CREATE TABLE table_45353 ("Rank" TEXT, "Badge/Serial Number" TEXT, "Tenure" TEXT, "Date of death" TEXT, "Cause of death" TEXT)

What is the Tenure of the Officer who died in a helicopter accident with Badge/Serial Number 16805?
SELECT "Tenure" FROM table_45353 WHERE "Cause of death" = 'helicopter accident' AND "Badge/Serial Number" = '16805'
SELECT "Tenure" FROM "table_45353" WHERE "Badge/Serial Number" = '16805' AND "Cause of death" = 'helicopter accident'