The Lockheed Martin/Northrop Grumman Longbow joint venture has joined with Westland Helicopter, Ltd. to supply the Longbow Radar and RF Hellfire fire-and-forget missile to the WAH-64 Apache helicopter in the U.K. and with McDonnell Douglas Helicopter Systems to supply the AH-64 helicopter in the U.S.
Also compatible with the RAH-66 Comanche, the Longbow system provides a fast reaction, low exposure, extremely accurate weapon system for attack helicopter missions during the day, night, bad weather, or battlefield obscurants. The radar searches, detects, locates, classifies and prioritizes fixed and mobile targets (tanks, air defense units, trucks, and aerial targets). An integrated RF interferometer passively locates and identifies emitting targets. These features combined with the fire-and-forget missile capability give Longbow-equipped helicopters a combat demonstrated improvement of twenty-four to one in loss exchange rate. No fratricide was experienced by friendly forces during operational test and evaluation.
The Longbow millimeter-wave fire control radar system is mounted on the helicopter's main rotor mast in order to take advantage of terrain masking. The conversion kit for the Longbow system, which includes an upgraded engine, can be installed on an AH-64D helicopter in less than 4 hours, including a 30-minute flight test.
The Longbow system has successfully completed Initial Operational Tests and Evaluation by the U.S. government and entered production.
Quelle: http://www.northrop-grumman.com/Corp_web/products_pages/longbow.html
Longbow Radar The Longbow radar system is the new heart of the Apache's sensor suite. The Longbow package consists of a mast-mounted millimeter-wave (MMW) fire-control radar dome, a programmable signal processor, and the new Longbow MMW Hellfire missile. This new sensor system is designed to quickly detect, classify, and prioritise targets. One this procedure has been done, the sensor system then hands off the targeting data to the Longbow Hellfire missile seeker.
The emissions of the Longbow radar are designed for a low probability of intercept by opposing forces, and can sweep an arc of 50 square km in front of the aircraft. The radar can detect moving targets at ranges up to 8 km while the detection range for static targets is reduced, at 6 km. At this time, the Longbow system can display, classify, and track up to 128 targets simultaneously.
While individual types of vehicles cannot be determined (such as a T-72 vs. a T-80), the Longbow package can identify and classify a vehicle based on the following criteria: tracked, wheeled, airborne, or air-defense. In addition, the radar can indicate to the crew whether the target is mobile or not. The Longbow radar is able to accomplish this by using radar waves of a very high frequency. Millimeter-wave is just that, radar waves which can be measured in the millimeters. This translates into a radar with a very fine resolution, a resolution which can identify particular features of the target being swept. The MMW radar essentially "feels out" the target to determine the class of the vehicle. The results of this process are then compared against a threat library, and when a match is found, the target can be catagorised.
Another component of the Longbow system is a radar frequency interferometer which allows passive detection of air-defense emissions. Data from this sensor can then be displayed on a display screen in the cockpit to indicate position and distance of the threat.
One of the principle displays for the crew-members is the Integrated Helmet And Display Sight System (IHADSS) designed by Honeywell. The IHADSS system is comprised of three main components: a pilot's helmet, a display system, and special head-tracking equipment. The display is attached to a folding arm mounted to the right side of the helmet. This side arm positions a small combiner-glass in front of the crew-member's right eye upon which a video-projection unit in the arm displays images.
Acting like an aircraft's HUD, the IHADSS Head Display Unit (HDU) can display video with flight data superimposed over it. As a result, critical information relating to the aircraft can be presented to the crew-member at all times, regardless of the direction the pilot is facing. Infrared sensors at either side of each headrest track the movement of each helmet. Atop the instrument panel of each cockpit is a lensed cylinder known as the Boresight Reticle Unit. This serves as a stable reference point which the pilot aims the IHADSS at when correlating the head-tracking system. The head-tracking data is passed on to the sensor appropriate to each crew-member so that if slaved to the helmet, it may follow the movements of the helmet. Thus, the crew control the sensors simply by looking at the point of interest, and the sensors can return information to their eyes.
Designed and built by Martin-Marietta (now Lockheed-Martin), this particular sensor suite is made up of the AN/ASQ-170 Target Acquisition and Designation System (TADS), and the AAQ-11 Mk III Pilot Night Vision System (PNVS). Both systems are separate from each other, occupying individual turrets. As a result, both pilot and co-pilot/gunner are provided with fully independent night vision systems. The drive mechanism of each turret contain both a "course" gimbal for rapid tracking and a "fine" gimbal for precision tracking of targets. In addition, both PNVS and TADS can be rotated to a rearward-facing position when not needed in order to preserve the optical components from the wear of particles in the aircraft's flightpath.
The PNVS is mounted above the nose structure of the aircraft, while the larger TADS turret occupies the underside of the nose section. It is this placement of the sensors on the nose of the Apache that is the major drawback of this sensor suite. Their location on this part of the airframe requires the Apache to completely unmask itself from cover in order to use those sensors. Before Longbow, virtually the entire aircraft would have to be exposed in order to guide missiles onto the target using its laser. Both turrets are manipulated by drive mechanisms comprised of both a "course" gimbal for acquisition and a "fine" gimbal for precision tracking of targets. Both PNVS and TADS can be slaved to the IHADSS or can be rotated to a rearward-facing position when not needed in order to preserve the optical components from the wear of particles in the aircraft's flightpath. All of the sensor optics are filtered in order to protect the crew from the damaging effects of battlefield lasers.
The Pilot Night Vision System (PNVS) consists of a Forward Looking Infrared (FLIR) device mounted in a small turret located above the Apache's nose section. This turns night into day for the pilot, a critical function for an aircraft which often must travel low and fast in order to survive. The turret is steerable to a maximum of 90 degrees off the centerline in the horizontal and +20 / -45 degrees in the vertical. The drive mechanism is capable of steering the PNVS at 120 deg./sec. horizontally and 93 deg./sec. vertically. The FLIR's field of view is 40 degrees horizontal x 30 degrees vertical. The FLIR imagery can be displayed in a 1:1 view, thus representing the true picture outside the aircraft.
The Target Acquisition and Designation System (TADS) is comprised of a FLIR device, two types of optical cameras, and a Laser Range-finder/Designator (LRF/D). All are mounted within the large drum turret below the nose structure. The TADS assembly is divided into night (starboard) and day (port) halves, each capable of independent elevation. The entire TADS unit can be steered 120 degrees to either side horizontally and +30 / -60 degrees vertically.
On the port side are three sensors for the detection and tracking of targets when there is daylight. They are mounted in a vertical column and consist of the Direct View Optics (DVO) sensor at the top, a TV optical sensor (DTV) below, and a laser range-finder/designator at the bottom. The DVO is an optical telescope with two magnifications: x4 magnification at 18 deg. FoV, or x16 magnification at 4 deg. FoV. The TV optical sensor offers up to x127 magnification with a corresponding FoV of 0.45 degrees. The laser range-finder/designator is a neodymium laser with an effective range of 20 km (12 miles). It can provide very accurate ranging information for targeting in addition to designating them with coded laser-energy for weapon guidance.
The starboard side of the TADS system houses the FLIR sensor which provides slightly better imagery than the PNVS. This FLIR sensor provides variable field of views ranging between 50, 10, 3.1, and 1.6 degrees FoV. The FLIR of the TADS unit can be switched between "white hot" and "black hot" in order to provide better contrast against the surrounding terrain for increased target discrimination. An adjustable gain selection also aids in this target enhancement.
The imagry from the TADS unit can either be displayed on the co-pilot/gunner's own IHADSS unit, on one of the MFDs, or via the primary display for the gunner, the Optical Relay Tube (ORT). In addition, a video-recorder can collect information from all of the TADS sensors. As a result, the Apache needs to unmask for only a short time to collect sensory input, which can be analysed in greater detail by the crew once the aircraft drops down behind cover once again. The recorder can also be used to record the aftermath of an attack for analysis upon return to base.
Both pilot and co-pilot/gunner sit in tandem, with the pilot behind and slightly above the gunner's position. The pilot is sufficiently elevated so that the gunner provides no obstruction to the flyer's view. The gunner sits immediately above the mounting for the 30mm chain gun. Between the two positions is a transparent blast shield. The Apache can be controlled from either position though each is optimised for its particular role.
The cockpit of the Apache has seen extensive redesign from the original A model. The previous Apache had some 1 200 switches as well as numerous dials, tape-strips, and other various indicators. The new design is known as the "Manprint" (Manpower Integration) cockpit. Many of the indicators and switches are replaced by a pair of Multi-function Displays (MFDs) in each of the two cockpits in addition to a Litton Canada Up-Front Display.
Pilot Position The most notable change from the A model Apache, is the pair of Bendix King MFDs. Measuring 6inches x 6 inches, each screen is surrounded by selection buttons mounted on the bezel of the unit, 6 buttons to a side. At the corners of each unit are controls for brightness, contrast, as well as other functions. During the operation of the displays, the outer edge of the screen feature menu selections that would correspond to each of the buttons.
In the vicinity above the starboard MFD, the Up-Front Display can show additional information in alpha-numeric form. Here, there is also a control for brightness as well as controls to scroll the display up or down. Above the port MFD is a very prominent Fire Warning display featuring warning indicators for both port and starboard engines as well as the Auxiliary Power Unit.
Above the instrument panel coaming are some traditional dial instruments to provide backup to the standard digital instruments. Both collective and cyclic controls are studded with various switches in order to allow the pilot to control various functions without the need of releasing the controls.
Co-pilot / Gunner Position Looking like some type of periscope, the most prominent feature of the front cockpit is the Optical Relay Tube (ORT) mounted in the center of the instrument panel. This is the key display and control unit for the CP/G, while performing tasks crucial to the gunner's role. Through this device, the CP/G can locate, identify, track, and engage targets.
There are three main sections form the ORT. At the top of the unit sits the Head Down Display (HDD). It is a monocle display unit surrounded by a rubber coaming which would surround the gunner's eyes when his head is down in the unit. It is this section which gives the ORT its periscope-like appearance. With the gunner's head down in the display, video is placed before the right eye by means of a lens. The area occupied by the left eye is thus far not in use and sealed with a plastic cover. From this display, data from the various sensors can be presented to the CP/G through a combination of video images and alpha-numeric symbology. Being that close to the display, fine details of video images can be seen by the CP/G, crucial for detection and identification of targets.
Below the HDD is a small screen which serves as an HDD repeater display. This allows the CP/G to avoid being tied to the HDD during all phases of the operation. On either side of the ORT's column are hand-grips which allow the CP/G to control various functions of the sensors and weapons, without breaking contact with the HDD. The T-bar grips are similar the HOTAS (Hands on Throttle and Stick) system found in today's modern fighters. They allow the CP/G to perform critical functions without requiring the gunner to lose site of the target, in this case by removing his/her head from the HDD. There are differences in the layout of both the right and left grips as there are differences in the functions that each perform.
The left hand-grip features the following controls:
The right hand-grip houses controls for the following:
In addition to the ORT, information can be presented to the CP/G via a pair
of Bendix King MFDs, exactly like the pair in the pilot's cockpit and capable
of displaying the same types of data. Also present in the front cockpit are
both cyclic and collective controls. The center-cyclic stick has the capability
of folding down to the floor of the cabin when not in use in order to not
interfere with the operations of the gunner's position. The Up-Front controller
occupies the space in the extreme top-right sector of the instrument panel.
Much like the pilot's cockpit, there is also the same Fire Warning display
located to the upper-left corner of the instrument panel. Also present are
control panels for the weapons, a data-entry keyboard, communications controls,
circuit breakers, as well as some of the other controls that would be necessary
for piloting the Apache from the front position.
Communications One of the key improvements to the Apache was an upgrade
to the communications system of the aircraft. One such upgrade can be seen
before the mission begins in the form of the Data Transfer Module (DTM).
The module allows for allaspects of the mission such as waypoints, battle
lines, unit positions, communications frequencies, and callsigns to be input
directly into the AH-64D's computers via a programmable cartridge.
However, a more striking improvement can be seen once the AH-64Ds take flight. Communications among aircraft has been improved dramatically through the Improved Data Modem (IDM), a device which will revolutionize the battlefield. The AH-64D will now be able to communicate crucial operational information with other aircraft in the flight, ground units, Air Force E-8 J/STARS, and the Tactical Operations Center (TOC).
The result will be the transformation of a group of units seeking the same operational goal into a highly cohesive force with unprecedented situational awareness. Each member of that force will gather battlefield information in its own way, and automatically supply that data to a growing body of knowledge about the operation from which every other member will draw automatically. In the end, an unprecedented picture of the battlefield will be created. The tactical advantages brought about by this level of situational awareness can thus be applied against the opposing forces.
The IDM transfers data at a rate of 16 KB/sec, a very high rate of speed for such equipment in the military. The IDM is able to communicate with the variety of aircraft that it is able to due to the recently developed Variable Message Format (VMF) which revolves around the 18820 protocol. VMF is utilised by all of the US forces regardless of branch, so information is shared between the various services participating in the operation.
Due to this communications breakthrough, a single Longbow can lead the attack by locating targets, providing the necessary information to both the rest of the flight and the battlefield commanders, and then anybody in the loop can make the decision as to which aircraft will attack which targets. All of this occurs in real-time, allowing for changes in tactics to occur immediately as conditions change.
One such scenario could involve a single Apache hiding behind a terrain feature,
while the rest of the group hides behind another at a greater distance. The
lead Longbow would unmask its radar and sweep a given area for targets. Once
this task is performed, the data can be immediately analysed by tacticians
at the battlefield level. The lead Longbow can then assign Primary Fire Zones
(PFZs) to individual aircraft who would then be responsible for the targets
within that zone. In addition, the lead Apache or the commanders may decide
on what targets to fire upon first, which should be consider secondary, and
which to leave alone entirely. This ensures two key purposes. First, that
overkill is avoided, thus sparing rounds. Second, that non-critical targets
are left for clean-up forces. This can translate into a swifter, more devestating
attack while at the same time, sparing valuable Hellfire rounds that would
ordinarily be wasted on inappropriate targets.
Defenses The Longbow radar system allows for passive detection of
targets through use of a Radar Frequency Interferometer (RFI) which can locate
and identify and air-defense system by analysing its emissions. The RFI is
located in the mast-head unit in order to allow for the aircraft to passively
seek out threats, while still masked by terrain features. The AH-64D's RFI
provides 360 degrees of coverage with the forward half consisting of "fine"
coverage and the aft hemisphere consisting of "coarse" coverage.
For instances when the aircraft must protect itself against such air-defense systems, the Apache is equipped with the ALQ-136 radar jammer. The receiver for the jammer is located on top of the fuselage between the aft cockpit and the rotor mast. The transmitting antenna for the jammer is located on the port side of the structure between the PNVS and TADS turrets. The jammer operates by transmitting inaccurate range and angle information to the hostile radar. Further countermeasure against radar-guided SAMs is provided by the 30-round M130 chaff launcher. The box-like launcher-unit is located on the port side of the tailboom just forward of the point where the structure sweeps up to form the tail-rotor housing.
Protection against IR threats is supplied by the AN/ALQ-144 "disco light" jammer. Located directly behind the rotor mast, the copper-coloured, segmented cylinder looks very much like its namesake. Consisting of an electronically heated source, perhaps a ceramic block, the jammer emits modulated radiant energy at high and low frequencies in order to confuse the seekers of IR guided missiles.
Quelle: http://www.interlog.com/~vf84/64d-av.htm