Apache

The Apache Helicopter The Ultimate Killing Machine 11/7/2011

In this topic, we look at the Apache's amazing flight systems, engines, weapon systems, sensor systems and armor systems. Individually these components are remarkable pieces of technology. technology. Combined together they make up an unbelievable fighting fighting machine - the most lethal helicopter ever created.

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Contents  Introduction ………………………………………………………………………………………….5  

A Helicopter ………………………………………………………………………………………….6 Principle of Flight …………………………………………………………………………………7

 The need for the apache ……………………………………………………………………….9  Power system………………………………………………………………………………………10 

Survivability and Structural Advances …………………………………………………. 13 Weapons ……………………………………………………………………………………………. 16

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Controls ……………………………………………………………………………………………… 18

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 Sensors ……………………………………………………………………………………………….19 

Armour and Defence ………………………………………………………………………….. 20

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Self sealing fuel system ……………………………………………………………………….21 Specifica tions ………………………………………………………………………………………21

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 Limitations …………………………………………………………………………………………. 22  Applications ……………………………………………………………………………………….. 22  Bibliography ……………………………………………………………………………………….. 23

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Introduction The AH-64 Apache attack helicopter was developed by Boeing. It is one of the most advanced attack helicopter in service today. It is a multi-mission attack helicopter and a very advanced and accurate battlefield weapon-delivery platform. It has day or night and all-weather flight capabilities in any climate zone. Primary mission for the AH-64 Apache is high-value target destruction. It is armed with a 30-mm M230 chain gun, Hydra 70 rocket pods and Hellfire missiles. It can carry up to 16 Hellfire anti-tank laser-guided missiles. This missile has a range of fire in up to 8 kilometres and can be also used against buildings and other material targets. Hydra rockets are mainly used against soldiers or light armoured vehicles. The 30-mm chain gun has a combat load of  1 200 rounds. It can also carry air-to-air missiles for a close-range air defence. These include AIM 92 Stinger, AIM-9 Sidewinder, Mistral or Sidearm. This helicopter has a number of survivability equipment, while some of its vital mechanisms can resists hits from 23-mm gun fire. It has a common attackhelicopter arrangement with a co-pilot/gunner seating in front and the pilot behind him. The AH-64 Apache is powered by two General Electric gas turbine engines. Each of them delivers 1 890 shaft horse power. In case one of the engines is damaged or failed, this helicopter can continue to fly powered by a single unit. The AH-64 has a maximum cruising speed of 230 km/h with a flight endurance of over three hours. Combat radius of this helicopter is approximately 150 kilometres. There are two main variants of the AH-64. The AH-64A and improved AH-64D Longbow Apache. US Army and NATO countries operate over 800 Apache helicopters of both variants.

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 A Helicopter  A helicopter (informally known as a "chopper") is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft would usually not be able to take off or land. The capability to efficiently hover for extended periods of  time allows a helicopter to accomplish tasks that fixed-wing aircraft and other forms of vertical takeoff and landing aircraft cannot perform.

The First helicopter 

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Principle of Flight  Helicopters were developed and built during the first half-century of flight, with the Focke-Wulf Fw 61 being the first operational helicopter in 1936. Some helicopters reached limited production, but it was not until 1942 that a helicopter designed by Igor Sikorsky reached full-scale production, with 131 aircraft built. Though earlier designs used more than one main rotor, it was the single main rotor with anti torque tail rotor configuration of this design that would come to be recognized worldwide as the helicopter.

DRAG: Drag is an aerodynamic force that resists the motion of an object moving through a fluid. The amount of drag depends on a few factors, such as the size of the object, the speed of the car and the density of the air.

THRUST: Thrust is an aerodynamic force that must be created by an airplane in order to overcome the drag. Airplanes create thrust using propellers, jet engines or rockets.

WEIGHT: This is the force acting downwards or the gravitational force. LIFT: Lift is the aerodynamic force that holds an airplane in the air, and is probably the important of the four aerodynamic forces. Lift is created by the wings of the airplane. Lift is a force on a wing immersed in a moving fluid, and it acts perpendicular to the flow of the fluid but drag is the same thing, but acts parallel to the direction of the fluid flow. 1. Air approaching the top surface of the wing is compressed into the air above it as it moves upward. Then, as the top surface curves downward and away from the air stream, a low pressure area is developed and the air above is pulled downward toward the back of the wing.

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2. Air approaching the bottom surface of the wing is slowed, compressed and redirected in a downward path. As the air nears the rear of the wing, its sped and pressure gradually match that of the air coming over the top. The overall pressure effects encountered on the bottom of the wing are generally less pronounced than those on the top of the wing.

FOR STRAIGHT AND LEVEL FLIGHT  The following relationships must be true:

THRUST = DRAG WEIGHT = LIFT If for any reason, the amount of drag becomes larger than the amount of  thrust, the plane will slow down. If the thrust is increased so that it is greater than drag, the plane will speed up. If the amount of lift drops below the weight of the airplane, the plane will descend. By increasing the lift, the pilot can make the airplane climb. 7

The Need for the Apache The conflict in Vietnam conclusively demonstrated the importance of  helicopter-provided close air support. Armed helicopters could move readily within a theatre of operations and bring significant firepower to bear to, among other things, support beleaguered ground units, and hold enemy combatants in place for a ground attack, and secure a landing zone as part of a vertical envelopment operation. The attack helicopter function was initially performed by transport and scout helicopters, most notably the Bell UH-1 Huey and the OH-6A Cayuse, retrofitted with additional armament. The Army’s first purpose-built attack helicopter, the Bell AH-1G Cobra, was deployed to Vietnam in 1967. While the Cobra, based on the UH-1, was a step forward in helicopter technology, the experience in Vietnam revealed some key deficiencies. The Cobra’s engine often could not provide the power to carry a full load of fuel or

ammunition to the fight, and the aircraft proved vulnerable to ground fire. The latter issue was of particular importance to the Army because the anticipated future combat environment, on the plains of central Europe against an adversary with modern air defences, promised to be even more hazardous to helicopters than Vietnam. The first attempt to build an improved, more survivable attack helicopter was unsuccessful. The Advanced Aerial Fire Support System program, begun in the mid-1960s, produced Lockheed’s AH-56A Cheyenne. The Army tested prototypes of the aircraft, but ultimately rejected it. The Cheyenne was an improvement in some areas, but it suffered from assorted technical shortcomings. In addition, the Army had reassessed the threat environment and its aviation needs. The Cheyenne had been designed to engage ground targets while making swift passes. This was the way in which the Cobra was employed, but this type of operation was made significantly more dangerous by the proliferation of effective, man-portable, antiaircraft missiles. The North Vietnamese forces had some success against U.S. helicopters with the SA-7 shoulder-fired anti-aircraft missile, a type of weapon the Soviet bloc would have in great supply. These losses, and subsequent experience that showed that helicopter gunships could adjust and sustain low-level operations, prompted the Army to rethink helicopter tactics and the capabilities that the next aircraft would need.

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Power System The apache is blessed with the twin rotor General electric T700 GE 701C turbo shaft engine creating a massive 1,700 horse power each. The engine is connected to drive shaft which in turn is connected to the gear box which transmits the power to the transmission. The transmission transmits the power to the main rotor assembly and the shaft which leads the power to the tail rotors.

T700 Engine A turbo shaft engine is a form of gas turbine which is optimized to produce free turbine (see graphic at below) shaft power, rather than jet thrust. In concept, turbo shaft engines are very similar to turbojets, with additional turbine expansion to extract heat energy from the exhaust and convert it into output shaft power. Turbo shaft engines are commonly used in applications which require a sustained high power output, high reliability, small size, and light weight. These include helicopters, auxiliary power units, boats and ships, tanks, hovercraft, and stationary equipment. A turbo shaft engine is made up of two major parts assemblies: the gas generator and the power section. The gas generator consists of the compressor, combustion chambers with igniters and fuel nozzles, and one or more stages of turbine. The power section consists of additional stages of  turbines, a gear reduction system, and the shaft output. The gas generator creates the hot expanding gases to drive the power section. Depending on the design, the engine accessories may be driven either by the gas generator or by the power section.

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In most designs the gas generator and power section are mechanically separate so that they may each rotate at different speeds appropriate for the conditions. This is referred to as a free power turbine. A free power turbine can be an extremely useful design feature for vehicles, as it allows the design to forego the weight and cost of complex multi-ratio transmissions and clutches. The general layout of a turbo shaft is similar to that of a turboprop. The main difference is that a turboprop is structurally designed to support the loads created by a rotating propeller, as the propeller is not attached to anything but the engine itself. In contrast, turbo shaft engines usually drive a transmission which is not structurally attached to the engine. The transmission is attached to the vehicle structure and supports the loads created instead of the engine. However, in practice many of the same engines are built in both turboprop and turbo shaft versions, with only minor differences. An unusual example of the turbo shaft principle is the Pratt & Whitney F135PW-600 engine for the STOVL F-35B - in conventional mode it operates as a turbofan, but when powering the Lift Fan it switches partially to turbo shaft mode to send power forward through a shaft (like a turboprop) and partially to turbojet mode to continue to send thrust to the rear nozzle.

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Transmission Work on the transmission was equally important to the Apache’s power

system development. The transmission, initially designed by Hughes, takes input power from the two T700 engines, reduces the speed of rotation, and transfers the power to the main rotor shaft, accessory gearbox, and tail rotor assembly. Between each engine output shaft and the main transmission is an engine nose gearbox. Each gearbox is equipped with an over-running clutch. If  the shaft from the transmission is running faster than the corresponding shaft from the turbine, the clutch disengages. When the opposite is true or the speeds of rotation are equal, the clutch is engaged. The turbine output shafts rotate at 20,900 rpm. This is reduced in the gear box at the front of the engine by reduction gears by a factor of 2.129; the transmission and subsequent gear boxes then further reduce the rotational speed such that the main rotor turns at about 200-400 rpm. This is a total gear reduction of about 50:1 (compared to an automobile in which the gear reduction is only about 4:1). The transmission also required considerable work on advanced gear technology by the Army/NASA Glenn staff. For gears and bearings, the Army/NASA work overcame barriers to higher performance in terms of speed, loading, and operating temperatures. Work on double-vacuum melted, high hot-hardness bearing steel and on gear alloys “doubled the power density compared to previous engines and vastly improved reliability.

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Survivability and Structural Advances Some of the most important innovations on the Apache had is keeping the crew safe. Crew safety was a fundamental requirement. The helicopter is able to withstand hits from heavy machine guns, and its crew has 95 percent chance of surviving a crash at a vertical speed of 42 feet per second.In this topic we first present with two categories of survivability: vulnerability (reducing the likelihood of a kill if hit) and susceptibility (reducing the likelihood of being hit in the first place). This is followed by a discussion of  important structural advances.

Vulnerability and Susceptibility Reduction The Apache benefited from a range of noteworthy advances designed to protect the crew and the aircraft from hostile fire. Important strides were made in ballistic protection. In the mid-to-late 1970s, using about $200,000 per year of 6.2 funds, the Army Materials Laboratory at Watertown developed the concept of using a transparent laminate armour material to separate front and rear cockpits. The material, a glass/polycarbonate laminate, was patented by Army researchers and used above the seat line. With this shielding system in place, the likelihood that both the Apache pilot and gunner would be injured by a single hit was significantly reduced. The development of ceramic composite materials by industry and the Army laboratory at Watertown led to additional ballistic protection for Apache crew members. Seats that provided ballistic protection had their origin in the mid1960s, when work at Watertown showed that ceramic materials, with their high hardness and stiffness, were effective against small arms ammunition of  the type encountered in Vietnam. Boron carbide was demonstrated to be the most effective ceramic material; when coupled with glass-reinforced composite back-up material, it was able to defeat small arms threats. Following the Vietnam War, the use of Kevlar was proposed by Watertown as a material for the rear of the boron carbide armour. This combination provided even

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better weight efficiency and was chosen for use in the Apache for the helicopter crew seats.

Structural Advances During the Apache development, the idea of using integral armour for structural load-carrying purposes as well as for ballistic protection was advanced by Hughes Helicopter during discussions with Army materials scientists. Hughes utilized this innovative approach to realize significant weight savings. For example, the company made extensive use of electro-slag, highstrength steel for integral armour application in such components as hydraulic actuators, rotor pitch links, bearing sleeves, and crank assemblies. Fabrication from steel that exhibited high hardness and strength as well as high toughness enables the components to sustain ballistic impact and continue to function.

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Rotors and Blades of Apache The main rotor is used to rotate the blades of the helicopter but the main rotor exerts the rotation force on the helicopter itself. This force is countered by the two rotors situated at the tail of the helicopter. Each of the tail rotors has two blades. These blades are rotated in a direction opposite to that of the rotation force caused by the main rotor thus it restricts the helicopter from turning. By adjusting the pitch of the blades pilot can turn the helicopter in any direction he wants. The blades are made up of five stainless steel components which is then laminated with fibre glass to provide much greater a strength. The front end of  the blade is made up of titanium and the rear end is made up of a composite of  graphite. The titanium provides good reliability against the minor obstacles when helicopter is flying low.

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Weapons The main aim of the apache helicopter is to target and destroy the heavy enemy targets such as tanks and heavy guns and artillery’s. And to do this

lethal machine is fitted with the most accurate targeting system and heavy missiles to destroy the targets in one shot.

Hellfire missiles Apache’s primary weapon is hellfire missiles. Each of these missiles is a unique

aircraft in itself. It has its own guidance computer, steering control and propulsion systems. The warhead payload is also quite unique, it is laden with copper and has enough power to burn through armour of any tank. The missiles are connected to the four firing rails attached to masts on its wings. There are two masts on each wings and each can support four missiles. So, an Apache can be used to carry as many as 16 missiles at time. The target and the other data are received by the missile from the main computer of the helicopter. This then sends the launch signal. After the launch signal from the computer missiles ignites the propellant. As the missile march off to the target the velocity and the fins of the missile changes its direction towards the target. When the missile strikes the target the impact sensor senses the impact and triggers the warhead, thus detonating the explosive. Hellfire is a LASER guided weapon, this system has great advantages but have some drawbacks:  

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Any obstacle between the laser beam and the target could make it difficult for the missile to lock on to a particular target. If the missile passes through the cloud it may lose the location of the target as it will not be able to detect the laser, which might be able to have been obstructed due to the clouds. The helicopter has to make the laser fix on the target until the missile hits the target; this is quite a complicated job.

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Guns and rocket launchers:

Apache usually uses the hydra rocket launcher. The hydra rocket launchers contain about 19 2.5 inches fin rockets in its launching tube. Apache can fire single rocket at a time or can fire them in groups. The main advantages of the rocket are that it works with lots of warheads designs. So, it might be able to be powered with high power missiles or with some low explosive for small targets. Apache also has M320 30 mm automatic cannon for close targets and for dog fights. The cannon are a chain gun type design which is powered by motors that rotates the chain and the mechanism to load and eject the cartridges. The magazine can hold about 1200 rounds and the gun can fire it at the rate of  about 600 to 650 rounds per minutes. These bullets can penetrate light armours also.

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Controls Its cockpit is divided into two parts. The front part contains the co-pilot of the gunner and the rear section is occupied by the pilot. Both the section contains full support to the firing and flying operation as in case if one pilot needs to take the full control. The flying control is similar to the other helicopters i.e. the use of collective and cyclic controls. It contains digital stabilization system which stabilizes the helicopter and makes changes in the hydraulic system to make it fly as smoothly as possible. The cockpit allows pilots to keep an eye on everything through digital displays.

Fire Control  The Apache’s fire control system integrates the data needed to ensure that the aircraft’s crew can accurately fire on the targets they identify using TADS/PNVS and other sensors. The heart of the fire control system is the helicopter’s on -

board fire control computer. Important work on fire control for Army rotorcraft was done at BRL during the 1970s and early 1980s. BRL research provided a general 6-degree of freedom (6-DOF) model for ballistic weapons, namely gun ammunition and rockets, which could compensate for helicopter downwash, projectile drag, aircraft motion, atmospheric conditions, etc. This model was integrated with Apache’s on-board fire control computer; combined with target motion data from the TADS, it provided significantly increased engagement accuracy.

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Sensors The apache is laden with the sensors. It senses anything that comes within its range by use of millimetre radio waves. The radar is mounted on its mast. The signal received by the radar is processed by computer with the series of pre stored images to determine the excepted shape of the target. And displays this potential target on the screen of the gunner. The Apache is equipped with night vision which enables it see in the dark. It also contains normal camera and telescope. The computer displays each pilot the video feed into their helmets which have inbuilt screens. So, each pilot can move the sensor by using his or her head. Arrowhead is an advanced electro-optical and fire control system that AH-64 Apache helicopter pilots use for combat targeting of their Hellfire missiles and other weapons, as well as safe flight in day, night, or bad weather missions. Arrowhead’s forward-looking infrared (FLIR) sensors use advanced image processing techniques to give pilots the best possible resolution to avoid obstacles such as wires and tree limbs during low-level flight.

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 Armour and Defence As I said earlier the apache is built to fly low on ground hence the safety is of  quite a high concern. It contains radar jammer that messes up with the radar signal and can confuse the enemy. Another high-tech system called black hole infrared suppression system is used to reduce the infrared signal to evade the heat seeking missiles. It actually did by cooling the exhaust gases by mixing it with air flowing around the helicopter. It also has an infrared jammer that emits infrared radiations of variable frequencies to confuse heat seeking missiles. Apache is heavily armoured and is also coated with Kevlar for extra protection. The cockpit is protected by reinforced armours and bullet proof glass.

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Self Sealing Fuel System In aviation, self-sealing fuel tank is a fuel tank technology in wide use since World War II that prevents fuel tanks primarily on aircraft from leaking fuel and igniting after being damaged by enemy fire. Self-sealing tanks have multiple layers of rubber and reinforcing fabric, one of  vulcanized rubber and one of untreated natural rubber that can absorb oil and expand when wet. When a fuel tank is punctured, the fuel will seep into the layers, causing the swelling of the untreated layer, thus sealing the puncture.

Specifications The following is the specification of apache AH- 64D……………….

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Limitations a. As it is a helicopter it can’t be used at high altitudes with loads. b. Highly trained and professionals are required to handle this lethal weapon, THE APACHE. c. Hellfire missiles which are the primary weapon may lose their target in clouds. d. Any obstacle between the laser beam and the target could make it difficult for the missile to lock on to a particular target. e. The helicopter has to make the laser fix on the target until the missile hits the target; this is quite a complicated job.

 Applications a. The apache is mostly used in wars for destruction. b. It can also be used in rescue operation of soldiers. c. Apache can be deployed at border areas for quick response and patrolling.

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Bibliography  a. www.wikipedia.org b. www.google.com c. seminar/Apache%20Helicopters%20%E2%80%93%20The%20Ultimat e%20Killing%20Machine%20%20%20DAILY%20WIKI.htm d. www.howstuffworks.com e. seminar/Helicopter%20Priciples.htm

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