21.77—Duration.
(a)
Unless sooner surrendered, superseded, revoked, or otherwise terminated, provisional type certificates and amendments thereto are effective for the periods specified in this section.
(d)
An amendment to a Class I or Class II provisional type certificate is effective for the duration of the amended certificate.
(e)
A provisional amendment to a type certificate is effective for six months after its approval or until the amendment of the type certificate is approved, whichever is first.