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Airflow influence on static port

PostPosted:Tue Feb 05, 2019 2:59 pm
by tail2


Altimeter accuracy depends on static port position
Air flow parallel to static port.
Wrong static port position will cause altimeter shows change in altitude when aircraft speed("airspeed") increase although the plane is flying at the same height.(because of bernoulli effect)

How find neutral static port position on fuselage where airflow will not disturb altimeter accuracy, (like do in my video)?
And how desing static port holes to avoid this problem?

Re: Airflow influence on static port

PostPosted:Wed Feb 06, 2019 1:46 pm
by ChrisRowland
The aircraft designer will design the position of the static ports where they are only slightly affected by the airflow. They will test using a static bomb hung under the aircraft which will give a known good static pressure.
Or there will be a pitot/static probe with both.
The correction between indicated and corrected should be in the flight manual.

Re: Airflow influence on static port

PostPosted:Wed Feb 06, 2019 2:23 pm
by PaulSS
I've seen people put a "C" shaped piece of wood/metal/plastic behind the static port if they have an over-reading ASI. This slows the airflow and reduces/eliminates the problem. For an under-reading ASI I've seen a flush static vent being 'built up' with a rivet to form a dome shape. This accelerates the air over the port, reducing the static pressure and solving that problem.

I would like to have the equivalent airspeed of that compressor over my static ports :D

Re: Airflow influence on static port

PostPosted:Thu Feb 07, 2019 12:11 pm
by ChrisRowland
PaulSS wrote:I've seen people put a "C" shaped piece of wood/metal/plastic behind the static port if they have an over-reading ASI. This slows the airflow and reduces/eliminates the problem. For an under-reading ASI I've seen a flush static vent being 'built up' with a rivet to form a dome shape. This accelerates the air over the port, reducing the static pressure and solving that problem.

I can understand that being done as part of the design/development process but not by a random user.

Re: Airflow influence on static port

PostPosted:Thu Feb 07, 2019 4:25 pm
by PaulSS
I've seen both done on homebuilts.......not certified.