SafeAir Static Ports
 

I'm not trying to start a debate, just curious of people using the Safeair ports without any issues?

I've done searches, seen/read all the issue people have had with these ports in the past, but I can't find any information if SafeAir redesigned there ports at some point, or is anyone using a recent variant of the SafeAir port that works fine for them? Also it seems like most of the past issues were more with people flush mounting them. I'm not opposed to doing something different, but I have the ports that came with my tubing kit from Safeair and would hate to trash them if there really isn't an issue anymore.

Thanks,
Lynn

Lynn,
Don't trash them! The SafeAir static ports (and the entire system) is fantastic. I use it for my static as well as my Dynon pitot/AOA line runs. These plumb up into my dual SkyView ADAHRS systems. They're great!

The best thing to do would be ask Safeair....

But I think they did redesign them at some point so that they mimic the shape of the blind rivet used in the static system kit sold by Vans.
If the ones you have wont mimic the blind rivet shape once installed, the results you will get are unknown.

I thought about asking SafeAir, but I was really wanting some real world responses, since I'm sure they will say there latest design is good to go. Nothing against them, but I'm sure they wouldn't still be selling it if they thought it didn't work just fine.

Lynn

Emailed
 

I have the same question and just I emailed SafeAir1. Will let you know.

Mine are a few years old and work just fine. IIRC the original ports were basically flush or had a very minimal protrusion that led to static system errors. The ones I have distinctly protrude beyond the side skin.

Mine were vintage 2008/9, they protruded and the position error was Unacceptably large for me. (Main gripe was actually the erroneous altitude was unacceptable for IFR)
It's as much about the shape as the height.
After wasting many many hours experimenting with different solutions I now have the Cleveland ones.
I'm building a 10 now and it will have pop rivets....
Cheers

How did your Cleveland solution worked?

Great. Pos error dropped from 6/7+ ktas at cruise to only a few knots.
More importantly though the altitude came back into line. I'd imagine that my altitude would have been quite innacurate at cruise speeds until rectified.

At approach speed on an ILS at the MM it was more than 50' out.

Cleaveland ports here...very accurate based on GPS and other aircraft (friends' RVs in loose formation at same altitude). Either we're all wrong, or mine are working just fine.

Safe Air here
 

I put the safe air units on my RV9 in January. They protruded from the surface. As a previous user indicated I had a +/- 6 mph error when flight testing. I installed crescent shaped fences in front of the vents to bring them into calibration. It took several tries and Kevin Hortons assistance to get the error to nil but all worth it. Now I know I have an accurate system and will check it for leaks every condition inspection to maintain it that way.

Thanks for all the responses. Anyone have the Rivet part number for the pop rivets Van's uses in there system?

Thanks again,
Lynn

Back in 2007 I mounted mine on the exterior of the skin because of some reported issues and after seeing them mounted in a similar manner on a business jet. In this configuration, they have worked great! (When I had the plane painted, I had them leave the entire fitting unpainted.)


(Click to enlarge)

I used the original SafeAir static ports mounted inside. Had issues and ended up grinding them completely flush, drilling em out and gluing in the body of one of Van's pop rivets. Problem solved.

I am using the latest safe air ports and have had excellent results. Mine are mounted from their inside, the fuse is painted, the button head port is not

Works great
 

Installed static ports with rivets and sealed with pro-seal from the inside on my RV8. Work great and numbers are spot on between my Dynon FightDEK180 and my TruTrak Gemini ADI. Just confirmed the accuracy with an avionics shop pitot static calibration and transponder check last month. Pitot and AOA connections are with the Safe-Air system also.

Used the full safair system in mine. No issues to report.

Aren't both systems connected to the same static/pitot? If so one would expect to get the same numbers and if there are errors as the result of static port, both will have the same errors. I am also curios how did the shop test for accuracy if not just for the leak and with his machine which would not account for inaccurate static port or location of the port.

Yep...an on-ground pitot/static test will tell you if the equipment is measuring the difference in pressure correctly, and if the altimetry portion is properly calibrated based on the suction that is being pulled on the static ports, but it can't tell you anything about *in-flight* errors due to the ports being in or out of the free stream, etc.

In other words, it can tell you that if the static ports "see" pressure equivalent to a certain altitude, that that altitude is what is being reported. But it can't tell you that the installation will actually "see" that pressure in flight at that altitude...

Where did you get the "crescent shaped fences" or did you fabricate them?

:cool:

Correct.

Most any static port (shape or location ) can pass a ground test as long as the system has no leaks and the the EFIS/Instruments are working properly and are correctly calibrated.

The true test of a system accuracy is in flight. That is when the location and /or shape of the ports come into play. The desire is that with the dynamics of flight and high speed airflow, the system is still able to sense what the "static" pressure of the air is at a given altitude.

To add a bit more, based on my experience, the inaccuracies are seldom liner and more noticeable in IAS than indicated altitude. Although I have seen it in a few Planes that when the static port is not of the correct type for that plane, right after take off you see an altitude drop maybe even lower than the field altitude before it raises up.

To add another 2c,
I spent probably a year getting this right after installing non standard static ports. Dozens of test flights. Experimenting with fences / ramps / tape etc.
Hours and hours with the NTPS spreadsheets.
I generally found it interesting and knew what I was trying to achieve and I needed it to be accurate to get an IFR cert here in OZ.

All of this would likely have been circumvented with 2 pop rivets.

I'd strongly suggest that anyone considering deviating from the factory design understand fully what influences IAS / CAS / TAS / PALT / PEC etc . Else it just won't be accurate which may or may not be important for your mission.

Seasons greetings all.

Since it depends on the position of the ports on the plane, do some RV's work and others don't because of where they are placed?

Lynn

That is assuming, of course, that the Van's-specified pop rivets are *themselves* somehow designed in such a way that they are always accurate.

I have a hard time believing that they're any better or any worse than numerous other types of static ports, simply by virtue of coming from Van's.

The thing I don't like about the pop rivets is that's not much for the very small plastic tubing to hold on to and the tubing tends to come off or develop leaks. I had problems with them on both my RV-4s that I outfitted for IFR and ended up going with SafeAir ports on the second one; (they were very accurate with my Dynon.)

Static Source Error
 

Static source error can only be determined through flight test. Ground test (including normal pitot/static checks) does not measure static source pressure error. Each aircraft is different, but systems installed in accordance with the drawings and using pop rivets have been shown to generally give good results. However, that can only be verified by flight test. The Cleveland ports mimic the geometry of the rivet. Anicdotal evidence in previous board discussions on this topic may indicate that ports flush with the skin on RV-types induce more error into the system than ports that protrude a bit. The most efficient way to test static source pressure error is in conjunction with using GPS to test airspeed performance. A simple manometer can be constructed to conduct ground test required to gather data that will support flight test.

Paper hole reinforcements can be cut in half, or layers of masking tape can also be used ahead or behind the existing port (depending on perceived airspeed error). Once an appropriate thickness has been determined, an appropriately thick washer can be glued in place to bias flow around the port, if desired.

Kevin Horton has an excellent write-up on his site regarding appropriate test techniques:

http://www.kilohotel.com/rv8/index.p...d=3&Itemid=218

Most of the modern EFIS systems minimize actual instrument/sensor error, but system (i.e., "installation") error is always a factor, and actual system error can only determined through a combination of ground and flight test along with appropriate data reduction. Although it sounds complicated, the basic test techniques are straight forward, and a good spreadsheet will take care of the math and make the analysis/hardware tweaking fairly easy.

By and large, I would estimate most homebuilders don't perform static source testing and it's not something that all pilots are aware of, so in many cases, the first time folks in the RV community run into the topic is on this board. There are also several other threads on this topic that will turn up in a search--it's a fairly common question that pops up at regular intervals.

Hope this sheds some helpful light on the topic.

Happy New Year,

Vac

Hi Folks,

I picked up a SafeAir kit from Avery about 1.5 years ago .. and was curious what configuration I received based on this thread.

Here's a photo of the static port .. it's 0.25" in diameter and is shaped similar to a LP 4-3 pop rivets -- which are slightly smaller in diameter, at about 0.23".



Looks like a close approximation of a pop rivet to me.

To clarify, the early SafeAir static ports were designed to sit flush with the skin, which caused problems. By mounting them as I did, eliminated the issue.

Later SafeAir ports stood proud of the skins, also eliminating the problem.

WJB - those are the exact vents I used as mentioned in post #11. I mounted them per the instructions on the inside of the airframe in the location set by the plans. The vent protruded through the skin and set proud of the surface. I had to use some crescent shaped pieces mounted in front of the vents to get my airspeed correct. FYI your results may vary - only detailed flight test will tell.

Crescent
 

Ted,
My airspeed may be high. Do you have a picture of the crescent you put on your plane in front of the static port? When you tried different shapes, how much impact did you see?

"Crescent" dimensions
 

Jay,

I used paper hole re-inforcements cut in half--you know, the kind you buy at the Office Depot that we used to use in the last century when you accidentally pulled a sheet out of a three-ring binder and tore the holes...back in the days when we were using white out on the computer screen ;). I simply stuck 'em to the fuselage ahead of my originally flush ports.

If you suspect fast, put the "crescent" behind the static port. My data showed a nominal 1/2 MPH bias per layer. You could run a quick evaluation by making a quick known power run at say 4K, landing, sticking on four layers or so, and the repeating the speed run under similar conditions and noting any delta...then you can decide if its worth testing further to quantify. If you have good corrected speed data for your current static configuration, then you can skip the first step.

If you decide you want to peel the onion back farther, drop me an e-mail and I'll share a spread sheet that will do the math with your GPS speed run and ground test data. To use it, you'll need to know the instrument error for your altimeter (that may be available from a pitot/static check or on the 8130 that came from the instrument shop with the altimeter if it's a conventional type) and your airspeed indicator instrument error (that can be determined by building a simple manometer--google "checking your airspeed error" or something similar to pull up some good advice on how to go about this). Bottom line is that you have to have instrument error data before you flight test. If you've got an EFIS, it's likely the airspeed error is negligible. If you do have an EFIS, be careful with ground testing--improperly applying pitot pressure can ruin the calibration on the transducers since most systems utilize pitot/static input as part of the attitude algorithm. Most manufacturer's publish guidance on how to conduct a pitot/static check that may provide some additional insight.

To flight test, standard 3 leg GPS airspeed runs at known power settings will suffice. The objective is to bias flow around the port tor reduce CAS and altitude errors as much as practical.

After quite a bit of testing, I determined simply offsetting the static source away from the fuse worked best (that's why the pop rivet design works well in RV's). I ended up retrofitting Cleveland ports which mimic the rivet dimensions as do the new safe air ports (based on a photo earlier in this thread). I also suspect a conventional Cessna-type port that stands proud of the fuselage would give good results as well.

Likely more info that you need, if so disregard. If you have any questions, don't hesitate to drop a line.

Good luck,

Vac

Correct me if I'm wrong but if your IAS is higher than it should be then the crescent goes behind the port. If your IAS is lower than it should then the crescent goes in front of the static port.

:cool:

Jay - I used paper hole reinforcements cut in half as Vac did. I got similar measured results. The only way you can get it accurate is by flight testing the plane especially with autopilot altitude hold and at the same density altitude. An EFIS and accurate engine power information is super helpful. Make absolutly sure your static system is leak free.

Fly the plane, collect the data, do the spread sheet calculation, add more to the stack height of the crescents, fly again etc., etc., etc. till its spot on. If you get it within a knot or two that's probably as close as your gonna get without precise measuring equipment and data logging. Every plane will be different. I used to think I had a fast RV9 until I calibrated the airspeed.

Out of curiosity, how close to the calculated speed have people been able to get? I got mine to within 2kt but wonder if this is close enough for practical purposes especially since it also affects altitude indications.

:cool:

Whoops
 

Galin,

You are correct, Sir. Corrected my post above!

Cheers,

Vac

LOL! My buddy calls these "paper butts". :)

My solution was to buy two extra fuel tank drain flanges from Vans (can't recall the P/N right now). I pro-sealed and riveted those to the inside of the skin and installed the pop-rivet as usual with a little pro-seal under the head. Now I have a nice 1/8" NPT fitting on the inside and the default pop-rivet on the outside. Seems like the best of both worlds to me. if I were to do it again, I would probably skip the rivets and just bond the flange in place.

Colin,

That looks great. I think I've about decided to do something similier and grind the safeair ports flat, drill them for the pop rivet and just proseal them to the skim and insert the rivet from the outside for the profile.

Lynn

Colin, I did similar but the flange idea is great.