A switch that selectively changes radio frequency signals includes at least three FETs, which are connected in series. A cover plate secured onto a side of the rotor disk includes a plurality of cooling air injectors directed to discharge cooling air into an annular groove formed on the underside of the vane endwall adjacent to the rotor disk to form an air cushion that seals the rim cavity from hot gas ingestion. The inner sleeve is detachably and slidably positioned within the outer sleeve, and includes a first port for receiving and dispensing washing liquid, a second port defining a liquid flow path between an interior of the inner sleeve and an interior of the outer sleeve, and a filter disposed in the second port.