Lieutenant, junior grade ranks above ensign and below lieutenant and is equivalent to a first lieutenant in the other uniformed services (the Army, Marine Corps and Air Force) and sub-lieutenant in the Royal Navy and the navies of many Commonwealth countries. The time for promotion to LTJG is a minimum of two years after commissioning in the Navy or 18 months in the Coast Guard. Lieutenants, junior grade typically lead petty officers and non-rated personnel, unless assigned to small aircraft or on staff duty. A LTJG's usual shipboard billet is as a Division Officer.