Water in the Pitot Tube

km74 · Post by **km74** » Sat Aug 09, 2003 4:43 am

After the last couple of heavy rains, my pitot tube got a little water in it and the airspeed indicator read incorrectly. After disconnecting the tube at the indicator and blowing it out it seemed to read fine. Could I have done any damage to the airspeed indicator with water in the tube migrating to the indicator itself? The first time it happened I flew with it like that for a few hours and blew it out on landing. Not the best thing to do but I was stuck in Watson lake Yukon for a few days and just wanted to get to Whitehorse.I know I should have just aborted take off but I had a bad case of getthereitis. I think I am going to put another cover over the swinging one that is there already. Anyone else have this problem?

Ken

N1478D · Post by **N1478D** » Sat Aug 09, 2003 5:18 am

Yes, one time last year a couple hundred miles from home a big storm came thru. The airplane was stuck outside but thankfully tied down very well. The winds were strong and blowing rain. The next morning when I went to leave, the airspeed indicator was stuck on 70 MPH and there was water in the line, blown in by the strong winds. I walked around scratching my head and an airport bum came out and walked around scratching his head too. Had the getthereitis also, and wanting to get the heck out of Dodge too. Took off and flew home, the airspeed indicator if I remember right cleared up on the trip home, or shortly there after. Have not had any trouble that I am aware of, but would have strongly preferred not to have had the water get in there. Hopefully you will be as lucky.

Roesbery · Post by **Roesbery** » Sat Aug 09, 2003 4:47 pm

Bend that sucker slightly downhill when parked and you will be rid of the problem.

Post by **GAHorn** » Sat Aug 09, 2003 10:23 pm

In the Service Manual, 1962 and Prior, is a pattern that the curve of the original pitot tube should match. A pitot tube that has no air-leaks does not allow actual flow of air to take place, but only allows air "pressure" to register. Therefore, no water should be capable of travelling up-hill into the wing leading edge far enough to ever make it to the indicator. This is not to say that condensation cannot put water into the indicator, however.
On later 100 series Cessna installed a pitot "sump" jar in the left sidewall below the level of the indicator. This is probably a good mod for those experiencing such problems. The parts are sold by Spruce (illustrated in their catalog) and by Cessna.