---------------------------------------------------------- RV10-List Digest Archive --- Total Messages Posted Tue 08/18/15: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 09:04 PM - Bug in the (Gretz) Pitot (Bill Watson) ________________________________ Message 1 _____________________________________ Time: 09:04:43 PM PST US From: Bill Watson Subject: RV10-List: Bug in the (Gretz) Pitot Well, it finally happened to me - an insect built a home in my uncovered pitot tube. At about 600 hours I had my first declared emergency. I lost my airspeed indication in IMC conditions. Fortunately I was hand flying the plane at the time and didn't notice the drop until I engaged the Trutrak AP. When I did that, the airspeed was still 'okay' but dropping. When it reached a certain threshold, the AP responded by flagging "AS" and diving to prevent a stall. I disengaged and repeated the same operation while not quite allowing the "AS" flag to sink in. It seemed like a good idea to ask for vectors to VMC and the nearest airport which I did. When asked if declaring I said 'yes' and landed without incident in the unfortunately named town of Lynchburg. The '10 flies quite easily without reference to airspeed so no problem. Problem determination pointed to some kind of clog in the Gretz unit which in fact seemed clogged. I was hesitant to stick anything in it so I blew it out with shop air and soaked in alcohol overnight hoping to dissolve any organic material. It seemed to still be partially clogged but I decided to test fly it and all seemed well. The next several flight involved flying in rain but each time I enountered even the lightest precip, the airspeed would begin to drop. Heavy rain would effectively disable use of the AP. But after some dry air flying things would return to normal. A call to Andrew at Angus Aviation, current owner of the Gretz heated pitot, indicated that the pitot is simply a copper tube with external heating elements and that poking it with a pipe cleaner or whatever would be no problem. I poked some things through there and determined that yes there was organic material in there. Apparently just enough to restrict airflow a bit but not enough to prevent accurate airspeed indications. However, with application of a bit of moisture it swelled up and blocked the pressure. All good now. Use your pitot cover! Bill "exhausting every possibility before doing the obvious" Watson ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rv10-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/RV10-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/rv10-list Browse Digests http://www.matronics.com/digest/rv10-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.