NATO Airborne Early Warning and Control Aircraft: How the Class Was Born
Aircraft Boeing E-3D Sentry (in RAF - Sentry AEW1) of the Royal Air Force over North Yorkshire
The idea of raising radar into the air arose from a simple limitation of ground stations: the Earth is round, and ground-based radars simply cannot detect low-flying targets beyond the radio horizon. Raising the antenna to a height of several kilometers pushes the radio horizon hundreds of kilometers further—and with it, the detection limit. This idea gave rise to airborne early warning and control aircraft (AEW&C), today one of the most discussed classes of combat aircraft. aviationThe debate is about whether large radar platforms will survive into next-generation wars—or whether they will be supplanted by distributed sensor networks and Drones, are underway right now. These debates will be discussed in the second part. Here, we'll trace the class's origins and development: from the first experiments to AWACS helicopters.
What is AWACS?
Airborne Early Warning and Control (AEW&C) is an airborne radar system designed to detect aircraft, ships, vehicles, cruise missiles (and in some modern systems, as an early warning element for ballistic threats) at long ranges, as well as for air combat management: guiding and informing friendly fighters. AEW&C aircraft are used both for surveillance of ground and sea targets and for combat management command and control (battle management command and control).
At altitude, the radar system of such an aircraft allows operators to detect, track, and classify targets, as well as perform identification (friend or foe) in real time and at a significantly greater range than ground-based radars. Like ground-based radars, airborne systems can be detected and engaged by the enemy. However, due to the carrier's mobility and greater detection range, they are generally less vulnerable than fixed stations; however, the specific weapon determines the outcome. AWACS aircraft are used in defensive and offensive operations and serve the same role for the Air Force as combat information centers on naval ships.
This role has proven so in demand that leading naval powers are using AWACS aircraft and helicopters from the decks of aircraft carriers. A prime example is the carrier-based Northrop Grumman E-2 Hawkeye The US Navy, covering the carrier group; more on this in Part II.
Terminology in this field has historically been mixed. The designation AEW (Airborne Early Warning) was applied to earlier radar picket vehicles, such as Fairey Gannet AEW.3 и Lockheed EC-121 Warning Star; The Royal Air Force also uses it for its Sentry AEW1The acronym AEW&C emphasizes command and control functions that simpler and cheaper patrol vehicles might not have. AWACS (Airborne Warning and Control System) is, strictly speaking, the name of a specific system in American Boeing E-3 Sentry and Japanese Boeing E-767, but in practice it is often used as a general synonym for AEW&C. This distinction is maintained where possible.
Modern AWACS systems detect low-flying aircraft and cruise missiles at ranges of several hundred kilometers (up to 400 km) when flying at high altitudes—significantly further than the range of most anti-aircraft missiles; the specific range depends on the altitude, the target's radar cross-section, and the operating mode.
It's worth examining one common figure here. A frequently cited estimate claims that a single aircraft, from an altitude of 9000 meters, "covers" approximately 3,120,000 square kilometers, meaning three aircraft would be sufficient to cover all of Central Europe. The key figure here is the coverage area of a single aircraft, and it is clearly overstated. This area corresponds to a circle with a radius of approximately 1000 kilometers—and this far exceeds the radio horizon for low-flying targets: from an altitude of 9 kilometers, it is only 350–400 kilometers, yielding a circle of approximately 500,000 square kilometers (more than six times smaller). The larger figure likely refers to high-altitude targets or to the combined coverage area of a network of several platforms, rather than to the horizon of a single aircraft for ground-based targets.
AWACS systems expand the coverage area of ground posts and allow strike aircraft to avoid having to constantly keep their own radars on, which would otherwise unmask them, and also guide fighters to targets.
First steps
After its creation in the 1930s Chain home — the first ground-based radar warning system — the British attempted to place radar on an aircraft for "airborne interception." The goal was to cover the northwestern sea approaches to the British Isles, where German long-range maritime reconnaissance bombers Focke-Wulf Fw 200 Condor threatened shipping. Bomber Vickers wellington (serial R1629) was equipped with a rotating antenna; it was tested against air and then surface targets - German torpedo boats (German. speedboat, Brit. E-boat). Other Wellington with a different radar system served in the Fighter Interception Unit (FIU): the Germans launched some of the V-1 bombs not from ground catapults, but from bombers He 111, and the Wellington crew, with its radar, searched for these carrier aircraft, giving targeting information to fighter-interceptors, including Bristol Beaufighter.
In February 1944, the US Navy commissioned the development of an airborne radar system under Project Cadillac. A prototype was built and tested in August on a modified torpedo bomber. TBM Avenger; the system detected low-flying aircraft at a range of more than 100 miles (160 km). This was followed by a small order TBM-3W — the first production AWACS aircraft to enter service. Equipped with radar AN/APS-20, TBM-3W entered service in March 1945; a total of 27 aircraft were built. Recognizing that a larger carrier would allow for a more powerful radar, the same radar—with improved anti-aircraft capabilities—was installed on several bombers under the Cadillac II program. Boeing B-17G Flying Fortress.
These machines were replaced by large specialized aircraft; the most famous of them is Lockheed EC-121 Warning Star — discussed below. In parallel with aircraft platforms, a separate branch of the AWACS role—N-class airships—developed: they filled gaps in radar coverage in the continental United States, and their endurance of over 200 hours was a significant advantage. After a series of disasters, the US Navy decommissioned AWACS airships in 1962.
Lockheed EC-121 Warning Star — an American radar surveillance and early warning aircraft of the United States Navy (USN) and United States Air Force (USAF), 1950s–1970s
Warning Star: A Quarter Century in Service
EC-121 Warning Star was built on the basis of the family Constellation and first took to the air in 1949; the US Navy was the first to receive it - the versions were designated WV-1 (PO-1W), WV-2 and WV-3. The US Air Force received the machine later: the first deliveries took place in 1954, combat operation in the Air Force ended in 1978, and the only specially modified electronic warfare aircraft remained in service with the US Navy until 1982. Air Force aircraft were used in Vietnam, including as electronic monitoring equipment and provided primary radar cover for American troops until they were replaced by more advanced Boeing E-3 Sentry AWACS. Air Force crews adopted the civilian nickname "Connie" (from Constellation), Navy crews called their machines "Willy Victors".
WV-2/EC-121D carried two radars: the upper one AN/APS-45 with an antenna in a fiberglass fairing above the center section - for high-altitude purposes, and a lower search AN/APS-20 in a fairing under the center section - for low-flying and surface targets. There is little information about the upper radar, but the lower one has a remarkable story.
The AN/APS-20 Radar and Its Long Life
Radar AN/APS-20 S-band radar has been used by the US military and several other countries since World War II. Users include the French Navy, the Japan Maritime Self-Defense Force (JMSDF), the Royal Air Force (RAF), and the Royal Canadian Air Force (RCAF). Designed for aircraft detection, it was widely used in anti-submarine warfare and maritime patrols and was among the first radars for hurricane research—it was used, in particular, by the US agency ESSA (one of the agencies that preceded today's NOAA). It was mass-produced. General Electric и Hazeltine.
The numbers will follow, but the point is this: it was the antenna power, length, and operating frequency that determined how far away the AWACS vehicle could actually see a target. It's worth clarifying right away: the letter indexes for the versions (A, B, E, F) reflect not so much chronology as their purpose and configuration, so a "later" letter in the alphabet doesn't always indicate a newer modification. The first version, the AN/APS-20A, had an 8-foot-4-inch (2,54 m) antenna and operated at 2850 MHz in the S-band; it was distinguished by large sidelobes. Later, a slightly smaller antenna—8 feet (2,4 m)—was used.
- The scanner rotation speed is two-stage, 3 and 6 rpm.
- The pulse repetition frequency is 300 Hz, the pulse duration is 2 μs.
- Peak power is 1 MW (for the AN/APS-20B version, for larger carriers, it is 2 MW).
- The AN/APS-20B has a beam width of 1,5° horizontally and 6° vertically.
- Range of early versions: against low-flying aircraft - 65 nautical miles (120 km), against ships - 200 nautical miles (370 km).
The radar provided direction and range to the target, but not its altitude—that is, it operated in two dimensions, without altitude determination. Over time, it was repeatedly upgraded, and later versions could detect aerial targets significantly further away.
Avro Shackleton AEW.2 (RAF), in service from 1972 to 1991; pictured is an aircraft of No. 8 Squadron RAF
The AN/APS-20F could detect aircraft at a range of up to 80 nautical miles (150 km), while the more advanced AN/APS-20E could detect an aerial target with an RCS of 1 m² at 115 nautical miles (213 km). The AN/APS-20E, which entered service in 1953, was a tri-band variant, operating in L-, S-, and X-bands with switchable parameters: the band was selected for the task (S for long-range surveillance, L for increased range and penetration, X for higher resolution), and each offered different repetition rates and pulse durations. It also offered more: automatic target illumination, a choice of three course-determining and stabilization schemes, adjustable beam width in azimuth and elevation, and gain control, including automatic operation.
This same radar AN/APS-20, removed from airplanes Gannet, installed on modified patrol vehicles Shackleton MR 2, converted into a variant AEW.2: They served in the Royal Air Force from 1972 to 1991 with No. 8 Squadron at RAF Lossiemouth. All 12 aircraft, as per tradition, were given "cheesy" names - characters from the British children's television series The Magic Roundabout and The Herbs. The planned replacement for British Aerospace Nimrod AEW3 fell through due to unsolvable technical development problems, and Britain chose ready-made Boeing E-3 Sentry - after which the resource has been exhausted Shackleton finally removed from service.
On deck and on a helicopter
That's the story AN/APS-20 It's not over. The Falklands War clearly demonstrated what it's like for a unit without radar coverage over the horizon—and they even managed to install radar on AWACS helicopters: two Sea King AEW.2A and one Sea King AEW.5 (converted from anti-submarine Sea King HAS.2) for three British light aircraft carriers - HMS Invincible (R05), HMS Illustrious (R06) and HMS Ark Royal (R07).
Later, both radars on the EC-121 were replaced with more modern AN/APS-103 and AN/APS-95 radars, respectively, although the upgrades were not simultaneous. The EC-121 typically had a crew of 18: six officers (two pilots, two navigators, and two weapons control operators) and 12 enlisted men (two flight engineers, a radio operator, two mechanics, five radar operators, and two radar technicians). However, when the North Korean Air Force shot down a U.S. Navy EC-121 in 1969, it was discovered that it had an increased crew of 31 on board.
A U.S. Department of Homeland Security P-3AEW&C used to track light aircraft carrying drug smugglers.
In the 1960s, Lockheed attempted to develop an AWACS and CAS aircraft based on the Orion patrol aircraft. The military failed to take interest in the project, but the US Department of Homeland Security did, ordering several aircraft.
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