Misplaced Pages

#698301

134-581: MIL-STD-1553 was first published as a U.S. Air Force standard in 1973, and first was used on the F-16 Falcon fighter aircraft. Other aircraft designs quickly followed, including the F/A-18 Hornet , AH-64 Apache , P-3C Orion , F-15 Eagle and F-20 Tigershark . It is widely used by all branches of the U.S. military and by NASA . Outside of the US it has been adopted by NATO as STANAG 3838 AVS . STANAG 3838, in

268-528: A thermographic camera that precisely locates muzzle flashes. In 2014, it was announced that new targeting and surveillance sensors were under development to provide high-resolution color imagery to crews, replacing older low definition black-and-white imaging systems. Lockheed received the first contract in January 2016, upgrading the Arrowhead turret to provide higher-resolution color imaging with longer ranges and

402-565: A "flak trap" among terrain and effectively employed their guns . Iraqi officials claimed a farmer with a Brno rifle shot down the Apache, but the farmer denied involvement. The AH-64 came down intact and the crew were captured ; it was destroyed via air strike the following day. This incident had significant consequences for the AH-64 helicopter because it revealed an important vulnerability. Despite being considered by army aviators as flying tanks at

536-459: A 1553 link with the capability to carry a 100 Mbps signal on the same wire without interfering with old signaling. The concept is similar to how ADSL avoids voice frequencies, but done at higher bandwidths. In addition to 1553B, it also runs over coax, twisted pair, Power-Line Carrier, and existing ARINC 429 links. DIGIBUS (or Digibus , GAM-T-101) is the French counterpart to MIL-STD-1553. It

670-532: A 1553 or 1773 link with additional high-speed 20 Mbps buses, either optical or electrical. In the STANAG form, the 1553/1773 low-speed link serves as the control channel for the high speed link. In the EFABus Express (EfEx) form, the high-speed link acts as its own control channel. Either way, high and low-speed buses share the same addressing model and can communicate with each other. STANAG 7221 (E1553) expands

804-453: A 2–10 kW beam with the diameter of a penny out to a range of 5.4 nmi (10.0 km; 6.2 mi). On the Apache, the laser could be used to destroy enemy communications or radio equipment. On 26 June 2017, the Army and Raytheon announced they had successfully completed the first-ever helicopter-based flight demonstration of a high energy laser system from an AH-64. On 14 July 2016, it

938-459: A BC that is external to the aircraft, but connected to the bus. Procedures for handover in fault and failure conditions generally involve discrete connections between the main and backup BCs, and the backup monitoring the actions of the main BC during operation. For example, if there is a prolonged quiescence on the bus indicating that the active BC has failed, the next highest priority backup BC, indicated by

1072-421: A DC component. Manchester coding's data rate is only half that of a non-coded signal, which limits its usefulness to systems where bandwidth is not an issue, such as a local area network (LAN) . Manchester encoding introduces difficult frequency-related problems that make it unsuitable for use at higher data rates. There are more complex codes, such as 8B/10B encoding , that use less bandwidth to achieve

1206-502: A Soviet-made Strela 2 (SA-7) in Iraq, despite it being typically able to avoid such missiles. In 2007, four Apaches were destroyed on the ground by insurgent mortar fire using web-published geotagged photographs taken by soldiers. Several AH-64s were lost to accidents in Afghanistan . Most Apaches that took heavy damage were able to continue their missions and return safely. By 2011,

1340-569: A bigger group of AH-64As. The results demonstrated the AH-64D to have a sevenfold increase in survivability and fourfold increase in lethality compared to the AH-64A. On 13 October 1995, full-scale production was approved; a $ 1.9-billion five-year contract was signed in August 1996 to upgrade 232 AH-64As into AH-64Ds. On 17 March 1997, the first production AH-64D flew. It was delivered on 31 March. Portions of

1474-424: A circular connector is used, its center pin is used for the high (positive) Manchester bi-phase signal. Transmitters and receivers couple to the bus via isolation transformers, and stub connections branch off using a pair of isolation resistors and, optionally, a coupling transformer. This reduces the impact of a short circuit and ensures that the bus does not conduct current through the aircraft. A Manchester code

SECTION 10

#1732852196699

1608-485: A close range rocket-propelled grenade (RPG) hit; the crew survived. While effective in combat, the AH-64 presented serious logistical difficulties. Findings reported in 1990 stated "maintenance units could not keep up with the Apache's unexpectedly high work load..." To provide spare parts for combat operations, the U.S. Army unofficially grounded all other AH-64s worldwide; Apaches in the theater flew only one-fifth of planned flight-hours. Such problems were evident before

1742-477: A crew of two. Nose-mounted sensors help acquire targets and provide night vision . It carries a 30 mm (1.18 in) M230 chain gun under its forward fuselage and four hardpoints on stub-wing pylons for armament and stores, typically AGM-114 Hellfire missiles and Hydra 70 rocket pods. Redundant systems help it survive combat damage. The Apache began as the Model 77 developed by Hughes Helicopters for

1876-539: A data bus providing a single data path between the Bus Controller and all the associated Remote Terminals. There may also be one or more Bus Monitors (BM); however, Bus Monitors are specifically not allowed to take part in data transfers, and are only used to capture or record data for analysis, etc. In redundant bus implementations, several data buses are used to provide more than one data path, i.e. dual redundant data bus, tri-redundant data bus, etc. All transmissions onto

2010-520: A fleet of 42 by 2000. The IAF's choice to buy Apaches over upgrading its AH-1 Cobra attack helicopters was controversial. In 2000, Israel was interested in acquiring up to 48 AH-64Ds, but U.S. reluctance to share the source code complicated the prospect. In April 2005, Boeing delivered the IAF's first AH-64D. In 2001, the U.S. government was allegedly investigating misuse of the Apache and other U.S.-supplied military equipment against Palestinians . In 2009,

2144-399: A function of the impedance presented by the stub and terminal input impedance. To minimize signal distortion, it is desirable that the stub maintain high impedance. This impedance is reflected back to the bus. At the same time, however, the impedance must be kept low so that adequate signal power will be delivered to the receiving end. Therefore, a tradeoff between these conflicting requirements

2278-407: A high–low signal sequence and a logic 1 is represented by a low–high signal sequence. If a Manchester encoded signal is inverted in communication, it is transformed from one convention to the other. This ambiguity can be overcome by using differential Manchester encoding . The existence of guaranteed transitions allows the signal to be self-clocking, and also allows the receiver to align correctly;

2412-467: 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 crew compartment also incorporates a transparent blast shield between the pilot and gunner seats so that at least one crew member can survive in the event of a direct hit, but the canopy and windows are otherwise unrated against ballistic threats. The aircraft

2546-462: A long-term plan for Leonardo and other UK companies to "do most of the work" on the new fleet. The deal included an initial support contract for maintenance, spare parts, and training simulators; components from the older WAH-64s "will be reused and incorporated into the new helicopters where possible." The type entered service with the British Army in 2022. Approval for the re-manufacture of fifty of

2680-515: A major frame or major cycle, which is often subdivided into minor cycles. In such a cyclic executive schedule structure, transfers that occur in every minor cycle (rate group 1) happen at the highest rate, typically 50 Hz, transfers that occur in every other minor cycle, of which there are two groups (rate group 2.1 and 2.2) happen at the next highest rate, e.g. 25 Hz. Similarly, there are four groups (3.1, 3.2, 3.3, and 3.4) at, e.g., 12.5 Hz and so on. Hence, where this scheduling structure

2814-664: A missile. The UK previously operated a modified version of the AH-64D Block I Apache Longbow; initially called the Westland WAH-64 Apache, it is designated the 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

SECTION 20

#1732852196699

2948-489: A prolonged legal dispute between Teledyne Ryan and Boeing. The AH-64D program cost a total of $ 11 billion (~$ 15.6 billion in 2023) through 2007. In April 2006, Boeing was awarded a $ 67.6 million (~$ 98.3 million in 2023) 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 into AH-64Ds. Since 2008, nations operating

3082-411: A prominent role in the 2006 Lebanon War , launching strikes into Lebanon targeting Hezbollah forces. IAF Apaches also attacked civilian targets, killing many, including women and children. During this war, two AH-64As collided, killing one pilot and critically wounding three. In another incident in the conflict, an IAF AH-64D crashed due to a main rotor malfunction, killing the two crew. In late 2007,

3216-495: A service ceiling of 21,000 feet (6,400 m). However, on a hot day, when temperatures are 70 °F (21 °C), its vertical rate of climb is reduced to 1,595 fpm (486 m/min), and service ceiling is reduced to 19,400 feet (5,900 m) due to less dense air. One of the revolutionary features of the Apache was its helmet mounted display , the Integrated Helmet and Display Sighting System (IHADSS); among its capabilities, either

3350-472: A single or multiple stub connections. These provide the required shielding (≥ 75 percent) and, for transformer coupled stubs, contain the coupling transformers and isolation resistors. They have two external connectors through which the bus feeds, and one or more external connectors to which the stub or stubs connect. These stub connectors should not be terminated with matching resistors, but left open circuit when not used, with blanking caps where necessary. One of

3484-469: A specific (transmit) sub-address (data buffer). The time at which this data is written to the sub-address is not necessarily linked to the time of the transaction, though the interfaces ensure that partially updated data is not transmitted. The Bus controller commands the RT that is the destination of the data (e.g. RT2) to receive the data at a specified (receive) data sub-address and then commands RT1 to transmit from

3618-999: A strongly worded memo to the Chief of Staff about training and equipment failures. Almost no pilots were qualified to fly with night vision goggles, preventing nighttime operations. The Washington Post printed a front-page article on the failures, commenting: "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". Although no Apache combat missions took place, two were lost in training exercises. An effective network of Yugoslav air defenses stopped Apaches from being deployed on combat missions in Kosovo. U.S. Apaches served in Operation Enduring Freedom in Afghanistan from 2001. It

3752-662: A target designator to conserve the Apache's own munitions. The Apache was first used in combat in 1989, during Operation Just Cause , the invasion of Panama . It participated in over 240 combat hours, attacking various targets, mostly at night. General Carl Stiner , the commander of the operation, stated: "You could fire that Hellfire missile through a window from four miles away at night." Nearly half of all U.S. Apaches were deployed to Saudi Arabia following Iraq 's invasion of Kuwait in 1990. During Operation Desert Storm on 17 January 1991, eight AH-64As guided by four MH-53 Pave Low IIIs destroyed part of Iraq's radar network in

3886-583: A valid command within 4–12 microseconds. In the example, the Response Time is 8.97 μs, therefore within specifications. This means that the Remote Terminal (RT) number 3 has responded to the Bus Controller query after 8.97 μs. The amplitude of the query is lower than the amplitude of the response because the signal is probed at a location closer to the Remote Terminal. In the Status Word, the first 5 bits are

4020-483: A valid command within 4–12 μs and are considered to not have received a command or message if no response has started within 14 μs. All communication on the bus is under the control of the Bus Controller using commands from the BC to the RTs to receive or transmit. The sequence of words, (the form of the notation is <originator>.<word_type(destination)> and is a notation similar to CSP ), for transfer of data from

4154-437: A value of 0.75 Zo ± 2.0 percent, where Zo is the characteristic impedance of the bus at 1 MHz. In a direct coupled stub, the length of stub cable should not exceed 1-foot, but again this may be exceeded if installation requirements dictate. The isolation resistors R have to have a fixed value of 55 ohms ± 2.0 percent. Stubs for RTs, the BC, or BMs, are generally connected to the bus through coupling boxes, which may provide

MIL-STD-1553 - Misplaced Pages Continue

4288-535: A wider field of view. In 2014, the U.S. Army was adapting its Apaches for increased maritime performance as part of the Pentagon's rebalance to the Pacific. Additional avionics and sensor improvements includes an extended-range radar capable of detecting small ships in littoral environments, software adaptions to handle maritime targets, and adding Link 16 data-links for better communications with friendly assets. The AH-64

4422-414: Is 18–27 V. The bus can be made dual or triply redundant by using several independent wire pairs, and then all devices are connected to all buses. There is provision to designate a new bus control computer in the event of a failure by the current master controller. Usually, the auxiliary flight control computer(s) monitor the master computer and aircraft sensors via the main data bus. A different version of

4556-516: Is adaptable to numerous different roles within its context as Close Combat Attack (CCA). In addition to the 30 mm M230E1 Chain Gun , the Apache carries a range of external stores and weapons on its stub-wing pylons, typically a mixture of AGM-114 Hellfire anti-tank missiles, and Hydra 70 general-purpose unguided 70 mm (2.756 in) rockets. The Hellfire is designed to defeat stationary or moving tanks as far away as 6,500 meters. Since 2005,

4690-480: Is built as follows. The first 5 bits are the Remote Terminal address (0–31). The sixth bit is 0 for Receive or 1 for Transmit. The next 5 bits indicate the location (sub-address) to hold or get data on the Terminal (1–30). Note that sub-addresses 0 and 31 are reserved for Mode Codes. The last 5 bits indicate the number of words to expect (1–32). All zero bits indicate 32 words. In the case of a Mode Code, these bits indicate

4824-420: Is equal to the average rise time of a 1553B signal. According to MIL-HDBK-1553A, when a signal's propagation delay time is more than 50% of the rise or fall time, it is necessary to consider transmission line effects. This delay time is proportional to the distance propagated. Also, consideration must be given to the actual distance between the transmitter and receiver, and the individual waveform characteristics of

4958-449: Is even more critical in new composite aircraft where the skin of the aircraft no longer provides an inherent Faraday shield as was the case with aluminum skinned aircraft. In a transformer coupled stub, the length of the stub cable should not exceed 20 feet (6.1 m), but this may be exceeded "if installation requirements dictate." The coupling transformer has to have a turns ratio of 1:1.41 ± 3.0 percent. The resistors R both have to have

5092-620: Is intended for design verification of Remote Terminals designed to meet the requirements of AS 15531 and MIL-STD-1553B with Notice 2. This test plan was initially defined in MIL-HDBK-1553, Appendix A . It was updated in MIL-HDBK-1553A, Section 100 . The test plan is maintained by the SAE AS-1A Avionic Networks Subcommittee as AS4111 . The RT Production Test Plan is a simplified subset of the validation test plan and

5226-464: Is intended for production testing of Remote Terminals. This test plan is maintained by the SAE AS-1A Avionic Networks Subcommittee as AS4112 . The bus hardware encompasses (1) cabling, (2) bus couplers, (3) terminators and (4) connectors. The industry has standardized the cable type as a twinax cable with a characteristic impedance of 78 ohms , which is almost the midpoint of the specification range of 70 to 85 ohms. MIL-STD-1553B does not specify

5360-486: Is necessary to achieve the specified signal-to-noise ratio and system error rate performance (for more information, refer to MIL-HDBK-1553A). Each terminal, RT, BC, or BM, is connected to the bus through a stub, formed of a length of cable of the same type as the bus itself. MIL-STD-1553B defines two ways of coupling these stubs to the bus: transformer coupled stubs and direct coupled stubs. Transformer coupled stubs are preferred for their fault tolerance and better matching to

5494-514: Is not defined in the standard, so the system designers must specify what values from what RTs mean what action the Bus Controller is to take. This may be to schedule an acyclic transfer either immediately or at the end of the current minor cycle. This means that the Bus Controller has to poll all the Remote Terminals connected to the data bus, generally at least once in a major cycle. RTs with higher-priority functions (for example, those operating

MIL-STD-1553 - Misplaced Pages Continue

5628-487: Is performed under the Aerial Weapons Scoring System Integration with Longbow Apache Tactical Engagement Simulation System (AWSS-LBA TESS), using live 30 mm and rocket ammunition as well as simulated Hellfire missiles. The Smart Onboard Data Interface Module (SMODIM) transmits Apache data to an AWSS ground station for gunnery evaluation. The AH-64's standard of performance for aerial gunnery

5762-418: Is similar to MIL-STD-1553 in the same notion of Bus Controller, Remote Terminal, monitor, same transmission speed, but the difference is that DIGIBUS uses separate links for data and commands. Boeing AH-64 Apache The Boeing AH-64 Apache ( / ə ˈ p æ tʃ i / ə- PATCH -ee ) is an American twin- turboshaft attack helicopter with a tailwheel-type landing gear and a tandem cockpit for

5896-465: Is still used in consumer IR protocols, RFID and near-field communication . It was and still is used for uploading commands to the Voyager spacecraft . Manchester coding is a special case of binary phase-shift keying (BPSK), where the data controls the phase of a square wave carrier whose frequency is the data rate. Manchester code ensures frequent line voltage transitions, directly proportional to

6030-558: Is the last revision made in February 2018. Revision C is functionally equivalent to Revision B but contains updated graphics and tables to ease readability of the standard. The MIL-STD-1553 standard is maintained by both the U.S. Department of Defense and the Aerospace branch of the Society of Automotive Engineers . A single bus consists of a wire pair with 70–85 Ω impedance at 1 MHz. Where

6164-566: Is to achieve at least 1 hit for every 30 shots fired at a wheeled vehicle at a range of 800–1,200 m (870–1,310 yd). The AH-64 was designed to perform in front-line environments, and to operate at night or day and during adverse weather conditions. Various sensors and onboard avionics allows the Apache to perform in these conditions; such systems include the Target Acquisition and Designation System, Pilot Night Vision System (TADS/PNVS), passive infrared countermeasures , GPS , and

6298-412: Is used to present both clock and data on the same wire pair and to eliminate any DC component in the signal (which cannot pass the transformers). The bit rate is 1.0 megabit per second (1-bit per μs ). The combined accuracy and long-term stability of the bit rate is only specified to be within ±0.1%; the short-term clock stability must be within ±0.01%. The peak-to-peak output voltage of a transmitter

6432-441: Is used, the transfers are all at harmonically related frequencies, e.g. 50, 25, 12.5, 6.25, 3.125, and 1.5625 Hz (for a major frame comprising 32 minor cycles at 50 Hz). Whilst RTs cannot start a transfer directly on their own, the standard does include a method for when an RT needs to transmit data that is not automatically scheduled by the Bus Controller. These transfers are often called acyclic transfers as they are outside

6566-682: The AGM-122 Sidearm anti-radiation missile were evaluated for use upon the AH-64. The Stinger was initially selected; the U.S. Army was also considering the Starstreak air-to-air missile. External fuel tanks can also be carried on the stub wings to increase range and mission time. The stub-wing pylons have mounting points for maintenance access; these mountings can also be used to secure personnel externally for emergency transport. Stinger missiles are often used on non-U.S. Apaches, as foreign forces do not have as many air superiority aircraft to control

6700-493: The Future Vertical Lift Capability Set 3 (medium rotorcraft) without the attack requirement, while the U.S. Army's FARA should replace the retired Bell OH-58 Kiowa scout and up to half of the AH-64 fleet. 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 co-pilot/gunner. Both crew members are capable of flying

6834-610: The 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 Hamid Karzai International Airport , as part of

SECTION 50

#1732852196699

6968-842: The United Arab Emirates . It has been built under license in the United Kingdom as the AgustaWestland Apache . American AH-64s have served in conflicts in Panama , the Persian Gulf , Kosovo , Afghanistan , and Iraq . Israel uses the Apache to fight in Lebanon and the Gaza Strip . British and Dutch Apaches were deployed to wars in Afghanistan and Iraq in 2001. After the AH-56 Cheyenne

7102-727: The United States Army 's Advanced Attack Helicopter program to replace the AH-1 Cobra . The prototype YAH-64 first flew 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 acquiring 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

7236-510: The University of Manchester , where the coding was used for storing data on the magnetic drums of the Manchester Mark 1 computer. Manchester code was widely used for magnetic recording on 1600 bpi computer tapes before the introduction of 6250 bpi tapes which used the more efficient group-coded recording . Manchester code was used in early Ethernet physical layer standards and

7370-443: The al-Aqsa Intifada in the 2000s, AH-64s were used to kill senior Hamas figures, such as Ahmed Yassin , Abdel Aziz al-Rantisi , and Adnan al-Ghoul . Human Rights Watch documented instances of IAF Apaches attacking civilian homes during the 2002 Jenin operation , killing one civilian. Consequently, HRW urged the US government to seek written assurances from Israel that Apaches would not be used to violate humanitarian law in

7504-467: The 1553 data bus. However, recording all of the transactions on a busy data bus might be impractical, so a BM is often configured to record a subset of the transactions, based on some criteria provided by the application program. Alternatively, a BM is used in conjunction with a Backup Bus Controller. This allows the Backup Bus Controller to "hit the ground running", if it is called upon to become

7638-547: The 1553B was to provide flexibility without creating new designs for each new user. This was accomplished by specifying the electrical interfaces explicitly so that electrical compatibility between designs by different manufacturers could be assured. Six change notices to the standard have been published since 1978. For example, change notice 2 in 1986 changed the title of the document from "Aircraft internal time division command/response multiplex data bus" to "Digital time division command/response multiplex data bus". MIL-STD-1553C

7772-572: The AH-64 to scout would be less expensive than Kiowa upgrades or purchasing a new scout helicopter. AH-64Es can control UAVs like the MQ-1C Grey Eagle to perform aerial scouting missions; a 2010 study found the teaming of Apaches and UAVs was the most cost-effective alternative to a new helicopter and would meet 80 percent of reconnaissance requirements, compared to 20 percent with existing OH-58s and 50 percent with upgraded OH-58s. National Guard units, who would lose their attack helicopters, criticized

7906-532: 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. Upon fielding the Apache, capabilities such as the FLIR's use in extensive night operations made it clear that it was capable of operating beyond the forward line of own troops (FLOT) to which previous attack helicopters were normally restricted. It

8040-577: The AH-64E accumulating 11,000 flight hours, each helicopter averaging 66 hours per month. The AH-64E flies 20 mph (32 km/h) faster than the AH-64D, cutting response time by 57 percent, and has better fuel efficiency , increasing time on station from 2.5–3 hours to 3–3.5 hours; Taliban forces were reportedly surprised by the AH-64E attacking sooner and for longer periods. AH-64Es also worked with medium and large unmanned aerial vehicles (UAVs) to find targets and maintain positive ID, conducting 60 percent of

8174-557: The AH-64E models. The Dutch government initially showed an interest in acquiring Apache helicopters in the late 1980s, when it stated that it may purchase as many as 52. A competition held in 1994 against the Eurocopter Tiger and the Bell AH-1 SuperCobra led to the Royal Netherlands Air Force ordering 30 AH-64D Apaches in 1995. Deliveries began in 1998 and ended in 2002. The RNLAF Apaches are equipped with

SECTION 60

#1732852196699

8308-538: The Apache Modular Aircraft Survivability Equipment (AMASE) self-protection system to counter infrared (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

8442-487: The Apache are produced by other aerospace firms. AgustaWestland has produced a number of components for the Apache both for the international market and for the British Army 's AgustaWestland Apache . Since 2004, Korea Aerospace Industries has been the sole manufacturer of the Apache's fuselage. Fuselage production had previously been performed by Teledyne Ryan Aeronautical . The transfer of fuselage production led to

8576-413: The BC to a terminal is and for terminal to terminal communication is This means that during a transfer, all communication is started by the Bus Controller, and a terminal device cannot start a data transfer on its own. In the case of an RT to RT transfer the sequence is as follows: An application or function in the subsystem behind the RT interface (e.g. RT1) writes the data that is to be transmitted into

8710-540: The Composite Structures Division of Alcoa Composites, were added to the list. The steel-composite rotors could not meet the Army specification for a life of 1500 flight hours, and needed replacement after just 146 hours. After six changes to the design, the rotor blade life was extended to 1400 hours by early 1991. During the 1980s, McDonnell Douglas studied an AH-64B, featuring an updated cockpit, new fire control system and other upgrades. In 1988, funding

8844-501: The Dutch contribution to ISAF, on 10 April 2004, a pair of Dutch Apaches came under light gunfire close to Kabul . On 17 December 2007, an RNLAF Apache flew into power lines during a night flying exercise in the Netherlands, forcing an emergency landing and causing a lengthy blackout in the region. On 17 March 2015, a RNLAF Apache crashed during a training mission in Mali. Both pilots died. The Ministry of Defence opened an investigation into

8978-730: The Gulf War. 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 for combat in Kosovo. These required 26,000 tons of equipment to be transported 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. In 2000, Major General Dick Cody , 101st Airborne's commanding officer, wrote

9112-515: The Hellfire missile outfitted with a thermobaric warhead is designated AGM-114N; this missile version is intended for use against ground forces and urban warfare operations. In October 2015, the U.S. Army ordered its first batch of Advanced Precision Kill Weapon System (APKWS) guided 70 mm rockets for the Apache. Starting in the 1980s, the Stinger and AIM-9 Sidewinder air-to-air missiles and

9246-485: The Hellfire. The latest AH-64D-I integrates Israeli systems such as Elta communications suite, Elbit mission management system, Rafael Combat Net system and Elisra self-protection suite. IAF AH-64s occasionally saw use in the air-to-air role. The first operational air-to-air kill took place on 24 May 2001, when an IAF shot down a Lebanese civilian Cessna 152 aircraft. Israeli and Lebanese officials presented differing versions: Lebanon said Israel first intercepted

9380-715: The IAF put further purchases and deliveries of AH-64Ds on hold while its performance envelope was investigated. Israeli officials praised the Apache for its role in Operation Cast Lead in 2008, against Hamas in Gaza . IAF Apaches have often patrolled the skies over Gaza; strikes against insurgents by these helicopters has become a frequent occurrence. In the 2010s, the IAF pursued upgrades to its AH-64A fleet as new AH-64D orders had been blocked. In June 2010, Israel decided not to upgrade all AH-64As to AH-64Ds due to funding constraints and lack of U.S. cooperation. In December 2010,

9514-600: 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 . By 2013, IAF AH-64As were receiving a comprehensive upgrade of their avionics and electrical systems. The AH-64As are being upgraded to the AH-64Ai configuration, which is near the AH-64D standard. IAF Apaches can carry Spike anti-tank missiles instead of

9648-535: The IHADSS. Longbow-equipped Apaches can locate up to 256 targets simultaneously within 50 km (31 mi). In August 2012, 24 U.S. Army AH-64Ds were equipped with the Ground Fire Acquisition System (GFAS), which detects and targets ground-based weapons fire sources in all-light conditions and with a 120° visual field . The GFAS consists of two sensor pods working with the AH-64's other sensors, and

9782-651: The Iraqi Army's Mosul offensive and provided support during the Battle of Mosul , sometimes flying night missions supporting Iraqi operations. In December 2019, two Apaches provided overwatch for U.S. Marines to secure the U.S. embassy in Baghdad, Iraq after armed militants, supported by Iran, attempted to storm the facility. In March 2024, two Apache crashes within two days increased scrutiny and made national news. The Israeli Air Force (IAF) first received AH-64As in 1990, for

9916-517: The Longbow Radar in the absence of armored threats. On 21 December 2009, a pair of U.S. Apaches attacked a British-held base in a friendly fire incident, killing one British soldier. In 2003, the AH-64 participated in the invasion of Iraq during Operation Iraqi Freedom . On 24 March 2003, 31 Apaches were damaged; one was shot down in an unsuccessful attack on an Iraqi Republican Guard armored brigade near Karbala . Iraqi tank crews had set up

10050-519: The Mode Code number (e.g., Initiate Self Test and Transmit BIT Word). The Status Word decodes as follows. The first 5 bits are the address of the Remote Terminal that is responding. The rest of the word is single bit condition codes, with some bits reserved. A 'one' state indicates condition is true. More than one condition may be true at the same time. The image below exemplifies many of the protocol and physical layer concepts explained above. For example,

10184-457: The RT address contained in the Command Word has a value of 0x3 (in range of 0 to 31). The sixth bit is 1, indicating a Transmit from the RT. The sub-address is 0x01. The last 5 bits indicate the number of words to expect, which has a value of 1, which is matched by the single Data Word (value 0x2) after the Status Word. Also as explained above, devices have to start transmitting their response to

10318-575: 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. On 11 July 2016, the Ministry of Defence confirmed a U.S. Foreign Military Sale (FMS) worth $ 2.3 billion (~$ 2.86 billion in 2023) for 50 AH-64Es to be built in Mesa, Arizona. Leonardo Helicopters in the UK will maintain the current fleet of Apaches until 2023–2024, with

10452-471: The U.S. Army Apache fleet had accumulated more than 3 million flight hours since the first prototype flew in 1975. A DOD audit released in May 2011 found that Boeing had frequently overcharged the U.S. Army for routine spare parts in helicopters like the Apache, ranging from 33.3 percent to 177,475 percent. On 21 February 2013, the 1st Battalion (Attack), 229th Aviation Regiment at Joint Base Lewis–McChord became

10586-473: 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 (1,260  kW ). The AH-64 was named the Apache in late 1981, after the Apache tribe, following the tradition of naming Army helicopters after Native American tribes. It was approved for full-scale production in 1982. In 1983,

10720-416: 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

10854-456: The UAV's armaments; and LOI 4 takes over flight control. UAVs can search for enemies and, if equipped with a laser designator , target them for the Apache or other friendly aircraft. Boeing has suggested that the AH-64 could be fitted with a directed energy weapon . The company has developed a small laser weapon, initially designed to engage small UAVs, that uses a high-resolution telescope to direct

10988-690: The UK's WAH-64 Mk 1 fleet to AH-64E Apache Guardian standard was given by the Defense Security Cooperation Agency in August 2015. They utilize the General Electric T700 engine rather than the Turbomeca RTM322 of the WAH-64; the first off-the-shelf purchase of a GE engine by the Ministry of Defence. The first two AH-64Es were delivered to the British Army on 26 November 2020. The older AH1 (WAH-64) were retired by 2024 in favour of

11122-499: The active Bus Controller. A Remote Terminal can be used to provide: For example, in a tracked vehicle, a Remote Terminal might acquire data from an inertial navigational subsystem, and send that data over a 1553 data bus to another Remote Terminal, for display on a crew instrument. Simpler examples of Remote Terminals might be interfaces that switch on the headlights, the landing lights, or the annunciators in an aircraft. Test Plans for Remote Terminals: The RT Validation Test Plan

11256-437: The address of the Remote Terminal that is responding, in this case 0x3. A correct Transfer exhibits the same RT address in the Command Word as in the Status Word. Figure 1 shows a sample MIL-STD-1553B system that consists of: There is only one Bus Controller at a time on any MIL-STD-1553 bus. It initiates all message communication over the bus. Figure 1 shows 1553 data bus details: The 1553B spec dictates that all devices in

11390-577: 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 . 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 and rotor blades are designed to sustain

11524-432: The aircraft control surfaces) are polled more frequently. Lower-priority functions are polled less frequently. Six types of transactions are allowed between the BC and a specific RT or between the Bus Controller and a pair of RTs: MIL-STD-1553B also introduced the concept of optional broadcast transfers, in which data is sent to all RTs that implement the option, but to which no RTs respond, as this would cause conflicts on

11658-487: The aircraft over Lebanese airspace and its pilot, flying without his instructor, mistakenly entered Israeli airspace, while Israel says the aircraft was already in Israeli airspace when it was intercepted and repeatedly refused to answer or comply with air traffic control (ATC) warnings. The second air-to-air kill occurred on 10 February 2018, after an Iranian UAV entered Israeli airspace from Syria, an AH-64 destroyed it with

11792-418: The bus connectors may be terminated where the bus coupler is physically at the end of the bus cable, i.e. it is not normally considered essential to have a length of bus cable between the last bus coupler and the termination resistor. Both ends of the bus, whether it includes one coupler or a series of couplers connected together, must be terminated (in accordance with MIL-STD-1553B) with "a resistance, equal to

11926-428: The bus uses optical fiber , which weighs less and has better resistance to electromagnetic interference, including EMP . This is known as MIL-STD-1773. NASA's "AS 1773" experiment has a dual rate of 1 Mbit/s or 20 Mbit/s – probably a predecessor of STANAG 3910 . A MIL-STD-1553 multiplex data bus system consists of a Bus Controller (BC) controlling multiple Remote Terminals (RT) all connected together by

12060-442: The bus. These can be used where the same data is sent to multiple RTs, to reduce the number of transactions and thus reduce the loading on the data bus. However, the lack of explicit responses by the RTs receiving these broadcasts means that these transfers cannot be automatically re-tried in the event of an error in the transaction. Four types of broadcast transactions are allowed between the BC and all capable RTs: The Command Word

12194-486: The cause of the crash. Manchester code In telecommunications and data storage , Manchester code (also known as phase encoding , or PE ) is a line code in which the encoding of each data bit is either low then high, or high then low, for equal time. It is a self-clocking signal with no DC component . Consequently, electrical connections using a Manchester code are easily galvanically isolated . Manchester code derives its name from its development at

12328-407: The clock rate; this helps clock recovery . The DC component of the encoded signal is not dependent on the data and therefore carries no information. Therefore connections may be inductively or capacitively coupled, allowing the signal to be conveyed conveniently by galvanically isolated media (e.g., Ethernet) using a network isolator —a simple one-to-one pulse transformer which cannot convey

12462-420: The data bus are accessible to the BC and all connected RTs. Messages consist of one or more 16-bit words (command, data, or status). The 16 bits comprising each word are transmitted using Manchester code , where each bit is transmitted as a 0.5 μs high and 0.5 μs low for a logical 1 or a low-high sequence for a logical 0 . Each word is preceded by a 3 μs sync pulse (1.5 μs low plus 1.5 μs high for data words and

12596-439: The data has been received and that the result of the data transfer is acceptable. It is this sequence that gives MIL-STD-1553 its high integrity. However, the standard does not specify any particular timing for any particular transfer — that's up to the system designers. Generally (the way it is done on most military aircraft), the Bus Controller has a schedule of transfers that covers the majority of transfers, often organized into

12730-417: The discrete connections, will take over and begin operating as the active BC. A Bus Monitor (BM) cannot transmit messages over the data bus. Its primary role is to monitor and record bus transactions, without interfering with the operation of the Bus Controller or the RTs. These recorded bus transactions can then be stored, for later off-line analysis. Ideally, a BM captures and records all messages sent over

12864-420: The earlier 1975 specification MIL-STD-1553A, was published in 1978. The basic difference between the 1553A and 1553B revisions is that in the latter, the options are defined rather than being left for the user to define as required. It was found that when the standard did not define an item, there was no coordination in its use. Hardware and software had to be redesigned for each new application. The primary goal of

12998-586: The first U.S. Army unit to field the AH-64E Apache Guardian; a total of 24 AH-64E were received by mid-2013. On 27 November 2013, the AH-64E achieved initial operating capability (IOC). In March 2014, the 1st–229th Attack Reconnaissance Battalion deployed 24 AH-64Es to Afghanistan in the type's first combat deployment. From April through September 2014, AH-64Es in combat maintained an 88 percent readiness rate. The unit's deployment ended in November 2014, with

13132-408: The first half of the bit period, and a high level in the second half. For a 1 bit the signal levels will be high–low. This is also known as Manchester II or Biphase-L code. The second convention is also followed by numerous authors (e.g., William Stallings ) as well as by IEEE 802.4 (token bus) and lower speed versions of IEEE 802.3 (Ethernet) standards. It states that a logic 0 is represented by

13266-407: 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 (equivalent to $ 1,378,000,000 in 2023). 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

13400-547: The form of UK MoD Def-Stan 00-18 Part 2, is used on the Panavia Tornado ; BAE Systems Hawk (Mk 100 and later); and extensively, together with STANAG 3910 "EFABus", on the Eurofighter Typhoon . Saab JAS 39 Gripen uses MIL-STD-1553B. The Russian made MiG-35 also uses MIL-STD-1553. MIL-STD-1553 is being replaced on some newer U.S. designs by IEEE 1394 (commonly known as FireWire). MIL-STD-1553B , which superseded

13534-444: The future. In 2004, Israeli AH-64s carried out the assassination of Ahmed Yassin and also killed 7 bystanders. Ahmed Yassin was the spiritual leader of Hamas; given that he was also blind, paraplegic and in a wheelchair , Palestinians saw the killing as "a cowardly execution of a frail old man in a wheelchair who did not attempt to hide". The attack also killed 7 bystanders, and was internationally condemned. IAF Apaches played

13668-505: 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. In 1981, three pre-production AH-64As were handed over to

13802-519: The impedance of the bus, and consequent reduction in reflections, etc. The appendix to MIL-STD-1553B (in section 10.5, Stubbing) states "The preferred method of stubbing is to use transformer coupled stubs… This method provides the benefits of DC isolation, increased common mode rejection, a doubling of effective stub impedance, and fault isolation for the entire stub and terminal. Direct coupled stubs… should be avoided if at all possible. Direct coupled stubs provide no DC isolation or common mode rejection for

13936-403: The length of the cable. However, the maximum length of cable is directly related to the gauge of the cable conductor and time delay of the transmitted signal. A smaller conductor attenuates the signal more than a larger conductor. Typical propagation delay for a 1553B cable is 1.6 nanoseconds per foot. Thus, the end-to-end 100-foot bus (30 m) would have a 160 nanosecond propagation delay, which

14070-607: 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 the Advanced Attack Helicopter (AAH) program on 15 November 1972. As a sign of the importance of this project, in September 1973 the Army designated its five most important projects as the "Big Five", with the AAH included. Proposals were submitted by Bell , Boeing Vertol / Grumman team, Hughes , Lockheed , and Sikorsky . In July 1973,

14204-426: The older Apaches have been urged to undertake modernization programs as support for the AH-64A is withdrawn. By May 2019, Boeing tested in a wind tunnel a compound Apache scale model with a pusher propeller , a small wing to increase range and speed, and a counter-torque tail rotor like the cancelled Lockheed AH-56 Cheyenne of the 1960s. It competed for the U.S. Army's FLRAA unveiled in April, developed from

14338-414: The operation's first attack, allowing the attack aircraft to evade detection. Each Apache carried an asymmetric load of Hydra 70 rockets, Hellfires, and one auxiliary fuel tank. 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, for a total of over 500 kills. One AH-64 was lost in the war, crashing after

14472-603: The opposite for command and status words, which cannot occur in the Manchester code) and followed by an odd parity bit . Practically each word could be considered as a 20-bit word: 3-bit for sync, 16-bit for payload and 1-bit for odd parity control. The words within a message are transmitted contiguously and there has to be a minimum of a 4 μs gap between messages. However, this inter-message gap can be, and often is, much larger than 4 μs, even up to 1 ms with some older Bus Controllers. Devices have to start transmitting their response to

14606-515: The pilot or gunner can slave the helicopter's 30 mm automatic M230 Chain Gun to their helmet, making the gun track head movements to point where they look. The M230E1 can be alternatively fixed to a locked forward firing position, or controlled via the Target Acquisition and Designation System (TADS). On more modern AH-64s, the TADS/PNVS has been replaced by Lockheed Martin 's Arrowhead (MTADS) targeting system. U.S. Army engagement training

14740-646: The proposal. In March 2015, the first heavy attack reconnaissance unit was formed with 24 Apaches and 12 Shadow UAVs. In July 2014, the Pentagon announced that Apaches had been dispatched to Baghdad to protect embassy personnel from Islamic State militant attacks. On 4 October 2014, Apaches began performing missions in Operation Inherent Resolve against Islamic State ground forces. In October 2014, U.S. Army AH-64s and Air Force fighters participated in four air strikes on Islamic State units northeast of Fallujah. In June 2016, Apaches were used in support of

14874-453: The receiver can identify if it is misaligned by half a bit period, as there will no longer always be a transition during each bit period. The price of these benefits is a doubling of the bandwidth requirement compared to simpler NRZ coding schemes. Encoding conventions are as follows: [REDACTED]  This article incorporates public domain material from Federal Standard 1037C . General Services Administration . Archived from

15008-753: The sale of six AH-64Ds was reportedly blocked by the Obama Administration, pending interagency review, over concerns they may pose a threat to civilian Palestinians in Gaza. In IAF service, the AH-64A was named Peten ( Hebrew : פתן , for Cobra ), while the AH-64D was named Saraph ( Hebrew : שרף , for venomous/fiery winged serpent). During the 1990s, Israeli AH-64As frequently attacked Hezbollah outposts in Lebanon . On 13 April 1996, during Operation Grapes of Wrath , an Apache fired two Hellfire missiles at an ambulance in Lebanon , killing six civilians. During

15142-459: The same data rate but may be less tolerant of frequency errors and jitter in the transmitter and receiver reference clocks. Manchester code always has a transition at the middle of each bit period and may (depending on the information to be transmitted) have a transition at the start of the period also. The direction of the mid-bit transition indicates the data. Transitions at the period boundaries do not carry information. They exist only to place

15276-805: The selected cable nominal characteristic impedance (Zo) ± 2.0 percent." This is typically 78 ohms. The purpose of electrical termination is to minimize the effects of signal reflections that can cause waveform distortion. If terminations are not used, the communications signal can be compromised causing disruption or intermittent communications failures. The standard does not specify the connector types or how they should be wired, other than shielding requirements, etc. In lab environments concentric twinax bayonet style connectors are commonly used. These connectors are available in standard ( BNC size), miniature and sub-miniature sizes. In military aircraft implementations, MIL-DTL-5015 and MIL-DTL-38999 circular connectors are generally used. STANAG 3910 (EFABus) mates

15410-403: The signal in the correct state to allow the mid-bit transition. There are two opposing conventions for the representations of data. The first of these was first published by G. E. Thomas in 1949 and is followed by numerous authors (e.g., Andy Tanenbaum ). It specifies that for a 0 bit the signal levels will be low–high (assuming an amplitude physical encoding of the data) – with a low level in

15544-767: The skies. The AH-64E initially lacked the ability to use the Stinger to make room for self-defense equipment, but the capability was added back following a South Korean demand. The AH-64E is able to control unmanned aerial vehicles (UAVs), used by the U.S. Army to perform aerial scouting missions previously performed by the OH-58 Kiowa . Apaches can request to take control of an RQ-7 Shadow or MQ-1C Grey Eagle from ground control stations to safely scout via datalink communications. There are four levels of UAV interoperability (LOI): LOI 1 indirectly receives payload data; LOI 2 receives payload data through direct communication; LOI 3 deploys

15678-413: The status word, the Bus Controller may retry the transmission. Several options are available for such retries including an immediate retry (on the other data bus of a redundant pair of data buses) and a retry later (on the same bus) in the sequence of transfers. The sequences ensure that the terminal is functioning and able to receive data. The status word at the end of a data transfer sequence ensures that

15812-504: The structure used by the cyclic executive. In this sequence, an RT requests transmission through a bit in the status word, the Service Request bit. Generally, this causes the Bus Controller to transmit a Transmit Vector Word Mode Code command. However, where an RT only has one possible acyclic transfer, the Bus Controller can skip this part. The vector word is transmitted by the RT as a single 16-bit data word. The format of this vector word

15946-425: The subsystem behind the receiving RT interface may then access the data. Again the timing of this read is not necessarily linked to that of the transfer. The Bus Controller receives RT2's status word and sees that the receive command and data have been received and actioned without a problem. If, however, either RT fails to send its status or the expected data or indicates a problem through the setting of error bits in

16080-541: The system be connected to a redundant pair of buses to provide an alternate data path in the event of damage or failure of the primary bus. Bus messages only travel on one bus at a time, determined by the Bus Controller. While there may be only one BC on the bus at any one time, the standard provides a mechanism for handover to a Backup Bus Controller (BBC) or (BUBC), using flags in the status word and Mode Codes. This may be used in normal operation where handover occurs because of some specific function, e.g. handover to or from

16214-496: The terminal external to its subsystem. Further, any shorting fault between the subsystems [sic] internal isolation resistors (usually on a circuit board) and the main bus junction will cause failure of that entire bus. It can be expected that when the direct coupled stub length exceeds 1.6 feet (0.49 meters)], that it will begin to distort the main bus waveforms." The use of transformer coupled stubs also provides improved protection for 1553 terminals against lightning strikes. Isolation

16348-505: 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

16482-460: The time, it became clear that the AH-64 was actually highly susceptible to rifle fire. As a result, the army quietly disclosed in early 2006 that AH-64s would no longer have a major role in carrying out attacks deep inside enemy lines. By the end of U.S. military operations in Iraq in December 2011, several Apaches had been shot down by enemy fire and lost in accidents. In 2006, an Apache was downed by

16616-416: The transmit sub-address specified in the command. RT1 transmits a Status word, indicating its current status, and the data. The Bus Controller receives RT1's status word, and sees that the transmit command has been received and actioned without a problem. RT2 receives the data on the shared data bus and writes it into the designated receive sub-address and transmits its Status word. An application or function on

16750-437: The transmitters and receivers. MIL-STD-1553B specifies that the longest stub length is 20 feet (6.1 m) for transformer coupled stubs, but can be exceeded. With no stubs attached, the main bus looks like an infinite length transmission line with no disturbing reflections. When a stub is added, the bus is loaded and a mismatch occurs with resulting reflections. The degree of mismatch and signal distortion due to reflections are

16884-469: The unit's direct-fire engagements in conjunction with UAVs; Guardian pilots often controlled UAVs and accessed their video feeds to use their greater altitudes and endurance to see the battlespace from standoff ranges. In 2014, the Army began implementing a plan to move all Apaches from the Army Reserve and National Guard to the active Army to serve as scout helicopters to replace the OH-58 Kiowa . Using

17018-503: Was $ 7M and the average unit cost was approximately $ 13.9M based on total costs. A 1985 Department of Defense engineering analysis by the inspector general's office reported that significant design deficiencies still needed to be addressed by the contractor. The Army project manager Col. William H. Forster published a list of 101 action items. In 1986, the four 22-foot-long main rotor blades, each made from steel and composite material glued together to maximize strength and minimize weight by

17152-563: Was approved for a multi-stage upgrade program to improve sensor and weapon systems. Technological advance led to the program's cancellation in favor of more ambitious changes. In August 1990, development of the AH-64D Apache Longbow was approved by the Defense Acquisition Board . The first AH-64D prototype flew on 15 April 1992. Prototype testing ended in April 1995. During testing, six AH-64D helicopters were pitted against

17286-573: Was cancelled in 1972 in favor of projects like the U.S. Air Force A-10 Thunderbolt II and the Marine Corps AV-8A 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

17420-521: Was delivered to the Army in March 1997. Production has been continued by Boeing Defense, Space & Security . As of March 2024, over 5,000 Apaches have been delivered to the U.S. Army and 18 international partners and allies. Primarily operated by the U.S. Army, the AH-64 has also become the primary attack helicopter of multiple nations, including Greece , Japan , Israel , the Netherlands , Singapore , and

17554-459: 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. On a standard day, when temperatures are 59 °F (15 °C), the AH-64 has a vertical rate of climb of 1,775 feet per minute (541 m/min), and

17688-579: Was discovered that the Apache was coincidentally fitted with the Have Quick UHF radio system used by the U.S. Air Force, allowing inter-service coordination and joint operations such as the joint air attack teams (JAAT). The Apache has operated extensively with close air support (CAS) aircraft, such as the USAF's Fairchild Republic A-10 Thunderbolt II and the USMC's McDonnell Douglas AV-8B Harrier II , often acting as

17822-638: Was reported that the AH-64 had successfully completed testing of the MBDA Brimstone anti-armor missile. In January 2020, the U.S. Army announced it was fielding the Spike NLOS missile on AH-64E Apaches as an interim solution to acquire new munitions that provide greater stand-off capabilities. In January 1984, the U.S. Army formally accepted its first production AH-64A and training of the first pilots began later that year. The first operational Apache unit, 7th Battalion, 17th Cavalry Brigade, began training on

17956-400: Was the only Army platform capable of providing accurate CAS duties for Operation Anaconda , often taking fire and quickly repaired during the intense early fighting. Apaches often flew in small teams with little autonomy to react to threats and opportunities, requiring lengthy dialogue with centrally micromanaged command structures. U.S. AH-64Ds typically flew in Afghanistan and Iraq without

#698301