Yes, RUDDERS is a Scrabble word!

Letter values in Scrabble US: R 1, U 1, D 2, D 2, E 1, R 1, S 1.

Is it a valid word?

RUDDERS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a hinged vertical airfoil mounted at the tail of an aircraft and used to make horizontal course changes
(nautical) steering mechanism consisting of a hinged vertical plate mounted at the stern of a vessel