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Aviation History
1979
1979 - 4409.PDF
Conversion to two seots is catered for in the A-IO design specification. Modification took 13 months FLIGHT International, I December 1979 1845 hostile radar systems, flying at low altitude and using hills, valleys and forests for concealment. Sensors were required that would allow similar tactics to be used at night and in poor visibility. The company selected radar, forward-looking infra-red (Flir), iner- tial navigation system (INS), laser ranger and radar altimeter. Low-light television (LLTV) was also specified for comparison with Flir. The systems contribute as follows: Navigation Primary: INS. Secondary: radar, Flir, laser. Terrain avoidance Primary: radar. Secondary: Flir, laser, altimeter. Target detection Primary: radar. Secondary: INS, Flir. Target classification Primary: Flir. Secondary: radar. Weapon delivery Primary: Flir. Secondary: INS, radar, laser. The radar is a Westinghouse WX-50 modified weather radar. The equip ment has three modes. It can measure terrain contours 1 n.m. and 2 n.m. ahead of the aircraft, project ing these "slices" on to' the pilot's headup display (HUD). The Moving Target Indication (MTI) mode rejects clutter and displays those returns moving relative to the ground. The third mode is ground mapping. The radar scans +30° horizontally and has selectable 5 n.m., 10 n.m. and 15 n.m. ranges. The Flir is a Texas Instruments AAR-42. Two fields of view are avail able: wide (16°X12°) and narrow (4°X3°). The Flir can be slewed + 20° horizontally and +5°-35° vertically using a hand controller in the aft cockpit. The sensor is nor mally aligned along the aircraft flight- path and depressed 105 milliradians. The inertial navigation system is a Litton LN-39. This equipment also carries out the aircraft computing. Two Honeywell APN-194 radar alti meters are mounted i» the tailplane, giving continuous readout of height above the ground regardless of air craft attitude—useful when the air craft is jinking. The laser ranger is a Ferranti Type 105 and is bore- sighted to the Flir. The General Electric lowlight TV is carried on the Pave Penny pylon and output is selected as an alternative to Flir. The Flir pod is mounted on the centreline and houses the laser ranger. The radar is mounted under the inboard port wing. Changes to the forward cockpit are minimal. Flight instruments are rearranged to make room for a modi fied Kaiser HUD equipped to display projected images. Attitude director and vertical velocity indicators are smaller and the standby attitude indi cator is removed. The rear cockpit has the same arrangement of flight and engine instruments. Two Hartman cathode- ray tubes (CRTs) display Flir/LLTV (upper) and radar/Maverick missile (lower) output. An analogue radar altimeter instrument is fitted. Laser, Flir, radar and INS control panels are situated on the right sidepanel, as is the hand controller. This grip con trols Flir pointing, radar and Flir dis play cursor positioning and laser firing. Maverick missile functions are not active on the evaluator. Avionics Integration All the sensors come together on the pilot's HUD. The Flir image pro jected onto the HUD is two-dimen sional and therefore lacks depth. The 1 n.m. and 2 n.m. contours are superimposed on this picture to give some depth perception. These two displays are self checking as any discrepancy is immediately visible. Radar-altitude . and airspeed symbology bracket and sighting reticle. Heading commands from the INS appear below the reticle in ladder form. Information presentation is shown on page-1893. If the aircraft velocity vector sym bol is kept in the 12 n.m. terrain fol lowing command box—set at a pre selected altitude, normally 300ft—the aircraft will maintain a safe altitude. A director box, under the command of the rear-seat weapon-system opera tor (WSO) appears from time to time to point out targets or escape routes. This box is positioned using the hand controller. Should the WSO take the Flir off boresight, to investigate a target of opportunity or search for a landmark, the HUD is blanked off to avoid dis orientation. The pilot has the option of selecting LLTV output to take the place of Flir. The entire HUD display can be projected on the WSO's upper CRT if the aircraft is to be flown from the rear cockpit. During low-altitude penetration to the target area it is the pilot's task to fly the aircraft and avoid the ground. To do this he watches the contours and keeps the aircraft velocity vector in the terrain following box. By using these displays the pilot can safely fly between and around hills using ter rain masking. While this is going on the WSO handles navigation using the INS and radar ground mapping. He also monitors the radar homing and warning system displays. On the evaluator the Flir is carried in a centreline pod which also houses the laser ranger. The radar pod is mounted under the inboard port wing and the lowlight TV on the nose pylon
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