The Army's fixed-winged reconnaissance aircraft contributed significantly to Anierica's intelligence-gathering efforts.
By Terry M. Love
American forces made widespread use of reconnaissance aircraft during the Vietnam War. Each branch of the military had various types of aircraft for their own purposes. The U.S. Air Force operated the magnificent Lockheed SR-171 Blackbird, which flew at speeds of more than Mach 3 and altitudes above 80,000 feet. The U.S. Air Force also had the Lockheed U-2, the high-flying photo spy plane. In addition, the Air Force used the McDonnell RF-4C Phantom, which was preceded in the war by the McDonnell PF-1O1C Voodoo. The U.S. Navy used the Douglas RA-3B and EA-3B Skywarrior and the North American RA-5C Vigilante. The U.S. Marine Corps operated the McDonnell RF-4B Phantom and the Douglas EF-lOB Skyknight.
The U.S. Army extensively used the Grumman OV-1 Mohawk -- the supreme battlefield surveillance aircraft. But the Army also operated many lesser-known aircraft systems to gather intelligence. For the most part those systems were known by highly classified code names, and much of the information on those programs is just now being released.
In the early 1960s, the U.S. Army Security Agency (ASA) was assigned the letter strings LEF, LAF, CEF and CAF to identify its reconnaissance projects. If the word "Quick" was applied, it meant that a project had originated at Headquarters, Department of the Army. Among those missions was the "Quick Look" project for the OV-1 Mohawk. "Guardrail" originally was a National Security Agency project. After the ASA-type aircraft were replaced by Special Electronic Mission Aircraft (SEMA) in the mid-1970s, the code names were mostly replaced with acronyms, although the ARL-L program used the name "Crazy Hawk," and Guardrail still exists.
From the early 196Os, the U.S. Army employed a varied fleet of highly modified utility helicopters, utility aircraft, observation aircraft and cargo aircraft. These airborne platforms performed a wide range of highly classified missions, including communications intelligence (COMINT), electronic intelligence (ELINT), signals intelligence (SIGINT), and photographic (PHOTINT), infrared (IR) and radar surveillance. Later, in the mid-197Os, all of these aircraft became known as SEMA. The earlier aircraft systems, were developed through the combined efforts of ASA, the U.S. Army Electronics Command Electronics Warfare Laboratory (EWL) and private contractors, such as E-Systems in Texas. Their various successor organizations were involved as well.
The exceptions were the OV-1 Mohawk the Lockheed YO-3A and their associated sensors, which were developed by the basic airframe contractors and their subcontractors. Photo, infrared and radar surveillance missions were executed by the OV-1A (photo), OV-1B (radar), OV-1C (photo and infrared) and the OV-1D (combination of all the foregoing). The YO-3A was used for visual and infrared reconnaissance missions during the war.
In the early 1960s, the Electronics Warfare Laboratory developed airborne radio direction finding (ARDF) electronic gear and installed it in three de Havilland U-6A Beavers, redesignating them RU-6As. Apparently no special code names were applied to those aircraft at the time. Assigned to the Vietnam Flight Detachment of the 3rd Radio Research Unit in March 1962, those three aircraft became the first Army reconnaissance airplanes in Vietnam. In December 1962 the first six OV-1A Mohawks arrived, but they were almost immediately transformed into armed gunships and not used in the reconnaissance missions for which they had been designed. Those were followed in early 1963 by seven more RU-6As, code-named "Seven Roses." They were joined in 1963 by two RU-SD Seminoles, code-named "Checkmate," and one RU-8F aircraft. The RU-6A had armored protection and its crews carried parachutes. The RU-SDs had neither.
The direction-finding performance of the RU-SE however, was not satisfactory. Later that year, seven more RU-6A Seven Roses and 10 more RU-SD Checkmates arrived. The last group of RU-6As and RU-SDs to arrive were later designated either "Wine-bottle" or "Cefish Person" and totaled 41 RU-8Ds and a few RU-6As. Early arrivals in Vietnam, also included the one-of-a-king RCV-2B Caribou, called "Pathfinder" (tail No.62-4147); one RU-lA Otter, designated "Cafe Girl"; and two RU-lA Systems, called "Laffing Otter" (originally designated "Happy Nights"). All of these systems made up the first generation of ARDF aircraft that were used in Vietnam.
The rugged de Havilland U-lA Otter was very slow and had fixed landing gear. The reconnaissance versions, RU-lA Laffing Otters, were assigned to the 146th Radio Research Aviation Company. The Radio Research (RR) designation was used to classify all of the extra and numerous antenna on the aircraft. The RU-lA was withdrawn from service in January 1971, when America began pulling out of Vietnam. The main difference between the Cafe Girl and Laffing Otter was that the latter had a second on-hoard operator position. The Cafe Girl aircraft later was refitted with a second operator position. At least three aircraft were convened to accommodate two operators (tail Nos. 58-1714, 55-3271 and 55-2977).
An RU-lA (tail No.55-3271) was shot down over Cambodia on February 12, 1969. The aircraft, crewed by Major Querin Herlik, Chief Warrant Officer Grade 2 Laird Osbourn, Spec. 5 John Fisher and Spec. 5 Robert Pryor, was hit by a large-caliber anti-aircraft round. Herlik and Osbourn managed to crash the aircraft into a rice paddy, and after a 30-minute firefight they were captured by the North Vietnamese. The NVA turned Osbourn over to the Cambodian government immediately since he was badly wounded, but held the others for two days for interrogation before turning them over to the Cambodians for violating Cambodian airspace. President Richard M. Nixon was forced to apologize to the Cambodian government in order to secure their release one month later.
Another RU-lA (tail No.57-1714) later was converted for a project called "Sore Thumb," the first attempt at 360-degree VHF direction finding using 'a spinning Adcock array antenna. Sore Thumb was not very successful, but it became the predecessor of what was later known as the "Left Jab" direction-finding system.
Pathfinder was a one-of-a-kind, high-frequency direction-finding (HFDF) system in the RCV-2B aircraft. This type of Caribou also was assigned to the 146th Radio Research Aviation Company until it was turned over to the U.S. Air Force in April 1967.
The group of Seven Roses ARDF Beavers went to the Mekong Delta in 1964. Sometime before 1966, three RU-6A aircraft equipped with standard U.S. Army ARDF equipment were given to the South Vietnamese air force. Those systems worked so well that more Beavers and U-8Ds were converted under the Checkmate program, incorporating AN/ARD-15 surveillance equipment for Vietnam service.
Next came the Wine Bottle and Cefish Person conversions. This group of reconnaissance aircraft totaled 34 RU-6As and 41 RU-8Ds, respectively, and most were assigned to the 156th Radio Research Aviation Company. Strictly speaking, those systems were not true ARDF aircraft. They could home in on a transmitter but had great difficulty in determining the exact emitter location. The aircraft had to fly over the location before the precise position could be computed. RU-6A operations ceased in Vietnam on April 27, 1972, when the 156th Radio Research Aviation Company stood down and redeployed to Fort Bliss, Texas.
Radio "fingerprinting" equipment, known as "Short Skirt," and later as "Lefair Knee," was installed on approximately 12 RU-8D aircraft. Most were assigned to the 509th Radio Research Group, but several were assigned to a transportation company for a period. Some RU-8D aircraft used the side-looking airborne radar (SLAR) system that later was used on the OV-1B Mohawk.
The second generation of ARDF Army aircraft reconnaissance systems, "Laffing Eagle" and Left Jab, were the most sophisticated Army ARDF systems in Vietnam at the time. Laffing Eagle was an RU-21D aircraft that was a logical development of the RU-8D system. The system's frequency coverage was expanded and a second operator position added. The RU-21D had a much larger interior capacity than the RU-8D. Additionally, an AN/ASN-86 Internal Navigation System replaced the AN/ASN-64 Doppler navigation system used on the RU-8Ds. The new system proved very difficult to maintain, however, requiring constant support from contractor representatives and a 40-foot trailer full of test equipment. Later on, a system known as V-SCAN, which gave 240-degree direction-finding coverage centered around the nose and tail, was added to the RU-21Ds. Those aircraft arrived in Vietnam in December 1968 and were used extensively after that.
After the withdrawal of American forces from Vietnam, some RU-21Ds were transferred to the Aviation Detachment of the 7th Radio Research Station at Udorn Air Force Base, Thailand. On July 15, 1974, operations were transferred to U Tapao Air Force Base, Thailand, where they remained until May 1975, when all were re-deployed to the United States. Once back in America, approximately 16 RU-2lAs were retrofitted as the RU-21E "Left Foot."
In 1970 the Electronic Warfare Laboratory finished development of the Left Jab system for the JU-21A aircraft, which was the first Army airborne system to provide 360-degree direction-finding coverage. That system used some of the electronic equipment from the older "Left Bank" system Incorporating the AN/ARQ-38 radar, Left Jab was the first Army system to combine the use of a digital computer to store direction-finding calibration data and to take the aircraft's position from the internal navigation system in order to compute the locations of enemy emitters. At least three JU-2lAs (tail Nos. 67-18063, 67-18065 and 67-18069) were built, and all were assigned to the 138th Radio Research Aviation Company. The first Left Jab mission was flown in Vietnam on January 9, 1971. On March 4, 1971, a JU-21A (tail No.67-18065, call sign Vanguard 216) was shot down over North Vietnam, killing the entire crew of five. On February 16,1973, another Left Jab aircraft flew the last ASA mission in Vietnam.
Left Foot, a more sophisticated version of the Laffing Eagle system, combined the Laffing Eagle's "V-Scan" direction-finding system with the Left Jab-type computer and added a display so that the operator could view the direction-finding "cuts" on a cathode ray tube. In addition, the operators faced forward rather than sideways, for improved crew comfort. The addition of this system meant that the aircraft were redesignated as the RU-21E, 16 of which were built. There was no visible external difference between the RU-21D Laffing Eagle and the RU-21E Left Foot. The radio research units were being withdrawn from Vietnam by the time those aircraft were ready. But some sources indicate that a few of those aircraft went to Vietnam.
"Cefirm Leader" was an early attempt to build a completely integrated airborne intercept, direction-finding and jamming system. Originally known as "Crazy Dog," the project involved the development of a very complex system for the 2- to 80-MHz frequency range. After an extensive study by the TRW Corporation in 1967, the ASA issued the specifications for the system. The complete system, called V~SCANARDF, carried the ANIULQ-11 radar, and nine aircraft of three different models made up the fleet. The RU-21As (tail Nos. 67-18112, 67-18113, 67-18114 and 67-18115) were direction-finding aircraft using the ANI ARD-22 system. The RU-2lBs (tail Nos. 67-18077,67-18087 and 67-18093) were intercept aircraft using the ANIALT-32. The RU-2lCs (tail Nos. 67-18085, 67-18089 and 67-l8xxx) were jamming aircraft with the AN/ALT-29 system. All these aircraft also were configured with the AN/TRC-148, AN/TRC-149 and AN/ULQ-11 systems.
The Cefirm Leader fleet was intended for deployment to Vietnam, but the electronic systems and the airframes did not work very well together. Nonetheless, the RU-21B and RU-2 lOs were sent over. The electronic equipment worked far better on the follow on RU-21D and RU-21E aircraft, which remained in service well into the 1990s.