The International Cessna^® 170 Association

This one is killing me and getting real expensive.

I just went out to 81D and I have water in my airspeed indicator and the altimeter is fogged up.
I replaced the whole static system earlier this year and every gauge has been either overhauled or bought new.

It passed a static check too.

The static port doesn't have a drain but it is the lowest point in the system.

This is the SECOND time I've had this problem. The last time, it was the altimeter and I had to have it overhauled.
This time, the airspeed is trashed.

Has anyone ever heard of anything like this? I can't find anyone that has and I really don't want to pay a bunch of money to have it happen to me again.

Thanks much!

I had the same problem with my '52 170B. I installed the plastic sump bottle from Cessna (it was cheap, but that was 9 years ago). Never had the issue again.

Russ Farris

I just bought the sump and some fittings and will give it a try.

@Russ, you would see this much water in a gauge before the sump?
Thanks again.

Is that standing-water inside the glass? Have you been flying in rain? or has the airplane been stored outdoors in the rain? Check the pitot-pressure line for integrity. If a pitot/pressure fitting is loose/leaking near the gauge then an actual movement of air-pressure in the pitot line can carry water to the airspeed. (The static side would not do that.) With that much water I strongly suspect such is the case.

The pitot OR the static side can be a source for the water if the airplane has been pressure-washed.

(The sump bottle was standard equipment on later aircraft and is a good idea, although most of our airplanes haven't had this as a problem. It collects condensate from aircraft which are subjected to temperature extremes in humid climes or from aircraft which operate at extreme altitude changes in humid climes. Most 170's do not suffer from this.)

Standing water in the gauge, yep.

I do store the plane outside and it did rain two days ago but I haven''t flown in the rain.
I haven't washed the plane in months

The static system was leak checked, not sure about the pitot.

How could water go from the pitot to static tho? Worst case, I'd think it would fill the bellows but how could it pass from the bellows to the case in order to get to the static system? From what I understand, the ASI bellows is sealed to the pitot system just like the altimeter.

The altimeter is fogged and I the droplets in the static lines. The last time it happend (last month) the ASI was fine but the Altimeter had standing water. That really points to the static system as impossible as it seems.

But I'm not ruling anything out at this point.

Is it possible that this is condensation and not driving water?

As I recall that rain was not just a lazy drizzle. Do you have your pitot covered?

To be honest I might be looking for a fuselage leak at or in front of the windshield where water is leaking in and running down and over the instrument. And the water is seeping into the front of the gauge. Of course you would likely have a wet carpet if this was happening but I wouldn't rule it out.

The pitot as the little flapper cover (how's that for a technical term?)
I thought about water leaking under the panel but, everything appears dry to include the carpet.

If water could seep into the gauge like that, wouldn't that mean it would also fail a leak check?

bagarre wrote:The pitot as the little flapper cover (how's that for a technical term?)
I thought about water leaking under the panel but, everything appears dry to include the carpet.

I've seen those little flappers blow open in the rain. Makes you wonder what the chances the flapper would blow open and rain drops would hit and enter the pitot but it somehow does. Then I've also had the same flapper stick closed when I needed it open.

I like a Tennis ball or any other positive cover for the pitot than that flapper.

bagarre wrote: If water could seep into the gauge like that, wouldn't that mean it would also fail a leak check?

Yes you would think but as you already point out if it entered through the back how did it get past the bellows inside? I think water seeping in the front just as likely as it getting past the bellows and wouldn't rule it out.

bagarre,
If you have been flying again with the doors removed maybe the cold air blowing on the instrument face is causing the moisture on the inside to condense on the glass.

Did you go and use the "Drive Through" wash again????

If only there was some cold air, I would be flying with the doors off

I'm going to be out at the field tomorrow and will blow out the pitot system to see if it has any water in the line.
I'll be sure to disconnect the line and blow from the inside out.
If it's from there, I'd expect a fair amount in h20 in the low spots.

As far as the water in the gauges, what's the opinion on baking them for a few hours.
I'm thinking 200 degrees for a few hours should evaporate the water.

So far, I've heard this:
1. Add a sump.
2. Get a decent pitot cover
3. Don't fly in the cold with your doors open.

Appreciate the input.

bagarre wrote:I just bought the sump and some fittings and will give it a try.

@Russ, you would see this much water in a gauge before the sump?
Thanks again.

No, the worst I ever had was heavy condensation on the airspeed glass. My main problem was inaccurate airspeed and altimeter
readings.

It's hard to believe that much water could migrate though the pitot/static system on an airplane just sitting on the ramp.

You can dry out electronics by putting them in a bag of rice for 48 hours or so. Maybe that would work with instruments too.

Baking them for a few hours at 200 seemed to do the trick.

We'll see if they are still accurate but they still operate smoothly when pressure is applied.

Wont be able to put them back in until next weekend tho.

I thought I'd update this thread as I found the cause.
My static system had a loop in the line.

In order to hook up the encoder, the line did a vertical loop.
So, any condensation in the line could collect in the low point and cause a water trap.

I re-routed all the lines to avoid this condition and haven't had a problem since.