I'm no expert, but from what I could find out, DV video on tape (DV, DVCPRO, DVCPRO50) always has some kind of compression applied.
I am wondering how FCP recognizes the tape export codec when you do File --> Edit to Tape...? That might be some detail to look into.
I suspect your uncompressed options will not involve tape but instead creating a file on a hard drive. You'll need to find out what file formats the Avid system can import, and if it needs a PC formatted drive or can it handle a Mac formatted drive.
Here are the file ideas. Under FCP --> File --> Export you could use Compressor options or QuickTime options:
Using Compressor.. --> Advanced Format Conversions --> 8-bit Uncompressed NTSC.
Using QuickTime Conversion... --> QuickTime Movie --> Settings --> Compressor Type: Uncompressed 8-bit 4:2:2.