drapo Posted September 8, 2016 Report Posted September 8, 2016 Let me pick your brains on this one! Coming out of my annual on my 65 M20E, I had a problem with my ASI and took the Mooney twice to have it looked at. First time, nothing done, but I noticed a difference. Second time, 4 hours maintenance to suck everything out of the system and change the atlternate static valve, I saw a noticeable difference for one flight, then everything was back to "anormal". After take off, the speed would move down slowly then barely moved at all. Once on the ground, no change of indication, so attitude or altitude don't seem to be a factor. For troubleshooting sake, I went on alternate static and saw VSI and altimeter jump then settle at their correct values and ASI being at a normal value. When back on primary, ASI was again indicating incorrectly, sometimes on the high side, sometimes on the low side. My troubleshooting seems to point at a faulty primary static source, my mechanic is thinking about clogged or faulty plumbing along the line. Looking at my books, it looks as though the alternate static source joins the plumbing at a "T" joint almost at the start of the plumbing of both sources. Any ideas???
Marauder Posted September 9, 2016 Report Posted September 9, 2016 9 hours ago, drapo said: Let me pick your brains on this one! Coming out of my annual on my 65 M20E, I had a problem with my ASI and took the Mooney twice to have it looked at. First time, nothing done, but I noticed a difference. Second time, 4 hours maintenance to suck everything out of the system and change the atlternate static valve, I saw a noticeable difference for one flight, then everything was back to "anormal". After take off, the speed would move down slowly then barely moved at all. Once on the ground, no change of indication, so attitude or altitude don't seem to be a factor. For troubleshooting sake, I went on alternate static and saw VSI and altimeter jump then settle at their correct values and ASI being at a normal value. When back on primary, ASI was again indicating incorrectly, sometimes on the high side, sometimes on the low side. My troubleshooting seems to point at a faulty primary static source, my mechanic is thinking about clogged or faulty plumbing along the line. Looking at my books, it looks as though the alternate static source joins the plumbing at a "T" joint almost at the start of the plumbing of both sources. Any ideas??? Are you sure you are not dealing with just a flakey ASI? Has it ever been serviced?
Guitarmaster Posted September 9, 2016 Report Posted September 9, 2016 You might check the drains. I don't know if that would cause your symptoms, but maybe. Sent from my XT1254 using Tapatalk
Yetti Posted September 9, 2016 Report Posted September 9, 2016 lots of planes and rain lately... Battery compartment. remove tubing blow Back to the static drains. Do not blow forward. You can play with the drain if you have one at the battery compartment and still not get all the water out. Check the wing drain too. By the root of the left wing.
drapo Posted September 9, 2016 Author Report Posted September 9, 2016 2 hours ago, Marauder said: Are you sure you are not dealing with just a flakey ASI? Has it ever been serviced? Since it works fine with the alternate static, I was looking elsewhere. There is no drain in the system, I asked my AME to install one if he can as I also think it could be water or insect in the tubing. We'll see if that cures the problem! Thanks guys!
Yetti Posted September 9, 2016 Report Posted September 9, 2016 There should be at least one drain at the left wing root. I think the one by the battery access cover in the rear was a later addition.
drapo Posted September 15, 2016 Author Report Posted September 15, 2016 On 9 septembre 2016 at 9:22 AM, Yetti said: There should be at least one drain at the left wing root. I think the one by the battery access cover in the rear was a later addition. No drain at all in the system, it is now on the "to do" list for next annual. Thanks for the suggestions guys! 1
drapo Posted October 5, 2016 Author Report Posted October 5, 2016 Just as an update! Couldn't keep on relying on a moody airspeed indicator and the alternate static as an almost permanent solution. I tasked my AME to find the problem and repair it. $400 later, I now have a new static line from the back of the airplane to the panel all done in vinyl. The old one was of some kind of metal and was corroded from the inside, so the pressure wasn't steady. I now have a fully reliable ASI and am very happy about it! 1
Hank Posted October 5, 2016 Report Posted October 5, 2016 Good job! Thanks for the follow up. I replaced all of my static tubing a few years ago, the old stuff (especially the crimp connections) was hard and brittle.
John Mininger Posted December 17, 2016 Report Posted December 17, 2016 It was a beautiful cold and clear day in Pennsylvania yesterday. I took off in my 1977 M20J with a buddy to practice some approaches and found that the ASI moved back to 0 and the altimeter hadn't moved. I pulled the alternate static and after the initial jump, everything settled down to what seemed to be the correct readings. This plane came out of the south, and I doubt if it's seen 20F temperatures in the last 10 years. Anyway, we landed, pulled the plane into a heated hangar, and removed the static lines connected to the T above the drain located a little behind, and below the battery. It was full of water. Obviously the drain valve was/is not working. The assembly that holds the drain valve is riveted in place. My question is: Can the valve be replaced without removing the whole fixture? Or do the rivets have to be drilled out and the whole assembly replaced? Thanks John
Bob - S50 Posted December 17, 2016 Report Posted December 17, 2016 Might be a stupid question, but did you push on the static drain button to make sure it didn't drain?
John Mininger Posted December 17, 2016 Report Posted December 17, 2016 Pushed and pulled, nothing. The valve does move.
Marauder Posted December 17, 2016 Report Posted December 17, 2016 Pushed and pulled, nothing. The valve does move. John -- first, thanks for the vent adapter! I will give it a try this weekend. Appreciate the effort on it. The pitot valve is a spring loaded gizmo with a rubber gasket sealing it. If you cannot move the button from the skin side of the plane, you would be better served to replace the entire valve. When one of them goes that bad, it probably has rust pitting the seat and you may be able to grind it down and put a bigger gasket in, but it ain't gonna be a permanent fix. The valves are available at Lasar out in California. I replaced mine a year and half ago. Price then was $127. Here is a picture with part number on it. It does require to be riveted in place. Sent from my iPad using Tapatalk
John Mininger Posted December 17, 2016 Report Posted December 17, 2016 You're welcome for the parts. I hope they work out. I still have the one that's completely flat. You're welcome to that one also if you would like. I looked at Jack's F and saw that he doesn't have the same type of vent. That may be because of the Johnson bar. Regarding the static drain, when the T is off and the spring is out, does that plunger just push up and out through the top of the fixture?
N201MKTurbo Posted December 17, 2016 Report Posted December 17, 2016 7 minutes ago, John Mininger said: You're welcome for the parts. I hope they work out. I still have the one that's completely flat. You're welcome to that one also if you would like. I looked at Jack's F and saw that he doesn't have the same type of vent. That may be because of the Johnson bar. Regarding the static drain, when the T is off and the spring is out, does that plunger just push up and out through the top of the fixture? Yes
Marauder Posted December 17, 2016 Report Posted December 17, 2016 You're welcome for the parts. I hope they work out. I still have the one that's completely flat. You're welcome to that one also if you would like. I looked at Jack's F and saw that he doesn't have the same type of vent. That may be because of the Johnson bar. Regarding the static drain, when the T is off and the spring is out, does that plunger just push up and out through the top of the fixture? Post some pictures if you get the plunger out. My guess is the spring is pretty rusted and the rubber gasket is hard as a rock. What killed mine was the seat was so corroded, it couldn't be ground down any more -- and I was religious about replacing the gasket in it. Sent from my iPad using Tapatalk
RobertGary1 Posted December 17, 2016 Report Posted December 17, 2016 On 9/9/2016 at 6:22 AM, Yetti said: There should be at least one drain at the left wing root. I think the one by the battery access cover in the rear was a later addition. The one in the wing root is pitot. It's the same part as the static drain under the battery Fairly easy to service, just unscrew and replace the o-ring -Robert
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