What date did the episode with 8.28 million u.s. viewers originally air?
CREATE TABLE "table1_27910411_1" (
  "no_in_series" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "u_s_viewers_millions" text
);
SELECT "original_air_date" FROM "table1_27910411_1" WHERE "u_s_viewers_millions"='8.28';