On Jun 20, 12:51*pm, sisu1a wrote:

ATC- *?Type Certification *(I presume the A was meant to be an S, for
Standard, *and that is actually a typo...)

STC is more commonly associated with Supplemental Type Certificate,
which approves the modification of an aircraft such that it no longer
conforms to the specifications of its original Type Certificate.

Thanks, Bob K.