Saturday, May 2, 2015
Boeing AH-64 Apache
This model started off life as a toy.
However with a bit of effort it produces a fairly decent model.
The Boeing AH-64 Apache is a four-blade, twin-turboshaft attack helicopter with a tailwheel-type landing gear arrangement, and a tandem cockpit for a two-man crew. 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. It has four hardpoints mounted on stub-wing pylons, typically carrying a mixture of AGM-114 Hellfire missiles and Hydra 70 rocket pods. The AH-64 has a large amount of systems redundancy to improve combat survivability.
The Apache originally started 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 first production AH-64D Apache Longbow, an upgraded Apache variant, was delivered to the Army in March 1997. Production has been continued by Boeing Defense, Space & Security; over 2,000 AH-64s have been produced to date.
The U.S. Army is the primary operator of the AH-64; it has also become the primary attack helicopter of multiple nations, including Greece, Japan, Israel, the Netherlands and Singapore; as well as being produced under license in the United Kingdom as the AgustaWestland Apache. U.S. AH-64s have served in conflicts in Panama, the Persian Gulf, Kosovo, Afghanistan, and Iraq. Israel used the Apache in its military conflicts in Lebanon and the Gaza Strip; British and Dutch Apaches have seen deployments in Afghanistan and Iraq.
Following the cancellation of the AH-56 Cheyenne in 1972, in favor of U.S. Air Force and Marine Corps projects like the A-10 Thunderbolt II and Harrier, the United States Army sought an aircraft to fill an anti-armor attack role that would still be under Army command; the 1948 Key West Agreement forbade the Army from owning combat fixed-wing aircraft. The Army wanted an aircraft better than the AH-1 Cobra in firepower, performance and range. It would have the maneuverability for terrain following nap-of-the-earth (NoE) flying. To this end, the U.S. Army issued a Request For Proposals (RFP) for an Advanced Attack Helicopter (AAH) on 15 November 1972. As a sign of the importance of this project, in September 1973 the Army designated its five most important projects, the "Big Five" with AAH included.
Proposals were submitted by Bell, Boeing Vertol/Grumman team, Hughes, Lockheed, and Sikorsky. In July 1973, the U.S. Department of Defense selected finalists Bell and Hughes Aircraft's Toolco Aircraft Division (later Hughes Helicopters). This began the phase 1 of the competition. Each company built prototype helicopters and went through a flight test program. Hughes' Model 77/YAH-64A prototype first flew on 30 September 1975, while Bell's Model 409/YAH-63A prototype first flew on 1 October 1975. After evaluating the test results, the Army selected Hughes' YAH-64A over Bell's YAH-63A in 1976. Reasons for selecting the YAH-64A included its more damage tolerant four-blade main rotor and the instability of the YAH-63's tricycle landing gear arrangement.
The AH-64A then entered phase 2 of the AAH program under which three pre-production AH-64s would be built, additionally, the two YAH-64A flight prototypes and the ground test unit were upgraded to the same standard. Weapons and sensor systems were integrated and tested during this time, including the laser-guided AGM-114 Hellfire missile. Development of the Hellfire missile had begun in 1974, originally known by the name of Helicopter Launched, Fire and Forget Missile ('Hellfire' being a shortened acronym), for the purpose of arming helicopter platforms with an effective anti-tank missile.
The AH-64 Apache has a four-blade main rotor and a four-blade tail rotor. The crew sits in tandem, with the pilot sitting behind and above the copilot/gunner. Both crew members are capable of flying the aircraft and performing methods of weapon engagements independently. The AH-64 is powered by two General Electric T700 turboshaft engines with high-mounted exhausts on either side of the fuselage. Various models of engines have been used on the Apache; those in British service use engines from Rolls-Royce instead of General Electric. In 2004, General Electric Aviation began producing more powerful T700-GE-701D engines, rated at 2,000 shp (1,500 kW) for AH-64Ds.
The crew compartment has shielding between the cockpits, such that at least one crew member can survive hits. The compartment and the rotor blades are designed to sustain a hit from 23 mm (0.91 in) rounds. The airframe includes some 2,500 lb (1,100 kg) of protection and has a self-sealing fuel system to protect against ballistic projectiles. The aircraft was designed to meet the crashworthiness requirements of MIL-STD-1290, which specifies minimum requirement for crash impact energy attenuation to minimize crew injuries and fatalities. This was achieved through incorporation of increased structural strength, crashworthy landing gear, seats and fuel system.