> I have one simple question - when I insert value to CHAR(1) field on
> UNICODE_FSS database, SELECT returns 3 characters.

Of course. UNICODE_FSS uses variable length encoding -
one character can be 1 to 3 bytes long. And because CHAR datatype
does not carry information about real string length ...

> Is this bug or feature?

Neither. It is just result of inappropriate combinig of
variable length encoding and fixed length field.
You shoud use VARCHAR with UNICODE_FSS.

Ivan
http://www.volny.cz/iprenosil/interbase