My Winds Aloft Reading Error

[southtarnation]

I have a question about the attached photo. With regards to the Pitot static system I have a reading for the Wind Direction that is pretty accurate as are my IAS, TAS and GS So I (hope) dont think that the location of static port is an issue but the speed of the Wind and the XW component are way to high. I have displayed the nearest winds aloft cor comparison.

I have the Safeair static ports located in the traditional spot on an Rv-4 however I did maybe install them incorrectly. instead of drilling a small hole for the port to stick through and attaching the surface area of the port to the inside of the fuselage in installed with just the hole part of the port sticking through the body, I matted the large surface to the outside of the plane so there is what amounts to a medallion about the size and thickness of a 50 cent piece with the actual port hole sticking out maybe an 1/8th inch past that in the middle of it.


Any suggestions on what I may try to correct this error are appreciated.

Thank you.

 

[mmarien]

At lot of the error comes from the compass. If it's not calibrated it will throw the wind calculations out. Head into the wind (or with it even better) and check your magnetic compass (on DG outlined in white) against the GPS (on MAP outlined in magenta). If they are not the same then the wind calculations will not be correct.

 

[dynonsupport]

Checking for static errors is easy with a system like a SkyView:

1) Fly at cruise IAS, and note the GPS altitude and barometric altitude. Slow down to about 65 knots, and hold your GPS altitude. Your baro altitude should stay the same, but will likely go up as you slow down. This will cause your IAS to be high, and thus your TAS. Really common on RV's.

2) You can also do it the more fun way: Do a low pass over a runway with your hair on fire, and then one slow. Check the baro altitude on both passes.

Start here. If that is right, then your compass cal is almost for sure off. Have you run the in-air compass cal?

 

[DBRV10]

Or fly a GPS box test and compare the TAS you were doing with the GPS average, if it is within 2 knots it is good.

Our RV10 was 9 knots slow on IAS and TAS. I had to put a small fence in front of the static port.

 

[skysailor]

I have the same static port mounted the same way and it is fine. As long as the location is per the plans, the port should be fine. I agree that compass calibration should be checked.

 

[airguy]

I have the same static port mounted the same way and it is fine. As long as the location is per the plans, the port should be fine. I agree that compass calibration should be checked.

I had about 9-10 knots error in mine, and as Skysailor pointed out the port was fine - I found a leak in my tubing. I'm flying an RV9A. Once I got that leak fixed I'm showing less than a knot difference between GPS 3-direction calculated versus Dynon calculated TAS.

 

[dlloyd]

Your answer is in your picture. There is no way your 166 knot airplane needs 18 degrees crab to follow a course with only a forecast 14 knot wind. Get your compass calibration done 1st before chasing any possible static error.

 

[southtarnation]

Thanks for the advice. The mag comp calibration I had done previously must have not been accurate. Re calibrated on the ground and then did the in air calibration and all readings are very close now. Thank You.