"slowly" means a few seconds, about 10 or so.

i wouldnt expect a change in pressure in the static port to affect speed  measurement, but i dont know how this is handled in the D10A which is a lot more sophisticated than na ASI or altimeter

i will post a video of the test

this specific D10A was recently by Dynon for repair and this is the first time it was in use after that.





Dynon Support wrote on Apr 16th, 2018 at 5:21pm:
Airspeed will change with a change in the static pressure.

The instrument should meet FAR static leakage requirements. It depends on what "slowly equalizes" means. What is slowly? And how are you pressurizing the static line? Everything will leak eventually.

So your question becomes "is the equipment and static system within FAR requirements?" and depends on whether your test equipment is calibrated and accurate, and to what pressure you are subjecting it.

 
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Reply #3 - Apr 17th, 2018 at 10:27am

Dynon Support   Offline
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Concerning the airspeed, all pitot static systems work the same. Airspeed is just the difference in pressure between the pitot and static. So if the pitot is left at ambient air pressure (no ram air from moving or wind), and the static has a pressure applied to it, then airspeed will indicate that difference.

The pitot/static system inside the D10 is tested to meet FAA specs. Leaking down in seconds would not meet that spec. But first I would look at your test rig. Put soapy water on all of the connections in your test rig and see if any air is leaking. The leak could be coming from any of the connections or the analog altimeter or the electronic altimeter.
 

Please do not use Private Messaging on forum to contact. For private support:
Email: support at dynonavionics dot com
Phone: 425-402-0433 (7am-5pm Pacific weekdays)
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Reply #4 - Apr 18th, 2018 at 6:21am

gianmarko   Offline
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i found a doc describing the procedure to run a leak test, it says to change pressures at EFIS turned off. in fact, doing it that way the test is successful, so all is good Smiley

 
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