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Water in the Static Line


3914N

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Yesterday during preflight I found the airspeed indicator showing 50 knots while sitting on the ground. After some investigative work, I found quite a bit of water in the static line (lots of rainy weather here in SoCal). I depressed the static drain “button” and drained a lot of water out, which also reset the airspeed indicator back to zero. 

Howver, I’m still seeing a lot of water “bubbles” in the static line between the drain port and the actual static ports. I had to disconnect the static line and use my mouth to suck as much of the water out as I could, but there was still quite a bit of moisture there. 

So here are my concerns:

1. There was a LOT of water in the static line. I guess I need to get some static port covers from aircraft spruce? Anyone have other good solutions to this problem?

2. The static drain port didn’t get rid of all the moisture in the line.  So is opening up the tail and visually inspecting the static line a new preflight check item after rain?

3. What happens when I’m flying through moisture? Could I get water in the line causing a blockage? I don’t have an alternate static switch, so that seems like a major problem. 

I fly IFR a lot so I need to fix this issue as an inoperable airspeed indicator is an emergency in IMC. 

Anyone with similar experiences or suggestions?

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Two very interesting posts that revive my too dormant interest in the pitot static system.  Installing alternate static is a  really simple cheap insurance policy when dealing with this stuff in the air.  I had one put in a while back but would probably forget to use it without this reminder. You can make due without airspeed by flying known pitch power configurations.  Losing altitude seems a bit tougher.  GPS altitude of course helps if you recognize the issue.

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Just now, 3914N said:

@DXB what did you pay for your alternate static installation, if you don’t mind me asking?

I think it was the cost of the  tubing and valve and an hour or so of labor - that's it.  It is super simple - just splicing a T connector into the static line behind the panel and clamping the valve to bottom edge of the panel.  Something you could do easily yourself if it were legal.  

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Hello 3914N. I dealt with static line issues in my 1968 M20G for years. I rebuilt the aft static drain using a kit from Lasar. I replaced the alternate static and tubing under the pilot-side dash (because I didn't know how to use the one that was already installed - it was a somewhat rare pull-type model). In the end, it was a really talented mechanic in Melbourne, FL, who brought to my attention that all connections in the static system have to use small plastic sleeve-like connectors. None of those were present in the system aft of the cockpit. So he installed those, closed the system, and the system passed the leak-check with flying colors.

A couple of thoughts - clearing both static-line drains was always part of my preflight. Make sure you are doing that. Find a mechanic who understands static systems and ask him or her to check to make sure that yours is actually installed correctly. Consider rebuilding your aft drain. And check under your pilot-side dash to verify that you don't indeed, have an alternate static port already installed. If not, I highly recommend to install one. I once had my static system freeze in-flight, and it was not an experience I would like to repeat. Also, remember that in extremis, you can break the VSI glass to allow cabin air to be your alternate static.

One last thought - when my static system froze, it did so at 4000'. That flight, I was the most talented pilot in the world. Nothing I did would cause me to be off-altitude! When I descended, though, something unexpected happened. My airspeed indicator started showing greatly increased airspeed. Once I got down to 1600', though, the system started to thaw, and everything eventually returned to normal. So expect the unexpected in terms of indications.

Clear Skies!

Sean

 

 

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Thanks Sean.  I'm due for a pitot static inspection in a few months so I'll have my avionics guy take a closer check at the aft system.  Based on DXB's feedback I'll probably have him install an alternate static as well... sounds like a cheap way to mitigate a lot of risk.

In the meantime, I think opening up the tail and visually inspecting the static lines for water is now part of my IFR preflight.

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1 hour ago, Yetti said:

and make sure to remove it before flight.

Well that’s the part that I’m concerned about!

i might rig up a suction cup with a red “Remove Before Flight” streamer attached. 

Anyone know if putting a suction cup over the static port might damage the instruments? Somewhat concerned that I would be trapping pressure in the static system for days/weeks. I guess what I’m looking for is a water-tight, but not air-tight, cover?

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2 hours ago, 3914N said:

Thanks Sean.  I'm due for a pitot static inspection in a few months so I'll have my avionics guy take a closer check at the aft system.  Based on DXB's feedback I'll probably have him install an alternate static as well... sounds like a cheap way to mitigate a lot of risk.

In the meantime, I think opening up the tail and visually inspecting the static lines for water is now part of my IFR preflight.

I should point out that if you see water and open up the line to drain it, your plane's IFR 24 month static system check is now void until you get it rechecked by an A&P.

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1 hour ago, ArtVandelay said:


91.411 (a)(2). Except for the use of system drain and alternate static pressure valves...
Sounds like it’s not void to me.


Tom

That's if you USE an installed static drain.  The IFR static system inspection becomes void if you open it up anywhere else. 

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I’ve certainly had this happen a few times after being outside in hard rain.  I’ve since installed a simple alternate port in the form of a line with a cap that hangs down near my right knee.  Not quite as good as a valve, but I’ve use different it on a couple of occasions and it is adequate.  

The dynamics of the water getting in is kind of odd.  The static lines inside of the ports go up to the roof line.  I think it takes lots of water and a change in atmospheric pressure...pushing enough water in.  Would not recommend plugging the ports, more likely to forget and no fix in flight.  

I have, after washing the plane or occasionally after rain, lightly banged on the fuselage adjacent to the port.  This seems to work, but I mostly forget to do this.  One might put it on a preflight checklist, if they are religious about using one.  Freezing temperatures obviously compound the issue.

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11 minutes ago, Hank said:

I'm surprised by how many planes, even fancier models than my C, appear to have so much less standard safety equipment. Do so many of you not have these simple, safe items??? 

20190218_211617.thumb.jpg.f08b0598912639f24171314e7462eab5.jpg20190218_212040.thumb.jpg.98ad9d9e78906c321fe00e47058ce851.jpg

I got the pitot tube, but ‘64 didn’t have the drains or standby.

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On 2/18/2019 at 9:11 AM, 3914N said:

Well that’s the part that I’m concerned about!

i might rig up a suction cup with a red “Remove Before Flight” streamer attached. 

Anyone know if putting a suction cup over the static port might damage the instruments? Somewhat concerned that I would be trapping pressure in the static system for days/weeks. I guess what I’m looking for is a water-tight, but not air-tight, cover?

Just attach the streamer to the canopy cover?

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Years ago the shop that does my IFR Static test rerouted the the static tubing in the tail section.   From the static ports they ran the line upward to the top of the tail cone and then back down and forward.  Cured my water in the static line problem and cost was minimal as it was done while doing the 24 month certification.   

Edited by N9434V
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On 2/22/2019 at 2:10 PM, N9434V said:

Years ago the shop that does my IFR Static test rerouted the the static tubing in the tail section.   From the static ports they ran the line upward to the top of the tail cone and then back down and forward.  Cured my water in the static line problem and cost was minimal as it was done while doing the 24 month certification.   

That is exactly how mine is routed..I thought it came that way from the factory:blink:

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