The Apache AH-64:Achilles Heel?

An Apache AH-64 armed and in low flight

     Recent reports indicate that the helicopter is vulnerable to ground forces in certain environments, such as when operating in urban terrain. Since 2003, Iraqi ground troops and insurgents were able to damage propulsion and flight control systems with ground fire, sometimes forcing the helicopters to make immediate emergency landings or shooting them down. During Operation Iraqi Freedom, some Apaches were damaged in combat, including one captured by Iraqi troops near Karbala on March 24, 2003, and shown on Iraqi television. The captured helicopter was destroyed via airstrike the day after it was captured.The March 24 attack, against an armored brigade of the Iraqi Republican Guard's Medina Division, was largely unsuccessful, apparently because the tank crews had set up a "flak trap" in broken terrain, employing their HMG*s to good effect.More recently two Apaches were lost along with their crews between January 28 and February 2, 2007 to Iraqi insurgent ground fire in Taji and Najaf.
     There are various factors that contribute to this vulnerability. First, Apaches were designed to engage and destroy armor at safe ranges, where they could not be fired upon. Secondly, infantry are less easily detected than armor. In Iraq, the close quarters, and ample cover afforded by the urban environment make it easy for ground forces to attack at close ranges (50 - 850 m). This environment brought out the Apache's vulnerability to close range attacks from heavy caliber machine guns (0.5 inch). Also, since the Apache is only capable of firing at a single target at a time, it is vulnerable when attacked from several dispersed positions. Combat utility helicopters like the UH-60 Black Hawk may not suffer this disadvantage, as they have multiple manned side armaments, adding extra protection in certain tactical situations. However, the Apache has superior maneuverability, armament, and speed.
In either case, the Apache's use in both attack and support roles in urban environments has proven effective. Apaches have been successful working in support roles with ground troops, and as an observation platform for directing artillery. Despite the Apache's vulnerability in urban operations, it is currently rated as one of the most survivable of all military helicopters.The vast majority of Apache helicopters that have taken heavy combat damage have been able to continue their assigned missions and return safely to their bases. For example, of the 33 Apaches employed in the March 24, 2003 attack, 30 were damaged by Iraqi ground fire with several being write-offs, but only one of these did not make it back to base (although in this case, the mission objective was apparently not achieved).
[*HMG:- Heavy Machine Gun,refers to either a larger-caliber, high-power machine gun or one of the smaller, medium-caliber (rifle caliber) machine guns meant for prolonged firing from heavy mounts, less mobile, or static positions (or some combination of the two).]

     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.
[**FLIR:The Apache is specially designed to operate at night, the two censors located on the nose make this possible. The basic principle that makes vision at night reality, is called FLIR (Forward Looking Infra-Red). All objects have a certain temperature, by measuring differences in that temperature a video-image can be produced that can be produced that can be used for both flying and target acquisition/designation.]
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.