It was there in front of our faces with the exception of doing a chown and chmod.Someone else please confirm I will post steps.

1. Disconnect airport disk and plug into computer as a USB drive directly.
2. Set up time machine to use this volume.
3. In terminal cd to volume “cd /Volume/HDD”
4. In terminal “touch .com.apple.timemachine.supported” this will create an invisible file.
5. In terminal “sudo chown root:admin .com.apple.timemachine.supported”
6. In terminal “sudo chmod 1775 .com.apple.timemachine.supported”
7. In terminal “ls -l -a” the .com.apple.timemachine.supported file should be -rwxrwxr-t
8. Eject disk, unplug from mac, plug into Airport.
9. Mount at mac using connect to server in finder (command k) and afp://airportname.local./HDname10) see if time machine now sees the drive and tries to use it.