lluciani
Active Member
This might be obvious to most folks here but it also might be useful to some. I have been flying my RV14A for almost 300 hours now and one thing that has bugged me the whole time was that the wind vector shown in my G3X display was always wrong. No matter what heading I flew, it almost always indicated a headwind. I even flew a rectangular course several times and proved this wasn’t just my negative thinking.
And on the ground, every time I started the engine, airspeed would jump up to over 20kts. Once for a test, I started the plane with the pitot cover in place and still had the same results. So the problem was not on the pitot tube side. I then disconnected the static tubing from the AHRS, went flying and there was no change. This seemed to indicate a leak in the static system but I checked it out and there were none.
So I started to suspect the port itself. The epiphany moment (happens a lot with me over little things) happened when I blew compressed air down the side of the fuselage tangent to the static port (with tape over the one on the other side). The airspeed display on the G3X registered 20kts.
I replaced the static port with one that was completely flat (from Spruce - intended for a Cessna) and the problem went away. The same test this time registered 0 kts. Yes!
The static port I had originally installed was really nice looking but had a slightly rounded dome in the middle. This is apparently enough for Bernoulli action to create a vacuum causing a greater delta-P between the static port and pitot tube, and showing an airspeed that was too high.
Here’s a picture of one of the two static ports that was causing problems. Notice the slight dome shape. It makes a big difference.
Maybe I should have just used rivets as static ports as Vans calls out and saved myself the aggravation. I hope this is useful to someone seeing the same problem.
And on the ground, every time I started the engine, airspeed would jump up to over 20kts. Once for a test, I started the plane with the pitot cover in place and still had the same results. So the problem was not on the pitot tube side. I then disconnected the static tubing from the AHRS, went flying and there was no change. This seemed to indicate a leak in the static system but I checked it out and there were none.
So I started to suspect the port itself. The epiphany moment (happens a lot with me over little things) happened when I blew compressed air down the side of the fuselage tangent to the static port (with tape over the one on the other side). The airspeed display on the G3X registered 20kts.
I replaced the static port with one that was completely flat (from Spruce - intended for a Cessna) and the problem went away. The same test this time registered 0 kts. Yes!
The static port I had originally installed was really nice looking but had a slightly rounded dome in the middle. This is apparently enough for Bernoulli action to create a vacuum causing a greater delta-P between the static port and pitot tube, and showing an airspeed that was too high.
Here’s a picture of one of the two static ports that was causing problems. Notice the slight dome shape. It makes a big difference.
Maybe I should have just used rivets as static ports as Vans calls out and saved myself the aggravation. I hope this is useful to someone seeing the same problem.