D HTML 3.2 Final//EN"> AH64 - Apache
1. Overview
2. Airframe
3. Crew Compartment
4. Stubwings
5. Landing Gear
6. Low Level Danger
7. The Rotor
8. Power Plant: T700-GE-701C
9. IR Suppression
10. Flight Controls
11. Flight Characteristics
12. Weapons
13. AGM-114 Longbow Hellfire
14. HYDRA 70 Rocket System
15. Ordonance Loads
16. M230E1 Chain Cannon
17. Longbow Radar
20. PNVS
21. TADS
22. Cockpit
23. Pilot Position
24. Co-pilot / Gunner Position
25. Communications
26. Defenses
In a war characterized by the performance of the USAF, it is ironic to note that the first shots of the Gulf War were in fact fired from US Army AH-64A Apaches as they cleared a corridor though Iraq's air defence net. With those first sorties, the Apache began to claw back a reputation that had suffered greatly from attacks by the media. Most of the criticism levelled against the Apache dealt with the Apache's reaction to the desert environment. Designed for a conflict against the USSR in Europe, the abrasive nature of the Saudi deserts became an obstacle to the aircraft's performance. Following some field-modifications the Apache was as ready as any other coalition aircraft, quickly establishing a name for itself as well as an impressive record both in terms of readiness and effectiveness. That first night of the war, AH-64A's cleared a 32 km-wide corridor in the forward line of the Iraqi air-defence. Minutes later, the first aircraft of the coalition roared overhead, using this corridor for safe entry into Iraq.
Despite its stellar performance in the Gulf, some shortcomings in the design became immediately apparent. The Apache was essentially an analogue aircraft on a digital battlefield. The key to supremacy on such a battlefield is information, flexibility, and precision. In terms of flexibility, the key limitation of the Apache was that once in flight, it was difficult for them to adapt to the ever-changing conditions of the battlefield. In addition, as information resources were beginning to be shared amongst aircraft, the Apache was unable to take part and contribute with ease to this process. As a result, the situational awareness of the pilots suffered as they were not as "plugged in" to the war around them. Looking at the lessons learned in the Gulf about the importance of information resources, intelligence gathering, and communication, the US Army looked at improving the existing Apache. The desired end was to turn this proven and formidable attack helicopter into an electronic warrior capable of providing and utilizing real-time data in order to take command of the battlefield.
The AH-64D Longbow Apache utilise advances in communications and sensors in order to give its pilots an improved view of the battlefield. Through real-time co-operation with other intelligence gathering sources, the situational awareness of the Longbow Apache crew has been improved to the extent that they may become actual players on the digital battlefield. The Longbow radar allows the crew to see farther with clearer vision than they enjoyed previously. At the same time, improvements in communication and how information is displayed give the crew a greater awareness of the battle going on around them. Improvements in the Hellfire missile now allow the Apache to strike further with a greater safety margin for the aircraft and crew. The digital battlefield is characterized by information. Victory in such an environment will depend on the ability to gather and control that information. The AH-64D Longbow Apache has allowed a cold warrior and Desert Storm hero to catch-up to the digital age, owning the information-processing realm of the battle which today is the vital key to victory.
Combat helicopters face many threats in their environment, most notably from surface-to-air missiles and anti-aircraft artillery. The AH-64 has been designed with survival mind. To increase resistance to ground-fire, the airframe of the Apache is made up of flat structural surfaces, reinforced by armour. From nearly every angle, the opposing projectile will face a strong, blunt surface which it must breach in order to damage the fuselage.
More critical areas of the Apache - the rotor, engines, and cockpit area - are designed to be able to withstand hits from 23mm rounds. In addition to the armoured fuselage, aircraft systems are protected by Kevlar, the light-weight material providing additional protection while keeping the weight down. The twin engines are mounted in pods along either side of the airframe. This separation reduces the chances of a single hit damaging both engines. The cheek-fairings on either side of the forward fuselage reduce cockpit exposure to ground-fire, while providing additional space for avionics equipment.
The cockpit of the AH-64 is a tandem arrangement with pilot sitting above and behind the co-pilot/gunner, thus being afforded a nearly unobstructed view, though sitting in the rear. Crew protection is provided by boron armour shielding within the cockpit sides, flooring, and in the bulkhead between the cockpit positions. This shielding is resistant against armour-piercing rounds up to 12.7mm. In addition to the bulkhead, a transparent acrylic blast shield mounted between the two positions reduces the likelihood that a breach in the cockpit will eliminate both crew members, while still providing no visual obstruction. Crew survivability in the event of a crash is increased due to seats designed to withstand an aircraft impact of up to 42ft/s straight down. The structure of the seats are armoured with Kevlar shielding to provide additional protection against shells and shrapnel.
The crew compartment is covered by a cockpit canopy made up of 7 flat transparent panels. The curved canopies of previous attack helicopters have the disadvantage of glinting problems as the curved surfaces will reflect light in a number of different angles regardless of the attitude of the aircraft. Flat panels do not have this problem. However, the side panels of the canopy are slightly rounded in order to reduce aircraft-induced vibration to the transparencies.
Like other attack helicopters, the AH-64 mounts the majority of its weapons on a pair of stub wings attached to either side of the fuselage. Each wing features two hardpoints on the underside of the structure as well as an attachment point at the wingtip for a series of air-to-air weapons. The articulated pylons alter the vertical angle of the launchers in order to provide the most beneficial trajectory for the weapon. The wings provide an additional benefit for the Apache in reducing aircraft-induced vibrations during flight. During air transport the wings can be removed in order to reduce the space taken up by the airframe.
Unlike other types of aircraft, wings can have a debilitating effect aerodynamically on helicopters. This effect can be best seen during autorotation. This procedure requires the rotor to spin freely during an emergency unpowered descent, gathering as much potential energy as it can. This energy will then be utilized by the pilot to generate lift, providing control authority for a controlled landing.. By generating their own lift, the stub wings consume some of the potential lift that would normally be available to the rotor.
Unlike fixed-wing aircraft, the landing gear of the AH-64 is not retractable. However, the assembly can be folded rearwards, allowing the Apache to kneel in order to reduce its height for air transport. Each gear structure is anchored to the aircraft via a rotating bearing attached to the airframe as well as a nitrogen/oil dampening strut. Each strut passes through the cheek-fairing and is mounted to the airframe just above the side-pod by another rotating bearing. Landing forces compress the strut, causing the main assembly to pivot to the rear and upwards. These struts have been designed to absorb the forces associated with an emergency landing of up to 42ft/s. Each mainwheel incorporates a hydraulic braking system.
The tailwheel is located at the end of the tailboom on an A bracket and is dampened through an exposed strut. It too is designed with the same impact tolerances of the main gear. The fully castoring, self-centering tailwheel reacts to the movements of the taxying Apache, which can be steered on the ground through differential braking or via limited input from the tail rotor.
One of the dangers that low-flying helicopters face both in war and peacetime is from transformer lines that stretch across the landscape. Protecting helicopters from this danger today is the Wire Strike Protection System (WSPS). Made up of eleven deflectors and six cutter assemblies, the WSPS either steers the wires away from the aircraft, or guides them to the cutters. Deflectors are located around the TADS/PNVS, wiper assemblies, canopy, and the tail wheel. Wire cutters located between the TADS and PNVS turrets, the lower fuselage in front of the chain gun, on each leg of the main gear, and on the upper fuselage just forward of the rotor shaft.
Key to any helicopter is its rotor. Unlike other aircraft, there are no conventional wings to allow the structure to remain aloft. Rather, the helicopter depends on the correct operation of the spinning blades and the powerplant that allows the rotor to do this. Many pilots have been heard to say, "we don't fly, we beat the air into submission."
The rotor mast is attached to the airframe at eight separate points, with the drive-shaft running through it. As a result, flight loads are imposed on the mast as opposed to the drive-shaft, or the transmission. By not relying on these critical components to absorb flight stresses, the Apache's agility is greatly enhanced as is the reliability of the powerplant.
The four-bladed rotor head is fully articulated as opposed to the more traditional teeter-totter arrangement of previous helicopters. As a result, each blade can lead or lag individually, reacting to its own individual conditions. This greatly increases aircraft agility. The individual blades are able to move due to flexible elastomeric bearings wear the blade meets the rotor hub. These appear as large blocks at the rot of each blade.
The leading edge of the rotor is made up of titanium while the trailing edge is covered in a graphite composite material. Internally each blade consists of a glass-fiber honeycomb supported by five tubular spars of stainless steel which divide the blade into sections. Damage to the rotor blade should be confined to the particular section that was hit. For storage or transport, the blades can be easily folded or removed.
Most helicopters require a secondary rotor to counteract the torque of the main rotor. Without such a feature, the helicopter will simply rotate around its axis. The majority of helicopters employ a smaller rotor mounted vertically at the end of a tailboom. The tail rotor of the AH-64 consists of twin two-blade rotors mounted vertically side-by-side to the same hub. The dual rotors cross each other at an angle of 55 degrees which results in a reduction in noise from the tail rotor. Power to the tail rotor is delivered by Bendix-manufactured driveshafts which are capable of one hour of operation following ballistic damage. The gearboxes of this driveshaft are grease lubricated. Mounted at the end of the tailboom is a large horizontal stabilizer. The wing-like surface is capable of 30 degrees of travel and provides stability during hovering maneuvers.
8 - POWER PLANT: T700-GE-701C
Originally, the powerplant of the Apache was a pair of T700-GE-701. However, from the 604th production model of the AH-64A (delivered in 1990), the engines were upgraded to the -701C. The key benefit of the change was an increase in engine power. The -701C is rated at 1723shp (shaft horsepower). Transferring power from the engines to the rotors is the transmission system. To increase survivability in its hostile environment, the Apache's transmission was designed to operate for one hour without oil.
Ease of maintenance was a fundamental concept of the Apache program, and this concept was applied to the maintenance of the powerplant as well. Both engine covers are hinged at the bottom, opening downwards. When the powerplant is being serviced, these open cowlings act as catwalks for the maintenance personnel. The upper panels of the fuselage between the two engine pods also open up to serve as another work platform.
Engine efflux provides a very prominent target for Infrared detection systems, especially those guiding IR missiles. Originally the Apache was to utilise a cooling fan in order to reduce the IR signature from the engine exhaust and transmission components. However, this system increased the weight of the helicopter substantially, forcing Hughes Aircraft to find another solution.
Known as the "Black Hole" IR Suppression System, the principle revolves around directing the engine exhaust through special ducts which combine the efflux with the airstream passing over the aircraft. The airstream thus dissipates the hot exhaust that emerges from the vents evenly, rather than allowing hot spots to appear. Prior to exit, the temperature is further reduced through a unique process developed by Hughes aircraft. Before emerging from the aircraft, the exhaust must pass through a special liner made of a material known as Low Q. This material absorbs the heat from the efflux passing through it, radiating it slowly through the outlets.
The engine exhaust ports are angled outward from the airframe to better direct the output into the airstream. Secondary vents along the upper surface of the outlets help to dissipate the heat by diverting part of the emissions into the flow along the top of the airframe. To further reduce the IR signature of the aircraft, exhaust output is used to draw in fresh air in order to cool both the engines and transmission, the latter's cooling being assisted through oil heat exchangers.
The Flight Control System (FCS) of the Apache combines hydro-mechanical controls for both rotors with a Digital Stabilization System (DASE). The DASE translates the raw hydro-mechanical inputs into precise movements. Some of the features that DASE provides in addition to input stabilization is attitude hold for short-term hands-off flying, heading hold, turn co-ordination, and hover augmentation. Forming part of DASE, the Stability Augmentation System (SAS) dampens the effects of airframe movement, gust response, and weapons recoil in order to provide the pilot with limited hover-hold and low-speed velocity hold features. Presently, the hover-hold is not very reliable as it uses the Doppler navigation system for position updates. As a result, the aircraft may drift up to a rate of 21 ft/min during hover-hold.
The Back-Up Control System (BUCS) is a single-channel fly-by-wire system. To to engage the back-up system, the pilot must apply enough force to the cyclic control in order to break the shear pins of the Shear-Pin Actuated Decoupler System (SPADS). Once broken, the back-up system is then activated.
The fully articulated rotor system of the AH-64 combined with blade dampeners dramatically increase the Apache's flight envelope to allow for loadings of +3.5G to -2G. Loadings such as these provide the Apache with uncharacteristic agility. With a roll-rate of up to 100 deg/sec, the AH-64 is able to perform full corkscrew rolls when the aircraft's speed allows.
The Apache has a range of some 1 024 miles, allowing it to self-deploy across the Atlantic by way of Canada, Greenland, Iceland, and Scotland. Generally, AH-64s are deployed via air-transport aircraft. Prior to being loaded aboard the aircraft, the wings are removed as are the rotors. Two Apaches can be transported aboard a C-141 Starlifter, three aboard a C-17 Globemaster, and six aboard a C-5 Galaxy.
The weapons of the Apache can be classed in two categories: point attack and area effect weapons. Both categories reveal the flexibility that is called for in attack helicopters as they are tasked with both the anti-armour role as well as battlefield support. However, the emphasis placed on guided weapons has revealed the importance given to stealth and surprise in helicopter warfare technology. Future development in weapons for the new Longbow program will focus even greater attention on this latter consideration. The goal is to provide the AH-64D with total battlefield awareness and security while at the same time producing demoralizing confusion to its enemies.
Originally, the AAH program dictated that the TOW (Tube-launched Optically-tracked Wire-guided) missile was to be the principle anti-armour weapon. This missile, with a range of just over 2km was guided by electrical signals transmitted to the weapon via a thin wire that was unspooled behind the missile in flight. By keeping the target in the crosshairs, the gunner was able to direct the missile on target. The wire had the advantage of being invulnerable to electronic jamming, though it did restrict the range of the weapon somewhat. However, a new technology originally developed by Texas Instruments during the Vietnam war was opening an entirely new world in missile guidance technology - laser guided weapons.
Soon after the AAH finalists had been selected, the focus on TOW had switched to a new weapon which reflected the emerging guidance technology, the AGM-114 Hellfire (HELicopter-Launched FIRE-and-forget missile). Once it's left the launch rail, this missile homes in on the reflected radiation from a target, which has been illuminated by a separate laser designator. It travels at a speed of Mach 1.4 and has a maximum range of between 5-8km.
The designator - either on the aircraft or from another source - upon sighting the target, will directed its laser onto the target, thus "lazing" the target. The key to this process is that the missile must be able to see the reflected laser-light until it reaches the target. In addition, the laser is a coded pulse, meaning that it flickers in a predetermined pattern that the missile is prepared for. As a result, the designation can come from some other source, including ground troops who have slipped into the area. Because of this pulse, several different aircraft can engage in designating targets without confusion. Coding of the laser also minimizes the chances of the enemy forces creating a false designation in order to spoof the missile.
Today, the most predominant Hellfire in service today with the Apache is the AGM-114C. This is an upgraded version featuring Improved Low-Visibility (ILV) detection autopilot, and a low-smoke motor to reduce detection. The warhead is an 8kg shaped-charge with a copper liner. In shaped-charge warheads, the explosion collapses the cone into an armour-piercing jet of molten metal which incinerates the interior of the vehicle.
The newest Hellfire in production is the AGM-114K Hellfire II. The K-version has been completely redesigned, featuring a digital autopilot and redesigned warhead. The copper liner of the shaped-charge warhead has been replaced by molybdenum (a silvery metallic chemical element) steel liner. This is to increases the potency of the warhead and its effectiveness against new armour technology. In addition, the Hellfire II features what is known as a tandem warhead.
The tandem warhead emerged in response to "reactive" armour. The concept behind reactive armour is relatively simple. The armour of the vehicle is covered by blocks of plastic explosive sandwiched between two metal plates. When a shaped charge warhead comes into contact with this armour the explosion sets off the block of plastic, which in turn forces out the metal plate, the resulting kinetic energy dissipating the effects of the shaped-charge. The metal plate bears the brunt of the molten jet, allowing the armoured hull of the tank to receive only minimal or no damage.
The tandem warhead defeates the counter measure with two charges, a minor initial explosion followed by the main shaped-charge warhead. The initial charge sets off the reactive armour, causing the metal plate to be blasted outward prematurely. By the time the main shaped-charge detonates, the energy of the reactive plate has been dissipated while the plate itself is fractured and weakened. The main explosive force punches through the remenants of the reactive armour to penetrate the armour of the tank.
It is believed that the range of the Hellfire II is in excess of 8km. These newest features will most likely be included in the Longbow Hellfire, to be designated AGM-114L. The specifics of this version development are not yet available.

Specifications: AGM-114A

Manufacturer: Rockwell, Martin Marietta

Missile: 99 lbs.
Warhead: 20 lbs.

Length: 5.3 ft.
Diameter: 7 inches
Wingspan: 1.1 ft.
Guidance: semi-active laser homing
Propulsion: Thiokol TX-657 reduced-smoke solid-fuel rocket

Speed: Mach 1.1
Range: approx. 5-8 km
Warhead: 20 lb. impact-fused Firestone shaped-charge high-explosive

The principle area-effect weapon for the Apache is the Hydra 70 family of FFAR (Folding Fin Aerial Rocket). This unguided rocket measures 70mm in diameter and is characterized by a set of three wings which fold around the body of the Mk66 rocket motor when in its launcher. Upon exit from the launcher, the fins spring outward to aid in stability. Wingspan is 186mm when deployed. The maximum range is approximately 2.5km.
The Hydra 70 name denotes any warhead attached to the Mk66 rocket motor. Utilizing the same rocket motor reduces a number of logistical nightmares that can exist deep in the field. There are a variety of warheads that are available for use with the Mk66. As a result, the rocket can be tailored to suit a number of purposes.

M151 HE - This M151 is an anti-personnel, anti-material warhead to be used against "soft" targets. The 1.04kg of B4 explosive has a blast radius of 33 feet. The warhead is designed to fragment, showing the area with lethal shards of metal, lethal to a range of 164 feet.

M229 HE - This is a somewhat heavier version of the M151. The amount of B4 explosive has been increased to 2.17kg, which has a corresponding increase in the blast radius.

M261 HE MPSM - Designed for use against lightly armoured vehicles, the M261 MPSM (Multi-Purpose Sub-Munition) contains nine M73 shaped-charge sub-munitions. Using the M439 fuse to air-burst the munitions approximately 500 feet above the target area, each M73 deploys a ram-air decelerator in order to halt their flight. Once stabilized and descending, the shaped-charge munition explodes, collapsing its conical warhead into approximately 195 fragments descending at over 16000 ft/sec in order to penetrate the vehicles.

M255E1 - The M255E1 warhead contains 585 120-grain or 1180 60-grain flechettes to be used against opposing personnel or lightly protected targets. The flechettes are explosively released by a charge at the base of the warhead.

M257 - The M257 is an illumination warhead. Through a small parachute flare, the M257 can illuminate a one square kilometer area with one million candlepower for 100 seconds, effectively turning night into day.
The cylindrical launchers typically carry 19 rockets in a honeycomb pattern. They are light so as not induce heavy weight penalties once all of the rockets have been launched, yet they are durable enough to allow them to be used multiple times. In addition, their construction is simple enough and their cost inexpensive enough to be jettisoned without concern.
M230 30mm Cannon 1
AGM-114 Hellfire 4 4 4 4
Hydra 70 FFAR Pod 1 1 1 1
AIM- 92 Stinger 2 2 2 2 2 2
AIM-9 Sidewinder 1 1 1 1 1 1
Fuel Tank 1 1 1 1
The fixed weapon for the AH-64 is the M230E1 Chain Cannon designed by Hughes Aircraft specifically for their AAH helicopter entry. Unlike its Bell Cobra rival which mounts its gun in the lower nose, the cannon of the Apache is located beneath the fuselage, directly below the gunner's position. Above the chain gun mounting bracket, there exists a void space between the two cockpit positions. Should the aircraft be forced down and the landing structure collapses, the gun is designed to fold into this space so as not to enter the crew compartment.
The chain gun is electrically driven and steered. Elevation is provided via a single hydraulic actuator located on the gun's centerline just forward of the pivot point. Should the gun lose power, it is spring loaded to return to its natural position with the barrel angled up slightly. Thus, it can collapse cleanly into its crumple-zone in an emergency.
The chain gun name is derived from the way that ammunition is supplied to the weapon. To reduce jamming, the ammunition feed mechanism utilizes an electrically-driven one-piece chain to feed the linkless shells into the gun. Thus, the operation of the gun does not require that a round be fired in order for the next to be chambered. Misfired rounds are driven through by the chain to make way for the next round. The feed chute is a rectangular loop passing through the center of the mounting bracket, and attaching to either side of the gun. Ammunition travels down the starboard side of the chute while the spent casings are passed up the port side to be returned to the magazine.
Rate of fire for the M230 is 600-650 rounds per minute, the spool-up time to achieve this rate being a brief 0.2 seconds. 1200 rounds are carried in the magazine-pack above the gun. Each round takes approximately 2 seconds to travel 1000m. However, as the shell's energy dissipates, it takes some 12.2 seconds to cover 3000m.

Specifications: M230E1 Chain Cannon

Calibre: 30mm
Length: 1.68m
Weight: 57.5 kg
Rate of Fire: 600-650 rounds/min
Muzzle Velocity: 792 m/s

The ammunition typically used by the M230 is the 30mm M789 HEDP (high explosive dual-purpose). Each shell contains 21.5g of explosive charge sealed in a shaped-charge liner. The liner is designed to collapse into an armour-piercing jet of molten metal, capable of penetrating more than 2 inches of armour. The shell is also designed to fragment into shrapnel, deadly to unprotected targets, out to a distance of over 10 feet. The ammunition is cased in aluminum rather than the typical brass as it reduces the weight of the ammunition load by half. The ammunition is loaded into the Apache using a motorised loader by ground-support personnel
17 - Longbow Radar
The Longbow radar system is the new heart of the Apache's sensor suite. The Longbow package consists of a mast-mounted millimeter-wave (MMW) fire-control radar dome, a programmable signal processor, and the new Longbow MMW Hellfire missile. This new sensor system is designed to quickly detect, classify, and prioritise targets. One this procedure has been done, the sensor system then hands off the targeting data to the Longbow Hellfire missile seeker.

The emissions of the Longbow radar are designed for a low probability of intercept by opposing forces, and can sweep an arc of 50 square km in front of the aircraft. The radar can detect moving targets at ranges up to 8 km while the detection range for static targets is reduced, at 6 km. At this time, the Longbow system can display, classify, and track up to 128 targets simultaneously.

While individual types of vehicles cannot be determined (such as a T-72 vs. a T-80), the Longbow package can identify and classify a vehicle based on the following criteria: tracked, wheeled, airborne, or air-defense. In addition, the radar can indicate to the crew whether the target is mobile or not. The Longbow radar is able to accomplish this by using radar waves of a very high frequency. Millimeter-wave is just that, radar waves which can be measured in the millimeters. This translates into a radar with a very fine resolution, a resolution which can identify particular features of the target being swept. The MMW radar essentially "feels out" the target to determine the class of the vehicle. The results of this process are then compared against a threat library, and when a match is found, the target can be catagorised.

Another component of the Longbow system is a radar frequency interferometer which allows passive detection of air-defense emissions. Data from this sensor can then be displayed on a display screen in the cockpit to indicate position and distance of the threat.
One of the principle displays for the crew-members is the Integrated Helmet And Display Sight System (IHADSS) designed by Honeywell. The IHADSS system is comprised of three main components: a pilot's helmet, a display system, and special head-tracking equipment. The display is attached to a folding arm mounted to the right side of the helmet. This side arm positions a small combiner-glass in front of the crew-member's right eye upon which a video-projection unit in the arm displays images.

Acting like an aircraft's HUD, the IHADSS Head Display Unit (HDU) can display video with flight data superimposed over it. As a result, critical information relating to the aircraft can be presented to the crew-member at all times, regardless of the direction the pilot is facing. Infrared sensors at either side of each headrest track the movement of each helmet. Atop the instrument panel of each cockpit is a lensed cylinder known as the Boresight Reticle Unit. This serves as a stable reference point which the pilot aims the IHADSS at when correlating the head-tracking system. The head-tracking data is passed on to the sensor appropriate to each crew-member so that if slaved to the helmet, it may follow the movements of the helmet. Thus, the crew control the sensors simply by looking at the point of interest, and the sensors can return information to their eyes.
19 - TADS / PNVS
Designed and built by Martin-Marietta (now Lockheed-Martin), this particular sensor suite is made up of the AN/ASQ-170 Target Acquisition and Designation System (TADS), and the AAQ-11 Mk III Pilot Night Vision System (PNVS). Both systems are separate from each other, occupying individual turrets. As a result, both pilot and co-pilot/gunner are provided with fully independent night vision systems. The drive mechanism of each turret contain both a "course" gimbal for rapid tracking and a "fine" gimbal for precision tracking of targets. In addition, both PNVS and TADS can be rotated to a rearward-facing position when not needed in order to preserve the optical components from the wear of particles in the aircraft's flightpath.

The PNVS is mounted above the nose structure of the aircraft, while the larger TADS turret occupies the underside of the nose section. It is this placement of the sensors on the nose of the Apache that is the major drawback of this sensor suite. Their location on this part of the airframe requires the Apache to completely unmask itself from cover in order to use those sensors. Before Longbow, virtually the entire aircraft would have to be exposed in order to guide missiles onto the target using its laser. Both tur rets are manipulated by drive mechanisms comprised of both a "course" gimbal for acquisition and a "fine" gimbal for precision tracking of targets. Both PNVS and TADS can be slaved to the IHADSS or can be rotated to a rearward-facing position when not needed in order to preserve the optical components from the wear of particles in the aircraft's flightpath. All of the sensor optics are filtered in order to protect the crew from the damaging effects of battlefield lasers.
20 - PNVS
The Pilot Night Vision System (PNVS) consists of a Forward Looking Infrared (FLIR) device mounted in a small turret located above the Apache's nose section. This turns night into day for the pilot, a critical function for an aircraft which often must travel low and fast in order to survive. The turret is steerable to a maximum of 90 degrees off the centerline in the horizontal and +20 / -45 degrees in the vertical. The drive mechanism is capable of steering the PNVS at 120 deg./sec. horizontally and 93 deg./sec. vertically. The FLIR's field of view is 40 degrees horizontal x 30 degrees vertical. The FLIR imagery can be displayed in a 1:1 view, thus representing the true picture outside the aircraft.
21 - TADS
The Target Acquisition and Designation System (TADS) is comprised of a FLIR device, two types of optical cameras, and a Laser Range-finder/Designator (LRF/D). All are mounted within the large drum turret below the nose structure. The TADS assembly is divided into night (starboard) and day (port) halves, each capable of independent elevation. The entire TADS unit can be steered 120 degrees to either side horizontally and +30 / -60 degrees vertically.

On the port side are three sensors for the detection and tracking of targets when there is daylight. They are mounted in a vertical column and consist of the Direct View Optics (DVO) sensor at the top, a TV optical sensor (DTV) below, and a laser range-finder/designator at the bottom. The DVO is an optical telescope with two magnifications: x4 magnification at 18 deg. FoV, or x16 magnification at 4 deg. FoV. The TV optical sensor offers up to x127 magnification with a corresponding FoV of 0.45 degrees. The laser range-finder/designator is a neodymium laser with an effective range of 20 km (12 miles). It can provide very accurate ranging information for targeting in addition to designating them with coded laser-energy for weapon guidance.

The starboard side of the TADS system houses the FLIR sensor which provides slightly better imagery than the PNVS. This FLIR sensor provides variable field of views ranging between 50, 10, 3.1, and 1.6 degrees FoV. The FLIR of the TADS unit can be switched between "white hot" and "black hot" in order to provide better contrast against the surrounding terrain for increased target discrimination. An adjustable gain selection also aids in this target enhancement.

The imagry from the TADS unit can either be displayed on the co-pilot/gunner's own IHADSS unit, on one of the MFDs, or via the primary display for the gunner, the Optical Relay Tube (ORT). In addition, a video-recorder can collect information from all of the TADS sensors. As a result, the Apache needs to unmask for only a short time to collect sensory input, which can be analysed in greater detail by the crew once the aircraft drops down behind cover once again. The recorder can also be used to record the aftermath of an attack for analysis upon return to base.
Both pilot and co-pilot/gunner sit in tandem, with the pilot behind and slightly above the gunner's position. The pilot is sufficiently elevated so that the gunner provides no obstruction to the flyer's view. The gunner sits immediately above the mounting for the 30mm chain gun. Between the two positions is a transparent blast shield. The Apache can be controlled from either position though each is optimised for its particular role.

The cockpit of the Apache has seen extensive redesign from the original A model. The previous Apache had some 1 200 switches as well as numerous dials, tape-strips, and other various indicators. The new design is known as the "Manprint" (Manpower Integration) cockpit. Many of the indicators and switches are replaced by a pair of Multi-function Displays (MFDs) in each of the two cockpits in addition to a Litton Canada Up-Front Display.
The most notable change from the A model Apache, is the pair of Bendix King MFDs. Measuring 6inches x 6 inches, each screen is surrounded by selection buttons mounted on the bezel of the unit, 6 buttons to a side. At the corners of each unit are controls for brightness, contrast, as well as other functions. During the operation of the displays, the outer edge of the screen feature menu selections that would correspond to each of the buttons.

In the vicinity above the starboard MFD, the Up-Front Display can show additional information in alpha-numeric form. Here, there is also a control for brightness as well as controls to scroll the display up or down. Above the port MFD is a very prominent Fire Warning display featuring warning indicators for both port and starboard engines as well as the Auxiliary Power Unit.

Above the instrument panel coaming are some traditional dial instruments to provide backup to the standard digital instruments. Both collective and cyclic controls are studded with various switches in order to allow the pilot to control various functions without the need of releasing the controls.
Looking like some type of periscope, the most prominent feature of the front cockpit is the Optical Relay Tube (ORT) mounted in the center of the instrument panel. This is the key display and control unit for the CP/G, while performing tasks crucial to the gunner's role. Through this device, the CP/G can locate, identify, track, and engage targets.

There are three main sections form the ORT. At the top of the unit sits the Head Down Display (HDD). It is a monocle display unit surrounded by a rubber coaming which would surround the gunner's eyes when his head is down in the unit. It is this section which gives the ORT its periscope-like appearance. With the gunner's head down in the display, video is placed before the right eye by means of a lens. The area occupied by the left eye is thus far not in use and sealed with a plastic cover. From this display, data from the various sensors can be presented to the CP/G through a combination of video images and alpha-numeric symbology. Being that close to the display, fine details of video images can be seen by the CP/G, crucial for detection and identification of targets.

Below the HDD is a small screen which serves as an HDD repeater display. This allows the CP/G to avoid being tied to the HDD during all phases of the operation. On either side of the ORT's column are hand-grips which allow the CP/G to control various functions of the sensors and weapons, without breaking contact with the HDD. The T-bar grips are similar the HOTAS (Hands on Throttle and Stick) system found in today's modern fighters. They allow the CP/G to perform critical functions without requiring the gunner to lose site of the target, in this case by removing his/her head from the HDD. There are differences in the layout of both the right and left grips as there are differences in the functions that each perform.

    The left hand-grip features the following controls:
  • weapon trigger
  • switch to select between sensor modes (FLIR, DVO, DTV)
  • FoV selection (wide, medium, narrow, zoom)
  • weapon selection switch (gun, rockets, missiles)
  • auto-tracking controls
    The right hand-grip houses controls for the following:
  • laser range-finder/designator trigger
  • laser tracking controls
  • laser boresighting controls
  • FLIR "white hot" / "black hot" selector
  • manual turret controls
  • video-recorder controls
In addition to the ORT, information can be presented to the CP/G via a pair of Bendix King MFDs, exactly like the pair in the pilot's cockpit and capable of displaying the same types of data. Also present in the front cockpit are both cyclic and collective controls. The center-cyclic stick has the capability of folding down to the floor of the cabin when not in use in order to not interfere with the operations of the gunner's position. The Up-Front controller occupies the space in the extreme top-right sector of the instrument panel. Much like the pilot's cockpit, there is also the same Fire Warning display located to the upper-left corner of the instrument panel. Also present are control panels for the weapons, a data-entry keyboard, communications controls, circuit breakers, as well as some of the other controls that would be necessary for piloting the Apache from the front position.
One of the key improvements to the Apache was an upgrade to the communications system of the aircraft. One such upgrade can be seen before the mission begins in the form of the Data Transfer Module (DTM). The module allows for allaspects of the mission such as waypoints, battle lines, unit positions, communications frequencies, and callsigns to be input directly into the AH-64D's computers via a programmable cartridge.

However, a more striking improvement can be seen once the AH-64Ds take flight. Communications among aircraft has been improved dramatically through the Improved Data Modem (IDM), a device which will revolutionize the battlefield. The AH-64D will now be able to communicate crucial operational information with other aircraft in the flight, ground units, Air Force E-8 J/STARS, and the Tactical Operations Center (TOC).

The result will be the transformation of a group of units seeking the same operational goal into a highly cohesive force with unprecedented situational awareness. Each member of that force will gather battlefield information in its own way, and automatically supply that data to a growing body of knowledge about the operation from which every other member will draw automatically. In the end, an unprecedented picture of the battlefield will be created. The tactical advantages brought about by this level of situational awareness can thus be applied against the opposing forces.

The IDM transfers data at a rate of 16 KB/sec, a very high rate of speed for such equipment in the military. The IDM is able to communicate with the variety of aircraft that it is able to due to the recently developed Variable Message Format (VMF) which revolves around the 18820 protocol. VMF is utilised by all of the US forces regardless of branch, so information is shared between the various services participating in the operation.

Due to this communications breakthrough, a single Longbow can lead the attack by locating targets, providing the necessary information to both the rest of the flight and the battlefield commanders, and then anybody in the loop can make the decision as to which aircraft will attack which targets. All of this occurs in real-time, allowing for changes in tactics to occur immediately as conditions change.

One such scenario could involve a single Apache hiding behind a terrain feature, while the rest of the group hides behind another at a greater distance. The lead Longbow would unmask its radar and sweep a given area for targets. Once this task is performed, the data can be immediately analysed by tacticians at the battlefield level. The lead Longbow can then assign Primary Fire Zones (PFZs) to individual aircraft who would then be responsible for the targets within that zone. In addition, the lead Apache or the commanders may decide on what targets to fire upon first, which should be consider secondary, and which to leave alone entirely. This ensures two key purposes. First, that overkill is avoided, thus sparing rounds. Second, that non-critical targets are left for clean-up forces. This can translate into a swifter, more devestating attack while at the same time, sparing valuable Hellfire rounds that would ordinarily be wasted on inappropriate targets.
The Longbow radar system allows for passive detection of targets through use of a Radar Frequency Interferometer (RFI) which can locate and identify and air-defense system by analysing its emissions. The RFI is located in the mast-head unit in order to allow for the aircraft to passively seek out threats, while still masked by terrain features. The AH-64D's RFI provides 360 degrees of coverage with the forward half consisting of "fine" coverage and the aft hemisphere consisting of "coarse" coverage.

For instances when the aircraft must protect itself against such air-defense systems, the Apache is equipped with the ALQ-136 radar jammer. The receiver for the jammer is located on top of the fuselage between the aft cockpit and the rotor mast. The transmitting antenna for the jammer is located on the port side of the structure between the PNVS and TADS turrets. The jammer operates by transmitting inaccurate range and angle information to the hostile radar. Further countermeasure against radar-guided SAMs is provided by the 30-round M130 chaff launcher. The box-like launcher-unit is located on the port side of the tailboom just forward of the point where the structure sweeps up to form the tail-rotor housing.

Protection against IR threats is supplied by the AN/ALQ-144 "disco light" jammer. Located directly behind the rotor mast, the copper-coloured, segmented cylinder looks very much like its namesake. Consisting of an electronically heated source, perhaps a ceramic block, the jammer emits modulated radiant energy at high and low frequencies in order to confuse the seekers of IR guided missiles.