Boeing AH-64 Apache

The Boeing AH-64 Apache is a four-blade, twin-engine attack helicopter with a tailwheel-type landing gear arrangement, and a tandem cockpit for a two-man crew. Originally, the Apache started life as the Model 77 developed by Hughes Helicopters for the United States Army's Advanced Attack Helicopter program to replace the AH-1 Cobra, and was first flown on 30 September 1975. The AH-64 was introduced to U.S. Army service in April 1986.

The AH-64 Apache features a nose-mounted sensor suite for target acquisition and night vision systems. It is armed with a 30 mm 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 U.S. Army selected the YAH-64, by Hughes Helicopters, over the Bell YAH-63 in 1976, and later approved full production in 1982. McDonnell Douglas continued production and development after purchasing Hughes Helicopters from Summa Corporation in 1984. The first production AH-64D Apache Longbow, an upgraded version of the original Apache, was delivered to the Army in March 1997. Production has been continued by Boeing Defense, Space & Security; over 1,000 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; both British and U.S. Apaches have seen deployments in Afghanistan and Iraq.

Advanced Attack Helicopter
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 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. 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 began in 1974, originally known by the name of Helicopter Launched, Fire and Forget Missile ('Hellfire' being a shortened acronym), with the aim of arming helicopter platforms with an effective anti-tank missile.

Into production
In 1981, three pre-production AH-64As were handed over to the U.S. Army for Operational Test II. The Army testing was successful, but afterward it was decided to upgrade to the more powerful T700-GE-701 version of engine, rated at 1,690 shp. The AH-64 was named the Apache in late 1981, keeping with the Army's traditional use of American Indian tribal names for its helicopters and it was approved for full scale production in 1982. In 1983, the first production helicopter was rolled out at Hughes Helicopter's facility at Mesa, Arizona. Hughes Helicopters was purchased by McDonnell Douglas for $470 million in 1984. The helicopter unit later became part of The Boeing Company with the merger of Boeing and McDonnell Douglas in August 1997. In 1986, the incremental or flyaway cost for the AH-64A was $7M and the average unit cost was approximately $13.9M based on total costs.



In the mid-1980s, McDonnell Douglas studied an improved "AH-64B" design with an updated cockpit, new fire control system and other upgrades. In 1988 funding was approved for a multi-stage upgrade program to improve sensor and weapon avionic systems and incorporate some digital systems. However, rapidly improving technology led to the upgrade program being canceled in favor of more ambitious changes. Development of the more advanced AH-64D Apache Longbow was approved by the Defense Acquisition Board in August 1990. The first AH-64D prototype flew on 15 April 1992, testing of the prototypes ended in April 1995. During the testing, six AH-64D helicopters were pitted against a numerically superior group of AH-64A helicopters; the results demonstrated that AH-64D has a seven times increase in survivability and four times increase in lethality compared to the AH-64A. On 13 October 1995 full-scale production of the Apache Longbow was approved, and a $1.9-billion five-year contract was signed in August 1996 to upgrade and rebuild 232 existing AH-64A Apaches. The first production AH-64D flew on 17 March 1997 and was delivered on 31 March. The cost of the AH-64D program totaled $11bn through 2007.

Some parts of the Apache are produced by international partners. AgustaWestland has been producing Apache components for the international market and for the AgustaWestland Apache. Since 2004, Korea Aerospace Industries has been the sole manufacturer of the Apache's fuselage. Prior to this, fuselage production was handled by Teledyne Ryan Aeronautical throughout the 1980s and 1990s; a legal dispute between Teledyne Ryan and Boeing broke out over the eventual transfer of fuselage production.

In April 2006, Boeing was awarded a $67.6M fixed-price contract for the remanufacture of several existing U.S. AH-64As to the AH-64D configuration; between May 2009 and July 2011, a further five contracts were issued to remanufacture batches of AH-64As to the upgraded D variant. Since 2008, nations operating the older AH-64A have been urged to undertake modernization programs to become AH-64Ds, as Boeing and the U.S. Army plans to terminate support for the A-variants in the near future. The Apache's effectiveness against ground forces and in urban warfare operations was bolstered by the addition of the AGM-114N – a Hellfire missile fitted with a thermobaric warhead; the AGM-114N was approved for full production in 2005. The use of thermobaric "enhanced blast" weapons has been a point of controversy.

Overview
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 2000 shp 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 rounds. The airframe includes some 2500 lb 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. Up to six AH-64 Apaches can be safely fitted inside the cargo hold of a USAF Lockheed C-5 Galaxy.

Avionics and targeting


One of the revolutionary features at the introduction of the Apache was its helmet mounted display, the Integrated Helmet and Display Sighting System (IHADSS); among other abilities the pilot or gunner can slave the helicopter's 30 mm automatic M230 Chain Gun to his helmet, making the gun track head movements to point at where he looks. The M230E1 can be alternatively fixed to a locked forward firing position, or controlled via the Target Acquisition and Designation System (TADS). The AH-64's standard of performance for aerial gunnery is to achieve at least 1 hit for every 30 shots fired at a wheeled vehicle at a range of 800 –.

The AH-64 is designed to endure front-line environments and to operate during the day or night and in adverse weather via its avionics and onboard sensor suites. These systems include the Target Acquisition and Designation System, Pilot Night Vision System (TADS/PNVS), passive infrared countermeasures, GPS, and the IHADSS. A newer system that is replacing TADS/PNVS is Arrowhead (MTADS); it is manufactured by Lockheed Martin, a contract was issued in February 2005 to begin equipping all U.S. Apaches.

In August 2012, 24 AH-64D were equipped with the Ground Fire Acquisition System (GFAS); intended to detect and target ground-based weapons fire sources. The GFAS consists of two small sensor pods which home in on muzzle flashes; working with the AH-64D's own sensors, an infrared camera precisely locates present ground-based threats and relevant distance. The GFAS has a 120° field of vision and is effective in all-light conditions.

Armaments and configurations
The AH-64 is adaptable to numerous different roles within its context as Close Combat Attack (CCA), it has a customizable weapons loadout mounted on stub-wings for the role desired. In addition to the 30-mm M230E1 Chain Gun, the Apache carries a range of external stores on its stub-wing pylons, typically a mixture of AGM-114 Hellfire anti-tank missiles, and Hydra 70 general-purpose unguided 70 mm rockets.

Starting in the late 1980s, the Stinger and AIM-9 Sidewinder air-to-air missiles and the AGM-122 Sidearm anti-radiation missile were evaluated for use upon the AH-64. The Stinger was initially selected over the AIM-9, but the U.S. Army is considering the Starstreak air-to-air missile instead. External fuel tanks can also be carried on the stub wings to increase range and mission time. The stub-wing pylons have mounting points which make maintenance easier; these mountings can be used to secure personnel to the wings for transport for emergencies. Stinger missiles are more used by non-U.S. Apaches because foreign forces don't have as many other aircraft for air superiority to control the skies.

United States Army
The U.S. Army formally accepted its first production AH-64A in January 1984 and training of the first pilots began later that year. The first operational Apache unit, 7th Battalion, 17th Cavalry Brigade, began training on the AH-64A in April 1986 at Fort Hood, Texas. Two operational units with 68 AH-64s first deployed to Europe in September 1987 and took part in large military exercises there. The Apache was first used in combat in 1989, during Operation Just Cause, the invasion of Panama. The AH-64 participated in over 240 hours of combat attacking various targets, mostly at night. General Carl Stiner, commander of Operation Just Cause, praised the Apache for its precision: "You could fire that Hellfire missile through a window from four miles away at night".



As the Army began fielding the Apache, capabilities such as use of the FLIR for extensive night-flight operations made it clear that the AH-64 was capable of traveling and fighting well beyond the forward line of own troops (FLOT) that previous attack helicopters were normally restricted to. In addition to deep-strike capabilities, it was discovered that the Apache had, not by any intention, been fitted with the same Have Quick UHF radio systems used by the U.S. Air Force; once this was recognized, inter-service coordination and joint operations such as the joint air attack teams (JAAT) were encouraged and inserted into standard training. The Apache operated extensively with close air support (CAS) aircraft such as the Fairchild Republic A-10 Thunderbolt II and the USMC's McDonnell Douglas AV-8B Harrier II, often acting as a target designator so the Apache could conserve its own munitions.

A year after the Panama operation, close to half of all U.S. Apaches were deployed to Saudi Arabia in response to Iraq's invasion of Kuwait. During Operation Desert Storm on 17 January 1991, eight AH-64As guided by four MH-53 Pave Low IIIs destroyed a portion of the Iraqi radar network; the first attack of Desert Storm, an act to allow attack aircraft into Iraq without detection. The Apaches carried an asymmetric load of Hydra 70 flechette rockets, Hellfires, and one auxiliary fuel tank each. During the 100-hour ground war a total of 277 AH-64s took part, destroying 278 tanks, numerous armored personnel carriers and other Iraqi vehicles. One AH-64 was lost in the war, to an RPG hit at close range, the Apache crashed but the crew survived. To maintain Apache operations with spare parts and equipment, during the Gulf War the U.S. Army unofficially grounded all other AH-64s worldwide; additionally Apaches in the war zone flew only one-fifth of the flight-hours the Army had planned for.

The AH-64 played roles in the Balkans during separate conflicts in Bosnia and Kosovo in the 1990s. During Task Force Hawk 24 Apaches were deployed to a land base in Albania in 1999 to participate in the Kosovo engagement; this required 26,000 tons of equipment to be transported and over 550 C-17 flights, at a cost of US$480 million. During these deployments the AH-64 encountered problems such as deficiencies in training, night vision equipment, fuel tanks, and survivability. On 27 April 1999 an Apache crashed during training in Albania due to a failure with the tail rotor, causing the entire fleet in the Balkans to be grounded in December 2000.

Major General Dick Cody, then the commanding officer of the 101st Airborne, wrote a strongly worded memo to the U.S. Army Chief of Staff about the failures in training and equipment. The Washington Post also dedicated a front-page article to the failures in Kosovo, commenting that: "The vaunted helicopters came to symbolise everything wrong with the Army as it enters the 21st century: Its inability to move quickly, its resistance to change, its obsession with casualties, its post-Cold War identity crisis". The Apache did not conduct any combat missions over Kosovo due to fears over the risk of casualties; in addition, none of the pilots were qualified to fly with night vision goggles, preventing nighttime operations.

U.S. Apaches have served in Operation Enduring Freedom in Afghanistan from 2001. The Apache was the only platform capable of providing accurate CAS duties for Operation Anaconda; although they regularly took fire during the intense early fighting, they were kept operational by their ground crews. American AH-64Ds typically flew in Afghanistan and Iraq without the Longbow Radar as there were no armored threats remaining. On 21 December 2009, a pair of American Apaches attacked a British-held base in a friendly fire incident, killing one British soldier.

The AH-64 took part in invasion of Iraq in 2003 during Operation Iraqi Freedom. In one engagement on 24 March 2003, 31 Apaches were damaged, and one Apache was shot down and captured by Iraqi troops near Karbala. The intended attack against an armored brigade of the Iraqi Republican Guard's Medina Division was unsuccessful. The tank crews had set up a "flak trap" among terrain and employed their guns to good effect. Iraqi officials claimed a farmer with a Brno rifle shot down the Apache, but the farmer denied involvement. The helicopter came down intact, and both the pilot and co-pilot were captured. The AH-64D was destroyed via air strike the following day.



Most Apache helicopters that have taken heavy combat damage have been able to continue their missions and return safely. In 2006, an Apache helicopter was downed by a Soviet-made Strela 2 (SA-7) in Iraq. The Apache is typically able to avoid hits by such missiles but in this instance it did not. The coordination of Apaches in the war was discussed by Thomas Adams, who noted the helicopters tended to fight in small teams but had little autonomy to react to local threats and opportunities, requiring lengthy dialogue with command structures in an effort to centrally micromanage each unit.

By the end of U.S. military operations in Iraq in December 2011, several Apache helicopters had been shot down by enemy fire during the Iraq War, with others lost in crashes. In 2007, four Apache helicopters were destroyed on the ground by Iraqi insurgent mortar fire; the insurgents had made use of embedded coordinates in web-published photographs (geotagging) taken of the helicopters by soldiers. As of 2012, several AH-64s have been lost to accidents in Afghanistan.

According to Boeing, the U.S. Army Apache fleet has accumulated more than 3 million flight hours since the first prototype aircraft flew in 1975. According to a DOD audit released in May 2011, Boeing had significantly overcharged the U.S. Army on multiple occasions, ranging from 33.3 percent to 177,475 percent for routine spare parts in helicopters like the Apache.

On 21 February 2013, the 1-229th Attack Reconnaissance Battalion at Joint Base Lewis-McChord became the first unit in the U.S. Army to field the AH-64E Apache Guardian. The battalion had received 8 helicopters since January, with a total of 24 to be received by April 2013.

Israel
The Israeli Air Force (IAF) first received AH-64As in 1990, for a total fleet of 42. There was some controversy over the Air Force's choice to purchase Apaches over upgrading existing AH-1 Cobra attack helicopters. In 2000, Israel was interested in acquiring up to 48 Apache AH-64Ds, but U.S. reluctance to share the software source code complicated the prospect. In April 2005, Boeing delivered the first AH-64D to the IAF. In 2009, an arranged sale of six AH-64Ds was reportedly blocked by the Obama Administration (pending interagency review) over concerns the helicopters may pose a threat to civilian Palestinians in Gaza. Also, in February 2001 reports emerged the U.S. government was investigating alleged misuse of the Apache and other US military equipment against Palestinian leaders and facilities.

In IAF service, the AH-64A was named as the Peten (פתן, for Cobra), while the AH-64D was named Saraph (שרף, also as "Seraph", Hebrew for venomous/fiery winged serpent).



The AH-64A was used frequently during the 1990s to attack and destroy Hezbollah outposts in Lebanon,  attacking in many weather conditions – day and night. On 13 April 1996, during Operation Grapes of Wrath, an Israeli Apache fired two Hellfire missiles at an ambulance in Lebanon, killing six civilians. During the al-Aqsa Intifada in 2000, the IAF used the AH-64 to kill senior Hamas figures, such as Ahmed Yassin and Adnan al-Ghoul, with guided missiles. On 24 May 2001, a privately owned Lebanese-registered Cessna 152 flew into Israeli airspace and was intercepted by two Israeli AH-64s, one of which shot down the Cessna with an AGM-114 Hellfire missile, killing the pilot. On 22 March 2004, an Israeli AH-64 used a Hellfire missile to kill Hamas leader Ahmed Yassin, also killing both his bodyguards and nine bystanders. IAF Apaches played a prominent role in the 2006 Lebanon War, launching strikes into Lebanon targeting Hezbollah forces.

There have also been accidents involving the Apache helicopter in Israeli service. During the Lebanon War in 2006, two IAF AH-64A helicopters collided, killing one pilot and critically wounding three. In another incident in the conflict an IAF AH-64D crashed due to a malfunction in the main rotor, killing the two crew. In late 2007, the Israeli Air Force put further purchases and deliveries of AH-64Ds on hold during an investigation upon the aircraft's performance envelope. However, Israeli officials have since praised the Apache for its role in Operation Cast Lead in 2008, against Hamas in Gaza.

In June 2010, Israel decided against upgrading its existing AH-64A to the -D configuration, due to budget restrictions. As of December 2010, the IAF was examining the adoption of a new missile system as a cheaper and lightweight complement to the Hellfire missile, either the American Hydra 70 or the Canadian CRV7. In recent years, Israeli Apaches have been used to patrol the skies over Gaza; strike operations against insurgents using these helicopters has become a frequent occurrence.

United Kingdom


The UK operates a modified version of the Apache Longbow initially called the Westland WAH-64 Apache, and is designated Apache AH1 by the British Army. Westland built 67 WAH-64 Apaches under license from Boeing, following a competition between the Eurocopter Tiger and the Apache for the British Army's new Attack Helicopter in 1995. Important deviations made by AgustaWestland from the U.S. Apache variants include changing to more powerful Rolls-Royce engines, and the addition of a folding blade assembly for use on naval ships.

The Netherlands


The Dutch government initially showed an interest in acquiring Apache helicopters in the late 1980s, where it stated that it may purchase as many as 52. A competition held in 1994 against the Eurocopter Tiger and the AH-1 SuperCobra led to the Royal Netherlands Air Force ordering 30 AH-64D Apaches in 1995. Construction for the order started in December 1997, deliveries began in 1999. The Apaches of the RNLAF are equipped with the Apache Modular Aircraft Survivability Equipment (AMASE) system. The AMASE is an advanced Electronic Warfare self-protection system against Infra-Red (IR) missile threats.

The RNLAF Apaches' first deployment was in 2001 to Djibouti, Africa. They were also deployed alongside U.S. AH-64s in support of NATO peacekeeping forces in Bosnia and Herzegovina. In 2004, six Dutch AH-64s were deployed as part of the Netherlands contribution to Multinational force in Iraq to support the Dutch ground forces. The Apaches performed close combat support and display of force missions, along with providing reconnaissance information to ground forces. 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.

Shortly after Apaches were deployed to Kabul airport as part of the Netherlands contribution to ISAF, on 10 April 2004 a pair of Dutch Apaches came under light gunfire close to the Afghan capital. On 17 December 2007, a RNLAF Apache flew into powerlines during a night flying exercise in the Netherlands, forcing an emergency landing and causing a lengthy blackout in the region.

Saudi Arabia
In the aftermath of the Gulf War of 1991, in which many U.S. Apaches operated from bases in Saudi territory, the government of Saudi Arabia purchased twelve AH-64As for its army. In the Middle East, Israel procured the Apache in response to the 1992 Saudi purchase.

In August 2006, the Saudi Arabian government began negotiations to spend as much as $400M on Apache upgrades, possibly remanufacturing them into the AH-64D Longbow configuration. In September 2008, the U.S. Government approved the purchase of twelve AH-64Ds requested by Saudi Arabia. In October 2010, Saudi Arabia requested a further 70 AH-64Ds as part of a possible, massive US-Saudi arms deal.

In November 2009, the Royal Saudi Air Force, as part of a military effort against insurgent intrusions of the kingdom's border, started using the Apache in Operation Scorched Earth; this involved launched air strikes against Houthi rebels operating inside neighboring Yemen as well. In January 2010 the rebels claimed to have shot down an Apache; this was denied by the Saudi military. In late January 2010, the leader of the Shiite rebels announced their withdrawal from Saudi territory, this announcement followed a key battle on 12 January when Saudi forces reportedly took control of the border village of Al Jabiri.

Egypt
In 1995, the Egyptian Air Force placed an order for 36 AH-64A helicopters. These Apaches were delivered with most of the advanced avionics used on the U.S. fleet at that time, with the exception of localized radio equipment. In 2000, Boeing announced that an order to remanufacture Egypt's existing Apache fleet to the AH-64D configuration. Notably, the AH-64D upgrade did not include the procurement of the Longbow radar, the supply of which had been refused by the U.S. government. Egypt requested a further 12 AH-64D Block II Apaches through a Foreign Military Sale in 2009.

In August 2012, the Egyptian Armed Forces undertook a large-scale military operation to regain control of the Sinai Peninsula from armed militants. Air cover throughout the operation was provided by the Egyptian Air Force's Apache helicopters; reportedly the Apaches destroyed three vehicles and killed at least 20 militants.

Other users


The United Arab Emirates purchased 30 AH-64A helicopters in 1991 and 1994, which they are now upgrading to AH-64D specification. In 2005 Kuwait purchased 16 Longbow helicopters.

In September 2003, Greece ordered 12 AH-64D in addition to existing fleet of 20 AH-64A+. By 1995 they had received 20 AH-64As; another 12 AH-64Ds were ordered in 2003. Singapore purchased 20 AH-64D Longbow Apache aircraft in two batches between 1999 and 2001; during October 2010 Apache training was suspended following the forced crash-landing of an Apache.

Japan ordered 50 AH-64Ds, which are being built under license by Fuji Heavy Industries, designated AH-64DJP. The first helicopter was delivered to the JGSDF in early 2006.

Future and possible users
In 2008, the Indian Air Force (IAF) released a tender for 22 attack helicopters; there were six contending submissions - Sikorsky's UH-60 Black Hawk, Boeing's AH-64D, Bell's AH-1 Super Cobra, Eurocopter's Tiger, Mil's Mi-28 and AugustaWestland's A129 Mangusta. Boeing and Bell initially backed out of the competition in October 2008. In 2009, the competition was restarted and Boeing submitted a new Apache proposal. In December 2010, India requested the possible sale of 22 AH-64Ds and associated equipment. In October 2011, it was reported that the AH-64D had emerged as front-runner ahead of the Russian Mi-28N. On 5 October 2012, IAF Chief NAK Browne confirmed that the AH-64D Block III had been selected. In October 2012, the Indian government transferred control of most attack and armed helicopters from the Indian Air Force to the Army Aviation Corps. In spite of the transfer, the Indian Air Force sought to maintain control of the 22 proposed Apaches, wanting the type for air combat missions; the Indian Army arguing that the AH-64s would be better used supporting army operations. In April 2013, the Indian Ministry of Defence (MoD) decided that the 22 AH-64s would go to the Indian Air Force due to the procurement being an ongoing acquisition. In May 2013, the Indian Army requested an acquisition of 11 AH-64Es for the Army Aviation Corps.

South Korea showed interest in acquiring Apache attack helicopters. This move may be related to U.S. plans to withdraw many of its Apaches from South Korea. On 21 September 2012, the U.S. Congress was notified of the possible purchase of 36 AH-64D Block III Apaches, along with associated equipment and armament. The Apache was competing against the Bell AH-1Z Viper and the TAI/AgustaWestland T-129 for the order; a decision was expected in late 2012. In April 2013, it was announced that South Korea is to purchase 36 AH-64E helicopters. The Apaches are to be delivered from 2016 to 2018.

The Republic of China (Taiwan) reached an agreement with the U.S. to purchase 30 AH-64D Block III Apaches with weapons, and associated equipment in June 2011. In February 2012, Indonesia's deputy minister of defense Sjafrie Sjamsoeddin stated that the Indonesian National Armed Forces plans to buy eight AH-64s. On 26 August 2013, the U.S. and Indonesia formalized a deal for 8 AH-64E Apaches worth $500 million. Qatar requested the sale of 24 AH-64D Apaches in July 2012, along with associated equipment and armament. Iraq requested the sale of 24 AH-64s, and is waiting for congressional approval.

AH-64A


The AH-64A is the original production attack helicopter. The crew sit in tandem in an armored compartment. It is powered by two GE T700 turboshaft engines. The A-model was equipped with the −701 engine version until 1990 when the engines were switched to the more powerful −701C version. The Japanese Apache variant is based on the AH-64A. Japan's AH-64DJP can also be equipped with the AIM-92 Stinger air-to-air missiles for defense.

U.S. Army AH-64As are being converted to AH-64Ds. The service's last AH-64A was taken out of service in July 2012 before conversion at Boeing's facility in Mesa, Arizona. On 25 September 2012, Boeing received a $136.8M contract to remanufacture the last 16 AH-64As into the AH-64D Block II version, to be completed by December 2013.

AH-64B
In 1991 after Operation Desert Storm, the AH-64B was a proposed upgrade to 254 AH-64As. The upgrade would have included new rotor blades, a Global Positioning System (GPS), improved navigation systems and new radios. Congress approved $82M to begin the Apache B upgrade. The B program was canceled in 1992. The radio, navigation, and GPS modifications, were later installed on most A-model Apaches through other upgrades.

AH-64C
Additional 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 −700C engine versions. However, the C designation was dropped after 1993. With AH-64As receiving the newer engine from 1990, 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; thus the decision was made to simply designate both versions AH-64D.

AH-64D


The AH-64D Apache Longbow, is equipped with an advanced sensor suite and a glass cockpit. The main improvement over the A-variant is the dome installed over the main rotor, housing the AN/APG-78 Longbow millimeter-wave fire-control radar (FCR) target acquisition system and the Radar Frequency Interferometer (RFI). The raised position of the radome enables the detection of targets and launching of missiles while the helicopter is behind obstacles (e.g. terrain, trees or buildings). The AN/APG-78 is capable of simultaneously tracking 128 targets and engaging the 16 most dangerous ones, and can initiate an attack within 30 seconds, while passing data on the other targets to other Longbow Apaches via data link. The data link is housed in a radio modem integrated with the sensor suite allows data to be shared with ground units and other D-models; allowing them to fire on targets detected by a single helicopter.

The aircraft is powered by a pair of uprated T700-GE-701C engines. The forward fuselage was expanded to accommodate new systems to improve survivability, navigation, and 'tactical internet' communications capabilities. The first of the upgraded Block II Apaches was delivered to the U.S. Army in February 2003. Block II includes upgrades to the digital communications systems.

AH-64E
Formerly known as AH-64D Block III, in October 2012 the type was redesignated AH-64E and received the name Guardian. The new designation represents the significantly increased capabilities of the upgrades featured. Full rate production was approved on 24 October 2012. AH-64E includes the following upgrades: improved digital connectivity, the joint tactical radio system, more powerful T700-GE-701D engines, an upgraded transmission with new split-torque face gears to accommodate more power, capability to control Unmanned aerial vehicle (UAVs), new composite rotor blades, full IFR capability, and improved landing gear. The new blades, which successfully completed flight testing in May 2004, increase cruise speed, climb rate, and payload capability. Deliveries began in November 2011. Changes in production lots 4 through 6 shall include a cognitive decision aiding system, new self-diagnostic abilities, Link-16 data-links, and radar improvements. The updated Longbow radar has an oversea capacity, potentially enabling naval strikes; an AESA radar is under consideration.

Sea Apache


Naval versions of the AH-64A for the United States Marine Corps and Navy were examined from 1984 to 1987. Multiple concepts were studied with altered landing gear arrangements, improved avionics and weapons. Funding for the naval version was not provided, and the Marine Corps has continued to use the AH-1. The Canadian Forces Maritime Command also examined the prospect of using a modified Apache in naval service. The British Army's AgustaWestland Apache went through trials in 2004 onboard HMS Ocean (L12) to test its suitability for use. The U.S. expressed interest in these trials. The British Army made extensive use of its Apaches during the 2011 military intervention in Libya, operating directly from HMS Ocean, a Landing Platform Helicopter of the Royal Navy. In the summer of 2013, AH-64Ds of the U.S. 36th Combat Aviation Brigade were tested on a variety of U.S. Navy ships. There are no plans for full deployment at sea, though.

Export Apaches
Several models have been derived from both AH-64A and AH-64D for export. The British-built AgustaWestland Apache (assembled from kits purchased from Boeing) is based on the AH-64D with several different systems, including more powerful engines, folding rotor blades, and other modifications for operation from Royal Navy vessels.

Block modification
While a major change in design or role will cause the type designator suffix to change, for example from AH-64D to AH-64E the helicopters are also subject to Block modification. Block modification is the combining of equipment changes into blocks of modification work orders, the modifications in the block (sometimes called a block package) are all done to the helicopter at the same time.

Operators



 * Egyptian Air Force - 35 AH-64Ds
 * Hellenic Army - 29
 * Indonesian Army - (8 on order)
 * Israeli Air Force - 45
 * Japan Ground Self-Defense Force - 10 AH-64Ds
 * Republic of Korea Army - (36 AH-64E on order)
 * Kuwait Air Force - 16 AH-64Ds
 * Royal Netherlands Air Force 29 AH-64Ds
 * Royal Saudi Land Forces - 12
 * Republic of Singapore Air Force - 19 AH-64Ds
 * Republic of China Army - (30 on order)
 * United Arab Emirates Air Force - 30 AH-64Ds
 * See AgustaWestland Apache
 * United States Army - 669
 * Royal Netherlands Air Force 29 AH-64Ds
 * Royal Saudi Land Forces - 12
 * Republic of Singapore Air Force - 19 AH-64Ds
 * Republic of China Army - (30 on order)
 * United Arab Emirates Air Force - 30 AH-64Ds
 * See AgustaWestland Apache
 * United States Army - 669
 * Republic of China Army - (30 on order)
 * United Arab Emirates Air Force - 30 AH-64Ds
 * See AgustaWestland Apache
 * United States Army - 669
 * See AgustaWestland Apache
 * United States Army - 669
 * United States Army - 669