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#1
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"Mark Hansen" wrote in message ... On 5/17/2005 17:28, Mike Ferrer wrote: "A Lieberman" wrote in message ... Unpleasant surprise on my .411 .413 check. Person doing the check would not certify the inspection. He said that the VSI is not connected to the pitot static system. Interesting point. Although the VSI should be connected to the static system, it is not required by 91.411 or FAR Appendix E. In other words, he could have certified the system and you could have had an A&P investigate why the VSI wasn't hooked to the static system afterwards. But if the VSI is not connected to the static system, what has happed to the point where it was connected? Is the static line simply venting to the area behind the panel? Won't this affect all the other static-based instruments? ... unless someone took the time to plug the hole in the static line... The VSI will operate even though it is not connected the the official static system. However, it should be fixed. Mike -- Mark Hansen, PP-ASEL, Instrument Student Sacramento, CA Or if it was never connected to the static port. Miie MU-2 Or |
#2
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Allen,
For an instrument pilot especially, a complete understanding of all of your airplanes systems is imperative. Your knowledge of the airplane systems normal operations, failures, possible causes, and indications may be all that saves you if you have a failure while IMC. A quick google for "pitot static system" will bring up plenty of hits to start your way towards a better understanding of why your VSI may appear to work but may also not be connected to your static system. I would also strongly recommend sitting down with your instructor and your mechanic for a quick review of your aircrafts systems, possible failures, how to recognize them and the proper decision making action to take once a failure occurs. While turning it over to your local repair shop may be the easiest solution, you will get more for your money if you stand over their shoulder, watch, learn, and ask plenty of questions. You also probably already know more than you think, don't sell yourself short! You said that they told you the VSI was unhooked, right? Unhooked from what? The only thing the VSI is hooked to is the static line, which leads to the static port, typically on the exterior of the airplane so it can vent to the outside static air pressure. Remember, the VSI is similar to the altimeter, but instead of having a sealed bellows like the altimeter, the VSI contains a bellows that has a small hole through which the air pressure inside the bellows can slowly be equalized until it reaches the outside static air pressure. Thus, measuring a "rate" of change in air pressure which is indicated on the face of the VSI as a rate of climb or descent. Now, if it is unhooked, what is the VSI measuring? Well, since the instrument is inside the cockpit, it must be reading the interior cockpit air pressure. Now the question becomes, is there that much difference between the outside air pressure and the inside air pressure? It "seems" to be working, so it must be operational, but is it accurate? Normally, if you have an alternate static source that is vented inside of the cockpit, when you open it your VSI will momentarily indicate a climb because the cockpit pressure is less than the outside air pressure but then it should settle towards a normal indication. After this initial adjustment to the cabin air pressure the accuracy of the indications of your VSI should be suspect due to the non-constant air pressures inside the cockpit. Truthfully, I'd be more concerned with your VSI sucking in dust and dirt due to the lack of a filter than the accuracy of the instrument. Talk with your instructor, pester your mechanic, watch, ask, listen, learn, live, and fly safe! Jim |
#3
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On Tue, 17 May 2005 20:05:31 -0700, Jim Burns wrote:
Talk with your instructor, pester your mechanic, watch, ask, listen, learn, live, and fly safe! Jim, Thanks for your quality post! I am taking your advice to heart, especially about watching the process and learning what could have gone wrong (and can go wrong). Like you are implying, IMC is not the place to learn about what is going wrong..... I am trying to find a place that can check this out, and I am planning to stay and observe if they allow me to do so. I was told the inspection takes 2 hours without problems and 3 to 5 hours if problems are encountered. The last .411 and .413 check, I dropped the plane off, they did their thing, and I picked it up. Because this came up, I am more interested in getting the plane "right" rather then just passing the inspection. Your above statement cannot be said any better. I am a strong believer flying safe includes doing it right... As far as the VSI, it's the original that came with the plane. Plane has a little more then 2300 hours on it. I am planning down the road, upgrades, but I do want to preserve what I have now, so I can do the upgrade right the first time. Allen |
#4
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Great Allen! I'd be willing to bet and I hope that you'll come away from
your experience with more questions than answers. Let us know what you find!! Knowledge about your airplane is like altitude below you, runway in front of you, and fuel in your tanks.... the more you have, the better off you are and the safer you are. (Ok Ok, I know... unless you are out of oxygen or on fire, but you know what I mean Jim |
#5
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"A Lieberman" wrote in message ... Unpleasant surprise on my .411 .413 check. Person doing the check would not certify the inspection. He said that the VSI is not connected to the pitot static system. I am the first to say I am clueless about "systems". He said I would have to take it to a certified repair place to get it fixed. The VSI works, so I don't get this at all. It passed 2 years ago, with no problems. Do things "disconnect" on it's own or what's up with my VSI. Everything else appears to work just fine (ASI, altimeter and VSI). My plane does not have an alternate static in the plane. What should I expect when I take it to a repair center? Allen Check the Flight Manual/Maitenance Manual/Parts Manual to determine if the VSI is supposed to be hooked up to the static system. Some are not. Mike MU-2 |
#6
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Here is the mad solution: Take it out! The VSI is not
required for any kind of flight, including instrument flight. Put a cover there. Go get your signoff. Put it back. It will indicate a bit flakily when not connected to the static system. For example, it will take a jump when you open your pilot window in flight. I like Mike's solution: See if it was ever connected. I can't imagine that having it connected is required for the static check. Bill Hale |
#7
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wrote in message oups.com... Here is the mad solution: Take it out! The VSI is not required for any kind of flight, including instrument flight. Put a cover there. Go get your signoff. Put it back. It will indicate a bit flakily when not connected to the static system. For example, it will take a jump when you open your pilot window in flight. I like Mike's solution: See if it was ever connected. I can't imagine that having it connected is required for the static check. Bill Hale A lot of homebuilders don't use a static port at all. They just use the cabin air for static, this works fine for slower airplanes. Mike MU-2 |
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