The AH-64 Apache is the United States Army's principal attack helicopter, and is the successor to the AH-1 Cobra. The AH-64 is a two-seat attack helicopter powered by two General Electric T700 turboshaft engines. The crew sits in tandem, with the pilot sitting behind and above the copilot-gunner in an armoured crew compartment. The AH-64 is armed with a 30mm M230 chain gun and carries a mixture of AGM-114 Hellfire and Hydra 70 rockets on four hard points mounted on its stub-wing pylons. Designed by Hughes Helicopters in response to the Army's Advanced Attack Helicopter Program, it was built to endure front-line environments and to operate during the day or night and in adverse weather using avionics and electronics, such as the Target Acquisition and Designation System, Pilot Night Vision System (TADS/PNVS), passive infrared countermeasures, Global Positioning System (GPS), and the Integrated Helmet And Display Sight System (IHADSS). McDonnell Douglas purchased Hughes Helicopters and continued the development of the AH-64 resulting in the AH-64D Apache Longbow which is currently produced by Boeing Integrated Defence Systems.