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64-431: LANTIRN consists of a navigation pod and a targeting pod mounted externally beneath the aircraft. The AN/AAQ-13 navigation pod provides high-speed penetration and precision attack on tactical targets at night and in adverse weather. The navigation pod contains a terrain-following radar and a fixed thermographic camera , which provides a visual cue and input to the aircraft's flight control system, enabling it to maintain

128-618: A Stores Management System (SMS) that included air-to-ground options as well as rudimentary software in the AWG-9 . Early flight clearance work to clear the aircraft for air-to-ground were suspended due to development delays with the F-14 and it being shifted away from the air to ground mission. At the time, the Tomcat was so expensive (and lacked proper defensive electronic countermeasures ( DECM ) and radar homing and warning ( RHAW ) for overland operations) that

192-410: A pencil beam radar signal towards the ground area in front of the aircraft while the radar scans up and down. The signal is sent as a series of brief pulses and the reflections of these pulses off the ground produces very powerful returns. The time the pulse takes to travel to and from the terrain produces a range measurement to the terrain in front of the aircraft. The angle relative to the aircraft

256-411: A building's vertical walls produces a partial corner cube that returns a signal that is about 10 million times stronger than the signal from sand or dry ground. To deal with the rapidly changing signals, an automatic gain control with 100 dB of range was developed. The beamwidth of the radar was small enough that objects to either side of the aircraft's flight path might be a potential hazard if

320-519: A fleet aircraft to integrate the digital 1553 -based pod on an analog F-14B. In March 1995 a VF-103 fleet aircraft successfully dropped the first laser-guided training rounds (LGTR) and quickly laser-guided bombs (LGB). Due to the early success and interest from Fleet Commanders, NAVAIR began to procure pods and control units for deployment, resulting in VF-103 receiving the first LANTIRN pod June 14, 1996 in time for its upcoming deployment. The basic LANTIRN

384-564: A minimum altitude. The concept was initially developed at the Cornell Aeronautical Laboratory in the 1950s. It was first built in production form starting in 1959 by Ferranti for use with the TSR-2 aircraft, flying for the first time in an English Electric Canberra testbed in 1962. While the TSR-2 project was ultimately abandoned, the concept was widely deployed in 1960s and 70s strike aircraft and interdictors , including

448-554: A pre-selected altitude above the terrain and avoid obstacles. This sensor displays an infrared image of the terrain in front of the aircraft, to the pilot, on a Head-up display . The navigation pod enables the pilot to fly along the general contour of the terrain at high speed, using mountains, valleys and the cover of darkness to avoid detection. The pod was the USAF 's first wide-field, forward looking infrared navigation system for air superiority fighters . A downgraded version for export with

512-503: A price tag of around 3 million US Dollars each and due to these high costs, only 75 were bought for fleet use. Typically, an F-14 squadron brought 6 to 8 pods with them on deployment, which would be permanently fitted to the non- TARPS jets. The first combat use of the LTS was in December 1998 during Operation Desert Fox by VF-32. Terrain-following radar Terrain-following radar (TFR)

576-509: A radar beam vertically in front of the aircraft and comparing the range and angle of the radar reflections to a pre-computed ideal manoeuvring curve. By comparing the distance between the terrain and the ideal curve, the system calculates a manoeuvre that will make the aircraft clear the terrain by a pre-selected distance, often on the order of 100 metres (330 ft). Using TFR allows an aircraft to automatically follow terrain at very low levels and high speeds. Terrain-following radars differ from

640-692: A single pass. A downgraded version for export with the AGM-65 Maverick air-to-ground missile compatibility deleted is designated as AN/AAQ-19 Sharpshooter . The research and development program began in September 1980 with Martin Marietta Corp. (now Lockheed Martin ), Orlando, FL, as contractor. Initial operational test and evaluation of the LANTIRN navigation pod was successfully completed in December 1984. The Air Force approved low-rate initial production of

704-502: Is a military aerospace technology that allows a very-low-flying aircraft to automatically maintain a relatively constant altitude above ground level and therefore make detection by enemy radar more difficult. It is sometimes referred to as ground hugging or terrain hugging flight. The term nap-of-the-earth flight may also apply but is more commonly used in relation to low-flying military helicopters , which typically do not use terrain-following radar. TFR systems work by scanning

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768-452: Is fed to the pod by the Tomcat's AWG-9 (F-14A and F-14B) and AN/APG-71 (F-14D) radar, but the LTS in turn only sends video and guidance symbology to the crew's cockpit displays. This means that few wiring and software changes had to be made to the Tomcat in order for it to operate the LTS. All pod controls are in the RIO's cockpit, but the bomb release button is situated with the pilot. The LTS had

832-581: Is known as terrain masking . However, radar emissions can be detected by enemy anti-aircraft systems with relative ease once there is no covering terrain, allowing the aircraft to be targeted. The use of terrain-following radar is therefore a compromise between the increased survivability due to terrain masking and the ease with which the aircraft can be targeted if it is seen. Even an automated system has limitations, and all aircraft with terrain-following radars have limits on how low and fast they can fly. Factors such as system response-time, aircraft g-limits and

896-420: Is known as the angle error . To guide the aircraft, a series of these measurements are taken over the period of one complete vertical scan out to some maximum distance on the order of 10 kilometres (6.2 mi). The maximum positive or minimum negative value of the angle error during the scan is recorded. That voltage is a representation of the change in pitch angle the aircraft needs to fly at to keep itself at

960-440: Is primarily used by military strike aircraft, to enable flight at very low altitudes (sometimes below 100 feet/30 metres) and high speeds. Since radar detection by enemy radars and interception by anti-aircraft systems require a line of sight to the target, flying low to the ground and at high speed reduces the time that an aircraft is vulnerable to detection to a minimum by hiding the aircraft behind terrain as far as possible. This

1024-408: Is returned by a sensor on the vertical gimbal that returns a calibrated voltage. At the same time that the radar is sending out pulses, a function generator is producing a varying voltage representing a preferred manoeuvring curve. This is similar in shape to a ski jump ramp, flat under the aircraft and then curving upward in front of it. The curve represents the path the aircraft would take if it

1088-558: The General Dynamics F-111 , Panavia Tornado and Sukhoi Su-24 "Fencer". The wider introduction of stealth aircraft technologies through the 1990s has led to a reduction in low-altitude flight as a solution to the problem of avoiding anti-aircraft weapons and the technique is no longer common. Most aircraft of this class have since retired although the Su-24 and Tornado remain in use in some numbers. The system works by transmitting

1152-691: The Phantom II , the Army's Grumman OV-1 Mohawk , and the advanced AN/APQ-110 system for the General Dynamics F-111 . For a variety of reasons, the TSR-2 project was cancelled in 1965 in favor of purchasing the F-111, a platform of similar concept based around a similar radar. In contrast to Ferranti's design, the APQ-110 offered several additional controls, including a ride quality setting for "hard", "soft" and "medium" that changed

1216-767: The Tornado IDS have two separate radars, with the smaller one used for terrain-following. However, more modern aircraft such as the Rafale with phased array radars have a single antenna that can be used to look forward and at the ground, by electronically steering the beams. Terrain-following radar is sometimes used by civilian aircraft that map the ground and wish to maintain a constant height over it. Military helicopters may also have terrain-following radar. Due to their lower speed and high maneuverability, helicopters are normally able to fly lower than fixed-wing aircraft. Systems are now available that mount to commercial UAV's, allowing

1280-483: The USAF Aeronautical Systems Division . This led to the development of a system known as "Autoflite." Early radars installed in aircraft used conical scanning systems with beamwidths on the order of four degrees. When the beam hits the ground, some of the signal scatters back toward the aircraft, allowing it to measure the distance to the ground in front of it. When looking downwards at an angle,

1344-546: The television antennas at Cairn O' Mounth and the Kirk o' Shotts transmitting station , bridges over the River Forth , and overhead power lines . In spite of the early start of Cornell's work, for reasons that are not well recorded, further development in the US ended for a time with the concept in a semi-complete form. This changed dramatically after the 1960 U-2 incident , which led to

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1408-515: The $ 1.6B Block 1 Strike program was canceled in budgetary cuts by 1994 with only enough funding to integrate the JDAM, which was years away. In late 1994, an unsolicited proposal from Martin Marietta was initiated to demonstrate how a USAF LANTIRN targeting pod could be rapidly integrated onto the Tomcat. This effort was done under the auspices of Commander, Naval Air Forces Atlantic Fleet (COMNAVAIRLANT) using

1472-417: The G force of the calculated curve's descent profile from 0.25 to 1 G, while always allowing a maximum 3 G pullup. It also included a second set of electronics to provide hot-backup in case the primary unit failed, and fail-safe modes that executed the 3 G pullup in the case of various system failures. Ultimately the F-111 ran into delays and cost overruns not unlike the TSR-2. After examining several concepts,

1536-663: The Navy did not want to risk it in the air-to-ground role. However, the TARPS mission had proven the Tomcat was survivable overland and upgrades to the Tomcat's DECM, expendables and RHAW gear were developed to increase its survivability. With the end of the Cold War and de-emphasis on the Fleet Air Defense mission, NAVAIR had renewed flight clearance work before Desert Storm so the F-14 could carry gravity bombs as well as laser-guided bombs if

1600-612: The RAF eventually decided to use the Buccaneer. Although this platform had been extensively tested with the Ferranti radar, this potential upgrade was not selected for service. Unhappiness with this state of affairs led the RAF to begin discussions with their French counterparts and the emergence of the BAC/Dassault AFVG , an aircraft very similar to the F-111. After successful initial negotiations,

1664-740: The UK dropped its options on the F-111K. Shortly thereafter, Marcel Dassault began to actively undermine the project, which the French eventually abandoned in 1967. The next year, the UK government began negotiations with a wider selection of countries, leading eventually to the Panavia Tornado . Texas Instruments used their experience with the F-111 TFR to win the radar contract for the Tornado IDS. Terrain following radar

1728-417: The accuracy required for terrain following, TFR systems have to be based on the monopulse radar concept. The monopulse technique produces a beam of the same width as a traditional design, but adds additional information in the radio signal, often using polarization , which results in two separate signals being sent in slightly different directions while overlapping in the center. When the signals are received,

1792-438: The aircraft can then be calculated through h = H - R sin φ , where H is the altitude over the ground measured by the radio altimeter, φ is the angle and R the range measured by the radar, with h being the resulting height of the object over the current flight path. The clearance between the aircraft and terrain is then H - h . The TFR concept traces its history to studies carried out at the Cornell Aeronautical Laboratory for

1856-432: The aircraft except in high sea states . In such conditions, the system would fail back to a constant clearance using a radio altimeter . Terrain avoidance normally works in a relative fashion; that is, the absolute altitudes of objects are not important. In some cases, it is desirable to provide an absolute number to indicate the amount of clearance or lack of it. The height of the top of any particular feature relative to

1920-414: The aircraft was blown sideways or started a turn close to the object. To avoid this, the radar scanned in an O-shaped pattern, scanning vertically from 8 degrees over the flight path to 12 degrees below it, while moving a few degrees left and right of the flight path. Additionally, the system read turn rates from the instruments and moved the scanning pattern further left or right to measure the terrain where

1984-409: The aircraft would be in the future. Tests of the system were carried out using Ferranti Test Flight's existing DC-3 Dakota and, starting over the winter of 1961/62, an English Electric Canberra . The test aircraft carried cameras looking in various directions, including some looking at the aircraft instruments and radar displays. This allowed the system to be extensively examined on the ground after

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2048-424: The aircraft's autopilot system and all control was manual. The curve was chosen to produce a one-half G maximum load. The path to fly was indicated by a dot in an AIRPASS heads-up display . The pilot followed the computed path by pitching until the aircraft's velocity vector indicator, a small ring, was centred around the dot. In tests, the pilots very quickly became confident in the system and were happy to fly it at

2112-424: The angle is fixed. When then pulse is sent, the function generator is triggered. When the return is seen, the system sums the output from the generator at that instant with the output from the angle sensor on the radar. The resulting voltage represents the angle between the actual and preferred location. If the voltage is positive, that means the terrain lies above the curve, negative means it is below. This difference

2176-525: The carriage of Ground Penetrating Radar or magnetometry sensors for sub-surface survey. This is being exploited in finding unexploded ordnance and in archaeology. There are very few alternatives to using terrain-following radar for high-speed, low altitude flight. TERPROM , a terrain-referenced navigation system provides a limited but passive terrain-following functionality. Martin Marietta The Martin Marietta Corporation

2240-533: The case of the Lightning, the monopulse signal was used to accurately measure the horizontal angle, in order to allow the AIRPASS computer to plot an efficient intercept course at long range. For TFR use, all that had to change was that the antenna would be rotated so it measured the vertical angle instead of horizontal. Unsurprisingly, Ferranti won the contract for the radar component sometime in 1957 or 58. Shortly after

2304-399: The crest of a hill. This results in the aircraft flying over the peak while still climbing and taking some time before it begins to descend again into the valley beyond. This effect was known as "ballooning". To address this, real-world units had an additional term that was applied that caused the aircraft to climb more rapidly against larger displacements. This resulted in the aircraft reaching

2368-430: The desired clearance altitude above the terrain while manoeuvring at the selected load factor. This can be fed into an autopilot or displayed on the pilot's heads-up display . This process produces a continually computed path that rises and falls over the terrain with a constant manoeuvring load. One problem with this simple algorithm is that the calculated path will keep the aircraft in positive pitch as it approaches

2432-469: The desired clearance altitude earlier than normal and thus levelling off before reaching the peak. Because the radar only sees objects in the line-of-sight, it cannot see hills behind other hills. To prevent the aircraft from diving into a valley only to require a hard pull-up, the negative G limit was generally low, on the order of one-half G. The systems also had problems over water, where the radar beam tended to scatter forward and returned little signal to

2496-436: The early versions, the LTS performed all weapon release calculations and presented release cues that it had generated to the aircrew. The LTS also had a masking avoidance curve display (preventing firing the laser at the jet) and eventually a north orientation curve and 12,200 m (40,000 ft) capable laser. The latter became very useful allowing F-14s to employ LGBs above potential threat systems and it came into its own in

2560-422: The flight. Each flight returned data for flights over about 100 miles, and over 250 such flights were carried out. Early tests showed random noise in the measurements which rendered the measurements useless. This was eventually traced to the automatic gain control using very high gain while at the top of the scanning pattern where the terrain was normally at long distances and required the most amplification. This had

2624-507: The higher terrain in Afghanistan during Operation Enduring Freedom . The LTS could also generate coordinates for any target located on the FLIR, and a latter software modification, known as T3 (Tomcat Tactical Targeting) increased the accuracy of the coordinates produced by the LTS and allowed generated coordinates for GPS/INS guided weapons ( JDAM , JSOW and WCMD ). The first combat use of this

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2688-465: The majority of Martin Marietta shares and in effect owned the company. However, Martin Marietta's management used the short time separating ownership and control to sell non-core businesses and launch its own hostile takeover of Bendix (known as the Pac-Man defense ). Thomas G. Pownall, CEO of Martin Marietta, was successful and the end of this extraordinarily bitter battle saw Martin Marietta survive; Bendix

2752-454: The minimum clearance setting even in bad weather. As the pilots became familiar with the system, the engineers continually reduced the selected clearance downward until it demonstrated its ability to safely and smoothly operate at an average of only 30 metres (98 ft) clearance. This was tested against rough terrain, including mountain ridges, blind valleys and even cliff faces. It was also found to property guide over artificial objects like

2816-462: The monopulse technique is that the signals overlap in a very specific way; if you invert one of the signals and then sum them, the result is a voltage output that looks something like a sine wave . The exact midpoint of the beam is where the voltage crosses zero. This results in a measurement that is both precisely aligned with the midline of the signal and is easily identified using simple electronics. The range can then be accurately determined by timing

2880-737: The navigation pod in March 1985 and full-rate production in November 1986. The first production pod was delivered to the Air Force March 31, 1987. LANTIRN represented a major advance in the U.S. military's ability to carry out operations in darkness and adverse weather, and has been developed further into its successor, the AN/AAQ-33 Sniper pod. Until the early 1990s, the F-14 Tomcat didn't have clearance to drop bombs even though all Tomcats were built with

2944-470: The near and far side of the radar's circular beam was spread out into an ellipse on the ground. The return from this pattern produced a "blip" that was similarly spread out on the radar display and not accurate enough for terrain avoidance. It was, however, accurate enough to produce a low-resolution map-like display of the ground below the aircraft, leading to the wartime development of the H2S radar . To provide

3008-461: The original vacuum tube electronics to be increasingly transistorized , producing a much smaller system overall. As the system was further developed it was moved to a Blackburn Buccaneer for higher-speed testing. The tests were carried out from RAF Turnhouse at the Edinburgh Airport , close to Ferranti's radar development site in the city. During testing, the radar was not connected to

3072-481: The precise moment when the zero-crossing occurs. Accuracies on the order of a meter for measurements of objects kilometers away are commonly achieved. The Cornell reports were picked up in the UK where they formed the basis of an emerging concept for a new strike aircraft , which would eventually emerge as the BAC TSR-2 . The TSR-2 project was officially started with the release of GOR.339 in 1955, and quickly settled on

3136-402: The project started, in 1959 the project lead, Gus Scott, left for Hughes Microcircuits in nearby Glenrothes , and the team was taken over by Greg Stewart and Dick Starling. The initial system was built from a surplus AI.23B AIRPASS, and could be mounted to a trailer and towed by a Land Rover for testing. A significant issue is that the amount of signal returned varies greatly with the terrain;

3200-401: The radar is normally used by the navigator and this allows the pilot to focus on other aspects of the flight besides the extremely intensive task of low flying itself. Most aircraft allow the pilot to also select the ride "hardness" with a cockpit switch, to choose between how closely the aircraft tries to keep itself close to the ground and the forces exerted on the pilot. Some aircraft such as

3264-623: The rapid switch from high-altitude flying over the USSR to the low-altitude "penetrator" approach. In the short term, a number of terrain avoidance radars were introduced for a variety of aircraft. The first true TFR in the US was the Texas Instruments AN/APQ-101, which launched the company as the market leader in TFR for many years. In the early 1960s, they developed TFR systems for the RF-4C version of

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3328-422: The receiver uses this extra information to separate the signals back out again. When these signals are oriented vertically, the signal from the lower beam hits the ground closer to the aircraft, producing a spread-out blip as in the case of earlier radars, while the upper beam produces a similar blip but located at a slightly further distance. The two blips overlap to produce an extended ellipse. The key feature of

3392-465: The side-effect of making spurious reflections in the antenna's side lobes being amplified to the point of causing interference. This was addressed by moving from an O-shaped pattern to a U-shaped one, and only allowing the gain to increase when scanning upward to prevent it from re-adjusting to high gain when moving downward and thereby avoiding low-lying terrain appearing in the sidelobes with high gain. Advances in electronics during development allowed

3456-459: The similar-sounding terrain avoidance radars; terrain avoidance systems scan horizontally to produce a map-like display that the navigator then uses to plot a route that avoids higher terrain features. The two techniques are often combined in a single radar system: the navigator uses the terrain avoidance mode to choose an ideal route through lower-altitude terrain features like valleys, and then switches to TFR mode which then flies over that route at

3520-434: The target to the pilot), a laser designator / rangefinder for precise delivery of laser-guided munitions , a missile boresight correlator for automatic lock-on of the AGM-65 Maverick imaging infrared missiles, and software for automatic target tracking. These features simplify the functions of target detection, recognition and attack and permit pilots of single-seat fighters to attack targets with precision-guided weapons on

3584-513: The target was lased by another jet (first Tomcat LGB drop in combat was made by VF-41 in 1995 during operations over Bosnia with an A-6 Intruder providing the requisite target illumination). Meanwhile, the decision had been made by Chief of Naval Operations (OPNAV) to retire the A-6 altogether and allow the F-14 Block 1 Strike variant to take over as the precision strike platform for the air wing. However,

3648-504: The terrain-following radar deleted is designated as the AN/AAQ-20 Pathfinder , which is only capable of providing a visual cue/picture of ground features in darkness and adverse weather generated by the infrared sensor, and pilots must rely on their own skill to avoid ground obstacles at low altitude flight. The AN/AAQ-14 targeting pod contains a high-resolution, forward looking infrared sensor (which displays an infrared image of

3712-675: The use of TFR to provide the required low-level performance. The Royal Aircraft Establishment built a simulator of the system using discrete electronics that filled a room. During this same period, the Royal Air Force was introducing its newest interceptor aircraft , the English Electric Lightning . The Lightning was equipped with the world's first airborne monopulse radar, the AIRPASS system developed by Ferranti in Edinburgh . In

3776-401: The weather can all limit an aircraft. Since the radar cannot tell what is beyond any immediate terrain, the flight path may also suffer from "ballooning" over sharp terrain ridges, where the altitude becomes unnecessarily high. Furthermore, obstacles such as radio antennas and electricity pylons may be detected late by the radar and present collision hazards. On aircraft with more than one crew,

3840-613: Was an American company founded in 1961 through the merger of Glenn L. Martin Company and American-Marietta Corporation . In 1995, it merged with Lockheed Corporation to form Lockheed Martin . Martin Marietta formed in 1961 by the merger of the Glenn L. Martin Company and American-Marietta Corporation . Martin, based in Baltimore , was primarily an aerospace concern with a recent focus on missiles , namely its Titan program. This program

3904-408: Was during Operation Enduring Freedom when an F-14 generated coordinates for a B-52 that dropped a CBU-103 WCMD from over 40,000 feet (12,000 m). These weapons scored hits on a vehicle convoy that had stopped after the first vehicle was destroyed by the Tomcat with LGBs. The pod also featured an internal computer with ballistics data for the various precision munitions carried by the F-14. Data

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3968-538: Was established in 1955 when the company secured the U.S. Air Force contract to build the country's second intercontinental ballistic missile (ICBM). American-Marietta was headquartered in Chicago and produced paints, dyes, metallurgical products, construction materials, and other goods. In 1982, Martin Marietta was subject to a hostile takeover bid by the Bendix Corporation , headed by William Agee . Bendix bought

4032-409: Was manoeuvring at a constant g-force , while the flat area under the aircraft extends forward a short distance to represent the distance the aircraft moves in a straight line before starting that manoeuvre due to control lag. The resulting compound curve is displaced by a pilot-selected desired clearance distance. The timing of the pulses is much faster than the vertical scanning, so for any one pulse

4096-402: Was modified into LANTIRN Targeting System (LTS), the navigation pod was removed from the two-pod system and the targeting pod was improved for Tomcat use. The LTS featured a Global Positioning System and inertial measurement unit that provided the pod line-of-sight cueing and weapon release ballistics and eliminated the need for external cumbersome and time-consuming boresight equipment. Unlike

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