An Army helicopter is a type of aircraft used by the military for transportation, reconnaissance, and combat. The four most common types of Army helicopters are the CHINOOK, Huey, APACHE, and COBRA. The CHINOOK is a twin-engine, tandem rotor heavy-lift helicopter. The Huey is a single-engine, single-rotor utility helicopter. The APACHE is a twin-engine attack helicopter. The COBRA is a single-engine attack helicopter. All four of these helicopters are used by the Army for various missions.