The Boeing AH-64 Apache

v1.0.0 / 01 aug 03 / greg goebel / public domain

* Helicopter gunships tend to be ugly machines that look like something out of science-fiction movies, projecting menace and firepower instead of grace and elegance. One good example of the style is the Boeing (previously McDonnell Douglas and originally Hughes) "AH-64 Apache" gunship, the mainstay of the US Army's attack helicopter force, and also in service with several foreign nations. This document provides a history of the Apache.

[4] AH-64D


* In the 1960s, the US Army pinned its hopes for a front-line attack helicopter on the advanced Lockheed AH-56 Cheyenne gunship, adopting the less sophisticated Bell AH-1 HueyCobra as an interim solution until the Cheyenne became available. Like many interim solutions, the HueyCobra would remain in service for far longer than originally expected, since in the end the Cheyenne proved to not be quite the machine that the Army really wanted. It was a hefty, powerful "flying tank" that put a premium on raw speed and firepower at the expense of agility and treetop operation, and the Army decided that a somewhat smaller and more maneuverable gunship would be more survivable.

The collapse of the Cheyenne program led the Army to issue a new request for proposals (RFP) for an "Advanced Attack Helicopter (AAH)" in August 1972. Five manufacturers submitted designs, and on 22 June 1973 the Bell "Model 409 /YAH-63" and the Hughes "Model 97 / YAH-64" were selected as finalists, with each contractor to build two flight prototypes and a ground-test machine for evaluation.

Bell believed their YAH-63 was the front-runner because of the company's proven experience with the HueyCobra, and in fact their contender was basically a bigger and badder HueyCobra. The initial YAH-63 prototype performed its first flight on 1 October 1975, with the second machine flying on 21 December.

The first Hughes YAH-64 actually beat the first Bell prototype into the air by one day, performing its first flight on 30 September 1975. The second YAH-64 performed its initial flight on 22 November 1975. The Army put all four machines through an intensive test program. A separate competition was conducted for the sensor and targeting suite for the AAH, with Martin Marietta and Northrop submitting proposals in November 1976.

Late in the prototype evaluation, the Army threw Bell and Hughes a curve ball by changing the specification for the primary antitank weapon for the AAH from the proven TOW wire-guided missile to the new Hellfire laser-guided missile, with longer range and greater killing power than TOW. This was risky because Hellfire hadn't even been flown at the time, with the initial development contract with Rockwell International signed in October 1976.

* In any case, the Hughes YAH-64 was declared as the winner on 10 December 1976. Both designs were regarded as very good, but the Hughes design seemed to have an edge in survivability. The "Phase 2" development program funded development of three preproduction "AH-64s", as well as bringing the two YAH-64 flight prototypes and the ground test machine up to the same specification.

The Phase 2 program suffered through a number of delays for various reasons and stretched out to over five years. First Phase 2 flight, of an upgraded initial prototype, was on 28 November 1977, with first flight of a new-build preproduction prototype on 31 October 1979. Initial Hellfire launches had already taken place by that time, with first firings in April 1979. A competitive evaluation of preproduction machines, one fitted with the Martin Marietta sensor / targeting suite and the other fitted with the Northrop suite, was performed, with Martin Marietta winning the competition in April 1980.

An initial production order for 11 "AH-64A Apache" attack helicopters was finally issued on 26 March 1982, with a follow-on order for 48 more machines delayed until the government and Hughes could work out some differences.

The first production machine was formally rolled out at the Hughes factory in Mesa, Arizona, on 30 September 1983. An Apache tribesman, in native dress and on horse with a Winchester rifle, helped honor the occasion, though embarrassingly the Hughes in-house newspaper failed to report his name while listing every other person of importance who attended.

* Initial production hand-over to the US Army was on 26 January 1984, with the machine painted in dark green colors that would become standard for the Apache. By that time, the helicopter had become the "McDonnell Douglas (MDD) Apache" as MDD had bought out Hughes Helicopters in December 1983. MDD was bought out in turn by Boeing in the late 1990s, and so the machine is now the "Boeing Apache".

The AH-64A reached formal operational status with the US Army in July 1986, and went into service with the Army National Guard in 1989. The Army initially planned to buy 536 Apaches. Rising costs of the type ended up forcing cutbacks to 436 machines, but additional procurement eventually led to acquisition of 807 machines by 1994, not counting the six prototypes. A number of attrition replacement machines were also ordered, bringing the total of US Army production AH-64As to 821, with final deliveries in 1996.



* The Apache is of conventional configuration for a modern attack helicopter. It has a main-tail rotor arrangement, a tandem-seat cockpit, nose-mounted sight, and two stub wings with a total of four pylons for underwing stores. The airframe is made mostly of aircraft aluminum alloys, but is designed to withstand 12.7 (0.50 caliber) millimeter projectile hits from all quarters, and can tolerate 23 millimeter projectile hits. A "wire strike protection system (WSPS)" is fitted, with six cutters and eleven deflectors protecting the machine from collisions with cables.

The gunner sits in the forward seat and the pilot in the rear seat, which is raised 49 centimeters (19 inches) to give the pilot a view over the gunner's head. The gunner's position actually has simple backup flight controls, and the gunner is formally referred to as the "Co-Pilot / Gunner (CPG)". Both crew are protected by boron armor shields lining the cockpit, and their Kevlar seats are designed to help absorb the shock of a crash landing.

The AH-64A has fixed taildragger landing gear, with the main gear on heavy-duty shock mounts for survivability in hard landings. On very hard landings the main gear struts will collapse in a controlled fashion to further soften the impact. The landing gear can "kneel" to ease transport of the helicopter. The seats and the landing gear provide a surprising amount of crew protection, as demonstrated by one of the prototype machines that suffered a catastrophic engine failure at an altitude of about 90 meters (300 feet). The crew walked away from the crash, banged up but otherwise unharmed.

The crew gets into and out of the cockpit through upward-hinging canopy panels. Various handholds and steps are fitted to the machine to ease entrance and exit. Detonation cord rings the canopy panels on both sides to blow off the windows in an emergency for a faster exit.

* The AH-64A is powered by twin General Electric T700-GE-701 turboshaft engines with 1,265 kW (1,696 SHP) each. Prototypes and test machines had used the less powerful T700-GE-700. while AH-64As from the 604th production item on were fitted with uprated T700-GE-701C engines, with 1,342 kW (1,800 SHP) each.

The engines are mounted in pods alongside the fuselage to permit easy maintenance. The wide separation of the pods also helps reduce the chance that both engines will be knocked out by ground fire. The engine exhausts are shielded to protect the helicopter from heat-seeking missiles using a three-nozzle "black hole" exhaust suppressor for each engine. The transmission system can run for an hour after complete loss of lubricating oil. There is a Garrett GTCP 36 auxiliary power unit with 93 kW (125 HP) in the fuselage between the engine pods for main engine start and ground power.

The main and tail rotors are both four-bladed. The main rotor has wide-chord blades, with swept tips to reduce noise and improve rotor aerodynamic efficiency. The tail rotor has a "scissors" configuration, with the blades arranged at alternating 55 and 125 degree intervals, also to reduce rotor noise. There is a moving horizontal tailplane at the base of the tailfin. Incidentally, the tailplane was mounted on top of the tailfin in the YAH-64s.

Each main rotor blade has five stainless steel spars to allow it to resist projectile strikes and stainless steel skinning on the outer part of the rotors, with the rest of the blade structure consisting of synthetic Nomex honeycomb and fiberglass skin, and the main rotor can be removed for air transport on cargolifter aircraft. The main rotor head design is based on that of the earlier Hughes OH-6 scout helicopter. An air data sensor is prominently mounted on top of the rotor head.

The Apache is very agile, and in fact in its early days it was regarded as one of the most maneuverable helicopters in the world. It can tolerate gee limits from +3 to -2 gees, has pitch limits of 30 degrees, and roll limits of 60 degrees. It apparently can actually perform a barrel roll, but it's not something that pilots who have done it want to see in the record books.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   main rotor diameter     14.63 meters        48 feet 
   tail rotor diameter     2.79 meters         9 feet 2 inches
   fuselage length         14.97 meters        49 feet 2 inches
   footprint length        17.76 meters        58 feet 3 inches
   max height              4.30 meters         15 feet 4 inches

   empty weight            5,165 kilograms     11,385 pounds
   MTO weight              9,525 kilograms     21,000 pounds

   max speed               295 KPH             185 MPH / 160 KT 
   service ceiling         6,400 meters        21,000 feet
   range, internal fuel    485 KM              300 MI / 260 NMI
   _____________________   _________________   _______________________

* The default armament of the Apache is a McDonnell Douglas M230 30 millimeter "Chain Gun" (a trademark, incidentally), which is a mechanically operated automatic weapon driven by a bicycle-style chain looped around the firing mechanism box. The scheme is simple -- in fact, so simple that in hindsight it is puzzling why it hadn't been invented decades earlier -- as well as lightweight and reliable.

The cannon is supplied with 1,200 rounds of ammunition and has a maximum rate of fire of 650 rounds per second. Its 30 millimeter ammunition is compatible with the British Aden and French DEFA 30 millimeter cannon. The usual ammunition is the "M789 High-Explosive Dual Purpose (HEDP)" round, which features an armor-piercing hollow charge with a fragmenting case. The HEDP round can penetrate 5 centimeters (2 inches) of rolled steel armor.

The Chain Gun is on a hydraulically-driven swiveling mount between the forward landing gear legs. It can be pointed 11 degrees up, 60 degrees down, and 100 degrees to either side. If hydraulics are lost, the cannon pops to its stowage position, with the barrel forward and up. There is a void in the nose above the cannon into which the weapon collapses in a crash, reducing injury to the crew.

The stub wings can pivot up and down to provide some lift control and to aim stores, and automatically level themselves on landing to make life easier for the armorers. The wings do interfere somewhat with hovering flight and, more significantly, can interfere with "autorotation", in which a helicopter that has lost power "flutters" to the ground since its rotor continues spinning. The wings generate lift that can work against the tendency to sink, with the result of a harder impact in the end.

The Apache's primary external armament is the laser-guided AGM-114 Hellfire antitank missile, with a stated range of 8 kilometers (5 miles). The initial Army variant of the missile, the AGM-114A, soon gave way to the improved AGM-114C model. The Apache can carry a rack for four Hellfires on each stores pylon, giving a maximum warload of 16 Hellfires.

Another common load are 19-round 70 millimeter (2.75 inch) "Hydra 70" unguided rocket pods. The rockets can be fitted with armor-piercing, general-purpose blast-fragmentation, flechette anti-personnel, smoke, illumination, or training warheads. Although unguided, the gunner can set fuzing options for the rocket warheads to provide a range of options for attacking different classes of targets -- contact detonation for targets in the open, delayed detonation for targets under cover, and timed detonation for "enfilade" attacks on targets hidden by terrain or other obstacles.

A mix of Hellfires, Hydra-70s, or other stores can be carried. The AH-64A can also be fitted with four 772 liter (204 US gallon) external tanks for ferry flights, giving the machine a range of 1,850 kilometers (1,150 MI / 1,000 NMI), impressive for a helicopter.

* The Apache's primary sensor suite is the "TADS/PNVS", where "TADS" stands for "Target Acquisition & Designation System" and "PNVS" stands for "Pilot's Night Vision System". It is a somewhat complicated multi-turret system fitted on a horizontal ring mount on the nose:

TADS/PNVS imagery can be backed up on a videotape recorder system for after-action / post-strike analysis, and for training purposes. The videotape system is now way out of date and not compatible with any modern standard videotape player, and work has been done in recent years to fit a modern high-resolution 8-millimeter video recorder in its place.

TADS/PNVS has a stabilization system, as well as fine and coarse aiming mechanisms. The sensor systems are somewhat maintenance-intensive, particularly because flight vibration can misalign them, undermining targeting accuracy. Ground crews spend a fair amount of effort making sure the systems are properly boresighted.

* The crew's primary interface to these sensor and targeting systems is the "Integrated Helmet And Display Sight System (IHADSS)", an early and somewhat bulky "smart helmet" with radio, laser-protective visor, and a "Helmet Display Unit (HDU)" known informally as the "hudu". TADS and PNVS can be "slaved" to the helmets, meaning the sensor (and, for TADS the laser target designator) follows the movement of the helmets. The Chain Gun can track TADS as well, which is logical as TADS is a sighting system.

The gunner also has a joystick to control TADs and can direct TADS imagery to a small monochrome (green-black) display designated the "Optical Relay Tube (ORT)" instead of the hudu. The pilot has a similar but larger "Video Display Unit (VDU)" for PNVS imagery. It would seem logical as well that the pilot has a joystick for PNVS, but if so this is not clear from sources.

* The primary piece of countermeasures gear originally fitted to the AH-64A was the AN/APR-39(V)1 radar warning receiver (RWR), with antennas on the left side of the TADS/PNVS turret assembly and on the rear of the tailfin.

The AN/APR-39(V)1 was linked to a small circular display in the pilot's cockpit that gave the bearing of the threat. The RWR also activated an alert lamp and produced an audio alarm in the crew's earphones if the helicopter was being illuminated by a radar. Incidentally, there were a set of different audio alarms for a wide range of problems, such as "engine out", "IFF activation", and so on. The AN/APR-39(V)1 could be set to respond to specific emitters, or to any emitter it detected.

The AH-64A was later fitted with the improved AN/APR-39A(V)1, which features a "threat library" that can identify a wider range of specific emitters. It can also produce audio warnings that describe the specific threat and give its direction. The AH-64A also carries an AN/AVR-2A(V) laser detector to determine when the gunship is being "marked" by a laser designator, with this piece of gear also proving useful as a training tool.

The Apache can be optionally fitted with M130 chaff dispensers on each side of the rear tailboom, with each containing 30 chaff cartridges. The M130s can also carry flares to distract heat-seeking missiles, but Apache crews rely on ground cover and not flares for protection. Flares can hit the tail rotor and can set ground vegetation on fire. However, the AH-64A does have an AN/ALQ-144 "disco light" heat-seeker jammer mounted just behind the rotor head.

Other avionics includes secure radios, "identification friend or foe (IFF)" systems, and a Doppler-radar based "Heading & Attitude Reference System (HARS)" for navigation. HARS is something of a weak point in the AH-64A's design, since it requires at least six minutes to align itself before the start of a mission.

* During the early days of the program, McDonnell Douglas offered versions of the Apache to the US Marine Corps and the US Navy. Both versions would have had corrosion protection for seaborne operation, main rotor blade folding, more tiedown points, and improved electromagnetic interference protection. The Marines were very interested and conducted a two-week evaluation of the Apache in September 1981, including shipboard operation tests.

The Marine version would have not had the Chain Gun, but it would have been able to carry TOW antitank missiles, pods for Zuni 12.7 centimeter (5 inch) heavy unguided rockets, and AIM-9 Sidewinders air-to-air missiles (AAMs) or the Sidewinder anti-radar missile (SideARM), with the Sidewinders fitted to wingtip launch rails. Sidewinder qualifications were performed with the Apache in 1987 and SideARM qualifications were performed in 1988. The Marines really liked the Apache, but the Corps always tended to be the last in line for funding and the money simply wasn't there.

Incidentally, the US Army had some interest in the Sidewinder and SideARM trials, and also performed test firings of the "AIM-28 Air-To-Air Stinger (ATAS)" heat-seeking AAM in 1989. The ATAS was carried in a two-round pod, allowing carriage of four missiles. It lacked the range of the Sidewinder, but the Sidewinder also produced excessive smoke and flame when launched that announced the location of the gunship launch platform. Further firings were also performed with the British laser-guided Shorts Starstreak / Helstreak AAM in 1991, which was also carried in a two-round pod.

The Navy "Sea Apache" version would have had a folding tail for shipboard storage; an AN/APG-65 maritime search and targeting radar replacing the TADS/PNVS turret and Chain Gun; a retractable in-flight refueling probe; and the capability to carry four Harpoon, Penguin, or other antiship missiles. The Navy didn't buy off on the concept.



* The AH-64A's introduction to service was not entirely smooth. Unit costs had rising sharply from projections and made the Apache a target in Congress, though it also had its powerful defenders in the legislature. To make matters more difficult, it was of course a complicated machine and suffered its fair share of teething problems, particularly cracking of blades due to a manufacturing glitch, leading to bad publicity.

System reliability for the Apache was initially only 3.83 hours, but given the complexity of the system that was expected and in fact the specification required only an MTBF of 2.8 hours. The MTBF has crept upward to over four hours.

In service, the Army devised tactics in which Apaches operated in groups of four that could split into twin teams. They could operate in conjunction with "forward air controllers (FACs)" on the ground or in the air that spotted targets for the gunships, and cooperate with Air Force Fairchild A-10 "Warthog" tank-buster aircraft. Teaming the Apache with the Warthog resulted in a lethal combination that was substantially more effective than either weapon operating on its own.

The first operational use of the Apache was in OPERATION JUST CAUSE, the American invasion of Panama to oust Panamanian strongman Manuel Noriega in late 1989. Their actual use in combat during this operation was somewhat minimal, though several were hit by ground fire and the gunships fired two Hellfires into Noriega's headquarters building.

The Apache came into its own during the Gulf War in 1991, when a US-led coalition drove the forces of Iraqi dictator Saddam Hussein out of Kuwait after his seizure of that country in 1990. In fact, the Apache began the air war of OPERATION DESERT STORM, as the effort was designated, on the dark hours of the morning of 17 January 1991, when they took out three Iraqi radar stations to allow air strike packages to fly through Iraqi air defenses undetected.

Apaches conducted further combat operations up to the beginning of the 100-hour ground war on 24 February 1991, when they went to work supporting the ground offensive. One US commander observed that he had expected the Apache crews to go through a learning curve in combat, but found that their peacetime training had made them perfectly competent at their lethal job: "The Apache crews quickly and methodically killed enemy formations in order of priority -- tanks with Hellfires, BMPs [Soviet-built infantry support vehicles] with rockets and 30-mm, and wheeled vehicles with 30-mm."

Some of the crews had never actually fired a live Hellfire before, with their training in that respect restricted to simulators. The training turned out to be effective, though the simulators were not entirely accurate. Some of the crews were startled and frightened (in combat the two are about the same thing) by the fact that the Hellfire had a two-second launch delay after pulling the trigger, and also generated a fair flash on launch. Simulators were modified after the war to provide more realistic behavior.

* 277 Apaches served in DESERT STORM. They destroyed about 500 Iraqi tanks, along with large numbers of other ground vehicles, artillery pieces, and nonflying aircraft. The campaign put an end to most of the doubts about the Apache.

The Apache continued to serve in the various "little dirty wars" of the post-Cold-War era. The AH-64A flew missions in the northern "no-fly" zone set up in Iraq after the conflict, in principle to help protect the local Kurdish population from Saddam Hussein though it didn't always work out that way.

In 1995 and 1995, US Army Apaches were sent to Bosnia in the former Yugoslavia to help enforce a cease-fire between the warring factions there, which they did with a minimum of violence. The Apaches strongly helped emphasize that taking on the peacekeeping force in the country would be unwise, and nobody wanted to try it.

The Apache served in the US intervention in Afghanistan in the winter of 2001:2002, providing major service in fighting with Taliban and al-Qaeda forces. The AH-64's most recent combat action was in the American invasion of Iraq in the spring of 2003. They suffered badly in the Iraq campaign, with all 32 Apaches dispatched to one attack shot up and one of them shot down.

This incident suggested to critics that the day of the manned helicopter gunship is ending and that it will soon be replaced by fixed-wing or rotary-wing robot gunships. Defenders of gunships reply that the fiasco was mostly due to unimaginative tactics plus the fact that the enemy had been alerted that the Apaches were coming. They further pointed out that most of the shot-up Apaches were back in service in a short time, as the type had been designed to absorb significant battle damage and go on fighting.


[4] AH-64D

* Although the AH-64A's service in the Gulf War in 1991 had been outstanding, the conflict still demonstrated that the machine had clear deficiencies. Its obsolescent analog navigation, sensor, targeting, and other avionics systems were simply not up to modern warfare. Apaches had to rely on special-operations Sikorsky Blackhawks and other platforms with modern avionics to lead the gunships to targets.

The Apache's Hellfire missile had also proven to have some deficiencies, for example in some cases homing off laser reflections from the sand and going into the dirt. The problems with the missile were quickly addressed. After the war, the Army fielded the improved "AGM-114K Hellfire II" variant, with a much smarter laser seeker and autopilot, more lethal warhead, and apparently longer range.

Improvements to the Apache itself were a bit more time-consuming to implement. McDonnell Douglas had proposed an improved Apache designated the "AH-64B" in the later 1980s and the Army also considered a upgrade program, but these efforts went nowhere because new technologies were becoming available that rendered the proposed improvements obsolete even before they got to the hardware implementation stage.

After the Gulf War the new technologies finally seemed mature enough to allow an upgrade program to go ahead. An "AH-64A+" upgrade program was proposed after the conflict. It was to be an incremental upgrade of 254 AH-64As featuring new rotor blades and improved avionics including a new navigation system with a Global Positioning System (GPS) satellite receiver and a backup inertial navigation system (INS); engine sand filters, since the Gulf War had demonstrated the necessity of such things in a desert environment; secure communications; and a datalink.

However, the AH-64A+ was cancelled in 1992, since the Army decided to go ahead with a much more capable "AH-64D" upgrade program. The development program for the AH-64D was given the green light in August 1990. Initial flight of the first of five AH-64D prototypes was on 15 April 1992, and a production contract was signed in 1996. Delivery of the first production AH-64D to the US Army was in the spring of 1997.

* The AH-64D features a largely revised avionics suite, including:

The AH-64D can be distinguished from the AH-64A by large "cheek" fairings to accommodate the new avionics. Electrical power capacity has been doubled.

* A portion of the AH-64Ds feature a rotor-mast-mounted drum to support the "Longbow" system, used to target the improved AGM-114L Longbow Hellfire missile. The Longbow system includes an "AN/APG-78 Fire Control Radar (FCR)" and a "AN/APR-48A Radio Frequency Interferometer (RFI)" passive emitter location system.

The Longbow system provides a better all-weather / day-night targeting system than TADS, allowing engagements at longer range with much less risk of firing on friendly forces. There were a number of such "friendly fire" incidents in the Gulf War, with Apaches scoring "kills" on US armored vehicles.

The mast mount for the Longbow also allows the Apache to target adversaries from cover in the treetops, a position impossible with the nose-mounted TADs. There had been thought of mast-mounting TADS back in the beginning of the Apache program, but such a fit was judged beyond the technology of the time. The Longbow radar can handle twelve targets simultaneously, with Longbow Hellfires tracking targets autonomously after launch. Both ground and airborne targets can be engaged.

Comparative tests of the AH-64A and AH-64D were performed at Fort Hunter-Liggett in California in the spring of 1995 and demonstrated just how big an advance the AH-64D really was. AH-64As were credited with 75 kills of adversary targets, along with losses of 28 gunships and 34 kills on friendly targets. AH-64Ds scored 300 kills on adversary targets, losing only four machines and no "friendly fire" kills. A British officer who qualified on the AH-64D in 1996 described the contrast between the old and new variants: "There's just no comparison."

The Apaches with Longbow radar are designated "AH-64D Longbow" Apaches, while those without Longbow are simply AH-64Ds. Confusingly, up to late 1993, the two updated variants were the "AH-64D" and the "AH-64C", but for whatever reason the Army decided not to use the AH-64C designation. The dividing line between the two subvariants is small, since an AH-64D can be field-upgraded to AH-64D Longbow configuration in a few hours.

* The exact number of AH-64Ds to be rebuilt from AH-6As is a bit confusing to pin down, as is the number of AH-64Ds to carry the Longbow system. The US Army had considered upgrading all its AH-64A helicopters to AH-64D configuration and putting Longbow radars on a third of them. However, the Army decided that they wanted more Longbow Apaches, and so decided only convert 501 AH-64As to AH-64Ds. This is somewhat short of the 600-Apache AH-64D fleet that the Army desires. Those AH-64As not upgraded to AH-64D spec will be passed on to the Army National Guard to replace AH-1 Cobras.

About half of the AH-64Ds will be fitted with uprated T700-GE-701C turboshafts engine. Apaches are also being fitted with an airbag system to protect the crew, with the update program for the airbags beginning in 1997. Another upgrade program is a blade-folding system, with initial deliveries of blade-folding kits in 2003.

Another effort is finally to qualify an AAM for the Apache, involving a competition between the Stinger and Starstreak missiles. The Starstreak is favored. Although early trials of AAMs on the Apache mounted the missiles on the outer wing stores pylons, work has been done to fitting a two-round box launcher to each wingtip. These AAMs are lightweight -- they have to be, they were originally designed to be carried by infantry -- and there is no good reason to carry them on a stores pylon that could be used to carry heavier stores.

In addition, the Army is working on a program to fit a new FLIR sensor to most of the service's Apache fleet that will double the FLIR's range, with follow-on work to provide a narrow-field mode with four times the current range. Status of the advanced FLIR program is unclear.

* The Army had expected to acquire over 1,200 Boeing Sikorsky RAH-66 Comanche scout / attack helicopters to replace the Apache, but in late 2002 the service decided to cut the Comanche build to 650. This means that the AH-64D will need to stay in service longer than previously expected, and the Army is now considering a a "Block 3" program to keep the AH-64Ds up to date.

Exact details of the Block 3 program have not been defined yet. The current schedule envisions a formal start to the program in 2005, with the first updated gunships going into service in 2008. Possible features of the Block 3 AH-64D include:

The modifications for maritime warfare are probably more interesting to foreign users than the US Army, but the Army is aware that the operational environment of the 21st century demands a higher degree of flexibility than was required in the past.



* The AH-64A was exported to a number of nations:

* The AH-64D is also getting sales on the export market. The Dutch ordered 30 AH-64Ds in 1995. They leased 12 US Army AH-64As for training in 1996. First AH-64D delivery was in 1998, with final delivery in 2003.

Britain also ordered the type in 1995, with the first of 67 Briticised "WAH-64" Apache helicopter gunship for Britain's Army Air Corps performing its first at GKN Westland's Yeovil facility in July 2000. version of the Boeing AH-64D Longbow Apache. The first eight in the set were built by Boeing's Mesa, Arizona, factory, and the rest are to be assembled from kits by GKN Westland at Yeovil in the UK. The WAH-64 is generally similar to the AH-64D Longbow Apache, but has a number of unique features:

Some of the British-specified kit, particularly HIDAS, is still in qualification. The WAH-64 should complete its evaluations in 2004 and then be ready for full operational service. Other nations are also acquiring the AH-64D:



* Sources include:

Information on current international deals was obtained from the Boeing website.

* Revision history:

   v1.0.0 / 01 aug 03 / gvg