First, the smaller more fragile tube would I think be more susceptible to bending and kinking or being crushed, which of course just wouldn't do. The 1/4" tube supplied is pretty stiff, which seems like a good property for this application.
My only question is where will you find the fittings for connecting the tubing to the instruments?
I have used flexible silicone tubing 1/8" I. D. pitot static lines in four RVs including my own without any problems at all. I use barb fitting connectors with pipe threads for the instruments and barbed T's for the interconnects.
I have used flexible silicone tubing 1/8" I. D. pitot static lines in four RVs including my own without any problems at all. I use plastic barbed connectors with pipe threads for the instruments and barbed T's for the interconnects. I use red tubing for the pitot lines and black for the static. I've never had any of these lines leak or come apart, and since they are so flexible they tend not to kink. I can do a complete pitot static system behind the instrument panel in about a half hour. I bought the tubing and connectors online at McMaster-Carr. I have often wondered why builders are still using 1/4" stiff poly pro lines and expensive connectors, when flexible silicone tubing and plastic connectors works so well, is inexpensive, and is so easy to modify.
I don't see how water could work itself up and into the line.
(b) The design and installation of a static
pressure system must be such that:
(1) positive drainage of moisture is
provided;
(2) chafing of the tubing, and excessive
distortion or restriction at bends in the tubing,
is avoided; and
(3) the materials used are durable,
suitable for the purpose intended, and protected
against corrosion.
Mike,
If pressure is all that is measured in a 1/4" line, then increasing or decreasing the dia of the line definitely changes the amount of pressure in the line. Wouldn't this pressure change reflect a gauge misreading? I don't know how this would effect a pitot tube but I process different diameters of neon tubing and different diameters require different pressures of gas to operate at the same level. Just asking
This makes no sense. If this to be true, then several small diameter tubes in parallel would give slower response time than one single? Don't think so. The pressure "velocity" in a pipe is directly proportional to the speed of sound in the pipe. In fact, the pressure "velocity" IS the speed of sound in a pipe. Changes in diameter is negligible, what counts is the properties of air, and pipe material and the diameter/tube wall thickness ratio e/D.Concerns with water in the lines might well be valid, but response time of the instrument will actually be slower with larger diameter tubing. (But I doubt that there's enough difference to worry about.) When you're measuring pressure, the entire 'vessel' must change in pressure for the measuring device to see the entire change. As an extreme example, using the same air compressor (altitude change for static; speed change for pitot), how long would it take to fill a 2 gallon tank vs a 20 gallon tank?
Guys flying computer-controlled engines deal with this all the time. Manifold pressure sensors do 'sampling', and since manifold pressure is very dynamic, it can drive the computer nuts. The cure is to add a significant air volume to the MP line to allow slowing/smoothing of the pressure in the line.
Charlie
Hey! Here's an even better question!
I think the glass manufacturers should come out with pitot tubes and static ports with pressure sensors built right into them! That we can just run a wire from the port to our EFISs and do away with pitot static tubing entirely! Alternate static source? No problem! Just flip a switch and use the backup!
Course I'll be wanting my royalties guys!
That doesn't make any sense Miles, especially in the case of steam gauges. The greater the volume in the instruments, the more air you're going to have to move to change the pressure.
Hey! Here's an even better question!
I think the glass manufacturers should come out with pitot tubes and static ports with pressure sensors built right into them! That we can just run a wire from the port to our EFISs and do away with pitot static tubing entirely! Alternate static source? No problem! Just flip a switch and use the backup!
Course I'll be wanting my royalties guys!
I almost hate to tell this story, but I had a substitute instructor once who argued with me about the Pitot-Static system. He asked me how it worked and when I gave him my understanding, he said I was wrong. Because the Piper he had been flying had "Vent" for the Static port, he said the air went into the Pitot probe on the wing, flowed through the air speed indicator and then vented overboard through the static "Vent."
Oh boy, and this guy had his CFII! How in the world did he get that far without understanding the Pitot-Static system? I only had him for the one lesson, and was glad to get my regular instructor back to complete my Private Pilot rating. That was over 30 years ago. I never did hear if he continued instructing. I think he was waiting to get a job with the airlines, but he probably got a job with the FAA!
How guys like this get their rating is beyond me, though - and a little scary that it can happen.
I have used flexible silicone tubing 1/8" I. D. pitot static lines in four RVs including my own without any problems at all. I use plastic barbed connectors with pipe threads for the instruments, barbed T's for the interconnects, and elbows for really tight places. I use red tubing for the pitot lines and black for the static. I've never had any of these lines leak or come apart, and since they are so flexible they tend not to kink. These components are so easy to work with that I typically can do a complete pitot static system behind the instrument panel in under an hour. I bought the tubing and connectors online at McMaster-Carr. I have often wondered why builders are still using 1/4" stiff poly pro lines and expensive connectors, when flexible silicone tubing and plastic connectors works so well, are inexpensive, and so easy to modify.
Hey! Here's an even better question!
I think the glass manufacturers should come out with pitot tubes and static ports with pressure sensors built right into them! That we can just run a wire from the port to our EFISs and do away with pitot static tubing entirely! Alternate static source? No problem! Just flip a switch and use the backup!
Course I'll be wanting my royalties guys!
...This is exactly what I use, and have since 1969! I actually fabricate a manifold for pitot & static lines providing a separate devoted line for each instrument. It is incredible how much space is gained behind the panel and how easily instruments can be manipulated with this small, very flexible line. I would never use anything else. Thanks, Allan..
Posted by Bob Turner
"If you have a small leak in one of your instruments, you might still pass the pitot static leak test with large tubing but fail the test with small tubing, due to the smaller reservoir of air. The volume goes like the diameter squared, so if your leak rate is 50' per minute with 1/4" id tubing it will be 200' per minute with 1/8" tubing. The first one passes, the second one doesn't. Go to 1/16" tubing and now you're 16 times more sensitive to the leak test, compared to 1/4".
Paul.
Just installed these neat push lock connectors and 1/8 tube from MSC supply.
Shown for comparison is the ubiqitous 1/4 tube.
The tube is a dime per foot and the fittings only a couple of bucks each.
Since a few of you have asked, the link to the fitting is here:
They are available in a wide variety of sizes and the tubing is too. I've never dealt with MSC before but they are fantastic. I'll be using them a bunch in the future.