Y'all,
I have been flying in an aircraft where ATC has occasionally mentioned that
there is a 3-4 hundred discrepancy betwee our
communicated altitudes and that of our blind encoder. We have
acknowledged the difference.

The altimeters were certified some 300 miles away only three months ago.

ATC has accepted continuation of our flights using our indicated altitudes
not those of the blind encoder. The transponder altituded gives encoder
altitudes..

What do the FARs require?
What are the options?
What warranty on altimeter work and for how long?
Opinions wanted.

Gene Whitt