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Pitot/Static Issue

jdfrey1

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Apr 13, 2010
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I brought my '79 Archer II to the shop the other day for it's IFR Cert and it has now been in the shop for 2 days. I'm concerned and have some questions for everyone. I brought it to a shop that is at my home field that services mostly corporate jets and was quoted roughly 4 hours to complete the job at $80/hour. Seemed reasonable especially since I didn't need to reposition the plane for the test. I decided to take the day off and work with them. Two days later the plane is all tore apart with the interior side panels off and I had to drive on my planned weekend trip.

The tech started by removing the pitot tube and hooking his system up to directly to the lines. He then tried to run leak checks on both the pitot and static side and both had significant leaks in them. Basically the pressure (or vacuum) dropped right off. After a lot of troubleshooting on the static system he found that the hose going to the static side of the airspeed indicator was the probably culprit. It was a clear nylon tube that didn't seemed to be sealed to well. The static system finally was leak free and all the encoder and altimeter checks were performed by the end of the first day without any issues.

The pitot side on the other hand is a different issue. On day 2 the tech continued to troubleshoot and isolate the leak in the pitot system. After another few hours he found a switch that is basically in parallel with the airspeed indicator and from research it looks like it is part of the electric trim system. It is a small grey switch and the part number is an MPL-501G. He didn't really have any idea what it was for and then had to do research on it and of course they didn't have one in stock. He even told me that most shops probably don't have leak check the pitot line and that this may be why it wasn't found in the past. Also, when I looked up the MPL switch on the internet it says that it's diaphram is good enough for dynamic applications but would require an additional gasket to provide a near bubble tight seal. Here is a link to the website: http://www.edmo.com/index.php?module...&prod_id=43730

So, after my long winded details of what is going on my questions are....is this common to have leaks in this switch? Is this shop going overboard by trying to get the pitot leak free? Supposedly there is not a specification for the leak rate on the Piper Archer II pitot system. Any suggestions on how to deal with this would be greatly appreciated.
 

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