Share:
Notifications
Clear all

Airspeed indicator water in pitot

13 Posts
5 Users
3 Likes
65 Views
Bret
 Bret
Trusted Member
Joined: 8 years ago
Posts: 55
Topic starter  

While returning home from a recent aviation event, I flew through some rain.  Not long after this my indicated airspeed went up to 140 MPH while landing at an airport for fuel.  After fueling I took off and the airspeed gauge indicated accurately.  However I had to fly through more rain.  Not long after flying through the additional rain, the indicated airspeed dropped to 40 MPH.  I continued the 2.5 hour flight home.

Today me and my mechanic took the pilot tube loose from the back of the airspeed gauge and blew out several ounces of water.  

The Stinson manual advises to remove the tube under the left side of the instrument panel connected to the pitot gauge to drain out water.  I am surprised that there is not a container in this are of the low point of the pitot tube to catch water before it can become a problem.  Also it would be extremely handy if there was a valve at the bottom of the container to drain water out.  If this had been available I probably could have drained water out in flight during the cross country and would have alleviated the problem of not having accurate airspeed.  How do other airplanes deal with water in the pitot tube system?

 

Bret C / N190C

 


   
Quote
resto108
Reputable Member
Joined: 17 years ago
Posts: 274
 

I added a tee fitting in each line with a clear tubing and an AN plug and B nut under the instrument panel. It just sticks straight down so I can look up in there for water or drain it. 


   
Bret reacted
ReplyQuote
Bret
 Bret
Trusted Member
Joined: 8 years ago
Posts: 55
Topic starter  

@resto108 That is a good solution.  Do you know of something that I can mount which would allow it to be drained while in flight?  Maybe something with a petcock valve?  On your clear tube solution, do you find that it collects water while flying in rain?  Thank you for your input.


   
ReplyQuote
resto108
Reputable Member
Joined: 17 years ago
Posts: 274
 

I believe the correct plan of action would be to land if experiencing suspected pitot/static blockage and troubleshoot; at which point water could be observed through the clear tubing and drained. Don't have any info about flying in rain.


   
Bret reacted
ReplyQuote
Bret
 Bret
Trusted Member
Joined: 8 years ago
Posts: 55
Topic starter  

@resto108 Thank you.


   
ReplyQuote
Michael
Reputable Member
Joined: 3 years ago
Posts: 276
 

Cessna uses a small clear plastic bottle with 1/8" pipe thread at the ends. They often fail a static test because of cracks at the ends,  so if you buy a used one, use some glue on the ends. Piper I think maybe, uses a quick drain, like in a fuel tank, under the dash, at a low spot.


   
Bret reacted
ReplyQuote
Bret
 Bret
Trusted Member
Joined: 8 years ago
Posts: 55
Topic starter  

Thank you Michael.  It sounds like Piper has the best idea.

 

Thanks

 

Bret


   
ReplyQuote
James
(@paxflyergmail-com)
Eminent Member
Joined: 2 years ago
Posts: 27
 

There should be a small hole on the bottom of your pitot tube to allow for water to drain in flight.  Check to ensure clear.


   
ReplyQuote
resto108
Reputable Member
Joined: 17 years ago
Posts: 274
 

So there should be an air leak in your pitot system?


   
ReplyQuote
James
(@paxflyergmail-com)
Eminent Member
Joined: 2 years ago
Posts: 27
 

I have a small hole at the bottom of the pitot tube, near front, circled in pic. I read this patten was filed in 1938.

 


   
ReplyQuote
James
(@paxflyergmail-com)
Eminent Member
Joined: 2 years ago
Posts: 27
 

Not sure if this helps but look for a clear water drain hole underside of pitot tube. Otherwise a drain valve under panel is likely best solution for the older designs.


   
ReplyQuote
Carsten H.
(@carl)
Estimable Member
Joined: 4 years ago
Posts: 116
 

@paxflyergmail-com 

This is a heated type pitot/static probe. I believe the holes are static ports. Ideally there should not be any leakage in the pilot system. Some of the aircraft I'm familiar with have a built-in reservoir to collect moisture. https://www.google.com/search?q=heated+pitot+static+tube&client=tablet-android-samsung-nf-rev1&prmd=sivn&sxsrf=ALiCzsaIA-rFtLm-ra9ku8hup_55qhAonA:1664297182953&source=lnms&tbm=isch&sa=X&ved=2ahUKEwi7yI-TtrX6AhWqEEQIHa79B4cQ_AUoAnoECAIQAg&biw=602&bih=964&dpr=1.33#imgrc=MRnEWUEENJOB1M&imgdii=fnKWnMq3lXq2IM

Carsten 

This post was modified 1 week ago by Carsten H.

   
ReplyQuote
James
(@paxflyergmail-com)
Eminent Member
Joined: 2 years ago
Posts: 27
 

The three holes behind are static.


   
ReplyQuote
Share: