My airspeed indicator is reading 15-20 mph higher than my gps under no wind conditions. How can I determine what is wrong with my airspeed indicator?
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My airspeed indicator is reading 15-20 mph higher than my gps under no wind conditions. How can I determine what is wrong with my airspeed indicator?
I assume you're already taking into account the conversions from indicated to calibrated to true airspeed in your calculation?
How's your static system? A leak in the static system to the cabin will cause a erroneously high reading.
A instrument/avionics shop may be able to lend a hand.
I will have to check for leaks. My plane is an open cockpit so I left the static port open on the back of the instrument. Do you think that is my problem?
Yep. There's your problem.Quote:
Originally Posted by LAWise
Think about out the slipstream line over the cockpit...it curves up at the windscreen then continues over your head until then coming down over the aft fuselage. Looks just like the slipstream line over the top of the wing. What is the result over the wing? Where does that Lift on the top of the wing come from? Low pressure. Same thing in an open cockpit.
Do you have a VSI? What does it show when you maintain a steady altitude on the Altimeter?
The posts above are correct. You should be looking at the static system (pitot pressure cannot read high in an unpressurized airplane). Another check is to check the altimeter, statically on the runway and then compare it to the value when doing a low ("higher speed") pass. This is how tower fly-by airspeed calibrations are done.
Yes. The windscreen will cause a negative pressure behind it. If your static source is open into the cockpit, the negative pressure will cause your ASI to read high.Quote:
Originally Posted by LAWise
Once upon a time I met a fellow with a little home built biplane that wanted to play tag with me in my Starduster 1. He was quoting performance numbers about the same as my Starduster. First time I got on his tail, I darned near ran over him. He had his static vented into the cockpit, so was drawing a negative pressure there. Made his performance numbers look incredible as compared to his actual performance. :cool:
-Cub Builder