Lockheed Constellation EC-121R «BatCat»

By the mid-1960s the air campaign against North Vietnam's logistics had failed as a means of pressure, and the Pentagon looked for another approach: a sensor barrier able to detect troops and trucks moving down the Ho Chi Minh Trail through Laos. The project went through many cover names before settling on Igloo White, a covert joint electronic warfare operation that ran from late January 1968 until February 1973. The system had three elements: sensors seeded along the infiltration routes, orbiting aircraft that received their signals, amplified them and retransmitted them, and an Infiltration Surveillance Center at Nakhon Phanom, Thailand, that analysed them.

The second element fell to the Constellation family. In 1966 Lockheed modified thirty retired Navy Super Constellations — two EC-121Ps (ex-WV-3) and twenty-eight EC-121Ks (ex-WV-2) — into EC-121Rs for the specialised reconnaissance mission. Transferred to the Air Force in 1966-1967, the aircraft were delivered during the course of 1967. The resulting configuration was nicknamed the BatCat. The Wikipedia article on the Warning Star gives a different figure in another passage, of some forty EC-121s modified and twenty-five deployed to Korat; the other sources consulted agree on thirty conversions.

The unit that flew them was the 553rd Reconnaissance Wing, established on paper on 9 February 1967 and organised on 25 February that year with two squadrons, the 553rd and 554th Reconnaissance Squadrons. From February 1967 the wing trained for the programme with its thirty EC-121Rs and a C-121G used to train pilots and flight engineers. From mid-September 1967 it moved in increments to Korat Royal Thai Air Force Base, and on 25 November 1967 it began unarmed day and night reconnaissance missions over Southeast Asia. Between October 1967 and December 1970 it had about twenty BatCats on hand at any time.

Unlike the College Eye early-warning EC-121s, which kept their usual finish, the BatCats wore the standard Southeast Asia tree-colour camouflage, because their work took them over hostile ground.

Each sortie lasted eighteen hours, eight of them on station in one of the eleven colour-coded orbits used over the life of the programme: three over South Vietnam, six over Laos, one over Cambodia and one over the Gulf of Tonkin. The wing flew over land and off the coast of Vietnam, over Laos and Cambodia, monitoring and retransmitting low-power signals; the usual task was to orbit the Ho Chi Minh Trail in eight-hour shifts.

The sensors, dropped by Navy Neptunes or Air Force helicopters, transmitted their data to the orbiting EC-121R, which relayed it over a 2200 to 2300 MHz radio link to Nakhon Phanom. There, at the Task Force Alpha centre, two IBM 360/40 computers (later two 360/65s) stored and collated the information to predict where and when a convoy would be, and strike aircraft were directed to those points.

Two BatCats were lost during the war, with twenty-two crewmen killed: one in a take-off accident during a thunderstorm in April 1969, and the other in September 1969, in a landing accident that also killed four Thai civilians.

The EC-121Rs proved expensive to operate and exposed a large crew to enemy fire, so the Air Force sought a much smaller replacement, intended even to fly unmanned: the QU-22 Pave Eagle. A wing detachment at Nakhon Phanom evaluated the YQU-22A between December 1968 and August 1969; the QU-22B went through combat evaluation from July to early September 1970 and entered full operation on 1 October 1970, reducing the need for the EC-121s. Because of mechanical problems, none ever flew an operational mission without a pilot.

The 553rd Reconnaissance Wing was inactivated on 15 December 1970. The 554th Squadron moved to Nakhon Phanom to fly the QU-22s, nicknamed "Baby Bats", while the 553rd Squadron, reassigned to the 388th Tactical Fighter Wing, stayed at Korat with initially eleven aircraft and spent another year gradually returning aircraft and crews to the United States. The final BatCat mission was flown on 6 December 1971; that same month C-130Bs took over the relay role, and in January 1972 the last administrative and support personnel returned to Otis Air Force Base. One former EC-121R ended up in storage at AMARC, Davis-Monthan Air Force Base, Arizona.