My ASI acting up - what should I look for ?

Gillie

Gillie

Well-known member
Joined
Sep 15, 2019
Messages
198
Location
Roundup , MT
On my usual morn hop around the basin here , I glanced at my asi and it said that I wasnt flying . GPS said 103 mph .
put her in a dive & it came alive but no matter which direction I flew it was showing 20-25 mph slower than the gps ground speed .
pitot fittings on the back of the asi and altimiter are tight ( altimiter reading is good ). Line connections from pitot to tubing in wing are secure and tight as are the connections from the wing tubing to the two alum tubes that connect to the asi/alt .
would you Brothers have any fix ideas/advise ?
 
You sure about the tubing? I would replace all the pitot flexible tubes - model airplane fuel line works, but is not PMA.
 
Thanks for the help Fellas . Had a small bit of water in my pressure line ( flew thru rain a few days ago ) blew it out from where the plastic hoses attach to the alum tubing in the wing root , took her up this morn and everything works as it should .
 
Gillie, good find. For those reading this archive in future, water in the pneumatic lines can also happen if you're not careful washing the aircraft; ran into that situation last week when an enthusiastic newbie got too enthusiastic with the hose. I've also run into mud daubers clogging pitot, and wax in the static port. Some static systems have a drain port that functions as an alternate (cockpit) static source, and some even have a sump for this eventuality.

I like to tape pitot and static over with color-contrast Scotch 35 electric tape when washing and remove immediately when done. Or use dehydrated water ;-)

Thanks. Scoutdog
 
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