Originally Posted by
DaveReidUK
There is something called the "Changed Product Rule" or CPR that governs derivative design certification. The details can get messy, but what CPR basically says is that if a system is unchanged it can retain it's original cert basis, but if it's changed then it has to step up to the latest regulations. There is a process for exceptions where the airframer can show that it's impractical to step up to the latest regulations
and it wouldn't meaningfully improve safety to step up. CPR is a 'harmonized' regulation - meaning EASA applies it as well. CPR has been applied to all the major derivative programs over the last 15 years - 737 MAX, A320 NEO, A330 NEO, 747-8/8F, 767-2C.
All that being said, there isn't much on the 777X that's common to current production. So while the 777X may have the same TCDS as the 777, most of the cert basis will be new.
Every Boeing aircraft certified in the last 20 years has been certified to both FAA and EASA - the lone exception is that the 767-2C/KC-46 will be certified FAA only since it's not expected to have any EASA customers.
But these days, they almost invariably do.
Ah, actually many of them don't. Obviously when you certify EASA, anyone in EASA must accept the cert, but many other countries do at least a cursory review of the cert basis before they accept it. Russia and China do much more than a cursory review - getting approval for the 747-8/8F and 787 required weeks of meetings and reviews with the Russian and Chinese authorities...
Now that sounds like illegal state aid.
You might be interested to know that EASA and most of the other non-US regulatory authorities bill Boeing for their costs associated with certifying. In fact I believe the FAA is the
only authority that doesn't bill foreign airframers for their services...