91.411 Checks on an HDX System

JohnAJohnson

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Apr 30, 2018
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I'm planning an STC HDX installation in my Cardinal and am curious as to how the Static/Altimeter/Encoder check is done every two years. I ask because if the technician needs access to the ADAHRS static port and/or the D10A static port, I'll plan my installation to make these more easily accessible. Any advise is appreciated!
 

airguy

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Nov 10, 2008
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Gods Country - west Texas
Generally speaking, the techs will want to connect to the pitot under the wing and the static port(s) on the aft fuselage. You should not need to have any additional connection points. I have had a shop tell me they couldn't get the pitot side to stabilize (leaking) because they forgot to block off (or didn't realize it existed) the drain port on the Dynon heated pitot.
 

JohnAJohnson

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Apr 30, 2018
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Thanks Airguy. My static ports are up front on my airplane, and difficult to get to without removing a lot of the interior. Historically, the avionics techs have disconnected the static line from the altitude encoder (Ack A-30 or similar) and at the altimeter.
 

kellym

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Sep 29, 2013
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Thanks Airguy. My static ports are up front on my airplane, and difficult to get to without removing a lot of the interior. Historically, the avionics techs have disconnected the static line from the altitude encoder (Ack A-30 or similar) and at the altimeter.
Unless there is something about the static port on the outside of airframe, that is where the connection should be made. Sometimes the surface prevents getting an airtight seal on suction cup, forcing connection inside. Some Cessnas have a problem with leakage between the static port inside the skin and the skin. Easily sealed with some RTV. Common on older C172s. Point is to find leakage between the hole on the outside and the altimeter. I've had things like a sharp paint line prevent sealing on the outside, but that should be the exception, not the rule.
 
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