In the second half of the 50s, the Americans realized that the continental United States was no longer an island isolated by the oceans, and so far the few Soviet strategic bombers are already quite capable of dropping nuclear bombs on American cities. Particularly vulnerable was the northeastern direction from Canada, which was the shortest route for Soviet long-range bomber aviation.
The response to this threat was the creation in the United States of the so-called "Barrier Forces" (more details here: North American air defense system (part 1)). For this, a network of radar stations was built in Greenland, Alaska and Northeast Canada, but the eastern direction from the Atlantic Ocean remained uncovered. The US Navy assumed responsibility for controlling the airspace over the Atlantic, starting the massive deployment of radar patrol ships and stationary radar platforms. The most important element of the "Barrier Forces" also became AWACS aircraft.
Back in 1949, Lockheed specialists attempted to create a heavy aircraft for the PO-1W radar patrol based on the Lockheed L-749 Constellation airliner. In order to eliminate "dead zones", radar antennas were placed in the upper and lower fuselage.
PO-1W
However, tests showed that "the first pancake came out lumpy" - the composition and layout of the radar and communication equipment were not optimal, and the reliability was low. A lot of criticism was caused by the placement of workplaces of radar operators and the protection of personnel from high-frequency radiation. Several built PO-1W, in fact, became flying laboratories, which worked out various options for avionics and tactics of using heavy AWACS aircraft. After the completion of the test cycle, the aircraft were renamed WV-1 and transferred to the US Federal Aviation Administration (FAA), where they flew until 1959.
The AWACS aircraft, originally known as PO-2W, has become truly massive. This machine was created on the basis of the long-haul transport and passenger four-engined Lockheed L-1049 Super Constellation. To increase speed, payload and fuel efficiency, the fuselage was extended on this model and installed Wright R-3350-75 Duplex-Cyclone turbocharged engines with 2500 hp. each. These engines, being an air-cooled, turbocharged, twin 18-cylinder sprocket, were among the most powerful serial piston engines. Initially, these aircraft engines were intended for B-29 bombers.
The aircraft with a normal takeoff weight of 66,000 kg developed a maximum speed of 467 km / h, the patrol speed was 360 km / h. With a full refueling, the PO-2Ws of early modifications could cover a distance of more than 6400 km, subsequently, thanks to the increased fuel tanks, the flight range increased by about 15%. From the very beginning, the military pointed to a relatively small ceiling - 5500 meters, which limited the range of airborne radars. But we had to come to terms with this, in the early 50s in the United States, with its developed aviation industry, there was no suitable platform with economical turbojet or turboprop engines and a pressurized cabin. The military rejected the version of the AWACS aircraft based on the Boeing B-50 Superfortress, since the bomber, with a comparable flight range, had smaller internal volumes compared to the Super Constellation and could not provide the placement of the necessary equipment and comfortable working conditions for the radar operators.
PO-2W in test flight
Compared to the original PO-1W, the extended PO-2W has become a fully-fledged airspace control aircraft. When designing and placing the equipment, the disadvantages of the previous model were taken into account. The PO-2W was equipped with an improved AN / APS-20E radar and an AN / APS-45 radar.
Radar indicator AN / APS-20
The characteristics of these stations still command respect. According to American sources, the AN / APS-20E radar with a peak power of up to 2 MW, operating at a frequency of 2880 MHz, could detect large sea targets at a range of up to 300 km. The B-29 bomber, flying at an altitude of 7000 meters, could be detected at a distance of 160 km, and the F-86 fighter - 120 km. The AN / APS-45 station, operating at a frequency of 9375 MHz, which controlled the lower hemisphere, could see targets of the B-29 type at a distance of up to 200 km.
AN / APS-45 radar control panel and antenna
The PO-2W was the first American "airborne radar picket" to use two radars simultaneously to monitor the lower and upper hemispheres, eliminating shadow zones. This became possible due to the large internal volume of the aircraft, which made it possible to place not only radars, navigation and communication equipment, but also to equip workplaces and rest areas for a large crew with sufficient comfort. On different aircraft modifications, there could be from 18 to 26 people on board. Taking into account that the average duration of the patrol was 12 hours, there was a supply of food, a refrigerator and a kitchen on board. Based on the experience of testing the PO-1W, special attention was paid to protecting the crew from microwave radiation.
In 1954, after the start of regular patrols, the US Navy aircraft was renamed WV-2. Initially, American admirals hoped that aircraft with powerful radars would be able to cover aircraft carrier groups with a "radar umbrella". During long flights, AWACS aircraft had to refuel in the air from refueling aircraft taking off from aircraft carriers. However, in practice, this was never implemented and the WV-2 could control the air situation in the area following the order only at a distance of several hundred kilometers from its shores. For this reason, the main area of activity of the WV-2 aircraft was operations as part of the "Barrier Forces". The first land-based AWACS aircraft were deployed in the United States at the Patuxent River airbase and in Canada in the Newfoundland and Barbers Point area. During 1955, naval specialists tested the WV-2, at the same time there was a process of getting rid of "childhood sores" and linking with ground control points, after which an order was placed for another 130 aircraft.
Almost simultaneously with the receipt of the new order, Lockheed offered a radically modernized version of the same machine with more powerful radars, new data transmission equipment and Allison T56 turboprop engines. It was also supposed to equip the aircraft with AIM-7A Sparrow air combat missiles, which had just been put into service. However, this project did not find support from the military and only a new avionics were introduced on the newly built AWACS aircraft.
The APS-20 airborne radar, designed during the Second World War, was replaced by a modern multifunctional AN / APS-95 radar operating in the 406-450 MHz frequency range. The AN / APS-95 station could detect air and surface targets at a distance of over 300 km and simultaneously track up to 300 objects. The information update rate was 12 seconds. The AN / APS-95 radar antenna was mounted inside a fairing with a diameter of 8 meters, on a massive pylon above the fuselage.
AN / APS-95 radar repair
The equipment for the automated transmission of radar data transmitted information about the range, azimuth and intended type of target to the ground control point or aircraft carrier. The transmission was carried out using a narrow beam antenna over the radio channel, which made interference suppression or interception difficult.
Workstations of the AN / APS-95 radar operator and the telecom operator
For its time, very advanced avionics were installed on the WV-2, which provided high capabilities for detecting air targets and processing information. By the standards of the 50-60s, these aircraft were considered real "electronic monsters", but their cost was not small. The first WV-2s cost the American treasury more than $ 2.2 million, and as the onboard filling was improved and new modifications appeared, the cost only increased. But even at an exorbitant price, 232 aircraft were built from 1953 to 1958.
In the late 50s - early 60s, the WV-2 patrol zone in the Atlantic included a vast territory up to the Azores, Greenland, Iceland and the British Isles. At the same time, AWACS aircraft made an intermediate landing in Iceland. On the Pacific coast, taking off from the Barbers Point airfield, the "air patrols" flew to Hawaii and landed at Midway airfield. In those years, the airspace adjacent to the United States was patrolled daily by at least five radar patrol aircraft, which carried out close cooperation with the ships of the US Navy. In total, taking into account the possible duplication at air bases, at least nine vehicles with crews were on alert around the clock.
In 1962, the aircraft was renamed the EC-121 Warning Star. Much later than the fleet, the air force became interested in AWACS aircraft. However, the lack of haste allowed the Air Force to adopt the EC-121C, which had already been "brought to mind", with more advanced radars and communications equipment. However, the EC-121Cs were soon replaced by the EC-121D with larger fuel tanks.
Aircraft AWACS EC-121 and interceptors F-104A
Since the second half of the 50s, the air defense of the North American continent relied on an automated guidance system for interceptors, and the integration of the Warning Starov into it became quite natural. The EC-121D aircraft were mainly redesigned. A total of 42 vehicles were upgraded to the EC-121H and EC-121J variants. Modifications of the EC-121N and EC-121J differed in the composition of the avionics and the placement of operator workplaces. The most advanced, but not numerous, modification in the Air Force was the EC-121Q. On this aircraft, the AN / APS-45 radar was replaced by the AN / APS-103 radar, which is able to steadily see targets against the background of the earth's surface. Twenty-two ES-121Ns, in the course of refurbishment and modernization, were equipped with new "friend or foe" equipment and improved means of displaying radar information. This variant is known as the EC-121T. In 1973, part of the least worn out ES-121T operated in the Pacific Ocean received AN / ALQ-124 electronic warfare stations.
As is often the case with technically complex weapons, when AWACS aircraft reached the peak of their combat readiness, their careers began to decline. The early versions were converted to the WC-121N weather reconnaissance aircraft and the EC-121S electronic warfare and EC-121M reconnaissance aircraft.
In the mid-60s, the intensity of patrol flights of AWACS aircraft as part of the Barrier Force operations declined, as the main threat to the United States began to be posed not by relatively small Soviet bombers, but by intercontinental ballistic missiles. By that time, twin-engine radar patrol aircraft began to appear on the decks of American aircraft carriers, capable of conducting long enough patrols, and the fleet also began to lose interest in the expensive Warning Stars, and these machines began to be switched to other tasks.
One of the main functions of the ES-121 was weather reconnaissance, powerful radars made it possible to detect approaching hurricanes and thunderstorms at a considerable distance. However, heavy piston aircraft did not always manage to retreat in a timely manner. So, on August 1, 1964, Hurricane "Clio" badly battered board # 137891. A hurricane wind blew off the end fuel tanks and deformed the fuselage, and close lightning discharges disabled most of the onboard electronics. The crew managed to safely land the heavily damaged vehicle, which was later written off as irreparable.
Various modifications of the EC-121 have participated in numerous new developments and research programs. Specially trained vehicles tracked test launches of ballistic missiles around the world, accompanied cruise missiles and target aircraft. In the early 60s, a WV-2E (EC-121L) aircraft with an AN / APS-82 radar, which had a rotating antenna in a disc-shaped fairing, was tested. This arrangement of the radar antenna on the AWACS aircraft later became classical.
WV-2E
The AN / APS-82 all-round viewing station demonstrated the ability to detect targets against the background of the earth, but during the tests, low reliability and the need for refinement were revealed. In addition, an aircraft with relatively low-power piston engines had a small practical ceiling, which made it impossible to realize all the advantages of a station with a rotating disk antenna (the higher the radar is located, the greater the range it can cover).
After the final curtailment of the regular patrols of the Barrier Force, a significant part of the EU-121 was transferred to airfields outside the continental United States: Atsugi in Japan, Milden Hall in the UK, Rota in Spain, Roosevelt Rhodes in Puerto Rico and Agana in Guam. From where the planes were used to track the airspace of the countries of Eastern Europe, the USSR, the PRC, the DPRK and Cuba.
US intervention in hostilities in Southeast Asia led to increased interest in AWACS aircraft. Already in 1965, several EC-121Ds were sent into the combat zone. Initially, the aircraft flew from Taiwan, and later flew to the Ubon airbase in Thailand. The main task of the crews of the "air radar pickets" was air traffic control over South Vietnam, as well as assistance in navigation for aircraft participating in raids on the DRV. However, already in 1967, the Warning Stars began to coordinate the actions of American fighters in air battles with North Vietnamese MiGs.
EC-121D
However, the humid tropical climate had a devastating effect on the electronic equipment of aircraft, and in 1970 EC-121Ds were replaced by EC-121Ts with more advanced avionics, they were placed at the Korat airbase in Thailand. The benefits of the EC-121T were much greater, the AWACS aircraft not only coordinated the actions of fighters in air battles, but also warned of the launches of SA-75 anti-aircraft missiles and jammed the North Vietnamese ground-based radar. With the informational support of the EU-121, more than a dozen MiGs were shot down over Vietnam and Laos, about 135,000 sorties of bombers and attack aircraft were carried out, more than 80 special and search and rescue operations were carried out.
During operation, most of the machines of later modifications underwent refurbishment and modernization. This was mainly related to the "electronic filling". Automated systems controlled by computers and modern means of displaying and transmitting data were introduced into the avionics. The switch from vacuum electronics to solid-state electronics reduced equipment weight and energy consumption. The service of AWACS, electronic warfare and electronic reconnaissance aircraft of the EU-121 family continued in the United States for almost 30 years. The last Warning Star in the US Air Force was decommissioned in 1982.
Over the years of operation in various flight accidents, the US Air Force and Navy have lost 25 aircraft and 163 crew members. There is a high probability that part of the EU-121 was lost as a result of "external influence" during provocative flights along the borders of the countries of the "communist bloc". It is reliably known about one ES-121M, shot down by North Korean fighters on April 5, 1969 - on the day of the celebration of Kim Il Sung's 57th birthday.
In the 1950s, the Americans, fearing nuclear bombings, spent billions of dollars on the creation of warning and interception systems. The creation of a radar network in Alaska, in the North of Canada and in Greenland, the construction and operation of sea radar platforms, ships and radar patrol aircraft required huge financial investments. One of the attempts to reduce the cost of lighting the air situation was the creation of sentinel airships, designated in the United States as N - class.
In the late 1940s, Goodyear Aircraft proposed a radar patrol airship to the US military. According to the calculations presented, the controlled device is lighter than air, it could be on patrol for more than 100 hours, which was several times higher than the capabilities of the AWACS aircraft. The tests of the ZPG-1 were generally successful. It was a "soft" type airship with an internal helium volume of 24777 m³. But the military wanted a more lifting platform. Soon after the first model, the ZPG-2W appeared with a volume of 28317 m³, equipped with an AN / APS-20 radar station. The radar antenna was located at the bottom of the airship nacelle.
The gondola, which housed 21 crew members, and the radar connected the tunnel, through which it was possible to get to the radar and eliminate the problems that had arisen. Two engines were installed in the nacelle, operating on one propeller, which made it possible, if necessary, to successfully fly on one engine.
Airship radar patrol ZPG-2W
A total of 12 serial AWACS airships were built. The first ZPG-2W joined the 1st Aircraft Wing at Lakehurst AFB in March 1953. Already in May 1954, the Snowbird set an international record for flight duration on the ZPG-2 W. The device lasted 200 hours and 24 minutes in the air.
The operation of airships in Lakehurst began long before the appearance of "air radar pickets", even during the war years in the United States they created airships intended for hunting submarines. Based on the experience of operating the ZPG-2W, the largest American AWACS airship, the ZPG-3W, was created. It was also a “soft” type apparatus with a shell volume of 42,500 m³. Its length exceeded 121 meters, and its shell was 36 meters wide. A large parabolic antenna of the AN / APS-70 radar with a diameter of 12.2 meters was located inside the shell. The maximum speed of the ZPG-3W was 128 km / h.
Airship radar patrol ZPG-3W
The first ZPG-3W entered service in July 1959, and the fleet received four such airships. Due to its high carrying capacity and rather comfortable living conditions, the ZPG-3W airship could be on duty for several days. However, these devices were very weather dependent and did not have a large margin of safety. In the event of a sudden deterioration of the weather, which is not uncommon in the sea, the speed and altitude of the airship, which also had a large windage, might not be enough to leave the bad weather zone, although thunderstorm fronts on the radar indicator were recorded at a much greater distance than air targets … Several times the airships were damaged due to strong winds, but for the time being, everything worked out.
On July 6, 1960, the ZPG-3W airship, assigned to Lakehurst Air Force Base, collapsed in the air over the ocean in the Long Beach Island area. In this case, the entire crew, consisting of 18 sailors, died. By that time, the fleet already had a sufficient number of coastal and deck-based AWACS aircraft. The economic benefits of operating the slow and highly weather-dependent airships were not obvious, and the incident was used by the Navy as an excuse to close the program. The last flight of the ZPG-3W took place on August 31, 1962, and the patrol airships were subsequently transferred to Davis Montan for storage. They were in the "bone graveyard" until 1993, after which they were "disposed of". One ZPG-3W escaped this fate, awaiting its turn for restoration at the National Museum of Naval Aviation at Pensacola Air Force Base, Florida.
