by Richard Sheffield
Avionics are the eyes of an aircraft, and the Apache probably has the best eyes of any helicopter in the world. The sensors aboard this aircraft are totally integrated; that is, they act together. This greatly reduces the work load and response time of the crew in battle conditions. A sensor system is specifically designed to meet the demands of each crew member's job function. These systems are known as TADS/PNVS.
TADS. The TADS (Target Acquisition Designation Sight) is primarily used by the copilot/gunner, or CPG. This system allows the gunner to see, identify, engage, and destroy targets at great range in day or night. To perform this task, a wide range of sensors are at the disposal of the gunner:
Direct-view optics. This system is for daytime use. It is basically a variable-power telescope with the image displayed in the gunner's cockpit via the Optical Relay Tube.
High-resolution TV system. This is an alternative sensor for daytime use. However, due to its ability to operate in the near-infrared range, it may prove to be of more use than the direct optics in real battlefield conditions. The infrared allows it to "see" through some of the smoke and dust which will likely be present on the battlefield.
FLIR (Forward Looking InfraRed) sensor. This sensor allows the gunner to search for and detect targets at night or in bad weather, including rain and snow.
Laser system. This is the range finder and tracking system for laser-guided weapons such as the Hellfire missile or smart artillery shells.
The information from these sensors is displayed in several ways. The HDD (Head Down Display), is a binocular-type eyepiece through which the gunner looks. It sticks up out of the control panel directly in front of the gunner. A video display screen, or CRT, is also used.
The most innovative and unique system is the IHADSSHDU (Integrated Helmet Display Sight System Helmet Display Unit). This helmet has an eyepiece attachment which displays sensor images and information on a clear piece of glass in front of the wearer's eye, much the same as a heads-up display in a jet fighter. The helmet is coupled to the movable sensor housing in the nose of the aircraft. To provide the appropriate images and target data, the sensor housing turns when the wearer's head turns. This is the what-you-see is-what-you-hit targeting system. The laser will point where the gunner looks to guide Hellfire missiles. The 30mm chain gun is also slaved to the sensors; so, to aim the gun, all the CPG has to do is look at a target.
PNVS. The PNVS (Pilot Night Vision Sensor) is generally used by the pilot to navigate the aircraft at night or in bad weather. The system provides a brightly illuminated view of the ground and allows the pilot to fly nap-of-the-earth maneuvers even in total darkness and rain. Infrared imaging is used by the PNVS which displays the image of the terrain on the eyepiece of the IHADSS helmet. Since there is no magnification on this system, the pilot sees the infrared image superimposed over the view outside. The helmet operates in the same manner as the gunner's, so the view changes accordingly when the pilot's head is turned. The pilot can even look through the bottom of the cockpit by simply looking down since the sensor for the PNVS is located in the nose of the aircraft and is not blocked by the fuselage.
The PNVS also displays such vital flight data on the eyepiece as airspeed, altitude, and heading. This lets the pilot fly without having to look down at the instrument panel.