Where to place static ports

[Jch]

Has anyone placed their static ports on the sides of the boot cowl? I looked for a reference in AC 43-13 but couldn't find anything specific. Advantages-mounting on a firm surface and shorter tube runs. Thoughts?

[Av8r3400]

I plan to vent static behind the panel. These are not sealed up cabins, so why bother with an external port?

[ackselle]

I too placed the static ports behind the panel.

[DesertFox4]

I also opted for the behind the panel porting. Works very well and is very simple. I put a tee back there with a short stub of tubing with a little auto fuel filter over it to keep dirt and what ever out of the static system.
When I bought my first Kitfox, a model 3, I did the same thing to it after the static port came unglued from the side of the fuselage. This was easier than trying to reattach in the original location and worked better.

[HansLab]

Not me, I put the static in the back of the fuse.
And after some stories in this very forum about Side-slips and loosing altitude indication, I put another one on the other side of the fuse.
Never gave me problems since then (7 hours :-))

[Dorsal]

I am planning on experimenting with this as mine are behind the panel but my airspeed is also off by 3-5 mph (to high). Have the kit to do as HansLab did, won't get to it till spring though.

[n85ae]

I have a heated pitot/static tube out on the wing. Works great, easy install
and it's not affected by fuselage airflow weirdness, or inside cabin problems.
The only downside was that it was a bit pricey.

Regards,
Jeff

[Dave S]

When constructing our KF, I spent a bit of time looking into this issue and thinking about it....Then went with the factory specified location. No matter where the port is installed it is probably not going to totally avoid every possible installation effect on static error.

I thought back on certified airplanes I have flown with alternate static ports vented to the inside of the cabin. Most of the time they would read a higher airspeed on alternate source than the outside static. Experimenting with those, it became apparent that a cabin can be either somewhat pressurized or somewhat subject to pressure lower than static depending on how the air flows over the numerous pneumonia holes in the airframe. I know a Cessna or Piper is not a KF; but I have since found through experimentation that my Kitfox is subject to cabin pressure variations to some extent depending on if the side vents are open, conditions of slip, how much power or speed is being carried...and on and on - can't say anything about open doors since I haven't tried that.

There can be variations on the factory KF location too....not all static ports will be installed in the airstream the same way and a minor variation or tilt on the static disk or mounting can change things.

Having said all that, I do find that the factory location, at least on my plane, results in readings that appear to be minimally affected by installation error. My main interest was in having a static signal that would provide a reasonably accurate input for the transponder encoder....ground calibration/certification of the encoder does not guarantee that reported and actual altitude aloft is correct if there is a significant static port error....so far the ATC folks have not had an issue with me other than the time the encoder pooped and read 2,000' higher than actual (OK, where the heck are you!!!).

I figure if my altimeter puts me at eye level with most other traffic in the pattern it can't be too far off; and, that in combination with the transponder calibration should mean that the system is not too far off. Airspeed values come reasonably close to design numbers.

But then, we do learn to fly our planes without looking at the ASI & ALT too often

Sincerely,

Dave S
KF 7 Trigear
915ULS Warp

[N981MS]

FWIW
Series 6 IO-240
Static port stock location (or really close) on left side only.
Gretz aero pitot on left wing.

Accurate and never lost any readings in 700 hours or so. Never noticed any problems doors open, closed, slips, or otherwise.

[av8rps]

My Model 4 had port on right side of fuselage a bit forward of the tail section, but it was pretty consistently off, showing 10 mph too slow on ASI (Stall looked great but cruise looked poor at best). I changed static to read behind panel and now ASI reads accurate within 1 to 2 mph regardless of whether vents are open or closed.

I also have a JA Highlander that had the same error with airspeed (pretty much identical to Kitfox, showing 10 mph slow). It had a static port on boot cowl just forward of left side cabin door. I disconnected it and ran static under instrument panel and found that one to be fixed just like my Kitfox. And it didnt seem to make any difference with vent position, but it does change slightly if I have the window on top half of door open, or if I fly with door open completely.

If I really felt I had to have an external static port I would use either a combo pitot and static out on wing in relatively clean air, or I would put a static port on both sides of the fuselage teed together approx midway between tail and back of wing. Just my two cents...