EC-121 Warning Star

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A United States Navy EC-121 Warning Star
A United States Navy EC-121 Warning Star
US Air Force College Eye EC-121D 53-555 at the National Museum of the United States Air Force
US Air Force College Eye EC-121D 53-555 at the National Museum of the United States Air Force

The EC-121 Warning Star was a US Air Force/US Navy airborne early warning radar surveillance aircraft. A military version of the Lockheed Constellation, it was designed to serve as an airborne early warning system to supplement the Distant Early Warning Line. It had two large radomes, one above and one below the fuselage, which gave it its nickname among its crews: "pregnant guppie". EC-121's were also used for intelligence gathering (SIGINT). It was introduced in 1955 and retired from service in 1978. The US Navy versions when initially procured were designated WV-2/3.

In 1969 North Korean fighters shot down a EC-121 off the country's east coast, killing all of the 31 crew on board.[1]

Contents

[edit] Vietnam War

EC-121s were used extensively in Southeast Asia between April 16, 1965, and August 15, 1973, particularly in support of Operation Rolling Thunder and Operation Linebacker/Linebacker II to provide radar early warning and limited airborne control of USAF fighter forces engaging MiG interceptors. Flying orbits over the Gulf of Tonkin and later over Laos, they were the forerunners of AWACS aircraft.

[edit] Big Eye

At the onset of Rolling Thunder, the North Vietnamese had an advantage in that their radar coverage could detect most US strike aircraft flying at 5000 feet or above virtually anywhere in the country, using a system that was difficult to jam. US forces countered with radar ships ("Crown") in the Gulf of Tonkin and a ground site at Nakhon Phanom RTAFB, Thailand, but both systems were line of sight and had serious gaps in coverage.

To increase coverage the Seventh Air Force requested airborne radar support and the Air Defense Command was directed to set up the Big Eye Task Force. Five EC-121s and 100 support personnel of the 552nd Airborne Early Warning and Control Wing at McClellan Air Force Base, California, were deployed to Tainan Air Station, Taiwan, with four of the EC-121s sent on to a forward operating location at Tan Son Nhut Air Base, near Saigon.[2]

The EC-121's were designed for detection of aircraft flying over water, and ground clutter (spurious signal returns off of terrain features such as mountains) caused interference with their radar pictures. Their crews, however, were experienced in tracking Soviet aircraft over Cuba and had developed a technique whereby an EC-121 flying at 50 to 300 feet could bounce a signal from its bottom-mounted APS-95 Search radar off the surface of the water and detect aircraft at medium altitudes out to 150 miles. Operating in pairs, one Big Eye EC-121 flew a 50-mile race track pattern approximately 30 miles offshore (the Alpha orbit), with the orbit's center at 19°25′N 107°25′E. The second flew a track at 10,000 feet (the Bravo orbit) farther from the coast, acting a spare for the Alpha EC-121. [3]

This provided a practical detection range of 100 miles, just enough to cover the Hanoi urban area and the main MiG base at Phuc Yen. A major disadvantage of this arrangement, however, was that most MiG contacts were beyond the 70-mile range of the Big Eye's APS-45 Height Finder radar, so that they were unable to provide this crucial data to USAF strike forces. Furthermore, technical shortcomings in the EC-121D's systems precluded either controlling a fighter intercept or identifying a specific flight under attack.[4]

The missions from Tan Son Nhut began April 21, 1965, using the call signs "Ethan Alpha" and "Ethan Bravo", which became their standard call signs. After refueling at Da Nang Air Base, Ethan Alpha made a wave-top approach to its orbit station, where it remained five hours. Because of the threat of MiG interception, EC-121s were protected by a MiGCAP of F-104 Starfighters, and if for any reason the MiGCAP could not rendezvous, the EC-121s cancelled their mission. Air conditioning systems aboard the EC-121 were virtually useless in this profile and the heat produced by the electronics, combined with the threat of being shot down, made Alpha orbit missions in particular highly stressful.[5] On July 10, 1965, in its first airborne-controlled interception, an EC-121 provided warning to a pair US F-4C fighters, resulting in the shooting down of two MiG-17's.[3]

The Big Eye Task Force remained at Tan Son Nhut until February 1967, when the threat of Viet Cong ground attacks prompted a move to Thailand.

[edit] College Eye

On March 1, 1967, Big Eye was renamed College Eye Task Force and relocated at Ubon RTAFB. Because of the complexity of the aircraft and its systems and the large support group it required, the CETF was not a welcome tenant at the relatively small Thai bases. It moved to Udon RTAFB in July and to its final station at Korat on October 17, 1967.[6]

From April 1965 to early 1966 and beginning again in late 1967, the EC-121s also controlled a flight of MiGCAP fighters for unarmed support aircraft operating over the Gulf. The EC-121's also served as an airborne communications relay center for strike aircraft to transmit mission results and position reports to the control center at Da Nang; directed operations of fighter escorts, MiGCAPs, C-130 flare ships, and A-26 strike aircraft along the North Vietnamese-Laotian border; provided radar and navigational assistance for Combat Search and Rescue missions; and assisted fighters in finding tankers for emergency refueling.

The government of China on May 12, 1966, formally protested an incursion by an F-105 25 miles into its territory in pursuit of a North Vietnamese MiG it subsequently shot down. A US board of inquiry recommended that College Eye also monitor the "no-fly zone" inside the North Vietnamese border with China, provide alerts to US aircraft nearing the buffer zone, and report border crossing violations by US aircraft.[3] This could not be done from the Gulf and a third orbit, called Ethan Charlie, was created in Laos. After tests in June and August, regular missions began August 24. There were not enough EC-121s or crews to support three orbits twice daily, so the Laotian orbit was only flown every third day, with Ethan Bravo missions cancelled on those days. After October 13, 1966, the Charlie orbit was flown every day and the Bravo orbit suspended altogether. In April 1967 four more EC-121s were deployed, two to Thailand on May 29, making for a total strength of 3 College Eyes in Taiwan and 6 in Thailand.

In April 1967 the Air Force began fitting its entire EC-121 fleet with the QRC-248 IFF transponder interrogator. The QRC-248 had been developed to surveil Soviet-export aircraft flown by the Cuban Air Force. The SRO-2 transponders installed in Soviet export MiGs enabled Cuban ground-controlled interception radars to identify and control their fighters. A test bed EC-121 called Quick Look had flown with College Eye in January 1967 to test the QRC-248 and found that North Vietnamese MiGs used the same transponder. QRC-248 accurately discriminated MiG radar returns from the myriad returns picked up during a mission, and extended the range of low-altitude detection to more than 175 miles, covering virtually all important North Vietnamese target areas.

By May 31, all College Eyes had been fitted with QRC-248. The mission of the Bravo orbit was changed from that of a backup for the Alpha orbit to being the primary QRC-248 listener. However College Eye was prohibited by the Joint Chiefs of Staff from actively "interrogating" MiG transponders, following a National Security Agency security policy protecting its "intelligence sources" (of which the QRC-248 was one), and thus was restricted to waiting for North Vietnamese GCI to interrogate its planes. QRC-248 began regular use on July 21, 1967, but by then North Vietnam's MiG force, which had suffered serious losses in May, had suspended combat operations.[7]

In the last week of August, however, after a period of intensive training and revision of tactics, the MiGs began to engage US strike forces again, scoring a number of kills. Seventh Air Force finally obtained permission for the Bravo orbit EC-121 to actively interrogate with the QRC-248 on October 6. By December 4 its success outweighed any value in flying the Alpha orbit, which was discontinued.[8][3]

On March 1, 1968, the College Eye calls signs were changed to Ethan 01, 02, 03, and 04 in conformity with standard Air Force procedures. Ethan 03 (the Laotian orbit) began "positive control" (airborne direction) of C-130 flare ship flights and A-26 night interdiction missions along the Ho Chi Minh Trail in Laos on April 19, 1968.[3]

The task force was scaled back on July 1, 1968, to four EC-121s and the Rivet Top test bed aircraft to allow for the basing of another College Eye detachment at Itazuke AB, Japan.[3] The name of the task force was discontinued on October 30, 1968, when it was redesignated a final time as Detachment 1 (Rotational), 552nd AEWCW. The EC-121s were completely withdrawn from Southeast Asia in June 1970.[9] However two EC-121Ds were assigned to support the Special operations mission to rescue prisoners at Son Tay prison on November 21, 1970, using the call signs Frog 01 and Frog 02.

[edit] Rivet Top

On August 9, 1967, while the College Eye Task Force was still based at Udon, another prototype EC-121 variation began operations testing new equipment as Detachment 2 of the Tactical Air Warfare Center. Known as Rivet Top, this modified EC-121K (later re-designated EC-121M) carried the QRC-248 newly installed in the College Eye aircraft, but also had electronic interrogators capable of reading two additional Soviet transponders, the SRO-1 and SOD-57. Its electronics were custom-built rather than off-the-shelf. [10] However its most important upgrade was the highly secret "Rivet Gym" installation. This consisted of the addition to the crew of Vietnamese-speaking intelligence specialists who manned four voice communication intercept stations able to monitor all communications between the MiGs and their GCI controllers.

Despite this advantage, the Rivet Top experienced two problems which reduced its effectiveness. Its listeners did not have radar scopes to correlate intercepted conversations with specific flights of MiGs, and thus could not determine which US aircraft might be under attack. Secondly, like QRC-248, Rivet Gym was a Signal Intelligence ("SIGINT") asset of NSA, and subject to even more stringent rules protecting knowledge of its existence. Even when real-time warnings to US aircraft were finally permitted in mid-1972, fighter crews were not made aware of the source of the warnings and because EC-121 radio communications were so poor, mandating the use of a radio relay aircraft that often failed, they tended to disregard the credibility of the source.[11]

The Rivet Top prototype moved to Korat along with the College Eye Task Force in October 1967. Originally scheduled to return to the United States in February 1968, because of its value it remained at Korat until 1969. Flying daily missions through its testing period, it began flying every-other-day missions over the Gulf of Tonkin after March 31, 1968, when Rolling Thunder operations were sharply scaled back. Rivet Gym installations were back-fitted to all College Eye EC-121s by the end of May 1968.

[edit] Disco

In October 1971 North Vietnamese MiGs, operating from forward bases opened after the end of Rolling Thunder, began to attempt intercepts of B-52 missions in southern Laos. On November 20 a MiG-21 actually launched air-to-air missiles at a B-52 which evaded them by dropping flares. As a result, Warning Stars of Det. 1 returned to Korat, Thailand, to provide radar support by flying the Laotian orbit again, using the call sign Disco.[12] Seven EC-121Ts, replacement aircraft for the earlier series, were based in Thailand and contained both QRC-248 and Rivet Top electronic suites.

When Operation Linebacker began on May 10, 1972, Disco was one of two principal GCI radars used by U.S. forces, although it continued to be handicapped by poor radio communications. In addition, its slow-turning radar limited its value as a controller of fighters during MiG engagements, and the size of USAF raids during Linebacker nearly saturated its capabilities.[13] However the improvements made in the systems since 1968 had enabled the radar operators to distinuish MiG types, and a color code system for them entered the air operations vernacular: "Red Bandits" (Mig-17s); "White Bandits" (MiG-19s); and "Blue Bandits" (MiG-21)s.[14]

On July 6, 1972, as the result of seven F-4 Phantoms shot down in one two-week period, a second Disco track was initiated near the former Alpha orbit over the Gulf of Tonkin to try to gain better low-altitude coverage in the Hanoi area. At the end of the month Disco was also integrated into the "Teaball" control center, which was a highly classified system established to collate all signal intelligence on North Vietnamese air activity gathered by all intelligence sources, including non-military. Disco was used as a conduit through which warnings and control vectors were given, but the delay in Teaball acquiring and relaying the information through Disco (which often had to relay its broadcast signal through an unreliable radio relay KC-135A Combat Lightning aircraft)[15] cancelled out its value for use in "real time", the fact that its existence was kept from US air crews damaged its credibility.

Disco EC-121s flew their final combat mission on August 15, 1973. On June 1, 1974 Detachment 1 was permanently withdrawn from Southeast Asia. Between 1965 and 1973 the EC-121s flew 13,921 combat missions; more than 98,000 accident-free flying hours; assisted in the shoot-down of 25 MiGs; and supported the rescue of 80 downed flyers. No Big Eye, College Eye, or Disco aircraft were lost.[16]

[edit] Batcat

During the Vietnam War some 30 EC-121s were modified from U.S. Navy WV-2 and WV-3 early warning Constellations for use with ground sensors to detect enemy troop movements along the Ho Chi Minh Trail, and 25 were deployed to Southeast Asia as a part of Operation Igloo White.[17] The resulting EC-121R configuration was nicknamed the Batcat.[18] Two Batcats were lost during the war, with the loss of 24 crewmen, one in a takeoff accident during a thunderstorm on April 25, 1969, the other on September 6, 1969 during a landing accident.

Batcat EC-121s were camouflaged in the standard three-color Southeast Asia scheme while the College Eye/Disco early warning aircraft were not. BatCat missions were 18 hours in length, with 8 hours on station at one of 11 color-coded orbits used during their 5 year history, three of which were over South Vietnam, six over Laos, one over Cambodia, and one over the Gulf of Tonkin.

EC-121Rs were operated by the 553rd and 554th Reconnaissance Squadrons of the 553rd Reconnaissance Wing, between October 19, 1967, and December 15, 1970, with approximately 20 Batcats on hand at any one time. The Wing was inactivated December 15, 1970, and the 554th RS relocated to Nakhon Phanom RTAFB to fly QU-22 sensor monitors nicknamed "Baby Bats". Initially with 11 aircraft, the 553rd RS continued operations for another year, gradually returning planes and crews to the United States. The final Batcat mission was flown December 5, 1971. The last remaining administrative and support personnel returned to Otis Air Force Base, Massachusetts, in January 1972.

[edit] Surviving examples

[edit] Operators

[edit] References

  1. ^ BBC News "N Korea in 'US spy plane' warning" 11 June 2006
  2. ^ Marshall L. Michel (1997). Clashes: Air Combat Over North Vietnam 1965-1972. Naval Institute Press. ISBN 1557505853. , 46
  3. ^ a b c d e f Extract of College Eye Report. Dean Boys. Retrieved on 15 Feb 2007.
  4. ^ Michel 47, 49
  5. ^ Michel, 48
  6. ^ Michel, 51
  7. ^ Michel, 100
  8. ^ Michel, 132
  9. ^ Michel, 193
  10. ^ Michel, 114
  11. ^ Michel, 115, 252, 284
  12. ^ Michel, 193
  13. ^ Michel, 225
  14. ^ Michel, 227
  15. ^ Michel, 252
  16. ^ Big Eye College Eye Twelve Year Combat Era Ends. Dean Boys. Retrieved on 15 Feb 2007.
  17. ^ Air Force Magazine November 2004, Vol. 87, No. 11
  18. ^ Batcat history

[edit] External links

[edit] Source


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