Radar warning receiver
Encyclopedia
Radar warning receiver (RWR) systems detect the radio
emissions of radar
systems. Their primary purpose is to issue a warning when a radar signal that might be a threat (such as a police speed detection radar) is detected. The warning can then be used, manually or automatically, to evade the detected threat. RWR systems can be installed in all kind of airborne, sea-based, and ground-based assets (such as aircraft
, ship
s, automobile
s, military base
s). This article is focused mainly on airborne military RWR systems, for commercial police RWR systems, see radar detector
.
Depending on the market the RWR system is designed for, it can be as simple as detecting the presence of energy in a specific radar band (such as police radar detectors). For more critical situations, such as military combat, RWR systems are often capable of classifying the source of the radar by the signal's strength, phase and waveform type, like pulsed power
wave or continuous wave
with amplitude modulation
or frequency modulation (chirp
ed). The information about the signal's strength and waveform can then be used to estimate the most probable type of threat the detected radar poses. Simpler systems are typically installed in less expensive assets like automobiles, while more sophisticated systems are installed in mission critical assets like military aircraft
.
or the type of vehicle that carries it, often with a distinction made between ground-based radars and airborne radars. Audible tones are usually assigned to each type of threat or type of radar
and are fairly distinctive. The more serious the threat, the more shrill the tone. For example, an active missile seeker might be represented by a high pitched, almost continuous trill, whereas the radar
of an obsolete fighter type or SAM system might be a low pitched, intermittent buzz.
The RWR is used for identifying, avoiding, evading or engaging threats. For example, a fighter aircraft
on a combat air patrol
(CAP) might notice enemy fighters on the RWR and subsequently use its own radar
set to find and eventually engage the bandit. In addition, the RWR helps identify and classify threats—it's hard to tell which blips on a radar
console-screen are dangerous, but since different fighter aircraft
typically have different types of radar
sets, once they turn them on and point them near the aircraft in question it may be able to tell, by the direction and strength of the signal, which of the blips is which type of fighter.
A non-combat aircraft
, or one attempting to avoid engagements, might turn its own radar
off and attempt to steer around threats detected on the RWR. Especially at high altitude (more than 30,000 feet AGL
), very few threats exist that don't emit radiation. As long as the pilot is careful to check for aircraft that might try to sneak up without radar, say with the assistance of AWACS or GCI
, it should be able to steer clear of SAMs, fighter aircraft
and high altitude, radar-directed AAA.
SEAD
and ELINT aircraft often have sensitive and sophisticated RWR equipment like the U.S. HTS (HARM
targeting system) pod which is able to find and classify threats which are much further away than those detected by a typical RWR, and may be able to overlay threat circles on a map in the aircraft's multi-function display
(MFD), providing much better information for avoiding or engaging threats, and may even store information to be analyzed later or transmitted to the ground to help the commanders plan future missions.
The RWR can be an important tool for evading threats if avoidance has failed. For example, if a SAM system or enemy fighter aircraft
has fired a missile
(for example, a SARH
-guided missile
) at the aircraft, the RWR may be able to detect the change in mode that the radar
must use to guide the missile and notify the pilot with much more insistent warning tones and flashing, bracketed symbols on the RWR display. The pilot then knows to take evasive action, and what type of evasive action to take to break the missile lock-on
or dodge the missile
. The pilot may even be able to visually acquire the missile after being alerted to the possible launch. What's more, if an actively guided missile is tracking the aircraft, the pilot can use the direction and distance display of the RWR to work out which evasive maneuvers to perform to outrun or dodge the missile. For example, the rate of closure and aspect of the incoming missile may allow the pilot to determine that if they dive away from the missile, it is unlikely to catch up, or if it is closing fast, that it is time to jettison external supplies and turn toward the missile in an attempt to out-turn it.
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
emissions of radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
systems. Their primary purpose is to issue a warning when a radar signal that might be a threat (such as a police speed detection radar) is detected. The warning can then be used, manually or automatically, to evade the detected threat. RWR systems can be installed in all kind of airborne, sea-based, and ground-based assets (such as aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
, ship
Ship
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...
s, automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
s, military base
Military base
A military base is a facility directly owned and operated by or for the military or one of its branches that shelters military equipment and personnel, and facilitates training and operations. In general, a military base provides accommodations for one or more units, but it may also be used as a...
s). This article is focused mainly on airborne military RWR systems, for commercial police RWR systems, see radar detector
Radar detector
A radar detector is an electronic device used by motorists to detect if their speed is being monitored by police or law enforcement using a radar gun. Most radar detectors are used so the driver can reduce the car's speed before being ticketed for speeding...
.
Depending on the market the RWR system is designed for, it can be as simple as detecting the presence of energy in a specific radar band (such as police radar detectors). For more critical situations, such as military combat, RWR systems are often capable of classifying the source of the radar by the signal's strength, phase and waveform type, like pulsed power
Pulsed power
Pulsed power is the term used to describe the science and technology of accumulating energy over a relatively long period of time and releasing it very quickly thus increasing the instantaneous power.-Overview:...
wave or continuous wave
Continuous wave
A continuous wave or continuous waveform is an electromagnetic wave of constant amplitude and frequency; and in mathematical analysis, of infinite duration. Continuous wave is also the name given to an early method of radio transmission, in which a carrier wave is switched on and off...
with amplitude modulation
Amplitude modulation
Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...
or frequency modulation (chirp
Chirp
A chirp is a signal in which the frequency increases or decreases with time. In some sources, the term chirp is used interchangeably with sweep signal. It is commonly used in sonar and radar, but has other applications, such as in spread spectrum communications...
ed). The information about the signal's strength and waveform can then be used to estimate the most probable type of threat the detected radar poses. Simpler systems are typically installed in less expensive assets like automobiles, while more sophisticated systems are installed in mission critical assets like military aircraft
Military aircraft
A military aircraft is any fixed-wing or rotary-wing aircraft that is operated by a legal or insurrectionary armed service of any type. Military aircraft can be either combat or non-combat:...
.
Description
The RWR usually has a visual display somewhere prominent in the cockpit (in some modern aircraft, in multiple locations in the cockpit) and also generates audible tones which feed into the pilot's (and perhaps RIO/co-pilot/GIB's in a multi-seat aircraft) headset. The visual display often takes the form of a circle, with symbols displaying the detected radars according to their direction relative to the current aircraft heading (i.e. a radar straight ahead displayed at the top of the circle, directly behind at the bottom, etc.). The distance from the center of the circle, depending on the type of unit, can represent the estimated distance from the generating radar, or to categorize the severity of threats to the aircraft, with tracking radars placed closer to the center than search radars. The symbol itself is related to the type of radarRadar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
or the type of vehicle that carries it, often with a distinction made between ground-based radars and airborne radars. Audible tones are usually assigned to each type of threat or type of radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
and are fairly distinctive. The more serious the threat, the more shrill the tone. For example, an active missile seeker might be represented by a high pitched, almost continuous trill, whereas the radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
of an obsolete fighter type or SAM system might be a low pitched, intermittent buzz.
The RWR is used for identifying, avoiding, evading or engaging threats. For example, a fighter aircraft
Fighter aircraft
A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets...
on a combat air patrol
Combat air patrol
Combat air patrol is a type of flying mission for fighter aircraft.A combat air patrol is an aircraft patrol provided over an objective area, over the force protected, over the critical area of a combat zone, or over an air defense area, for the purpose of intercepting and destroying hostile...
(CAP) might notice enemy fighters on the RWR and subsequently use its own radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
set to find and eventually engage the bandit. In addition, the RWR helps identify and classify threats—it's hard to tell which blips on a radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
console-screen are dangerous, but since different fighter aircraft
Fighter aircraft
A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets...
typically have different types of radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
sets, once they turn them on and point them near the aircraft in question it may be able to tell, by the direction and strength of the signal, which of the blips is which type of fighter.
A non-combat aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
, or one attempting to avoid engagements, might turn its own radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
off and attempt to steer around threats detected on the RWR. Especially at high altitude (more than 30,000 feet AGL
Above ground level
In aviation and atmospheric sciences, an altitude is said to be above ground level when it is measured with respect to the underlying ground surface. This is as opposed to above mean sea level , or in broadcast engineering, height above average terrain...
), very few threats exist that don't emit radiation. As long as the pilot is careful to check for aircraft that might try to sneak up without radar, say with the assistance of AWACS or GCI
Ground-controlled interception
Ground-controlled interception an air defense tactic whereby one or more radar stations are linked to a command communications centre which guides interceptor aircraft to an airborne target. This tactic was pioneered during World War II by the Royal Air Force with the Luftwaffe to follow closely...
, it should be able to steer clear of SAMs, fighter aircraft
Fighter aircraft
A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets...
and high altitude, radar-directed AAA.
SEAD
SEAD
Suppression of Enemy Air Defenses , also known as "Wild Weasel" and "Iron Hand" operations in the United States, are military actions to suppress enemy surface-based air defenses , primarily in the first hours of an attack.One fourth of American combat sorties in recent conflicts have been SEAD...
and ELINT aircraft often have sensitive and sophisticated RWR equipment like the U.S. HTS (HARM
AGM-88 HARM
The AGM-88 High-speed Anti-Radiation Missile is a tactical, air-to-surface missile designed to home in on electronic transmissions coming from surface-to-air radar systems. It was originally developed by Texas Instruments as a replacement for the AGM-45 Shrike and AGM-78 Standard ARM system...
targeting system) pod which is able to find and classify threats which are much further away than those detected by a typical RWR, and may be able to overlay threat circles on a map in the aircraft's multi-function display
Multi-function display
A Multi-function display is a small screen in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways. Often an MFD will be used in concert with a Primary Flight Display. MFDs are part of the digital era of modern planes or...
(MFD), providing much better information for avoiding or engaging threats, and may even store information to be analyzed later or transmitted to the ground to help the commanders plan future missions.
The RWR can be an important tool for evading threats if avoidance has failed. For example, if a SAM system or enemy fighter aircraft
Fighter aircraft
A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets...
has fired a missile
Missile
Though a missile may be any thrown or launched object, it colloquially almost always refers to a self-propelled guided weapon system.-Etymology:The word missile comes from the Latin verb mittere, meaning "to send"...
(for example, a SARH
Sarh
Sarh is the third largest city in Chad, after N'Djamena and Moundou. It is the capital of Moyen-Chari region and the department of Barh Köh. It lies 350 miles south-east of the capital Ndjamena on the Chari River...
-guided missile
Missile
Though a missile may be any thrown or launched object, it colloquially almost always refers to a self-propelled guided weapon system.-Etymology:The word missile comes from the Latin verb mittere, meaning "to send"...
) at the aircraft, the RWR may be able to detect the change in mode that the radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
must use to guide the missile and notify the pilot with much more insistent warning tones and flashing, bracketed symbols on the RWR display. The pilot then knows to take evasive action, and what type of evasive action to take to break the missile lock-on
Missile lock-on
Missile lock-on refers to a scenario where the guidance system for a missile can accurately track a target, and a fire-control system can calculate the required flightpath for the missile to hit the target...
or dodge the missile
Missile
Though a missile may be any thrown or launched object, it colloquially almost always refers to a self-propelled guided weapon system.-Etymology:The word missile comes from the Latin verb mittere, meaning "to send"...
. The pilot may even be able to visually acquire the missile after being alerted to the possible launch. What's more, if an actively guided missile is tracking the aircraft, the pilot can use the direction and distance display of the RWR to work out which evasive maneuvers to perform to outrun or dodge the missile. For example, the rate of closure and aspect of the incoming missile may allow the pilot to determine that if they dive away from the missile, it is unlikely to catch up, or if it is closing fast, that it is time to jettison external supplies and turn toward the missile in an attempt to out-turn it.
RWR types in service
- AN/ALR-46 (F-4 Phantom IIF-4 Phantom IIThe McDonnell Douglas F-4 Phantom II is a tandem two-seat, twin-engined, all-weather, long-range supersonic jet interceptor fighter/fighter-bomber originally developed for the United States Navy by McDonnell Aircraft. It first entered service in 1960 with the U.S. Navy. Proving highly adaptable,...
, RF-4 Phantom II, F-5F-5 Freedom FighterThe Northrop F-5A/B Freedom Fighter and the F-5E/F Tiger II are part of a family of widely-used light supersonic fighter aircraft, designed and built by Northrop...
, B-52G) - AN/ALR-56 (USA; F-15 EagleF-15 EagleThe McDonnell Douglas F-15 Eagle is a twin-engine, all-weather tactical fighter designed by McDonnell Douglas to gain and maintain air superiority in aerial combat. It is considered among the most successful modern fighters with over 100 aerial combat victories with no losses in dogfights...
, Canada; CC-130 Hercules) - AN/ALR-66 (USA; P-3CP-3 OrionThe Lockheed P-3 Orion is a four-engine turboprop anti-submarine and maritime surveillance aircraft developed for the United States Navy and introduced in the 1960s. Lockheed based it on the L-188 Electra commercial airliner. The aircraft is easily recognizable by its distinctive tail stinger or...
Orion) - AN/ALR-67ALR-67 Radar Warning ReceiverThe AN/ALR-67 Radar Warning Receiver is designed to warn an aircraft's crew of potentially hostile radar activity. It is an airborne threat warning and countermeasures control system built to be successor to the United States Navy's AN/ALR-45. Northrop Grumman Corporation's Electronic Systems...
(USA; AV-8B Harrier II, F-14 Tomcat, F/A-18E/F Super Hornet, EA-6B Prowler, Canada; CF-18 Hornet) - AN/ALR-69 (USA; B-52H Stratofortress, lacks Frequency Selective Receiver Capabilities (FSRS) capabilities however, A-10 Thunderbolt IIA-10 Thunderbolt IIThe Fairchild Republic A-10 Thunderbolt II is an American single-seat, twin-engine, straight-wing jet aircraft developed by Fairchild-Republic in the early 1970s. The A-10 was designed for a United States Air Force requirement to provide close air support for ground forces by attacking tanks,...
, AC-130 Spectre, F-16 Fighting Falcon, HH-53, MC-130, F-4E Phantom IIF-4 Phantom IIThe McDonnell Douglas F-4 Phantom II is a tandem two-seat, twin-engined, all-weather, long-range supersonic jet interceptor fighter/fighter-bomber originally developed for the United States Navy by McDonnell Aircraft. It first entered service in 1960 with the U.S. Navy. Proving highly adaptable,...
). - AN/ALR-76 (USA; S-3S-3 VikingThe Lockheed S-3 Viking is a four-seat twin-engine jet aircraft that was used by the U.S. Navy to identify, track, and destroy enemy submarines. In the late 1990s, the S-3B's mission focus shifted to surface warfare and aerial refueling. The Viking also provided electronic warfare and surface...
, EP-3) - AN/ALR-94 (USA; F-22F-22 RaptorThe Lockheed Martin/Boeing F-22 Raptor is a single-seat, twin-engine fifth-generation supermaneuverable fighter aircraft that uses stealth technology. It was designed primarily as an air superiority fighter, but has additional capabilities that include ground attack, electronic warfare, and signals...
) - AN/APR-39 (USA, AH-1, AH-64 Apache, CH-46 Sea Knight, CH-47 ChinookCH-47 ChinookThe Boeing CH-47 Chinook is an American twin-engine, tandem rotor heavy-lift helicopter. Its top speed of 170 knots is faster than contemporary utility and attack helicopters of the 1960s...
, CH-53, EH-60 Black Hawk, KC-130 Hercules, MH-47 ChinookCH-47 ChinookThe Boeing CH-47 Chinook is an American twin-engine, tandem rotor heavy-lift helicopter. Its top speed of 170 knots is faster than contemporary utility and attack helicopters of the 1960s...
, MH-60 Black Hawk, OH-58, OV-1 Mohawk, RC-12, RV-1, UH-1 Iroquois, UH-60 Black Hawk, V-22 OspreyV-22 OspreyThe Bell Boeing V-22 Osprey is an American multi-mission, military, tiltrotor aircraft with both a vertical takeoff and landing , and short takeoff and landing capability...
) - ALR-2002ALR-2002The AN/ALR-2002 Radar Warning Receiver is designed to warn an aircraft's crew of potentially hostile radar activity. British Aerospace Australia was the sole contractor for the AN/ALR-2002 Australian indigenous System...
(Australia; developmental, project being cancelled) - ALR-400 (Spain; EF-18A/B Hornet, Airbus A400M, C-295, CH-47 Chinook, Cougar, TIGER, NH90, CH-53)
- BOW-21 (Sweden; JAS 39 GripenJAS 39 GripenThe Saab JAS 39 Gripen is a lightweight single-engine multirole fighter manufactured by the Swedish aerospace company Saab. It was designed to replace the Saab 35 Draken and 37 Viggen in the Swedish Air Force...
Germany; Panavia TornadoPanavia TornadoThe Panavia Tornado is a family of twin-engine, variable-sweep wing combat aircraft, which was jointly developed and manufactured by the United Kingdom, West Germany and Italy...
) - SPO-15 Beryoza (India; MiG-29 Fulcrum, Russia; Su-27SK Flanker-B, China; J-11Shenyang J-11The Shenyang J-11 with NATO reporting name: Flanker B+ is a single-seat, twin-engine jet fighter based on the Soviet-designed Sukhoi Su-27 air superiority fighter produced by the Shenyang Aircraft Corporation...
) - Tarang (India; MiG-27 Flogger, LCAHAL TejasThe HAL Tejas is a lightweight multirole fighter developed by India. It is a tailless, compound delta-wing design powered by a single engine. It came from the Light Combat Aircraft programme, which began in the 1980s to replace India's ageing MiG-21 fighters...
Tejas, Jaguar, Su-30MKISu-30MKIThe Sukhoi Su-30MKI is an air superiority fighter jointly developed by Russia's Sukhoi and India's Hindustan Aeronautics Limited for the Indian Air Force...
Flanker)
See also
- Laser warning receiverLaser warning receiverA laser warning receiver is a type of warning system used as a passive military defence. It detects laser emission from laser guidance systems and laser rangefinders. Then it alerts the crew and can start various countermeasures, like smoke wall, aerosol screen A laser warning receiver is a type of...
- List of Rainbow Codes
- List of World War II electronic warfare equipment
- Monica tail warning radarMonica tail warning radarMonica was a range-only tail warning radar for bombers, introduced by the RAF in the spring of 1942. Officially known as ARI 5664, it operated at frequencies of around 300 MHz...
- Semi-active radar homingSemi-active radar homingSemi-active radar homing, or SARH, is a common type of missile guidance system, perhaps the most common type for longer-range air-to-air and surface-to-air missile systems. The name refers to the fact that the missile itself is only a passive detector of a radar signal – provided by an external ...
- Serrate radar detectorSerrate radar detectorSerrate was an Allied radar detection and homing device, used in Allied nightfighters to track German night fighters equipped with the earlier UHF-band BC and C-1 versions of the Lichtenstein radar during World War II....