The Lockheed C-121 Constellation was the military version of the Model 749 Constellation, designed for use as an intercontinental airliner and of the later Super Constellation, with a higher cargo capacity. It was used for an impressively wide range of functions, and in many different versions.
Work on the original Model 059 Constellation began in 1939. It emerged as a four engined engine aircraft capable of carrying 44 passengers in a pressurised cabin. TWA and Pan-American both placed orders for the type, but these were cancelled after the American entry into the Second World War. Fifteen were accepted by the USAAF as the C-69, but large orders were cancelled at the end of the war. Lockheed completed most of the Model 059s as civil airlines, but also began work on an improved version. The Model 649 used a 2,500hp Wright engine and had an improved passenger cabin.
The Model 649 was followed by the Model 749, which was designed for longer distance overseas routes. It had a stronger undercarriage, allowing it to take off at 133,000lb, although the licensed gross weight was 102,000lb. Extra fuel tanks were installed in the outer wing panels, giving it a capacity of 5,820 US gallons.
Twenty-three Model 749s were sold to US airlines, thirty seven to overseas airlines and ten to the USAF where it became the C-121A or VC-121B.
In February 1948 ten C-121As were ordered for use as cargo and personnel transports to be used by the Military Air Transport Service. Nine of these aircraft were delivered as C-121A with a reinforced cargo deck floor and a cargo loading door on the aft port side. They could carry 44 passengers or 20 stretcher cases and their medical attendants.
The first to be delivered was the VC-121B, which went to the 1254th Air Transport Squadron (Special Missions) in November 1948. This aircraft could carry 24 passengers during the day or 10 sleepers and 4 seated passengers during the night. It also had a stateroom. It was used to transport the Secretary of the Air Force and the Secretary of Defense and as a backup for President Truman's Douglas VC-118 Independence.
Eight of the C-121As went to the Atlantic Division of the Military Air Transport Service. In 1949 they were used on the transatlantic route during the Berlin Airlift. They were later converted into VIP transports as the VC-121A, and used by the 1254th ATS. General MacArthur and General Eisenhower each used one of these aircraft, named Bataanand Columbine.
The ninth C-121A went to the Lockheed Air Service International and was used to support their facilities at Keflavik, Iceland. In 1950 it too became a VC-121A, and was used by President Eisenhower until it was replaced by the VC-121E Super Constellation.
In the 1960s the VC-121As reverted to being C-121As. The last one was withdrawn from service in August 1968. Most were then sold off, with six becoming crop sprayers.
The Constellation was followed by the Model 1049 Super Constellation, a longer version of the aircraft designed to increase its cargo capacity and take advantage of the Wright Turbo-Cyclone Compound engines. The USAF ordered a number of C-121s of its own, but also gained aircraft that were transferred to it from the Navy. In addition the remaining Navy aircraft were given C-121 designations in the 1962 tri-service designation system.
A number of Army C-121s were used as airborne early warning aircraft. They entered service with the 552nd Airborne Early Warning and Control Wing in California, and were also used by the 551st 552nd Airborne Early Warning and Control Wing in Massachusetts, operating for NORAD. They then moved to South-East Asia, where they helped direct American air strikes during the Vietnamese War. Between April 1965 and August 1973 they flew 13,931 combat sorties in that theatre, a total of 98,777 hours.
Nine aircraft from the original order for ten Model 749s, delivered with a reinforced cargo deck floor and cargo loading bay on aft port side.
The first aircraft to be delivered from the original order for ten, completed as a VIP transport for the Secretary of the Air Force and the Secretary of Defense and as a backup for President Truman's Douglas VC-118 Independence
C-121C (Model 1049F)
The C-121C was a simple transport aircraft, similar to the Navy's R7V-1. It used four 3,400hp R-3350-34 engines and had a take-off weight of 133,000lb. Thirty three were delivered to MATS in 1955 and a thirty fourth was created by removing the extra equipment from a TC-121C. Four were converted into VC-121Cs, two into JC-121Cs and four into EC-121Ss.
RC-121C (Model 1049B)/ TC-121C/ EC-121C
Ten aircraft from the Navy's order for 65 R7V-1 Super Constellations were delivered to the USAF instead, where they became the RC-121C. They were completed as airborne early warning aircraft, although weren't quite as capable as the Navy's WV-2s, or the USAF's RC-121Ds. After one was lost in an accident the remaining nine were redesignated as the TC-121C AEW training aircraft. Later one of the nine was converted into a standard transport, and the remained eight became EC-121Cs.
Two C-121Cs and one TC-121Cs were converted into systems testing and electronic research aircraft, as the JC-121C.
The VC-121C was the designation for four VIP transports based on the C-121C and used by the 1254th Air Transport Squadron (Special Missions). One of them was used as a backup for the Presidential VC-121E. After they were no longer needed for VIPs they went to the Air National Guard.
RC-121D (Model 1049A) 'Warning Star'/ EC-121D
The RC-121D was an airborne early warning aircraft. It was originally ordered by the US Navy as the PO-2W/ WV-2, but 72 were transferred before being completed to the USAF. They were more advanced than the ten RC-121Cs, with wing tip fuel tanks and revised electronic equipment. In 1962 they were redesignated as the EC-121D.
VC-121E (Model 1049B)
The CV-121E was a Presidential transport, originally ordered by the US Navy as a R7V-1 transport. It was completed as the Columbine III and was used by the 1254th Air Transport Squadron. It was used during the Eisenhower administration, before being replaced by a Boeing BC-137C in October 1962.
YC-121F (Model 1249A)
The YC-121F was the designation given to two turbo-prop R7V-2s which were ordered by the US Navy but delivered to the USAF. They were powered by the 6,000 eshp Pratt & Whitney T-34-P-7 turbo-prop engine and were used by the Service Test Squadron (Turboprop) of MATS, based at Kelly Air Force Base, Texas.
The C-121G was the designation given to thirty-two Navy R7V-1 transport aircraft after they were transferred to the USA in the late 1950s.
The EC-121H was an upgraded version of the EC-121D, given new equipment that could feed its date directly into the Semi-Automatic Ground Environment system of NORAD. Forty two were produced by converted existing EC-121Ds.
The C-121J was the designation given to the remaining Navy R7V-1 transport aircraft in September 1962
Two EC-121Ds were given extra equipment and redesignated as the EC-121J.
The EC-121K was the initial designation given to the Navy's WV-2 airborne early warning aircraft under the 1962 tri-service designation system.
The JC-121K was a single EC-121K modified for electronic experiments for the US Army.
The NC-121K was a modified version of the EC-121K that took part in Project Magnet, which mapped the Earth's magnetic field.
The EC-121L was the designation given to the US Navy's WV-2E experimental radar aircraft and to the WV-2Q electronic counter-measure aircraft in 1962.
The EC-121M was the 1962 designation for the WV-2Q.
The WC-121N was the new designation for the Navy's weather reconnaissance WV-3s under the 1962 system.
The EC-121P was the designation given to several EC-121Ks that were given submarine detection systems.
The EC-121Q was a version of the EC-121D with more advanced electronics.
The first two EC-121Rs were Navy WC-121N weather reconnaissance aircraft, transferred to the USAF during the late 1960s. They were followed by thirty EC-121Ks and EC-121Ps. They were given new electronic equipment that could be used to analyse date from Air Delivered Seismic Intruder Devices, which were meant to detect movement on the Ho Chi Minh trail and allow the USAF to target their attacks. The EC-121Rs were based at Korat RTAF, Thailand, and were operated between October 1067 and December 1970.
The EC-121S was an electronic counter measures version of the aircraft.
The EC-121T was an upgraded version of the EC-121D, EC-121H and EC-121J, with more advanced electronics.
Model 749 C-121A
Engines: Four Wright 749C-18BD-1
Wing span: 123ft
Length: 95ft 2in
Height: 23ft 8in
Empty weight: 58,970lb
Maximum weight: 107,000lb
Maximum speed: 358mph at 19,200ft
Cruising speed: 327mph
Service ceiling: 25,000ft
Normal range: 1,760 miles carrying 16,300lb, 4,150 miles carrying 3,300lb
Engines: Wright R-3350-91 Turbo-Compound engines
Wing span: 119ft 1in
Length: 116ft 2in
Height: 24ft 9in
Empty weight: 76,162lb
Loaded weight: 150,000lb
Maximum speed: 506mph at 20,000ft
Cruising speed: 421mph
Service ceiling: 28,700ft
Normal range: 2,075 miles
Maximum range: 3,140 miles