21.A.51 Duration and continued validity

(a) A type-certificate and restricted type-certificate shall be issued for an unlimited duration. They shall remain valid subject to:

1.  the holder remaining in compliance with this Annex 1 (Part 21); and

2.   the certificate not being surrendered or revoked under the applicable administrative procedures established by the CAA.

(b) Upon surrender or revocation, the type-certificate and restricted type-certificate shall be returned to the CAA.