FAR 61.19(c) states...The holder of a pilot certificate issued on the basis of a foreign pilot license may exercise the privileges of that certificate only while that person's foreign pilot license is effective.
An EASA licence remains "effective" if it has not been suspended or revoked, regardless of whether the ratings on the licence are valid or not.
Provided the holder of a piggyback certificate issued under FAR 61.75 has completed a flight review under FAR 61.56 and complies with the currency requirements of FAR 61.57, he can use that certificate to fly a N reg aircraft even though his EASA ratings are not current.
I have to disagree. Part 61.19 has to do with expiration of a certificate, not whether you are current to fly. Just because it hasn't expired doesn't mean you can exercise its privileges.
A certificate issued under 61.75 is not an independent ICAO certificate. It is issued "on the basis of" another certificate. All underlying currency requirements of the foreign certificate must be met. If used as the basis for further ratings or certificates it must be revalidated.
If you can't fly today on your EASA licence then you can't fly today on your Part 61.75 FAA certificate. Unless I'm wrong, in which case I'll be happy to be corrected. (But 61.19.(c) is not the answer.)
Terry