The Lockheed EC-121 Warning Star was an American Airborne early warning and control radar surveillance aircraft operational in the 1950s in both the United States Navy and United States Air Force.
The military version of the Lockheed L-1049 Super Constellation was used to serve as an airborne early warning system to supplement the Distant Early Warning Line, using two large radomes (a vertical dome above and a horizontal one below the fuselage).
It replaced the TBM-3W used by the USN.
Some EC-121s were also used for signal intelligence gathering.
The EC-121 was introduced in 1954 and phased out in 1978, although a single specially modified EW aircraft remained in USN service until 1982.
The USN versions when initially procured were designated WV-1 (PO-1W), WV-2, and WV-3.
The USAF Warning Stars served during the Vietnam War both as electronic sensor monitors and as a forerunner to the Boeing E-3 Sentry AWACS.
USAF aircrews adopted its civil nickname, “Connie” (diminutive of Constellation) as reference, USN aircrews used the nickname “Willie Victor”.
Since 1943, the Lockheed Constellation had been in USAAF service as the C-69.
The use of the Constellation by the USN for patrol and airborne early warning duties was first investigated in 1949, when the USN acquired two Lockheed L-749 Constellations.
First flown on 9 June 1949, the PO-1W carried large, long-range radars in massive radomes above and below the fuselage.
As the radomes possessed considerably more side area, the vertical stabilizers of the PO-1W had to be enlarged.
After the PO-1W (redesignated WV-1 in 1952) had proved that operating large radars on aircraft was possible, the USN ordered the WV-2 based on the L-1049 Super Constellation.
The WV-1s were transferred to the Federal Aviation Agency in 1958–1959.
The WV-2/EC-121D was initially fitted with a dorsal AN/APS-45 height finder and a ventral AN/APS-20 search radar.
These were later upgraded to AN/APS-103 and AN/APS-95 radars, although not simultaneously.
The crew commonly numbered 18, six officers (two pilots, two navigators, and two weapons controllers) and 12 enlisted (two flight engineers, one radio operator, two crew chiefs, five radar operators, and two radar technicians).
However, when North Korea shot down a Navy EC-121 in 1969, a crew of 31 was on board.
Orders were placed totalling 142 PO-2W Constellations based on the Lockheed L-1049 Super Constellation, with deliveries beginning in 1953.
The PO-2W was redesignated WV-2 in 1954.
In 1962, with standardization of aircraft designations within the Department of Defence, the WV-2 then became the EC-121K.
In total, 13 of these were converted to WV-2Q electronic intelligence (ELINT) aircraft (becoming EC-121M in 1962).
Nine were converted to WV-3 weather reconnaissance aircraft (WC-121N in 1962).
The EC-121K was also operated by Training Squadron 86 (VT-86) at NAS Glynco, Georgia, for training of student naval flight officers destined to fly both the EC-121 and the Grumman E-2 Hawkeye.
At NAS Glynco’s closure, VT-86 transferred to NAS Pensacola, Florida, in 1973, the squadron’s last EC-121 was also flown to NAS Pensacola, being stored in the collection of the National Museum of Naval Aviation, where it still remains.
A single aircraft became an NC-121K, the electronic warfare variant assigned to Tactical Electronic Warfare Squadron 33 (VAQ-33) at NAS Key West, Florida.
The aircraft was the last EC-121 in operational service, flying until 25 June 1982.
The USAF received 10 RC-121C and 74 EC-121D Warning Stars also based on the L-1049, beginning with diversions from the Navy contracts in October 1953.
The 10 RC-121Cs became trainers, designated TC-121C. Between 1966 and 1969, 30 retired USN EC-121s were transferred to USAF and converted in EC-121Rs as sensor-monitoring aircraft.
Of the 74 EC-121s, 42 were converted to the EC-121H upgrade beginning in 1962, and in 1969, 15 of the remaining EC-121Ds and seven of the EC-121Hs were further upgraded into the final operational variant, the EC-121T, serving as an AWACS prototype in Southeast Asia in 1972.
Five EC-121Ds were modified to be broadcasting aircraft for psychological warfare operations, the predecessors of the EC-130 Commando Solo.
2 prototypes, L-749A Constellation, designated PO-1W before 1952
Main USN variant, designated PO-2W before 1952; 244 ordered, 142 produced (the rest to USAF).
One modified EC-121K used as a US Army avionics test bed
Unknown number modified as special mission aircraft
YEC-121K. One modified avionics test bed
One modified WV-2, test bed for rotating radar dome with an AN/APS-70 radar
ELINT collection variant, 13 modified WV-2
Weather reconnaissance variant, 8 modified WV-2
Unknown number modified from EC-121K as anti-submarine variant JEC-121P.
3 EC-121P used by the USAF
10 produced, initial USAF variant
2 converted from C-121C and 1 TC-121C as avionics test beds
9 RC-121C modified before 1962 as crew trainers
73 produced 1953–55 as main USAF variant and 1 converted from C-121C, originally designated RC-121D
EC-121D Quick Look
1 test bed for QRC-248 IFF transponder interrogator
42 USAF upgrades in 1962, 35x EC-121D and 7x WV-2s transferred from the Navy
2 USAF EC-121D modified with upgraded electronics
EC-121M Rivet Top
1 EC-121D test bed for Rivet Gym crypto logic linguist electronics suite, originally designated EC-121K
4 EC-121D modified with upgraded electronics for USAF Gold Digger missions
30 EC-121K / EC-121P transferred to USAF in 1966–1967 and converted to Batcat sensor signal processor
5 converted for Pennsylvania Air National Guard from USAF C-121 transports
Final USAF variant. A total of 22 T’s were converted from 15x EC-121D and 7x EC-121H.
Proposed naval development with new features such as 4 Allison T56-A8 turboprop engines, L-1649A Starliner wings and Bomarc missiles for defence.
None built; was designated L-084 due to the large differences from its predecessors.