The Vietnam War marked the birth of new class of helicopters capable of supporting ground troops with sufficient firepower and speed to be decisive in the effective ambushes organized by the Viet Cong. At first, the useful UH-1 Huey helicopters were equipped with machine guns, but that was not enough, so the first attack helicopter as we know it today, the AH-1 Cobra, was finally developed. This was the seed of all current attack helicopters, and especially the AH-64A Apache.The AH-1 Cobra helicopter had many qualities, but also great drawbacks, such as the impossibility of flying at night or in bad weather, so it was decided to start in 1964 with the Army’s Advanced Aerial Fire Support System (AAFSS) program to acquire a new most capable attack helicopter. This program led to the development of the Lockheed AH-56 Cheyenne (on the image), which after 5 years of testing (1967-72), was canceled due to enormous technical problems derived from its complex and advanced technology. After this cancellation, a new program known as the Advanced Attack Helicopter (AAH) program was started in 1972.In 1972 the US Army specified two basic requirements for the new helicopter. The first indicated that it must be a weapons system integrated with the main anti-armor combat mission. The second specified that the helicopter must carry two General Electric T-700 turboshaft engines and must have a 30mm gun for anti-armor and suppressive fire missions. The companies Bell, Boeing Vertol, Hughes, Lockheed and Sikorsky participated in this competition, and in June 1972 Bell Helicopter with its model 409 and Hughes with its model 77 were selected to build a static test airframe and two flying prototypes each. The Bell prototype was designated YAH-63 (on the image) and the Hughes prototype was designated YAH-64.In the fall of 1976, the US Army tested the Bell YAH-63 and concluded that it provided very few improvements over the AH-1 Huey Cobra, so it was quickly eliminated from the competition. Hughes’ YAH-64 made its first flight on September 30, 1975 and demonstrated from the beginning that it was a device completely designed from scratch with numerous technical innovations. It had two engines and a 4-bladed rotor with a fixed landing gear and a tandem cockpit with the gunner in front and the pilot behind. In addition, it had two stub wings with two weapon harpoints each and carried a gun under the front part of the fuselage, incorporating a space reserved in the nose for the installation of the fire control system.In early December 1976 the US Army announced that the Hughes YAH-64 prototype (on the image) was chosen to continue its development and be the next attack helicopter. The easy maintenance and survivability capabilities designed by Hughes had a lot to do with the decision. The main rotor was fully articulated, the engine access panels served as work platforms for the mechanics and the landing gear could be lowered to facilitate access to the highest parts of the aircraft. The cockpit had several Kevlar armor plates and both crew members were separated by a transparent blast shield that increased the chances of survival if the aircraft was hit. The engines, airframe, rotor blades and transmission could withstand impacts from 12.7mm ammunition without problems and some of these parts could resist impacts from 23mm caliber rounds without being disabled.In January 1977, the second phase of development began, which would last 56 months. In this period Hughes had to manufacture 3 other prototypes to continue development. These 3 aircraft left the factory with some modifications such as swept tips in the main rotor or larger diameter tail rotor. In this testing phase it was decided that the helicopter’s main weapon would be the new Rockwell Hellfire anti-tank missile, which was being developed in that same period and had greater capabilities than the TOW anti-tank missile, initially chosen. In March 1979, one of the YAH-64 prototypes (on the image) successfully fired a Hellfiremissile so it became evident that this helicopter-missile tandem would work perfectly.One of the tests required in this second phase was to achieve a vertical climb rate of 150 meters per minute loaded with fuel for almost 2 hours of operations, 8 Hellfire missiles and 320 30mm projectiles in an ambient temperature of about 35ºC. The prototype not only achieved this figure, but multiplied it by 3, reaching 450 meters per minute!. Between 1979 and 1983 the YAH-64 prototypes completed some 4,000 flight hours and numerous demonstrations, including a tour on different NATO countries in 1982 with a view to future sales. Also in 1982, the Marines tested one of the prototypes as a replacement for their AH-1T Sea Cobra helicopters, without any orders materializing. Around this time, prototype number 4 was destroyed when it collided in the air with a chase plane.In 1981 the YAH-64 helicopter was named Apache, continuing the US Army’s custom of naming its helicopters after North American Indian tribes. In 1982, the first order was placed for eleven AH-64As, which would carry new repowered General Electric T700-GE-701 engines of 1,723 hp. This engine had been developed for the US Navy’s SH-60 Seahawk helicopter, but after being tested on one of the YAH-64 prototypes, it was found that they were perfectly compatible with the airframe and it was decided to install it on all serial Apaches. In March 1982 Hughes began construction of a new plant to manufacture Apache helicopters in Mesa, Arizona. In February 1983 Hughes personnel occupied the new facilities and everything was prepared to start serial production in March 1983. The new helicopter would be manufactured under the official designation “AH-64A Apache” (on the image).The production AH-64A differed from the prototypes and carried all the modifications accepted during the testing phase. They had a new lower mounted stabilator, a larger diameter tail rotor, a larger lateral avionics bay, a new bulged canopy, new weapons pylons and a completely redesigned nose to house the TADS/PNVS turret sensor. Nevertheless, they retained protection against 12.7mm ammunition in all vital parts and against 23mm ammunition in the most sensitive areas, and the canopy protects the crew from small arms fire. It also had two self-sealing fuel cells with an inert nitrogen system that reduced the oxygen inside and thus the danger of fire. The fuselage could withstand a crash against the ground at 46 km/h and the canopy had anti-roll bars to protect the crew in the event of an accident.This helicopter is equipped with active defenses such as an AL/ANQ-144 IR jammer, an M-130 chaff/flare dispenser with 30 M-1 chaff rounds and a passive radar warning receiver, which together form a system called Aircraft Survivability Equipment ( ASE). In addition, the engine exhaust fitted the McDonnell Douglas “Black Hole IR suppression system”, which served to reduce the temperature of the exhaust gases and made their IR signature smaller. The 4 blades of the main rotor are foldable and made of stainless steel tube covered with an external skin of graphite composite. The tail rotor is “scissors” type with the 4 blades mounted at 60º and 120º to each other. The design of these rotors makes the Apache twice as quiet as other attack helicopters, making its location on the battlefield much more difficult.To facilitate repairs and maintenance tasks during operations, the transmission could be replaced without having to disassemble the main rotor and all electrical and hydraulic connections on the helicopter were of the “plug-in” type. An onboard fault detector/locator system was also installed, which showed the faults to the ground crew on a screen. The main parts of the aircraft were very resistant and were made of aluminum and the lubrication of many moving parts was done with grease instead of oil. The Apache had a 125 hp Garrett Air-Research APU (auxiliary power unit) incorporated that provided power to its electrical, pneumatic and hydraulic systems when it was on the ground and also served as a starter for the main engines.The ease of being able to perform some basic maintenance tasks on the battlefield is reflected in some curious data. For example, a two-person team can rearm 8 Hellfire missiles in 5 minutes and fill the fuel tanks in just 4 minutes. Another fact that reflects the Apache‘s survivability is that the Litton Precision Gear Division transmission could continue to operate for 1 hour without lubrication, as could gears and axles, which could continue to function after having suffered ballistic damage.The General Electric T700-GE-701 engines give the Apache exceptional performance and maneuverability, allowing it to perform loops, rolls and maneuvers never before seen in helicopters. It reaches a maximum speed of 293 km/h, with a design limit speed of 325 km/h, although during tests it reached a maximum of 391 km/h during a dive without suffering damage. Its range with internal fuel is about 500 km and the maximum range with external fuel tanks is 1,745 km. The vertical climb rate is 818 meters per minute and the service ceiling is 6,400 meters. Despite the 40 years that have passed since its entry into service, these features remain exceptional for an attack helicopter even today.Among the many innovations developed for the AH-64A, its modern integrated weapons, electronic and “visionic” (combined vision and electronics) systems stood out. This combined system was built by Martin Marietta Electronics and was made up of two primary sensor systems, the Target Acquisition and Designation System (TADS) and the Pilot Night Vision Sensor system (PNVS), which were mounted in a kind of turret in the nose. This turret also houses the radar jammer transmitter antenna, next to the TADS system, while the radar jammer receiver antenna is installed in front of the main rotor mast.TADS system is mounted on the lower part of the nose turret and contains high-power optical elements for direct observation. It has a high resolution TV system for daytime operations, a Forward Looking Infra Red (FLIR) sensor for nighttime operations, a laser spot tracker and a laser target designator/range finder. All target data acquired by TADS are presented to the crew members through the on-board computer. This system can move in a horizontal arc of 240º and in a vertical arc of -60º to +30º and is normally used by the gunner/copilot, although it can also be used by the pilot.The AN/AAQ-11 PNVS system is placed on top of the TADS and offers the pilot real-time thermal images of the surrounding terrain through the Integrated Helmet and Display Sighting System (IHADSS). The pilot can view these high-resolution images through a monocle located on the right side of the helmet along with other flight and available weapons data. This system allows operations to be carried out in total darkness or in bad weather. The helmet is linked to the PNVS sensor in such a way that the pilot directs the movement of the sensor with the movement of his head. This sensor can move in a horizontal arc of 180º and in a vertical arc of -45º to +20º.Along with the optronic equipment, the Apache also has a set of UHF-AM, VHF-AM and FM radios for secure air-to-air and air-to-ground communications and various navigation aids. Among the latter is an Automatic Directional Finder (ADF), a precise radar altimeter that operates between 0 and 500 meters, a Lightweight Doppler Navigational System (LDNS) and a Heading Altitude Reference System (HARS) that not only tracks the terrain, but stores data on target location during flight. The avionics are completed with an Identification Friend or Foe (IFF) transponder.Another innovative system is the Air Data Sensor (ADS), which is an equipment installed at the top of the rotor mast and which offers the pilot data related to lateral and longitudinal air, ambient temperature and pressure, angle of side slip and air density ratio. These data are sent to the on-board computer which, after analysis, offers the best options to the fire control system as well as data to the Digital Automatic Stabilization Equipment (DASE). The DASE system uses the data obtained by the ADS and HARS systems to help the pilot maneuver the aircraft through automatic control actions. This system allows the Apache to make turns of up to 130º at speeds between 200 and 230 km/h, maneuvers that very few helicopters can achieve.Each crew member has their own instrument panel adapted to their own tasks. The pilot panel (on the image) has a complete set of analogue indicators that show data regarding engine parameters like torque, oil pressure and gas temperature, and flight parameters like airspeed, vertical speed and altitude among others. It also has a Video Display Unit (VDU) that shows navigation and flight parameters, weapons systems available and terrain images obtained by FLIR and PNVS systems.The gunner/copilot panel (on the image) only has basic information about flight parameters and some engine parameters through analog indicators. Instead, he has a complete weapons system control panel along with a multipurpose sight. From this panel the gunner controls the weapons and the FLIR, TADS, Fault Detection/Location and Optical Relay Tube (ORT) systems. This last system is associated with several switches and manual controls that allow target tracking using IR, Laser and TV sensors in any weather condition. Of course, any of the weapon systems can be directed by the gunner or the pilot interchangeably through the TADS, FLIR and IHADSS systems under any weather conditions, day and night, which gives the Apache exceptional operational flexibility.The AH-64A Apache has three main weapons systems, gun, unguided rockets and anti-tank missiles. The gun is an electrically powered, air-cooled 30mm M230 Chain Gun that has a maximum rate of fire of about 600-650 rounds/min, but the practical rate is 300 to avoid overheating of the barrel. It is installed in a hydraulically operated mobile mount (chin turret) under the co-pilot station and can move in a horizontal arc of 220º and in a vertical arc of -60º to +11º. The Apache has the capacity to carry 1,200 rounds, although US Army helicopters only carry 300 as they carry a special internal fuel tank in that space. This gun uses 3 types of ammunition, the M-788 high explosive (HE), M-789 high explosive incendiary (HEI) and M-799 high explosive dual purpose (HEDP) rounds, although the most used by the US Army is the M-789 HEDP round, capable of penetrating 25mm of armor at 500 meters.During attack missions on infantry formations the Apache uses 70mm APKWS, Hydra 70 or CRV7 unguided rockets fired from 19-cell LAU-3 A or M-261 launchers. These rockets have a maximum range of 6 km and can be fired from any altitude. The US Army uses rockets with different warheads such as the M-255 or the M-261. The M-255 warhead contains about 2,500 one-ounce steel fragments and is suitable against personnel and soft skin vehicles. The M-261 warhead contains a shaped charge and is effective against armor vehicles.Despite being able to carry out any type of attack mission, the Apache is actually helicopter created for anti-tank combat. For this task it has the different variants of the effective AGM-114 Hellfire anti-tank missile. This missile has a maximum range of 8 km and is of the “fire and forget” type with laser guidance, but it needs a laser designator to illuminate the target. The AH-64A can carry a maximum of 16 missiles in groups of 4 on each of the 4 underwing pylons, although usually no more than 8 are carried per mission. These missiles can be fired from any altitude and at any speed, in direct or indirect fire mode following the laser beam provided by ground troops. There are three shooting modes, one by one, rapid and blank. Theoretically the Apache could fire the 16 missiles in 32 seconds, illuminating the targets consecutively, but in practice this is impossible to achieve.Apart from these weapon systems, some more have been tested such as air-to-air, anti-radiation or anti-ship missiles. Of the air-to-air type, the use of Stinger and Sidewinder (on the image) missiles was approved, more as self-protection weapons than as offensive weapons, although the American AH-64A do not usually carry them. AGM-122 Sidearm light anti-radiation missiles were also tested without their use being approved and regarding anti-ship missiles, it is known that the Harpoonand Penguinmissiles have been studied for naval variant of the Apache. They can also use other anti-tank missiles such as TOW, although all Apache users have opted for the much more effective Hellfire.With the operational use of the AH-64A some problems arose with the ammunition carrier, gun jamming and the premature breakage of some hydraulic lines. These problems were quickly solved and the opportunity was taken to incorporate some improvements and modifications to the new series Apaches such as wire cutters, an improved IR suppression system, an improved fire control computer, an improved helmet display unit, improved air conditioning system, installation of a GPS system, expansion of the forward avionics bay and improvement of air-to-air capacity. These improvements were also installed on the older AH-64A, which received kits with all this equipment for installation.
