an extended impingement cooling structure to cool outside an air supply plenum comprises an inner wall ; an impingement sheet ; a series of supports to maintain the inner wall in spaced relation to the impingement sheet , and a baffle supported between the inner wall and the impingement sheet . the baffle has a collector plenum area that receives impingement cooling air from the air supply plenum and a channel in fluid communication with the collector plenum and extending outside the air supply plenum with openings to allow impingement cooling air to pass therethrough and having a series of lands extending into the channel wherein the lands are located in proximity to impingement cooling air outlets in the inner wall .