The Boeing (formerly McDonnell Douglas, formerly Hughes) AH-64A Apache is the Army's primary attack helicopter. It is a quick-reacting, airborne weapon system that can fight close and deep to destroy, disrupt, or delay enemy forces. The Apache has been designed to fight and survive during the day, night, and in adverse weather throughout the world. The principal intended mission of the Apache is the destruction of high-value targets with the HELLFIRE missile, primarily hostile armor. It is also capable of employing a 30mm M230 chain gun and the Hydra 70 (2.75 inch) family of rockets that are lethal against a wide variety of targets. The Apache has a full range of aircraft survivability equipment and has the ability to withstand hits from rounds up to 23mm in critical areas. The AH-64 is air transportable in the C-5, C-141 and C-17.
The AH-64 Apache is a twin-engine, four bladed, multi-mission attack helicopter designed as a highly stable aerial weapons-delivery platform. It is designed to fight and survive during the day, night, and in adverse weather throughout the world. With a tandem-seated crew consisting of the pilot, located in the rear cockpit position and the co-pilot gunner (CPG), located in the front position, the Apache is self-deployable, highly survivable and delivers a lethal array of battlefield armaments. The Apache features a Target Acquisition Designation Sight (TADS) and a Pilot Night Vision Sensor (PNVS) which enables the crew to navigate and conduct precision attacks in day, night and adverse weather conditions.
The Apache program had the potential to evolve into four different models in service simultaneously. These models were, the AH-64A, an AH-64+ with product improvements applied, and an AH-64D Longbow Apache with glass cockpit display, advanced engines, wiring for Longbow systems, radar interferometer, and the Longbow missile system. This AH-64D standard was previously known as AH-64C. Approximately 1/3 of the Longbow fleet was planned to also be equipped with the Longbow millimeter wave fire control radar, the original AH-64D standard. Converting an A model to a D model costs about $10 million. The Longbow FCR adds another $3.6 million to the price tag.
As part of the reduction in the planned buy of the Comanche in late 2002, the Army was directed to formulate a service life extension program for the Apache. Although DoD did not provide the Army a specific end-date for the Apache, the AH-64 Longbow had the potential to remain in service until 2030.
The Apache can carry up to 16 HELLFIRE (Helicopter-Launched, Laser-guided, Fire and Forget) laser guided missiles. With a range of over 8000 meters, the HELLFIRE is used primarily for the destruction of tanks, armored vehicles and other hard materiel targets. The Apache can also deliver a maximum of 76, 70mm/2.75" wrap-around fin aerial rockets (WAFAR) for use against enemy personnel, light armor vehicles and other soft-skinned targets. Rounding out the Apache's deadly punch are 1,200 rounds of ammunition for its Area Weapons System (AWS), featuring the M230 30mm Automatic Gun.
An on-board video recorder has the capability of recording up to 72 minutes of either the pilot or CPG selected video. It is an invaluable tool for damage assessment and reconnaissance. The Apache's navigation equipment consists of a doppler navigation system, and most aircraft are equipped with a GPS receiver.
The Apache has state of the art optics that provide the capability to select from three different target acquisition sensors. These sensors are:
- Day TV - Views images during day and low light levels, black and white.
- TADS FLIR - Views thermal images, real world and magnified, during day, night and adverse weather.
- DVO - Views real world, full color, and magnified images during daylight and dusk conditions.
AH-64 aviators use the Integrated Helmet and Display Sighting System (IHADSS). The IHADSS helmet, at the time of its development, was lighter in weight and provided improved impact protection over the then-current SPH-4 series helmet. The IHADSS was the only helmet approved for the AH-64 and has been in use for over 20 years. A unique feature of the IHADSS helmet is that it serves as a platform for a Helmet Mounted Display (HMD). The HMD provides pilotage and fire control imagery and flight symbology. In order to view the HMD imagery, the helmet/HMD must be fitted such that the exit pupil of the HMD is properly aligned with the aviator's eye each time it is donned. This makes the fit and stability of the IHADSS helmet critical considerations. Achieving a proper fit of the IHADSS helmet is complicated by its intricate system of straps and pads. A proper, customized, repeatable fit is required in order to maintain the exit pupil position and optimize the resulting full Field of View (FOV). Fitting of the IHADSS helmet typically takes several hours to complete. This fitting process must be repeated every time aviators are transferred to a new duty station, as they cannot take the IHADSS helmet with them. It is part of the AH-64 aircraft system and is unit property.
The Apache has four articulating weapons pylons, two on either side of the aircraft, on which weapons or external fuel tanks can be mounted. The aircraft has a Laser Range Finder/Designator (LRF/D). This is used to designate for the HELLFIRE missile system as well as provide range to target information for the fire control computer's calculations of ballistic solutions.
Threat identification through the FLIR system is extremely difficult. Although the AH-64 crew can easily find the heat signature of a vehicle, it may not be able to determine friend or foe. Forward looking infrared detects the difference in the emission of heat in objects. On a hot day, the ground may reflect or emit more heat than the suspected target. In this case, the environment will be "hot" and the target will be "cool". As the air cools at night, the target may lose or emit heat at a lower rate than the surrounding environment. At some point the emission of heat from both the target and the surrounding environment may be equal. This is IR crossover and makes target acquisition/detection difficult to impossible. IR crossover occurs most often when the environment is wet. This is because the water in the air creates a buffer in the emissivity of objects. This limitation is present in all systems that use FLIR for target acquisition.
Low cloud ceilings may not allow the HELLFIRE seeker enough time to lock onto its target or may cause it to break lock after acquisition. At extended ranges, the pilot may have to consider the ceiling to allow time for the seeker to steer the weapon onto the target. Pilot night vision sensor cannot detect wires or other small obstacles.
Overwater operations severely degrade navigation systems not upgraded with embedded GPS. Although fully capable of operating in marginal weather, attack helicopter capabilities are seriously degraded in conditions below a 500-foot ceiling and visibility less than 3 km. Because of the HELLFIRE missile's trajectory, ceilings below 500 feet require the attack aircraft to get too close to the intended target to avoid missile loss. Below 3 km visibility, the attack aircraft is vulnerable to enemy ADA systems. Some obscurants can prevent the laser energy from reaching the target. They can also hide the target from the incoming munitions seeker. Dust, haze, rain, snow and other particulate matter may limit visibility and affect sensors. The HELLFIRE remote designating crew may offset a maximum of 60 degrees from the gun to target line and must not position their aircraft within a +30-degree safety fan from the firing aircraft.
Powered by two General Electric gas turbine engines rated at 1890 shaft horsepower each, the Apache's maximum gross weight is 17,650 pounds which allows for a cruise airspeed of 145 miles per hour and a flight endurance of over three hours. The AH-64 can be configured with an external 230-gallon fuel tank to extend its range on attack missions, or it can be configured with up to four 230-gallon fuel tanks for ferrying/self-deployment missions. The combat radius of the AH-64 is approximately 150 kilometers. With one external 230-gallon fuel tank the radius is approximately 300 kilometers. Both radii are dependent on temperature, pressure altitude, fuel burn rate, and airspeed. The addition of up to two wing tanks can further extend range. However, this configuration is currently authorized for ferry/self-deployment flights only. The Apache can attack targets up to 150 km across the FLOT. If greater depth is required, the addition of ERFS tanks can further extend the AH-64's range with a corresponding reduction in HELLFIRE missile carrying capacity (four fewer Hellfire missiles for each ERFS tank installed).
The Apache fully exploits the vertical dimension of the battlefield. Aggressive terrain flight techniques allow the commander to rapidly place the ATKHB at the decisive place at the optimum time. Typically, the area of operations for Apache is the entire corps or divisional sector. Attack helicopters move across the battlefield at speeds in excess of 3 kilometers per minute. Although dependent on mission, enemy, terrain, troops, time available, and civilian (METT-TC) considerations, typical planning airspeeds are 100-120 knots (185-222 km/hr) during daylight, and 80-100 knots (148-185 km/hr) at night. Speeds during marginal weather are reduced with respect to prevailing conditions.
The Russian-developed Mi-24 (NATO codenamed Hind) has been one of the Apache's closest counterpart. The Russians have deployed significant numbers of Hinds in Europe and have exported the Hind to many third world countries. The Russians have also developed the KA-50 (NATO codenamed Hokum) as their next generation attack helicopter. The Italian A-129 Mangusta is one of the the nearest NATO counterparts to the Apache. The Germans and French also co-developing the PAH-2 Tiger attack helicopter, which has many of the capabilities of the Apache.
Apache production began in FY82 and the first unit was deployed in FY86. As of November 1993, 807 Apaches were delivered to the Army. The US Army ordered 821 aircraft (excluding prototypes), with the last Army Apache delivery on December 1995. 33 attack battalions are deployed and ready for combat. The Army looked to procure a total of 824 Apaches to support a new force structure of 25 battalions with 24 Apaches for each unit (16 Active; 2 Reserve; 7 National Guard) under the Aviation Restructure Initiative. Army National Guard units in North and South Carolina, Florida, Texas, Arizona, Utah and Idaho have flown Apache helicopters. The Army has fielded combat-ready AH-64A units in the United States, West Germany and in Korea, where they have played a major role in achieving the US Army's security missions.
The Army announced 5 November 1999 that all its 660 AH-64A and 83 AH-64D models must be inspected before their next flight. The hanger bearing assemblies fore and aft house the drive train, which passes turbine engine power to the tail rotor. A failure in the flange area will result in loss of tail rotor thrust and such a failure could be catastrophic. Army investigators had identified the bearing assembly problem while looking into a January 1999 accident at Fort Rucker, Alabama, that destroyed an Apache and injured the 2-man crew. Army officials said stress corrosion fractures resulting from a hardness heat-treat process used during manufacture may cause the bearing assemblies to fail. Hanger bearing assemblies produced after the Army changed the manufacturing process in 1993 do not have the potential for such fractures. Army officials determined that at least 400 of 743 AH-64 Apache attack helicopters needed the new parts.
In December 2000 the US Army grounded its entire AH-64 Apache helicopter fleet as a precautionary measure, following the discovery of a faulty tail rotor swashplate assembly. Failure of a tailrotor swashplate assembly, which produces yaw control, could result in the loss of an aircraft and crew injuries. The Army ordered an inspection of all 742 AH-64A and D aircraft to locate specific swashplate assemblies identified as being potentially faulty, which would be replaced.
In early 2001, the Apache community was operating under a shortage of M299 launchers and a HELLFIRE missile restriction. The M299 launchers, under contract to Boeing St. Charles, suffered a failure in testing and had been deemed unsafe. The power supply card had to be redesigned, which was estimated to take 7-8 months to complete and qualify. Reverting to the old design was not an option. Required components were no longer in production. DCSOPS had published a distribution plan. The PM-ARM was responsible for the development and fielding of the launchers and is working to correct the problems. The HELLFIRE restriction was driven by the new spacer in the motor impacting and damaging the stabilator and potentially the tail rotor.
Damage to 19 of 43 Apache Helicopters was detected following HELLFIRE missile firing during the USAREUR training exercise Victory Strike in Poland between 6 and 18 October 2000. Damage to AH-64A Helicopter horizontal stabilators was initially attributed to ground debris then later to the HELLFIRE missile. Two Apache units fired 385 AGM-114C model missiles and numerous 2.75 inch rockets and 30mm rounds without incident. PEO Aviation System Safety Risk Assessment (SSRA) assigned a Category I-A risk (Catastrophic Probable) if missiles were fired from any position other than position number 4 on right outboard pylon. The SSRA applied only to the AH-64D Helicopter. SSRA for other helicopters was a "due-out" from PEO Aviation. AMCOM IMMC worldwide suspension of HELLFIRE missiles with the deficient Alliant/Hercules motors remained in place as of mid-2001. All HELLFIRE missiles with this motor were in CC-N, emergency combat use only. This included the entire inventory of the Longbow HELLFIRE Millimeter Wave (AGM-114L) missile, and nearly 90% of the latest Laser production assets (AGM-144K & K-2).
TURBO CADS (TC) was a TRANSCOM administered, JCS funded, MACOM supported, joint live ammunition containerization exercise. TC involved the relocation, retrograde, and call forward of theater ammunition stocks. TURBO CADS 1 arrived Chinhae Korea on 7 June 2001 and HELLFIRE missiles (720 Longbow Millimeter Wave (MMW) and 280 Laser Hellfire (HFII)) were off-loaded from the Maersk Alaska and were en route to storage areas at Chunchon and Uijongbu. Missiles would support the FUE in EUSA for 1st BN/2nd AVN. The Longbow Hellfire MMW remained in Condition Code N (CC N) - Emergency Combat use only, until modified by the PM ARM. EUSA would retrograde a total of 1,000 Laser HELLFIRE missiles (AGM-114C) in CCA, which enabled continuation of CONUS annual service practice training into FY02. PM ARM would design, develop and qualify a replacement ring grain spacer for Alliant-TECH/Hercules missiles. However, qualification and testing had to be completed before the new design motors would be manufactured and inserted into the on-going Longbow Hellfire missile production line currently scheduled in January 2002. An Unfinanced Requirement (UFR) of $35.718 million in FY02 Missile Procurement Army (MIPA) funds for retrofit of the ring grain spacer into extant inventory restricted the retrofit start date until second quarter FY03. Only Longbow and HF II missiles would be retrofitted with a projected completion date for FY05. This left some 45 percent of the remaining inventory of 12,000 missiles (AGM-114A, C and F models) to remain unmodified for either consumption in training or to become DEMIL candidates. Commander 101st Air Assault Division was in process of requesting release of Longbow missiles for storage at FT Campbell, Kentucky for the Division Ready Brigade aviation elements.
By the end of 2001 the crisis appeared to be over for the deliveries of the M299 Missile launchers. Deliveries were being accepted on schedule and the fielded units and units being fielded would have their full compliment of launchers by spring 2002. Lockheed Martin was being qualified to produce M299 launchers also. The existing SDZ firing restriction on the Hellfire missile was being analyzed. AMRDEC was conducting limited testing on the system until sufficient funding was provided to go ahead full force. AMRDEC expected to complete the analysis by the end of February 2002. The HELLFIRE motor retrofit effort was ongoing. Retrofitting of motors commenced in January of 2002 at the rate of about 60 missiles per month. A UFR has been submitted for the completion of 100% of all missiles requiring retrofit.
On 11 June 2001, an Israeli Air Force AH-64A experienced a catastrophic tail rotor failure in flight. The crew landed safely with no further damage to the aircraft. Investigation revealed that one of the four tail rotor blades had completely separated at the root area. Further investigation indicated that the blade failed due to metal fatigue cracking. Aviation and Missile Command (AMCOM) released Safety of Flight [SOF] message AH-64-01-04 on 15 June 2001. The SOF message established an interim 1,000 hour finite life (down from 6,201), for all AH-64A/D tail rotor blades (742 helicopters, four blades per helicopter). Aviation and Missile Command (AMCOM) released a follow up SOF message (AH-64-01-05) on 26 June 2001. This follow up SOF message established an interim recurring X-ray inspection of 125 hours. The X-ray inspection requires a specially trained technician certified to perform the procedure. This inspection was required before the next flight on tail rotor blades with 1000 hours or greater. For blades with less than 1000 hours, the X-ray inspection was due by 28 December 2001 or upon reaching 1000 hours, whichever came first. AMCOM estimated that 51 percent of the blades required the inspection before the next flight.
By July 2001 the Army was approaching 100 percent completion of inspecting all Active Duty, National Guard and Reserve AH-64 Apache tail rotor blades. As a precautionary measure, the Army deployed eighteen specially trained teams world wide to X-ray all Apache tail rotor blades. These teams have X-rayed over 99 percent of the over 3,000 tail rotor blades installed on aircraft and in the supply system, and have found none cracked. The teams proceeded to X-ray 100 percent of the tail rotor blades, to eliminate any possibility of a systemic problem. Although some Apache aircraft were grounded temporarily in the month of July, pending completion of tail rotor inspections, overall impact on the readiness of Army aviation was minimal.
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