airspeed indicator problem after TT2 transponder install

On Mar 3, 1:42*pm, Tim Taylor wrote:
On Mar 3, 10:26*am, Frank Paynter wrote:



I installed a TT21 transponder over the winter, and as per the
installation instructions, tapped into my ship's static line for
altitude reporting. *Yesterday I checked the transponder with Orlando
ATC and they reported a good signal and proper altitude reporting. *So
far, so good.

Then I noticed my airspeed indicator seemed to be reading
significantly higher than normal, and I confirmed this with a stall
series. *My Ventus 2bx, which normally stalls in the 40-45kt range
depending on bank angle, now is apparently stalling in the 50-55kt
range. *The ship actually feels pretty much the same as before,
although I haven't flown for 3 months so that's a bit hard to tell for
sure.

My dry flying weight is probably about 5-10lbs higher this year than
last, as I added the TT21 itself, plus a 5-lb battery to support it.
However, I'm pretty sure that by itself doesn't explain the
significantly higher apparent stall speed.

As a troubleshooting step, I removed and plugged the static line from
the airspeed indicator, so now the ASI takes it's static input from
cabin air, and everything else should be unchanged. *I haven't flown
it yet to try it out, but I will today. *I also have a spare airspeed
indicator that I can swap in if necessary.

Anything else I should be considering?

TIA,

Frank

As with all design work:

1. *Only make one change at a time.
2. If there is a problem, undo the change.
3. If the system returns to normal start testing other things.
If you start chasing options without checking if the original system
is still the same you may spend lots of time chasing the incorrect
problem.

I would put the system back to the pre trig state and leave the trig
in cabin static for the first test.

Are you sure you hooked it up to Static and not the TE probe?

Mike