Hi Jim, I’m on TDIU but want to return to flying. I understand how returning to work goes, but if the FAA issues a med certificate with full disclosure to both agencies (legally) but I have not returned to work, would VA lower my rating? If so, would it be as soon as the certificate is issued or after 12 months of holding such an FAA certificate?
The return to flying doesn't have anything to do with your TDIU rating. I don't know which two agencies you're thinking of when you talk of issuing a certificate but the VA won't want any such certificate and it won't affect your TDIU status. You can go fly, drive race cars, gamble your life away in Vegas and if you aren't earning above the poverty line by employment, VA doesn't pay attention.
You are not allowed to work and earn an income. I have known many vets who volunteered 40 hours each week at VA facilities and their TDIU was intact since they weren't earning above the federal minimum wage. That's pretty much the only thing VA notices after you've been rated TDIU. If you earn more money than allowed, your TDIU is going to be reviewed.
Otherwise...go fly. Good luck.