Pitot/Static/Transponder Problem

Kyle Boatright wrote:
"Kyle Boatright" wrote in message
...
I was using Flight Following yesterday and was reminded of a problem that
my RV has displayed for a long time: The transponder and altimeter do not
agree. In general, ATC sees my altitude as about 200' lower than what is
shown on my altimeter.

A couple of facts:

- The transponder/encoder always pass their certification checks.

- The pitot/static system is installed per plans.

Any thoughts?

KB

An update on this thread... There are no apparent loose hoses, etc between
the altimeter and encoder which would explain a discrepancy between the two.
Also, the altimeter is 30' off (it reads low) on the ground which is well
within limits. This 30' low reading is consistent in flight (to the best of
my ability to gauge it during a low pass).

Presumably, this means the encoder needs to be adjusted. Other thoughts?

Oh, and by the way, climbing under the panel of an RV-6 to check this stuff
ain't no fun...

KB

At a minimum you need to have your altimeter and encoder
correlated/adjusted by somebody rated to do that. In the mean time, turn
off the alt reporting at the transponder.
The adjustment can't be done without the proper equipment, sorry.
The next question is why did the encoder drift off by so much and will
it do it again? Since it's drifted that much, it might be worthwhile to
get a new encoder. They're pretty cheap.

The altimeter can only be legally adjusted by a certified repair
station. It's a good idea to make sure the altimeter is accurate when a
new encoder is installed.

Dave
www.craigmileaviation.com