CREATE TABLE table_73634 ("Episode number Production number" TEXT, "Title" TEXT, "Original airdate" TEXT, "Rating/Share in Households" TEXT, "18\\u201349 Rating Live+SD / Live+7" TEXT, "Share" TEXT, "Live+SD Total viewers" TEXT, "Live+7 Day DVR Total viewers" TEXT)

When did the episode that had 5.09 million total viewers (both Live and SD types) first air?
SELECT "Original airdate" FROM table_73634 WHERE "Live+SD Total viewers" = '5.09 million'
SELECT "Original airdate" FROM "table_73634" WHERE "Live+SD Total viewers" = '5.09 million'