Changing iPad Air 2 passcode with only having Touch ID I just recently purchased an iPad Air 2 and when setting it up, I successfully created the fingerprint ID but cannot remember my actual passcode.  I can still access the iPad using Touch ID but is there a way I can change the passcode without knowing it?
Yes and no. There's no easy way to just change your passcode.

There is a way to reset your passcode, but it involves erasing your iPad. You may need to know your Apple ID password.

Apple has steps here.

Those instructions basically involve going to iCloud.com or iTunes to erase your device. You then would be able to restore from a backup if need to.

I'm not sure if having Touch ID helps in any way. If you don't have a backup you can, possibly, use iTunes to make a backup first, unless it's brand new and you don't need to worry about restoring anything anyway.

Possibly you can just do erase all contents and settings in Settings > General > Reset and enter your Apple ID passcode too, but I'm not sure.

Whatever you do, avoid rebooting the iPad, because then TouchID will no longer work and you'll be forced to use the iCloud or iTunes erase and restore.