Air University Review, November-December 1979

From each of the major wars of this century have come one or two technological breakthroughs that have had a significant impact on changing the conduct of war. World War I gave us the tank and first use of the airplane. World War II introduced air power and nuclear weapons. Probably the greatest contribution stemming from the Southeast Asia campaign was the use of the helicopter in combat.

In Southeast Asia, the U.S. Army learned significant lessons about helicopter tactics and also determined what features it wanted in the next generation of combat choppers. Using this experience along with projections about the future combat arena, the Army is developing two new weapon systems: the utility tactical transport aircraft system (UTT AS) and the advanced attack helicopter (AAH).

The UTT AS, or Black Hawk as it is now called, is designed to be a tactical transport for troops and supplies and for combat support operations. The AAH is primarily a tank killer but also can be used in an armed escort or fire support role. They are much more than just replacements for current transports and attack ships, namely the UH-l Huey and the AH-IS CobraTOW. They have been designed from the ground up specifically to meet future military requirements and to exploit fully the full potential of the helicopter in combat.

Although both craft have the flexibility to perform a wide variety of missions to support the Army's global responsibility, the primary driver behind the design of both is the mid-intensity battlefield situation found in Europe. Thus performance, survivability, ability to operate under night and adverse weather conditions, and maintainability/reliability were key considerations.

There are two aspects to survivability: First, avoid detection and second, if detected, make the craft invulnerable to destruction by enemy action. Survivability is an especially crucial issue in the European environment, where the anti-helicopter threat is increasing both in quantity and sophistication. Since most of Europe is shrouded either by clouds or darkness 70 percent of the time, a fair weather, daytime-only capability is of little value. High reliability and ease of maintenance are not only needed to ensure a high level of availability but also ensure low lifecycle costs. Subsequently, we will see how the Black Hawk and AAH satisfy these requirements, but first let us look at a brief description of the two.

The UH-60A Black Hawk is the Army's first true squad-carrying helicopter. It is capable of carrying a full eleven-man fighting team and all their associated combat gear, as well as a three-man flight crew. Now the Army has the ability to deposit an entire squad onto the battlefield as an integral team ready and equipped for combat. The UH-l did not have this capability. In this combat assault mode, the Black Hawk has a useful capacity of almost 6000 pounds, which includes the 2600-pound, fully equipped squad and sufficient fuel for a 300-nautical-mile round trip. In front-line duty, the UH-60A can also be used to extract troops, replace and resupply troops, and reposition units.

Tee Black Hawk will also be used for aeromedical evacuation and administrative transport of command, medical, and maintenance personnel. As an air ambulance, it can be used to carry four litters, attending medical personnel, and life-sustaining equipment. The UH-60A can lift up to 8000 pounds suspended from an external sling.

The Black Hawk can cruise at over 145 knots and has a maximum flight speed of 165 knots. Its normal mission endurance is over 2¼ hours and thus has a range in excess of 300 nautical miles. The UH-60A has a service ceiling of 5000 feet and a vertical rate of climb of over 450 feet per minute. While primarily a troop transport, it does carry two M-60 weapons that fire 7.62-mm rounds. A total of 1100 rounds is carried for defensive and fire suppression purposes. Having the latest in rotary wing avionics, it can fly to the operational area under instrument conditions and, once in the operational theater, can deposit its load of troops or cargo whether it be daytime or nighttime.

The AAH represents a significant improvement over the very capable AH-1S Cobra-TOW and can operate under more demanding altitude, weather, and temperature conditions. Of the two, the AAH is more reliable and more survivable against future expected threats. It is also easier to maintain, and, more important, it carries some very capable weapon systems. While its primary mission is antiarmor, it can also be used to escort troop choppers to the battle zone, protect truck convoys, and, if needed, it can be used for scouting and reconnaissance. In essence, the Y AH-64 is an aerial extension of the firepower traditionally provided by tanks, anti armor weapons, artillery, and infantry weapons.

The AAH has a two-man crew. A copilot/gunner rides in the front seat. The pilot is in the rear seat for more precise control, especially when flying nap-of-the-earth (NOE). The YAH60 weighs nearly 14,000 pounds when loaded with crew, fuel, and weaponry for a normal mission. However, it is capable of carrying almost 4000 pounds of additional weight.

The AAH has the performance needed to survive in combat. It can cruise at 146 knots and has a maximum forward speed of nearly 200 knots. It can travel at 45 knots either sideward or backward. It can climb at a rate of 880 feet per minute vertically or at 3500 feet per minute in a forward flight climb. While its primary mission configuration calls for an endurance of 1.8 hours, by trading payload for fuel, its endurance can be increased to 2.6 hours. It can even be ferried over a distance of 880 nautical miles.

The YAH-64 carries a wide assortment of sophisticated weaponry. First of all there are the sixteen HELLFIRE missiles that can be carried in four-rail launchers mounted on the aircraft's winglets. The HELLFIRE uses a laser designated guidance system in which the target is illuminated by a laser beam, and the missile rides the beam to the target. The target can be illuminated by the gunner/copilot, by a scout on the ground, or even from a remotely piloted vehicle (RPV). This represents a significant improvement over the TOW missile equipped AH-1S Cobra-TOW. The TOW missile must be controlled directly by the launching aircraft, since it gets its command through wires unreeled from the launch platform. Thus, the TOW launcher must remain exposed and vulnerable to enemy fire all the while the missile is in flight. With the HELLFIRE, the AAH can launch the missile and then hide or take evasive action, provided the target is being illuminated by another source.

The second weapon on the AAH is the 30-mm, XM-230 chain gun. This externally powered, single barrel gun is capable of firing any size burst from a single shot up at 620 rounds per minute. As many as 1200 rounds can be carried in the ammunition drum. The chain gun weighs a mere 110 pounds, provides low air drag because of its small size, and is simple to build and maintain, having less than 150 parts. The XM-230 can fire either the high-explosive or armor-piercing rounds that are standard within NATO. It can also fire a dual purpose round that is effective simultaneously against armored vehicles and personnel. The weapon is accurate up to 3 kilometers and can be fired using the AAH's fire control system or a crew member's helmet-mounted gunsight.

The third weapon system carried by the AAH is the standard 2.75-inch Folding Fin Aerial Rocket (FFAR). This free-flight rocket can be equipped with a variety of payloads, including antipersonnel, shaped charge, high explosive, smoke, illumination, and chaff payloads. The AAH can carry as many as 76 FFARs in four winglet-mounted dispensers.

Besides having the latest in avionics gear for flight under all types of conditions, the AAH has a very sophisticated visionics system that allows it to deliver its weapons on target accurately. The key components include the Target Acquisition and Designation System (T ADS), the Pilot Night Vision System (PNVS), the Integrated Helmet and Display Sight System (IHADSS), video recording and playback equipment, and a Fire Control Computer (FCC).

The T ADS and PNVS provide the crew the capability to detect, recognize, and engage enemy targets at standoff ranges during the day or night and in adverse weather conditions. The TADS is used in conjunction with all three of the AAH's weapon systems. It can provide target acquisition and weapon pointing information using either its laser range finder and tracker or its infrared and TV sensors. The T ADS laser designator is used to illuminate the target for the HELLFIRE. All information acquired by the T ADS is fed into the Fire Control Computer, the brains of the weapon's delivery system. It accepts data from the TADS and other instruments and sensors on the AAH, computes trajectories, and issues firing and guidance commands. The FCC is capable of controlling either the HELLFIRE and chain gun or the FFARs and chain gun simultaneously.

The gas turbine has been found to be the most effective power plant for military helicopters from a weight, reliability, and maintainability standpoint. However, because of the relatively small size of the engines used in helicopters, turbine-powered machines have suffered somewhat when it comes to fuel economy. With the T700 engine, even this deficiency has been overcome. The 1500 horsepower T700 will power not only the Black Hawk and the AAH but a slightly more powerful version will be used in the Navy's new Light Airborne Multi-purpose System (LAMPS) antisubmarine warfare helicopter. The engine is also used in the Bell 214ST, a twin-engined version of the Huey built for Iran. In all these applications two engines are installed to give an additional margin of safety and ability to complete a mission.

The T700 engine, while producing 10 percent more horsepower than the engines used in the Huey and AH-1S Cobra-TOW, is 40 percent lighter, weighing slightly over 400 pounds. The T700 uses 20 to 30 percent less fuel than its predecessors.

The foremost goal for both the Black Hawk and AAH, when it comes to survivability, is to be able to reach the target, perform the mission, and return home undetected. The current threat scenario allows detection visually, audibly, or by radar or infrared signature. The primary means these two craft have for avoiding detection is superior nap-of-the-earth performance. That is, the ability to fly among trees, popping up to perform its mission, and then returning nearer the earth where visual, radar, and infrared detection is more difficult, if not impossible.

In addition to superior NOE performance, both craft have several features that reduce detectability. Both have suppression devices that cool the hot exhaust gases from the turbine engines before they are exhausted to the atmosphere, for the exhaust plume is the primary source of infrared radiation. Radar signatures are reduced by controlling the shape of the fuselage and through proper attention to the engine inlet screening and rotor head. In addition, both craft have black boxes that provide a warning when enemy radar is beamed at them. They also have means to jam enemy detection systems, by dispensing flares and chaff, for example.

While the characteristic sound of a chopper can never be eliminated, it can be definitely reduced by careful design of the main and tail rotors. For example, the tail rotor of the AAH has its four blades not spaced perpendicular to one another purposely to reduce tail rotor noise. Visual detection can be reduced by low reflectance and camouflage paint. In the case of the AAH, the nearly flat canopy glass goes a long way toward preventing reflections that could give away the aircraft's location.

But even if the Black Hawk and AAH are detected, they are designed to survive small arms fire. The Black Hawk is totally invulnerable to 7.62-mm rounds and has minimum vulnerability to 12.7-mm and 23-mm projectiles while in forward flight. The AAH can totally withstand the 12.7-mm threat and has minimum vulnerability to 23-mm high energy incendiary (HE I) rounds during hover and forward flight. The AAH has more stringent vulnerability requirements since it will have to operate in a more hostile environment.

Let us look at how these airplanes attain their high degree of survivability. From experience in Southeast Asia, the primary reasons for mission aborts, crashes, and forced landings were damage to engines, flight controls, and lubrication systems, or crew injuries.

The twin engines of the UH-60A and YAH-64 provide good single engine performance, which means that the craft can get home even if it loses one engine. The widely separated engines on both choppers reduce- the chance that both engines are knocked out. The T700 engine uses suction type fuel delivery rather than fuel pumps at the fuel tanks. Thus, if the fuel line is severed, fuel is not pumped into the air creating a fire hazard; instead the fuel lines are sucked dry. The self-sealing fuel tanks can survive a hit from a 23-mm HEI round.

The transmissions are designed to run 30 minutes without lubrication, and tests have demonstrated that they can actually run for up to an hour without any oil. The tail rotors are designed to shift automatically to the maximum thrust position if the controls are hit. Even if the tail rotor is shot away, the large vertical tails will provide sufficient stability in forward flight to ensure survivability. The main rotor blades of both craft can survive a hit from a 23-mm weapon and still function well enough to get home. The flight controls themselves have redundant mechanical, electrical, and hydraulic systems.

In both the Black Hawk and AAH, crew survivability is increased by lightweight boroncarbide armor which can defeat 12.7-mm fire. The windshield and instrument panel of the UH60A are made of a material that reduces spalling, a Source of many casualties. On the AAH, the two crewmen are separated by a clear blast fragment shield; if a 23-mm HEI round penetrates one compartment, the other crewman would be unaffected. All in all, studies and tests have shown that only 10 percent of the Black Hawk is vulnerable to 23-mm ammunition, and less than 5 percent of the AAH would fail to meet this threat.

Finally, there is the matter of crash survivability. Both choppers are designed to give maximum crew protection in case of a crash. In fact, both helicopters are among the most crashsurvivable aircraft ever built. For example, they are designed to let the crew walk away from a 2500-foot-per-minute vertical descent, and the critical fuel tanks are capable of sustaining drops of up to 3900 feet per minute. Crash survivability is given special attention in the Black Haw~ because of its troop-carrying mission. There are special crashworthy seats for both the crew and passengers. The cabin structure is designed to retain the engines and transmissions, to prevent them from crashing down into the cabin under high crash loads; and the fuselage is especially rigid, to prevent parallelogramming that could result in the jamming of doors and windows preventing escape. The location for the landing gears was picked so that during a crash they would not penetrate the cabin or fuel cells. Electrical lines are excluded from the bottom of the fuselage, to prevent severing during a slide along the ground and thus causing sparks that could set off a fire.

Because maintenance accounts for a significant portion of the life-cycle costs of any complex military weapon system and because when an aircraft is out of commission for repairs it is not available to fight, considerable thought went into the design of the Black Hawk and AAH to achieve helicopters with high reliability and which require a minimum of maintenance. These goals are met by using components with high mean-time-between-failure rates, incorporating features that make it easy to repair and remove components, eliminating the need to replace components at preset periodic intervals, and by having an on-board Fault Detection/Location System.

The high reliability of these two aircraft is achieved by making their designs as simple as possible and by derating, that is, operating components much below their fatigue failure limits. Most important, though, their reliability is attributable to the very low vibration levels found on the UTTAS and AAH. For example, there is no single component having an expected life of less than 4500 hours for the Black Hawk and 5000 hours for the AAH. When all the thousands of components are put together, the overall meantime-to-failure for the Black Hawk is projected to be 4.5 hours and 3.4 hours for the AAH. Here a failure is defined as any malfunction, even a burned out light bulb. If we talk about only those failures that would cause a mission abort, then the mean-time-to-failure goes up to 76 hours for the Black Hawk and 20 hours for the AAH. The more sophisticated mission equipment and more stringent mission requirements of the AAH account for its lesser reliability. The basic airframe of both aircraft are essentially equivalent in reliability.

The T700 engine is a perfect example of the ease of maintenance found in these two aircraft. It requires about 15 minutes to replace any of the two dozen flightline replaceable accessories, and all field maintenance can be done using only ten standard tools found in any mechanic's toolbox. The engine itself can be easily removed from the aircraft. During the YAH-64 flight test program, two men demonstrated that they could remove an engine in only 25 minutes. Since the engine is composed of only five separate modules, once it is out of the aircraft, the faulty module can be replaced and the engine reinstalled. Replacement of all five modules takes only about an hour and a half.

The AAH main transmission can be removed without having to touch any part of the rotor system. Other examples of the attention to detail that results in low maintenance costs include built-in work platforms and aircraft-mounted cranes that have essentially eliminated the need for workstands. All these features have reduced the maintenance man-hours per flying hour to 2.8 for the Black Hawk, a markedly low figure for a helicopter. The AAH requires about six man-hours per flying hour because it is a more complex aircraft flying a more sophisticated mission.

Current plans call for buying 1107 Black Hawks, the first production aircraft having been delivered in August of 1978. The total procurement of Black Hawks will take some eight years.

As a rough comparison of the capability of the UH-60A versus the UH-l, a combat lift company with 15 Black Hawks can provide the same lift capability as 23 UH-ls. Additionally, the cost of operating a UH-60A will be approximately the same as for one Huey, even though the UTT AS is more complex and with two engines uses more fuel.

While the decision has been made as to the configuration and contractor for the AAH, fullscale production will not take place until mid1981. During the intervening period some minor deficiences found during the test program will be corrected, but the bulk of the time and effort will be spent on developing and testing the mission equipment. The pacing items will be the Target Acquisition and Designation System and the Pilot Night Vision System. First the T ADS/ PNVS must be selected from designs proposed by two competing contractors. A major factor in this selection will be the results of actual testing of the two competitive designs of the AAH. The selection will be followed by extensive testing and engineering to ensure that the final AAH configuration is ready to be put into the hands of the operational pilot.

The AAH should be operational in the mid1980s with the main deployment in Europe, taking its place alongside the AH-IS CobraTOW with its TOW missile. A total of over 500 AAHs is planned.

The question often arises, do we need both the AAH and the Air Force A-IO? The answer is a definite yes since they serve distinctly different missions. The A-IO provides close air support in the form of air attacks against hostile targets that are near friendly forces, but it is not under the direct control of the ground commander. The AAH, on the other hand, will be directly controlled by the ground commander and will be used as a homogeneous component of the ground forces. The AAH performs the same tasks as the more conventional artillery, tank, and infantry weapons, but with greater firepower and mobility. The AAH and A-IO complement but do not duplicate the capabilities of one another.

One of the primary factors governing the size of these two new helicopters is being able to transport them in the USAF's C-130, C-141, and C-5A aircraft. Not only must they be transportable, but one must also be able to disassemble them for flight and reassemble them for action in a minimum amount of time. For example, one Black Hawk can be carried in a C-130, two in a C-141, and six to eight in the C-5A. To prepare the Black Hawk for air shipment, the rotor mast is lowered, the main and tail rotors are folded, and the tail section itself is folded. All of this, including loading into the aircraft, takes about two hours. To put everything back together at the end of the trip takes slightly more than two hours. Both aircraft can be ferried over long distances, over 800 nautical miles. This means that if air transportation becomes critical both aircraft could be ferried to Europe, since the longest leg across the Atlantic is not quite 800 nautical miles.

Many lessons have been learned about the use of helicopters in war since the first choppers were employed on the battlefield in the waning days of World War II. The Army has found the missions for which the helicopter is best suited and has refined helicopter tactics. With the advent of the Black Hawk and advanced attack helicopter, the U.S. Army will have helicopters that were designed from the ground up to be fighting vehicles.

Bauer, Daniel R. Major. "Tank Killer." Armor, May-June, 1977.

Butler, John K., Captain. "UTTAS." Armor. May-June 1977

Funk, David L., Lieutenant Colonel. "The Advanced Attack Helicopter Challenge." Armor. January February 1978.

Gormont, Ronald E. and Wolfe, Robert A. "The U.S. Army UTTAS and AAH Programs" Paper presented to the AGARD Rotorcraft Design Symposium. Moffett Field, California. May 1977.

Wolfe, Robert A. "Army UTTAS Program." Society of Automotive Engineers. Paper No. 770952.

Lieutenant Colonel William D. Siuru, Jr., (Ph.D., Arizona State University) is Chief Scientist at the Frank J. Seiler Research Laboratory (AFSC), USAF Academy, Colorado. Preceding this assignment, he was an assistant professor and course director at the United States Military Academy. Previous Air Force assignments have been in research and development. Colonel Siuru is the author of numerous articles and books and a frequent contributor to Air University Review.

Disclaimer

The conclusions and opinions expressed in this document are those of the author cultivated in the freedom of expression, academic environment of Air University. They do not reflect the official position of the U.S. Government, Department of Defense, the United States Air Force or the Air University.

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