Wash. Rev. Code § 14.16.080
Any aircraft used to carry persons or property for compensation, or any aircraft that is rented or leased without a pilot, shall be equipped with a fully functional downed aircraft rescue transmitter and it shall be unlawful for any person to operate such aircraft without such a transmitter: PROVIDED, HOWEVER, Nothing in this section shall apply to (1) instructional flights by an air school, with the exception of solo flights by students; (2) aircraft owned by and used exclusively in the service of the United States government; (3) aircraft registered under the laws of a foreign country; (4) aircraft owned by the manufacturer thereof while being operated for test or experimental purposes, or for the purpose of training crews for purchasers of the aircraft; and (5) aircraft used by any air carrier or supplemental air carrier operating in accordance with the provisions of a certificate of public conveyance and necessity under the provisions of the Federal Aviation Act of 1958, Public Law 85-726, as amended.
RCW 14.16.080