Monday, May 26, 2008

The AH-64 Apache is an all-weather day-night military attack helicopter and is the United States Army's principal attack helicopter, and is the successor to the AH-1 Cobra. The AH-64 is a twin-engined helicopter with four-bladed main and tail rotors. It has a crew of two which sit in tandem. The main fixed armament is a 30 mm M230 Chain Gun, it is also able to carry 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. 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 Defense Systems. The United States Army's Apaches have been in action in Panama, Gulf War (destroying 500 tanks[2]), Afghanistan, and Iraq.

Development
Advanced Attack HelicopterFollowing the cancellation of the AH-56 Cheyenne in favor of USAF and Marine projects like the A-10 and Harrier, the United States Army sought an aircraft to fill an anti-armor attack role that would still fall under Army command (the 1948 Key West Agreement having forbidden the Army from commanding fixed-wing aircraft). The Army wanted an aircraft better than the AH-1 Cobra in firepower, performance and range. It would have the maneuverability to fly nap-of-the-earth (NoE) missions. To this end, the US Army issued a Request For Proposals (RFP) for an Advanced Attack Helicopter (AAH) in 1972.[2]
Proposals were submitted by five manufacturers: Bell, Boeing-Vertol (teamed with Grumman), Hughes, Lockheed, and Sikorsky. In 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.[2]
Each company built prototype helicopters and went through a flight test program. Hughes' Model 77/YAH-64A prototype first flew on September 30, 1975, while Bell's Model 409/YAH-63A prototype first flew the following day.[2] After evaluating 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.[3]
The AH-64A then entered phase 2 of the AAH program. This called for building three preproduction AH-64s, and upgrading the two YAH-64A flight prototypes and the ground test unit up to the same standard.[4] Weapons and sensor systems were integrated and tested during this time,[2] including the new Hellfire missile.[4]
Into productionIn 1981, three pre-production AH-64As were handed over to the U.S. Army for Operational Test II. The Army testing was successful, but afterwards it was decided to upgrade to the T700-GE-701 version of engine, producing 1,690 shp (1,259 kW).[2] In late 1981, the AH-64 was named the "Apache" keeping with the Army's traditional use of Native American tribal names for its helicopters. Hughes was approved for full scale production in 1982.[2] In 1983, the first production helicopter was rolled out at Hughes Helicopter's facility at Mesa, Arizona. In 1984, Hughes Helicopters was purchased by McDonnell Douglas for $500 million. Hughes later became part of The Boeing Company with the merger of Boeing and McDonnell Douglas in August 1997. In 1984, the incremental or flyaway cost for the AH-64A was US$7.8 million and the average unit cost was approximately US$14 million with development costs included.[2]
In 2004, General Electric Aviation began producing more powerful T700-GE-701D engines, rated at 2,000 shp (1,500 kW) for AH-64Ds.[5] The total cost of the AH-64D program is US$10.5 billion through April 2007.[6]
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DesignThe AH-64 is powered by two General Electric T700 turboshaft engines with high-mounted exhausts on either side of the rotor shaft. The Apache has a four-blade main rotor and four-blade tail rotor. The crew sits in tandem, with the pilot sitting behind and above the copilot-gunner in an armored crew compartment. The crew compartment and fuel tanks are armored against 23 mm gunfire. The main rotor blade is designed to remain intact after sustaining hits by 23 mm rounds.[citation needed]
The helicopter is armed with a 30 mm M230 Chain Gun that can be slaved to the gunner's helmet-mounted gunsight, fixed to a locked forward firing position, or controlled via the TADS (Target Acquisition and Designation System). The AH-64 carries a range of external stores on its stub-wing pylons, typically a mixture of AGM-114 Hellfire anti-tank missiles, Hydra 70 general-purpose unguided 70 mm (2.75 in) rockets, and AIM-92 Stinger anti-aircraft missiles for defense. In case of emergency the pylons also have mounting points for personnel transfer (mounting points are handles normally used by maintenance personnel).[7]
The AH-64 is designed 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).
Operational history
United States An AH-64 provides air support over Tikrit, Iraq on February 24, 2006.The Apache was first used in combat during the 1989 invasion of Panama, Operation Just Cause. The AH-64A Apache and the AH-64D Apache Longbow have played important roles in several Middle Eastern wars, including the Gulf War, Operation Enduring Freedom in Afghanistan, and Operation Iraqi Freedom in Iraq. The Apaches were proven to be excellent tank hunters and also destroyed hundreds of armored vehicles (mainly of the Iraqi army).
During Operation Desert Storm on January 17, 1991, eight AH-64As guided by four MH-53 Pave Low IIIs, were used to destroy a portion of the Iraqi radar network to allow bomber aircraft into Iraq without detection.[2] This was the first attack of Desert Storm.[2] The Apaches carried an asymmetrical load of Hydra 70 flechette rockets, Hellfires, and one auxiliary fuel tank each.[8] During the 100-hour ground war, a total of 277 AH-64s took part. Apaches destroyed over 500 tanks, numerous armored personnel carriers and many other vehicles during Operation Desert Storm.[2]
AH-64A at Forward Operating Base Speicher, Iraq in 2005.During Operation Iraqi Freedom, some Apaches were damaged in combat, including one captured by Iraqi troops near Karbala on March 24, 2003, and shown on Iraqi television. The captured helicopter was destroyed via air strike the day after it was captured.[9] The March 24 attack, against an armored brigade of the Iraqi Republican Guard's Medina Division, was largely unsuccessful, apparently because the tank crews had set up a "flak trap" in broken terrain, employing their guns to good effect.[10][11] More recently two Apaches were lost along with their crews between January 28 and February 2, 2007 to Iraqi insurgent ground fire in Taji and Najaf.[12]
American AH-64Ds are currently flying in Iraq and Afghanistan without the Longbow Fire Control Radar as there are simply no armored threats for coalition forces to deal with.[13]
The vast majority of Apache helicopters that have taken heavy combat damage have been able to continue their assigned missions and return safely to their bases. For example, of the 33 Apaches employed in the March 24, 2003 attack, 30 were damaged by Iraqi ground fire with several being damaged beyond repair, but only one of these did not make it back to base.[11]
Israel IAF AH-64A "Peten" פתן Apache Longbow at the International Aerospace Exhibition 2006.The Israeli Air Force uses the Apache to strike various targets with guided missiles. The AH-64A attacked and destroyed some of Hezbollah outposts in Lebanon during the 1990s, attacking in many weather conditions — day and night. During the al-Aqsa Intifada, the IAF used the Apaches to kill senior Hamas figures, such as Ahmed Yasin and Adnan al-Ghoul, with guided missiles. In the Israel-Lebanon conflict of July – August 2006, two IAF AH-64A helicopters collided, killing 1 pilot and wounding 3, all critically. In another incident in the conflict, an IAF AH-64D Longbow crashed, killing the two pilots, due to a malfunction in the rotor hub.[14]
United KingdomMain article: Westland WAH-64 ApacheThe UK operates a version of the Apache called the Westland WAH-64 Apache, and is designated Apache AH Mk1 by the British Army. Westland has built 67 WAH-64 Apaches[15] under license from Boeing replacing the engines with more powerful Rolls-Royce units. A folding blade assembly for carrier operations is another important change so they can operate alongside amphibious forces off Royal Navy ships. The Westland Apache replaces the Westland Lynx as the British Army's tactical attack helicopter. The WAH-64s are currently deployed in Afghanistan.[16] British WAH-64 Apaches are using the Longbow Fire Control Radar in Afghanistan, saying that it improves situational awareness and avoidance of other aircraft during tactical maneuvers.[17]
The NetherlandsRoyal Netherlands Air Force ordered 30 AH-64D Apaches in 1996,[18] after leasing 12 AH-64As. The radar domes were not included, hence the Dutch AH-64Ds are not referred to as Longbows. Their first deployment was in Djibouti, Africa. They were also deployed alongside US AH-64s in support of NATO peacekeeping forces in Bosnia and Herzegovina. In 2004, Dutch AH-64s were deployed as part of the Netherlands contribution to Multinational force in Iraq.[19] At the same time Dutch Apaches were also deployed to Kabul as part of the Netherlands contribution to ISAF. In February 2006, the Netherlands contribution to NATO forces in Afghanistan was increased from 600 to 1,400 troops and 6 AH-64s were sent in support.[20]
Other usersIn September 2003, Greece ordered 12 AH-64D (in addition to the already existing fleet of 20 AH-64A+) for a total cost of $675 million (presumably including weapons and support), indicating a gross unit cost for the AH-64D of $56.25 million. Singapore purchased a total of 20 AH-64D Longbow Apache aircraft in two batches between 1999 and 2001. The United Arab Emirates purchased a total of 30 AH-64A helicopters in 1991 and 1994, which they are now upgrading to AH-64D specification.[21] Kuwait has purchased 16 Longbow helicopters.[22] Other countries with the Apache include Egypt, Holland, Israel, Japan and Saudi Arabia.[23]
Pakistan is thought to have ordered six Apache Longbow for its various anti-terrorism missions.[24][25][26]
South Korea had a plan to purchase 36 AH-64D but the plan was canceled in favor of co-developing a domestic attack helicopter, the Korean Attack Helicopter, (KAH) under the KAH program with partnership from Eurocopter, which will be based on the Eurocopter Tiger.
The Republic of China (Taiwan) plans to purchase 30 AH-64D from 2008 onwards for its Army.[27]
Variants Royal Netherlands Air Force AH-64D at the Farnborough Air Show, 2006. AH-64AThe AH-64A is the original production attack helicopter. It is powered by two GE T700 turbo-shaft engines. The crew sit in tandem in an armored compartment.
The helicopter is armed with a 30 mm M230 chain gun that can be slaved to the gunner's helmet-mounted gunsight. The AH-64A carries a range of external stores on its stub-wing pylons, including a mixture of AGM-114 Hellfire anti-tank missiles, Hydra 70 general-purpose unguided 70 mm (2.75 in) rockets, and AIM-92 Stinger anti-aircraft missiles for defense.
AH-64BIn 1991 after Operation Desert Storm, the AH-64B was a proposed upgrade to 254 AH-64As. The upgrade included new rotor blades, a Global Positioning System (GPS), improved navigaton systems and new radios. Congress approved US$ 82 million to begin the Apache B upgrade. The B program was canceled in 1992.[2] The radio, navigation, and GPS modifications, would later be installed on most A-model Apaches as part of an upgrade program.
AH-64CAdditional funding from Congress in late 1991 resulted in a program to upgrade AH-64As to an AH-64B+ version. More funding changed the plan to upgrade to AH-64C. The C upgrade would include all changes to be included in the Longbow except for mast mounted radar and newer engines. However, after 1993, the C designation was dropped.[2]
The upgrades would go forward. However, since the only difference between the C model and the radar-equipped D model was the radar, which could be moved from one aircraft to another, a decision was made to not distinguish between the two versions, despite the presence or absence of the radar.
AH-64D Israel Air Force AH-64D "Saraf" AH-64D at the Farnborough Air Show, 2006. Republic of Singapore Air Force AH-64D on static display during open houseThe advanced model, the AH-64D Apache Longbow, is equipped with an improved sensor suite and weapon systems. The key improvement over the A-variant is the AN/APG-78 Longbow dome installed over the main rotor which houses a millimeter-wave Fire Control Radar (FCR) target acquisition system as well as the Radar Frequency Interferometer (RFI). The elevated position of the radome allows detection and (arcing) missile engagement of targets even when the helicopter itself is concealed by an obstacle (e.g. terrain, trees or buildings). Further, a radio modem integrated with the sensor suite allows a D-variant Apache to share targeting data with other AH-64Ds that do not have a line-of-sight to the target. In this manner a group of Apaches can engage multiple targets but only reveal the radome of one D-variant Apache. Apaches that include all of the improvements of the Longbow Apache, with the exception of the Fire Control Radar are still designated as "AH-64D Apache Longbows", as the radome is removable and interchangeable between aircraft.
The aircraft was updated with more powerful T700-GE-701C engines, and a fully-integrated cockpit. The forward fuselage of the aircraft was expanded to accommodate new systems. In addition, the aircraft receives improved survivability, communications, and navigation capabilities. Most existing capabilities of the AH-64A Apache are retained.
The first of the upgraded Block II Apaches was delivered to the US Army in February 2003. Block II includes upgrades to the digital communications systems to improve communications within the 'tactical internet'.[28]
Block III improvements, slated for 2008 onwards, include increasing digitization, the joint tactical radio system, enhanced engines and drive systems, capability to control UAVs, new composite rotor blade and landing gear upgrades. The new blades, which successfully completed flight testing in May 2004, increase the Apache's cruise speed, climb rate and payload capability. The Block III System Development and Demonstration (SDD) contract was awarded to Boeing in July 2006.[28]
Export ApachesA number of other models have been derived from both AH-64A and AH-64D for export. The British-built Westland WAH-64 Apache (assembled from kits purchased from Boeing) is based on the AH-64D with several different systems, including newer, more powerful engines.
Sea ApacheA naval version of the AH-64A was proposed for the U.S. Marine Corps and U.S. Navy from 1984 to 1987.[3] Multiple concepts were studied with altered landing gear arrangements, improved avionics and weapons.[29] Funding for the naval version was not provided and the Marine Corps continues to use the AH-1 SuperCobra as of 2008.[3]

Thursday, May 15, 2008

VTOL is an acronym for Vertical Take-Off and Landing. VTOL describes fixed-wing aircraft that can lift off vertically. This classification includes only a very few aircraft; helicopters, autogyros; balloons and airships are not normally considered VTOL. Some aircraft can operate in VTOL mode in addition to others, such as CTOL (Conventional Take-off and Landing) and/or STOL (Short Take-Off and Landing). Others can only operate by VTOL, due to the aircraft lacking landing gear that can handle horizontal motion

In 1928, Nikola Tesla received patents for an apparatus for aerial transportation. Tesla called it the "Flivver". It is one of the earliest examples of VTOL aircraft.
In late World War II, German designers studied the possibility of a VTOL aircraft, the Heinkel Lerche, but the plan never got off the drawing board.
An early contribution to VTOL was Rolls-Royce's Thrust Measuring Rig ("flying bedstead") of 1953 . This led to the first VTOL engines as used in the first British VTOL aircraft, the Short SC.1 (1957) which used 4 vertical lift engines with a horizontal one for forward thrust.
The idea of using the same engine for vertical and horizontal flight by altering the path of the thrust led to the Bristol Siddeley Pegasus engine which used rotating ducts to direct thrust over a range of angles. This was developed side by side with an airframe, the Hawker P.1127, which became subsequently the Kestrel and then entered production as the Hawker Siddeley Harrier though the supersonic Hawker Siddeley P.1154 was cancelled in 1965 .
The Harrier is often flown in STOVL mode which enables it to carry a higher fuel or weapon load over a given distance. The Indian Navy operates Sea Harriers mainly from its aircraft carrier INS Viraat. The United States Marine Corps, and the Italian and Spanish Navies use the AV-8 Harrier II, an advanced derivative of the Harrier. The Harrier II will be replaced in the air arms of the US and UK by a STOVL variant of the F-35 Joint Strike Fighter.
NASA has flown other VTOL craft such as the XV-15 research craft (1977), as have the Soviet Navy and Luftwaffe. Sikorsky tested an aircraft dubbed the X-Wing, which took off in the manner of a helicopter. The rotors would become stationary in mid-flight, and function as wings, providing lift in addition to the static wings. Boeing X-50 is a Canard Rotor/Wing prototype that utilizes a similar concept.
In the 1960s France developed a version of the Dassault Mirage III capable of attaining Mach 1. The Dassault Mirage IIIV (not to be confused with the Mirage 5) achieved transition from vertical to horizontal flight in March of 1966 and reached Mach 1.3 in level flight a short time later.
The Soviet Yak-38 Forger was the Soviet Navy's VTOL aircraft for their light carriers, cargoships, and capital ships. It was developed from the Yak-36 Freehand experimental aircraft. Before the Soviet Union collapsed, a supersonic VTOL aircraft was developed as the Yak-38's successor, the Yak-141, which never went into production. The Yak-141, also called Yak-41 was further developed into the Yak-43.


A German V/STOL VJ101 "Starfighter" on display at the Deutsches Museum, Munich, Germany.
In the 1960s and early 70s Germany planned three different VTOL planes. One used the F-104 as a base for research for a V/STOL aircraft. Although two models (X1 and X2) were built, the project was canceled due to high costs and political problems as well as changed needs in the Luftwaffe and NATO. The EWR VJ 101C did perform free VTOL take-offs and landings, as well as test flights beyond mach 1 in the mid- and late 60s. One of the test-aircraft is preserved in the Deutsches Museum in Munich, Germany. The others were the VFW-Fokker VAK 191B light fighter and reconnaissance plane[1], and the Dornier Do 31E-3 (troop) transport[2], prototypes of the two can be seen at the Deutsches Museum branch at Oberschleißheim Airfield.
Canadair CL-84 Dynavert


CL-84-1 (CX8402) on display at the Canada Aviation Museum in Ottawa, Ontario
The CL-84 was a Canadian V/STOL turbine tilt-wing monoplane designed and manufactured by Canadair between 1964 and 1972. Only four of these experimental aircraft were built with three entering flight testing. Two of the CL-84s crashed due to mechanical failures, but no loss of life occurred as a result of these accidents. Despite the fact that the CL-84 was very successful in the experimental and operational trials carried out between 1972 and 1974, no production contracts resulted.
The Moller Skycar is a prototype personal VTOL aircraft -- literally, a "flying air vehicle" (PAV). It has, as of this date, never made the transition to level flight, nor has it ever flown with anybody on board.
Aircraft designed to operate in extraterrestrial environments often utilize VTOL. An example of this type of aircraft is the LLRV. Spacecraft typically operate in environments where runways or even a suitably flat surface for skids is nonexistent.

V-22


U.S. Marines jump from V-22Osprey, the first production tiltrotor aircraft.
The V-22 Osprey is the world's first production tiltrotor aircraft, with one three-bladed proprotor, turboprop engine, and transmission nacelle mounted on each wingtip. The Osprey is a joint service, multimission, military tiltrotor aircraft with both a vertical takeoff and landing (VTOL) and short takeoff and landing capability (STOL). It is designed to perform missions like a conventional helicopter with the long-range, high-speed cruise performance of a turboprop aircraft. The FAA classifies the Osprey as a model of powered lift aircraft.[citation needed]
F-35B
The most spectacular demonstration of the JSF qualifying flight trials was the X-35B's STOVL demonstration where it took off in less than 500 feet, went supersonic, and landed vertically -- a feat that Boeing's entry was unable to achieve.[1]
The JSF program was created to replace various aircraft while keeping development, production, and operating costs down. This was pursued by building three variants of one aircraft, sharing 80% of their parts:
F-35A, a conventional takeoff and landing (CTOL) variant.
F-35B, a short-takeoff and vertical-landing (STOVL) variant.
F-35C, a carrier-based variant.


X-35B lift fan; the VTOL propulsion system is designed and manufactured by Rolls-Royce plc
The F-35B is the short-takeoff and vertical-landing (STOVL) variant aircraft. The F-35B is similar in size to the Air Force F-35A, trading fuel volume for vertical flight systems. Like the AV-8 Harrier II, guns will be carried in a ventral pod. Vertical flight is by far the riskiest, and in the end, a decisive factor in design.
Instead of lift engines, or rotating nozzles on the engine fan and exhaust like the Pegasus-powered Harrier, the F-35B uses an innovative shaft-driven Lift Fan, patented by Lockheed Martin and developed by Rolls-Royce.[2] Somewhat like a turboprop embedded into the fuselage, engine shaft power is diverted forward via a clutch-and-bevel gearbox to a vertically mounted, contra-rotating lift fan located forward of the main engine in the center of the aircraft. Bypass air from the cruise engine turbofan exhausts through a pair of roll-post nozzles in the wings on either side of the fuselage, while the lift fan balances the vectoring cruise nozzle at the tail. This system is more similar to the Russian Yak-141 than previous STOVL designs, such as the Harrier with thrust vectoring.
Demonstrator X-35 aircraft flew in 2000;[3] a production model first took flight on 15 December 2006