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Static Ports

Bill.Peyton

Bill.Peyton

Well Known Member
I am not happy with the very cheesy looking static port (pop rivet) Vans provides (along with a lot of other cheesy Vans provided stuff IMHO). I am planning to replace this with a real static port/ports. What is the consenses of those who have flying aircraft for the style of port and quantity, and most important, the accuracy?
Bill
 
They may look cheesy, but the purpose of static ports is get good, accurate static information to your instruments. The fact is that it takes hundreds and hundreds of hours of flight testing and tweaking a new airframe design to figure out a good static source, and once that has been done, you have to ask yourself if you really want to go through that again.

The truth is a "Real" static source is one that works - take a look at lots of different airplanes, and you'll find lots of different designs. Van's found out that the pop rivet works well. The forums are FULL of threads by people who have had problems with calibrating their ASI's going with other ideas.

I am absolutely not against experimentation, or looking for better solutions - but it's important to recognize that you can (not will, but "can") go through a lot of trial and error with this particular change.

On our current project, we once again use the pop rivets (took two minutes to install and set), but are using the quick-connect fittings sold by Stein and SafeAir to do all the plumbing - a very nice upgrade from the old white nylon fittings that tend to leak if you don't hold your mouth just right.

Consensus? I can give you two data points on our -6 (2500 hours) and -8 (1250 hours)that have pop rivet ports and dead-solid static readings to the instruments.

Paul
 
I put very nice looking aftermarket static ports on my RV-10. They look great but I am still working to adjust them for accuracy. In general, I spared no expense on my airplane, but if I was doing it again, I would take Mel and Paul's advice and use the Van's supplied static ports. I did use the quick-connect fittings Paul references, and agree 100%. They are great.

Kevin Horton has some excellent articles published in Kitplane magazine in the past year about pitot and static systems.

exactly $.02 worth.
 
I have the nice flush Safe Air ports-----project came with them already installed, and plumbed.

I remember reading more than once, where the flush ports induced an error to the static reading, and folks had to glue a washer on the fuse around the port to get things accurate.

As of yet, I havent gotten to that point in my test program, so I have no empirical info.
 
one data point...

I have a heated pitot tube with the static ports on the tube as well. I have been calibrating my airspeed and there is a HUGE error in airspeed. I've made several attempts at a kluge fix and, while the airspeed is now within 2 1/2 kts at 160kts and 1 kt at 100kts, it indicates stall at 38 kts.

I am now down for annual and will install the standard static ports in the standard location and see if it's any better/easiear to calibrate with tape/washers etc. If not, I'll go back to the heated tube static source. Be very careful with calibrating airspeeds, no matter what your choice of static source is. A friend with the standard source needed to monkey with it too...

Jeremy Constant
7A 95hrs, down for annual and squawk fixes
 
Wow, Interesting response. It does indeed sound as if those who have changed the ports to an aftermarket have had some issues, and those that used the provided ports do not. I guess that makes the decision easy. I will go ahead and upgrade to the stein fittings. I have enough things going on to not want to spend addtional time experimenting.
Thanks for all the input!
Bill
 
I installed the pop rivets a few weeks ago...

They actually look nice from the outside. Inside is a different story with the fish tank air line, tee, silicone glob, but I am positive it will work just fine. I have tried to stick with plans as much as possible to make the build quicker and less expensive.
 
As Paul has correctly pointed out plenty have been down this road already, and those who haven't probably do not realise the errors they have, and should check!

The issue for me flying IFR is the altitude error created by a large static error :eek:

I first discovered it by wondering why I had the worlds slowest RV10 by -9knots. I researched here and found that static error was the issue so did the GPS box TAS test and sure enough the plane was as fast as it should be but the speed error meant I had a big static error, and altitude.

So I started by glueing a rivet head over the top of the static port.....Bingo! now I had the fastest RV10 on the planet, but of course that was now creating a lower static pressure, I filed edges and mucked around and could not get it right, so I looked at others with small fences so again just experimenting and by taping over one side and using a leaf blower down the side of the fuse looking for altimeter changes found that I had pretty much nailed it.

Went and test flew it with another GPS box and the TAS was within 1 knot and the altimetry was now consistent with the GPS (accounting for expected GPS error).

Now here is what I ended up with......and yes it is still that way. Was just an experiment but it works so as ugly as it is....it stays!

20072010001.jpg


The fence is aluminium TIG welding wire rolled into that shape!
 
Which way is the front of the plane???

Or, to put it another way, does the fence lead, or trail the static port??

Thanks,
 
I went with the SafeAir1 static port kit. I'm not flying yet, but if I end up having problems, I'll just use a rivet shaver to shave down the nub that sticks out, drill the hole big enough for the shank of the pop rivet and proseal a pop rivet in place. That'll get me the exact same airflow characteristics as a stand-alone pop rivet, but with the nice NPT threaded base and fittings.
 
Pretty sure it was this one from Aircraft Spruce.... but we screwed in AN fittings, yet it has no rivets. Not 100% sure now.

The photo is the starboard side so the front of the plane is to the right.

The safe air static kit mounts from the inside and it may be just the deal, but until you try it how would you know?

Just be prepared to get it right, do a GPS box and in my opinion if you are IFR it needs to be 2-3 knots MAX error at 170 knots approx. Otherwise your altimeter is going to be way out.

PEC is 50' for an ILS without the PEC chart for your plane for a good reason, so you do not want to be another 50 feet off now do you?

I wish there was a difinitive perfect answer, well I guess there is........test and test and experiment and test until its pretty darn accurate!

DB:cool:
 
I would suggest that your airspeed could be off due also to the pitot tube and it's angle of attack and other factors associated with its installation. I would have your altimeter checked on the ground, along with your encoder. Then when airborn use your GPS altitude page to read out your encoder and compare that to the chart you obtained from your ground static check. the airspeed issue may be totally divoriced from the static issue.
 
Bill.Peyton said:
I would suggest that your airspeed could be off due also to the pitot tube and it's angle of attack and other factors associated with its installation. I would have your altimeter checked on the ground, along with your encoder. Then when airborn use your GPS altitude page to read out your encoder and compare that to the chart you obtained from your ground static check. the airspeed issue may be totally divoriced from the static issue.
Click to expand...

It's certainly good to check out the entire system, but experience has shown that the pitot is pretty hard to mess up. Within the range that we all normally fly (and certainly in cruise), the pitot is fairly insensitive to angle of attack - so long as it is several inches away from the lower wing surface, any relatively forward-facing hole will provide an accurate source.

The discussion of altimeter error is really a great reminder (in this transponder age) that static error is more than just affecting your indicated airspeed - it can affect other airplanes if you are IFR!

Paul
 
GPS altitude

I was under the impression that the altitude shown by a GPS is the true altitude above the geoid model and that the baro altitude does not necessarily agree with it due to atmospheric conditions. In the summer I often see several hundred feet difference between baro and GPS altitude.
 
Interesting thread, because I too seem to have a static error.

Back when, I fired up the lathe and made some billet static ports. The shape is a copy of the standard pop rivet head, but they have a barb fitting on the inside. They are installed in the standard location for an RV-8.

But....my airspeed indicates faster than true, per the NTPS method.

Hmmm. Did I miss on the head shape, or does the fastback and one-piece bubble reduce pressure at the static port location as compared to a stock fuselage? I dunno....any other Showplanes kit guys with the same experience?

Anyway, confirm please....making the port more flush tends to increase pressure/lower IAS, and a more protruding head tends to lower pressure/increase IAS?
 
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elippse, that's true. There are procedures for testing your true airspeed error using GPS (search the forums and you'll find spreadsheets, etc - especially helpful are Kevin Horton's products). Since pitot air is hard to mess up (ref Paul's post), if you have a true airspeed error when using the GPS test procedures, you quite likely have a static air problem. That means you also have an altitude error, by definition. There are also methods for ground-testing your altimeter using a water column, etc.

Incidentally, just to add a data point, I also have a heated pitot with static source, and I also have had a static error, and I also am in the process of retrofitting the Van's standard pop-rivet static sources and Stein Air plumbing, on the advice of the community.
 
Static Port

I too did not like the maintainability of Van's "pop rivet" static ports. No question of their effectiveness, and I admire a simple design as much as anyone. But if the vinyl tubing from the pop rivet to the nylon tubing splits (which it seems prone to do), it results in erratic instrument readings and crawling into the tailcone to repair. So I machined (yep, it helps to have a lathe) a static port that duplicates the profile of the pop rivet head, has a 1-3/8" diameter x 0.090 flange that is riveted to the inside skin with 3 x AN426AD rivets and has a 5/8" diameter x 3/4" boss that is tapped 1/8" NPT. Had to mount this 9/16" ahead of the position shown on the plans for flange clearance but think this should be OK.

The 1/8" NPT thread in the boss allows the use of a 90 degree quick connect elbow so reliability and maintainability should be improved.
 
CAFE testing

DanH said:
Interesting thread, because I too seem to have a static error.

Back when, I fired up the lathe and made some billet static ports. The shape is a copy of the standard pop rivet head, but they have a barb fitting on the inside. They are installed in the standard location for an RV-8.

But....my airspeed indicates faster than true, per the NTPS method.

Hmmm. Did I miss on the head shape, or does the fastback and one-piece bubble reduce pressure at the static port location as compared to a stock fuselage? I dunno....any other Showplanes kit guys with the same experience?

Anyway, confirm please....making the port more flush tends to increase pressure/lower IAS, and a more protruding head tends to lower pressure/increase IAS?
Click to expand...

Dan,

The CAFE performance reports for the RV-8A and RV-9A compared IAS obtained from the aircraft pitot tube and pop-rivet static port, to CAS measured with a test boom. At cruise speeds the reported IAS was as much as 5 mph faster than CAS for the 8A, and up to 7 mph for the 9A.

I have flush static ports, which I used because of the barb fitting inside. I did fairly extensive testing of the system, using 4-way gps and Kevin Horton's spreadsheet. I found that my IAS was between 1-2 kts slower than CAS in the cruise range.

At face value these tests don't seem to support the idea that the pop-rivet static ports produce more accurate IAS. I know Kevin has found otherwise however, so maybe its aircraft-dependent?
 
Alan Carroll said:
At face value these tests don't seem to support the idea that the pop-rivet static ports produce more accurate IAS. I know Kevin has found otherwise however, so maybe its aircraft-dependent?
Click to expand...

Ah, but lots of testing by individual builders with the pop rivets argues on the other side. I know that mine is within measurement tolerances (1-2 knots) with the pop rivets by the same 4-way GPS and spreadsheets, and so have many others. Interesting about the CAFE tests, as this really supports hat every airplane must be tested to see how well it works...which is why we fly Phase 1 as a test program.
 
Does anyone have any experience with the Cleveland ports installed in the RV-10 standard location?

http://www.cleavelandtoolstore.com/prodinfo.asp?number=SPF50

These are what I installed early in the project without having talked to others about their static port choices on the -10. I wish I had gone the SafeAir route, but I'm curious to know if anyone has experience with these.

Thanks,
Phil


spf50_lg.jpg
 
O.K. folks...so at what airspeeds do we really need to be accurate? I got it close at both 160kts and 100kts, but way off on the low end. Will it be possible to get it within say, 2 or 3 knots all along the whole range from 5 or 10 kts above stall all the way to Vne or should I call it good?

Jeremy
 
pop rivet static port

As I've reported several times on the forum, the three RVs I've had the owners test, a -6, an -8A and a -9, all using the pop rivet, had errors from 9-12 mph. I think part of it is due to the curvature on the outside of the rivet which drops the pressure at the center. It's a simple job to fix it. Just add some tape in front, for low IAS or behind, for high IAS, and do the GPS comparison at cruise until it's right on. My druthers would be to have it correct around cruise and not worry about low speed..
I think what's making the difference on various planes of the same type that had their ports located the same but different results might be the fuselage flow from the different type of props that are used. Most CS props have really bad, aerodynamically speaking, root shapes which really turbulate the flow along the fuselage. A lot of FP props have really bad root shapes too, shown by a flat triangular area just outside of the spinner, and less than correct root pitch angle which, just as with the CS props, causes really turbulent flow along the fuselage. Just use the rivet and correct it!
 
Paul Dye is correct.

GPS altitude is only a guide as to whether you are close to the mark. Confirming your thoughts so to speak.

check your statics folks!:cool:
 
Phil said:
Does anyone have any experience with the Cleveland ports installed in the RV-10 standard location?

http://www.cleavelandtoolstore.com/prodinfo.asp?number=SPF50

These are what I installed early in the project without having talked to others about their static port choices on the -10. I wish I had gone the SafeAir route, but I'm curious to know if anyone has experience with these.

Thanks,
Phil
Click to expand...


Phil,

I don't have the links handy, but Tim had several write ups on his site. If my memory is correct, I think he ended up with the Cleaveland product and was fundemental in Cleaveland coming up with their second iteration of the product.

bob

p.s. I have these installed too.
 
Hey Bob,

Do yours have a dome or are they flat? Mine are dome shaped and the current photos are flat. I am wondering if I might have the first version?
 
Phil said:
Hey Bob,

Do yours have a dome or are they flat? Mine are dome shaped and the current photos are flat. I am wondering if I might have the first version?
Click to expand...


I believe the dome ones are the newer version. If I recall Tim's comments correctly, the original flat ones were generating inaccurate results. The newer ones I believe he was able to get it to less than one knot of error.

I'm sure Tim or Mike will chime in.....

bob
 
Yep, thanks!
I just found it on his site with 1.8 knots error. Now I just have to hope my NACA vents don't mess with it.

Thanks,
Phil
 
Just to be clear on the GPS altitude readout in flight. My KLN94 has a serial input from the encoding altimeter. It also has a Baro set page on bootup and when using it for an IFR approach it prompts for the Baro setting. The KLN94 then reads out the encoders altitude being provided to the transponder, adjusted for Baro. When you have your IFR pitot static test done, one of the requirements is to provide a table of actual verses encoder reported altitude. If you copy that table and bring it with you in flight, you can correct for the errors of the encoder and get a pretty good verification of your altitude, verses your altimeter, which btw, should also have a cal table after a PS test. I always use this feature to verify I have a good altimeter setting when I am flying IFR.
With that said, this does you no good in terms of checking the static port in flight because you don't really know your actual altitude.
 
Cleaveland Ports

The ports with the flat face (as in our old photo) are the old ones.

The new ports are domes so that they further protrude into the air stream.
 
Static and GPS

My BMA (and I'd bet most other panel mount systems) have a settings page for calibrating during the pitot/static check. The tech who did my initial check used his system to run my static system up to preset altitudes and we read the calibration numbers and entered them into an altitude table in my system. When done, he proceeded to do a normal check and my system checked out with 0 error at all altitudes. Hard to say about speed but my EFIS is in lockstep with my analog airspeed and my recorded indicated speeds are accurate enough for operations; at 8000+ feet I take airspeeds with a grain of salt anyway.
 
Flion and anyone else reading this.

READ THIS POST CAREFULLY

Do not assume your system is accurate just because you had your avionics checked by the avionics technician when you did your last AD Inst 8/9 or whatever you guys call it over there.

Your avionics as flion above points out above may be deadly accurate all the way to 20,000' and my Dynons were, better than the TSO'd Altimeter I have.

The problem is you are sitting in your hangar with a known static source testing your plane.

YOU ARE NOT dragging a static on a drogue 100 yards behind the plane comparing a "True and Known" static with the static in your aircraft at speed.

If you are not 100% sure of what I am saying go ask some test engineers to explain it better. Kevin Horton on this site is a classic for explaining it, search his name and threads.

Am I making myself clear. In flight static is not the same thing as when you get your altimetry checked out on the ground and can yield very big errors as I found when doing our test flights.

Oils aint Oils :cool:
 
rleffler said:
Phil,

I don't have the links handy, but Tim had several write ups on his site. If my memory is correct, I think he ended up with the Cleaveland product and was fundemental in Cleaveland coming up with their second iteration of the product.

bob

p.s. I have these installed too.
Click to expand...

I cant find the mentioned write ups. Can someone post the links ? Thank you.
 
RV10inOz said:
YOU ARE NOT dragging a static on a drogue 100 yards behind the plane comparing a "True and Known" static with the static in your aircraft at speed.
Click to expand...

Your point is well taken. My -6A is flying using the Van's method of pop-rivet static ports and I see no altitude error at speed. However, I'll be sure to double check when I get the -10 flying, as I will be using the flush ports.
 
RV10inOz said:
Flion and anyone else reading this.

READ THIS POST CAREFULLY

Do not assume your system is accurate just because you had your avionics checked by the avionics technician when you did your last AD Inst 8/9 or whatever you guys call it over there.

Your avionics as flion above points out above may be deadly accurate all the way to 20,000' and my Dynons were, better than the TSO'd Altimeter I have.

The problem is you are sitting in your hangar with a known static source testing your plane.

YOU ARE NOT dragging a static on a drogue 100 yards behind the plane comparing a "True and Known" static with the static in your aircraft at speed.

If you are not 100% sure of what I am saying go ask some test engineers to explain it better. Kevin Horton on this site is a classic for explaining it, search his name and threads.

Am I making myself clear. In flight static is not the same thing as when you get your altimetry checked out on the ground and can yield very big errors as I found when doing our test flights.

Oils aint Oils :cool:
Click to expand...

I don't think I ever implied that having a pitot static ifr check will verify the system is correctly reading in flight. I agree 100%, you can not calibrate nor check the system on the ground, other than for a leak and for the actual accuracy or the readout of the altimeter, the encoder and whatever other system you may have. The only way to verify the accuracy of the total system is in flight, and for altitude, with a known reference.
 
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Known reference?

I too have installed the flush static source in the 10 and had them installed in my 8.
The 8 was "accurate" in all phases of flight measured against the GPS.
Since a GPS is the only available tool to use as a reference, would you agree that this is an acceptable method to verify the Static system in flight?
 
David is correct on this one....several people here have the misconception that just because they pass a static/pitot test on the ground that they are good to go. There is much more to it than that and you could have major errors in your IAS and ALT readings. Certified birds have the luxury of having well proven certified static sources. The system works for them but with us we need to take it on ourselves to ensure accuracy.

I went thru this process myself and it can be frustrating to no end. I can tell you that for an RV7, it is very sensitive to port position, port shape, port protrusion etc when the port is in the area specified by the plans. Very small changes can make big changes in the results.....

RV10inOz said:
Flion and anyone else reading this.

READ THIS POST CAREFULLY

Do not assume your system is accurate just because you had your avionics checked by the avionics technician when you did your last AD Inst 8/9 or whatever you guys call it over there.

Your avionics as flion above points out above may be deadly accurate all the way to 20,000' and my Dynons were, better than the TSO'd Altimeter I have.

The problem is you are sitting in your hangar with a known static source testing your plane.

YOU ARE NOT dragging a static on a drogue 100 yards behind the plane comparing a "True and Known" static with the static in your aircraft at speed.

If you are not 100% sure of what I am saying go ask some test engineers to explain it better. Kevin Horton on this site is a classic for explaining it, search his name and threads.

Am I making myself clear. In flight static is not the same thing as when you get your altimetry checked out on the ground and can yield very big errors as I found when doing our test flights.

Oils aint Oils :cool:
Click to expand...
 
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Correct in software?

I'm curious -- with the combination of widely-used EFIS devices and static port errors... Why can't the errors be corrected in software?

I understand why a bad static port can't be fixed for an analog gage, since the gage assumes a fixed (linear?) relationship between static and pitot pressure. But what about for an EFIS? Can't you just do a series of flight tests at assorted known altitudes and airspeeds (say, flying in formation with a calibrated aircraft), plug in "this is how fast and high I am" and derive the pressure curves for your particular plane and installation?

I am a new builder, so please forgive my ignorance. I'm just curious why we have to go to such efforts with physical kludges when this sounds like a software problem to me.

Chris
 
static ?

My question----Has anybody tried 2 ports, one on each side of fuse, tied to static system on left and right sides of the instrument plumbing? Sort of an "averaging" of pressures. ignorance is bliss :eek:
 
mark schoening said:
My question----Has anybody tried 2 ports, one on each side of fuse, tied to static system on left and right sides of the instrument plumbing? Sort of an "averaging" of pressures. ignorance is bliss :eek:
Click to expand...

N427EF said:
I thought everybody uses dual static ports?
Click to expand...

Yea, most planes have a static port on either side of the plane, and these are tied into a Tee, which then is the static tube. Just imagine only having one static port in a crosswind.
 
If you want to install an untested static port on an IFR airplane, it would be advisable to test it. I suppose you could do this with a home-made trailing static cone and use a water manometer to compare the two static sources.
 
easy fix!

jjconstant said:
I have a heated pitot tube with the static ports on the tube as well. I have been calibrating my airspeed and there is a HUGE error in airspeed. I've made several attempts at a kluge fix and, while the airspeed is now within 2 1/2 kts at 160kts and 1 kt at 100kts, it indicates stall at 38 kts.

snip

Jeremy Constant
7A 95hrs, down for annual and squawk fixes
Click to expand...

Hey Jeremy:

Homey Depot sells the fix for your expensive heated pitot/static -- 1/16" rubber O rings! Install aft of the static holes to fix a fast-reading ASI, or in front of the holes for a slow-reading ASI. Keep making low passes at your home field (or another with a known elevation) to check your 'calibration' using your altimeter as the reference instrument. Once you get it right, a bit of RTV or Pro-seal will hold the O ring in place.

Every aft mounted static port I checked netted a 15% error @ cruise: look at the MPH scale and read it as knots. This was true using factory parts and location...YMMV of course!

FWIW, the altimeter is the only instrument you can actually use to check your static system. Use the low-pass method to see what yours tells you, and adjust from there. Do not rely on a pitot/static check to tell you that your static system actually works as it should in flight!

Carry on!
Mark
 
F1Boss said:
the fix for your expensive heated pitot/static -- 1/16" rubber O rings! Install aft of the static holes to fix a fast-reading ASI, or in front of the holes for a slow-reading ASI.

Mark
Click to expand...

O.K., are you cutting them in half first? so they look like the setup in this photo I borrowed from David?

20072010001.jpg
 
I can't believe I'm asking this question, but I can't think of a good answer...

In an unpressurized vessel (i.e. an RV) why can't you get a source of static air from within the plane itself? Something like an open port within the empennage?
 
Because the air inside the structure is NOT static. It changes depending on air entering and/or departing the airplane.
 
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