It features a nose-mounted sensor suite for target acquisition and night vision systems. It is armed with a 30 mm (1.18 in) M230 chain gun carried between the main landing gear, under the aircraft's forward fuselage, and four hardpoints mounted on stub-wing pylons for carrying armament and stores, typically a mixture of AGM-114 Hellfire missiles and Hydra 70 rocket pods. The AH-64 has significant systems redundancy to improve combat survivability. The Apache began as the Model 77 developed by Hughes Helicopters for the United States Army's Advanced Attack Helicopter program to replace the AH-1 Cobra. The prototype YAH-64 was first flown on 30 September 1975. The U.S. Army selected the YAH-64 over the Bell YAH-63 in 1976, and later approved full production in 1982. After purchasing Hughes Helicopters in 1984, McDonnell Douglas continued AH-64 production and development. The helicopter was introduced to U.S. Army service in April 1986. The advanced AH-64D Apache Longbow was delivered to the Army in March 1997. Production has been continued by Boeing Defense, Space & Security, with over 2,400 AH-64s being produced by 2020. For details of the development, design, operational history and variants of the AH-64, click here.