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Static Port Location

Bearhawk Builder

Bearhawk Builder

FRIEND
In the woods
Looking for ideas. I'm using Dynon's pitot tube which doesn't have a static port, they provide the disc type static ports designed to be in the side of the fuselage. I've always scratched my head about where to place these for best results. In aluminum skin is best for securing the port but that puts them ahead of the doors on the boot cowl, probably not the best place. In the fabric behind the baggage area is good placement but not that great for securing the port. I have glued a backer plate on the fabric and drilled through that but still not the greatest set up. Would out in the wing near the pitot tube but facing down through the aluminum skinned wing be a good place or would the air be too disturbed for accuracy? I can't think of any certified systems with this location, probably a reason?
 
Bearhawk Builder said:
I've always scratched my head about where to place these for best results. In aluminum skin is best for securing the port but that puts them ahead of the doors on the boot cowl, probably not the best place.
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What is you objection to mounting them on the boot cowl? That is where CubCrafters puts the static ports for all their aircraft that use the Garmin AOA/Pitot probe.

One Carbon Cub owner reported static errors that he corrected with fairing shapes but most owners seem to find any errors not to be worth correcting.
 
Outflow through the cowl cheeks on a standard Cub cowl would interfere I’d think. I used my original static line that Mike brazed into the forward left jury strut. It seems to work fine even with Garmin instructions to not place the static source under a wing. I didn’t see a better alternative.
 
My thought was that the boot cowl are gets too much turbulent prop blast. I would welcome that I'm wrong as this would be the easiest solution.


frequent_flyer said:
What is you objection to mounting them on the boot cowl? That is where CubCrafters puts the static ports for all their aircraft that use the Garmin AOA/Pitot probe.

One Carbon Cub owner reported static errors that he corrected with fairing shapes but most owners seem to find any errors not to be worth correcting.
Click to expand...
 
How bad it is to just vent it inside at the back of the instrument panel? These cubs are so "not sealed up" that it may not make much difference.
 
Bearhawk Builder said:
My thought was that the boot cowl are gets too much turbulent prop blast. I would welcome that I'm wrong as this would be the easiest solution.
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Recorded data for my Garmin G3X equipped FX-3 Carbon Cub shows some interaction between RPM and pressure altitude.
 

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The cleanest airflow would be back on the empennage. You're looking for smooth airflow with no induced pressure changes. Cessna can put them on the sides of the cabin as they don't have the 'cheeks' on the cowling that Cubs do. The stock style tube that Stewart used also works well. It's just a small diameter tube, pointed into the airflow, with the tip brazed shut and tiny holes drilled in the sides.

Since most Cubs have enough airflow through the cockpit to knock your cap off, I generally tie all static ports together, then leave that connection open to ambient air behind the panel.

Web
 
Sorry should have said from the beginning this is on a Bearhawk Patrol build, no cowl cheeks. What do you all think of the static port in the wing skin pointed straight down, seems it would be about the same as the tube with side facing holes. Or maybe the boundary layer and compressed air would mess things up? Good to know about CubCrafters, we are essentially the same set up. Venting into the instrument panel would be fine but I seal these planes up pretty good, not as drafty as my Cub.
 
I'd stay away from the wings unless you put the port down on a strut. Wings operate by pressure differential so I wouldn't even want to vent a static port in a wing root.

Web
 
frequent_flyer said:
Recorded data for my Garmin G3X equipped FX-3 Carbon Cub shows some interaction between RPM and pressure altitude.
Click to expand...

I should have added that I don't think the approximately 10 ft altitude difference seen between prop stopped and run-up rpm is cause for any concern. I suspect that variation with alpha will be far greater than any effect of prop wash.

No static system will be free of error. That's why big airplane air data computers include SSEC (static source error correction) and, in flight test, a trailing static cone is used to measure the real static pressure.
 
Piper likes the side fuselage in metal aircraft as does Beechcraft, Cessna likes the boot cowl area. Cirrus is tail again as in a number of others.
Never ever seen it in a wing. I’d guess that’s a bad location.


Sent from my iPhone using SuperCub.Org
 
Farmboy said:
Piper likes the side fuselage in metal aircraft as does Beechcraft, Cessna likes the boot cowl area. Cirrus is tail again as in a number of others.
Never ever seen it in a wing. I’d guess that’s a bad location.
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I'll guess you don't have much PA-28 time. The static port on these aircraft is typically integrated with the wing mounted pitot probe.
 
Notice the yarn behind the pitot/static tube. It's flowing straight aft at 20 degrees angle of attack as well as at zero degrees keeping the relative air flow within the recommended +/- 10 degrees.. This pitot/static location has been flight tested from 40 mph to 150 mph with zero error. I recommend this type of installation.


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Where to place a static port is an exercise in poking holes all over an airplane. They all have little idiosyncrasies which dictate the best location. Some are on the sides of the wrap around, some under the aft fuselage, some on the aft sides of the fuselage, some on a pitot/static probe on a mast sticking out of the wing leading edge. Some static ports have little turbulence generators to bias the pressure.
 
Bearhawk Builder,

Here’s a snapshot of my original Pitot and Static lines. I abandoned the Pitot when I added my Garmin AOA probe. I like these in the jury strut better than the Univair part. I replaced the Univair one on my -12 a couple of times after bumping and breaking it. I’ve never bumped these. FWIW the static line is approx 12” below the bottom of the wing. You can google instructions for making one. EAA has a good article about static lines. https://www.eaa.org/eaa/aircraft-bu...and-avionics/installing-a-pitot-static-system
 

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frequent_flyer said:
I'll guess you don't have much PA-28 time. The static port on these aircraft is typically integrated with the wing mounted pitot probe.
Click to expand...

A static port probe is not what I consider to be “in the wing” but perhaps I misinterpreted the question.


Transmitted from my FlightPhone on fingers… [emoji849]
 
Another thing....it is not just the location of the static port(s). When my 185 was painted the disks around the holes were painted (with my approval). On the way home from the paint shop the plane was 20 knots faster than normal :p. The paint had restricted the diameter of the static port hole. After cleaning the paint off the static disk and cleaning out the hole with a drill of the correct diameter turned by hand, the speed went back to normal.

It is only supposed to be a static sensing hole, but the diameter of the hole(s) does make a difference in the calibration.
 
dgapilot said:
Only the later PA-22s. PA-20 and early PA-22s had the static in a combined pitot static probe under the wing.


Sent from my iPad using Tapatalk
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My 1950 PA20 didn’t have a static port system…the VSI and mode C transponder were never very accurate. Quite a few times on my way into Merrill field ATC asked me to verify my altitude.


Sent from my iPad using Tapatalk Pro
 
Aeronca/Bellanca/Piper had a static port design like shown in #16. The holes were on both sides to minimize the effect of slips.


Gary
 

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