On December 22, 1961, Army Specialist 4th Class James T. Davis died in an ambush not far from Saigon�the first U.S. soldier to be killed in action in the Vietnam war. Davis did not wear the distinctive beret of some elite force; in fact he was not even part of a combat unit. SP4 Davis was a radio operator from the 3rd Radio Research Unit (RRU) of the U.S. Army Security Agency (ASA). He was killed while attempting to locate Viet Cong (VC) radio transmitters.

Radio direction finding (RDF) is one of the oldest tricks of the signal intelligence (SIGINT) trade, originating in the days before World War I. Not surprisingly, direction finding was one of the techniques employed in U.S. �counterinsurgency� operations early in the war. Elusive they may have been, but even the VC found it necessary to utilize radio communications. Consequently, ASA activated the 3rd RRU in May, 1961, to handle SIGINT operations in Vietnam. However, the low-powered transmitters such as Davis had been chasing proved difficult to fix by conventional ground-based RDF methods.

The solution seemed obvious, and not long after Davis� death both the army and air force began to experiment with airborne radio direction finding (ARDF). In March, 1962, a modified USAF C-54 was dispatched to Tan Son Nhut, the principle airfield in the Saigon area, under the project nickname Hilo Hattie. The aircraft was equipped with standard cameras as well as infrared (IR) and ARDF gear. An abundance of targets presented themselves, but the ARDF and IR systems "did poorly" in the 102 missions that were flown during the 10 months Hilo Hattie operated. Meanwhile, three ARDF-equipped DeHavilland L-20 (later designated U-6) Beavers were placed in service by the �aviation section� of the 3rd RRU, which coordinated the overall effort.

One shortcoming of the early army ARDF systems was the use of an �aural null� technique that required the aircraft to turn until the target could no longer be heard�the �null� signal�at which point the airplane was headed either directly toward or away from the target. A series of maneuvers was then required to obtain sufficient lines of bearing (LOB) to fix the target. For obvious reasons, repeatedly turning toward the target transmitter was not an ideal tactic. Furthermore, the method was time consuming and heavily dependant on operator technique to determine exactly when the null occurred. Since the aircraft were not equipped with any sort of navigational equipment, determining the position of the aircraft at the time the LOB was taken was difficult and that in turn made the fix less precise.

Air force legend has it that the idea of 360-degree ARDF capability came from General Curtis E. LeMay, long time leader of Strategic Air Command and later USAF Chief of Staff. Could not, LeMay is said to have inquired, some sort of �omni-in-reverse� be devised so that a transmitter could be pin-pointed by an aircraft flying by instead of the other way round? In its mature form, the Air Force ARDF system employed this principle of �phase angle discrimination� whereby the target signal was intercepted by a triangular antenna array, one set of dipoles mounted on each wing and the third on the forward fuselage just aft of the cockpit. The aircraft position at the moment of �lock-on� was determined by a Doppler navigation system, with precise heading information input from a gyro compass.

"Less than two seconds after signal lock�on", stated the navigator�s manual for the air force ARDF system, "the measurement was made automatically, without any human input or manipulation, [thus] eliminating any human error in the bearing angle measurement." In addition, "there was no 180 degree ambiguity in the angle measurement (as with the aural null). If the station stopped transmitting immediately after lock-on, the station direction was known without a doubt. Now the direction of the station could be determined from any location and from any aircraft heading."

Sanders Associates (now part of Lockheed Martin) of Nashua, New Hampshire, was selected to design and build a prototype phase angle measurement system and on September 26, 1962, the Warner Robbins [Georgia] Air Material Area (WRAMA) received a directive to begin the necessary modification work on a C-47D, serial number 45-925, then attached to the 1st Air Commando Wing at the Special Air Warfare Center (SAWC), Eglin AFB, Florida. Thus began project Hawkeye, out of which would eventually come the EC-47.

WRAMA was tasked to complete work on #925 by October 12 in order to meet a projected January 2, 1963, deployment date. TACAN, IFF, updated radios, a gyro compass, Decca navigation gear and Doppler equipment was installed and on October 18, the Hawkeye bird departed for Hanscom Field, Massachusetts, where the �breadboard� ARDF equipment was to be installed by Sanders. Further modifications were completed and on December 1 the aircraft, still minus the ARDF gear, made a successful test flight.

At this point, the documented trail of the Hawkeye aircraft virtually disappears. As the author of a WRAMA historical study points out, this was the time of the Cuban Missile Crisis. In any case, #925 reappeared at Eglin in early 1963, presumably with Sanders� prototype phase angle discrimination ARDF equipment aboard. By late April, however, evidence indicates the aircraft was in Korea. Whatever tests may have been conducted during the summer of 1963, #925 was scheduled back at WRAMA on October 7 for work on the navigational system. This was rapidly completed and on October 10, the Hawkeye aircraft returned to SAWC.

This time its ultimate destination was Vietnam, and 45-925 was to spend February-July 1964 there. About the same time, the army deployed another flock of RU-6A�s, referred to as �Seven Roses�, in the Mekong delta region southwest of Saigon. Due to time and budget constraints, the Hawkeye aircraft had been calibrated to within only 30 degrees of the fuselage centerline and was thus only marginally more capable than its army counterparts. When the navigation system failed completely in July, #925 was again sent back to the U.S. Shortly thereafter, events would fundamentally alter the nature of the war.

On August 2, the destroyer U.S.S. Maddox, supporting clandestine activities in the Gulf of Tonkin, exchanged fire with North Vietnamese patrol craft. A similar incident on the 5th was answered by USN air strikes against North Vietnamese coastal bases and oil depots. Two days later Congress passed the Tonkin Gulf resolution, giving President Lyndon B. Johnson authority to commit American forces to full scale involvement in the Vietnam war.

In January, 1964, Headquarters, U.S. Air Forces, Pacific, (PACAF) had requested 7 additional Hawkeye-type aircraft, but approval was delayed pending results of the Hawkeye tests. Again, official records are sparse concerning the whereabouts of #925 from July 1964 until late 1965. Apparently the aircraft was continuously modified and tested, with at least some of the activity taking place in Florida, presumably under SAWC direction.

Meanwhile, a program nicknamed Red Chief involved the modification of another gooney bird, this one HC-47 serial number 42-92916, to carry ARDF-associated equipment developed by the Baltimore facility of the Martin Company. Little is known of Red Chief operations, but the aircraft did fly missions in Vietnam during 1965. It was written off after catching fire on the taxiway at Bien Hoa on September 6. On October 31, the Hawkeye bird was back 'in country' and on December 13 scored big by fixing an enemy battalion in the Michelin rubber plantation.

By the end of 1965 the U.S. had completely cast aside the advisory role and taken virtually complete responsibility for war in South Vietnam. Earlier in the year, the Marines had been blooded in operations around Da Nang, and in November the newly formed 1st Cavalry Division (Airmobile) had first ridden its 'Hueys' into battle in the Ia Drang valley campaign. Likewise, the VC 'insurgents' had largely been superseded by regular units of the People's Army of Vietnam (PAVN), sent southward down the arduous Ho Chi Minh Trail winding through the mountains of eastern Laos and western Vietnam. It was these troops, under the overall command of the victor of Dien Bien Phu, General Vo Nguyen Giap, that the American 'grunt' would face for most of the long duration of the war.

The Hawkeye aircraft had been scheduled for a 120 day trial, but continued success prompted MACV (Military Assistance Command, Vietnam) to request an extension. The Army had continued to build its ARDF force and with 15 aircraft was now capable of providing some 240 hours per week of ARDF coverage versus Hawkeye's 32 hours. The overall ARDF effort was still coordinated by the army's 3rd RRU. In late December, Lt. Gen. Joseph H. Moore, commander of the USAF 2nd Air Division, citing the "short range" and "lack of all weather capability" of the army aircraft, pointed out "the need . . . to enter this special area of aerial reconnaissance as a proper role for [the] USAF."

Moore's views got immediate attention when in early January 1966, COMUSMACV announced intentions to increase weekly ARDF coverage by a factor of nine to 2,424 hours. Even with an additional 41 army aircraft already programmed, a shortfall of 1,252 hours per week was projected. A draft of the coordination letter concerning the increased coverage had originally stated that "It does not appear that the C-47 will meet this requirement in a timely manner." Gen. Moore had the sentence deleted. Furthermore, a MACV message was reported to have stated that a total of 79 army U6 and/or U8 aircraft would be required to make up the deficit. Second Air Division withheld approval until the wording was changed to omit reference to any particular type of aircraft.

Nonetheless, the air force was soon forced to admit, at least internally, that "No sustainable air force capability exists, either qualitatively or in suitable quantity. One C-47 aircraft (Hawkeye) is currently performing a minimal ARDF task using bread-board equipment designed and made in 1963."

Sensing the potential for a significant set back at the hands of the army, air force brass reacted swiftly. A briefing to the Commander in Chief, Pacific (CINCPAC), the overall commander of all U.S. forces in the area, had the desired effect. CINCPAC recommended to the Joint Chiefs of Staff that the USAF begin a crash program to deploy 35 ARDF C-47s to Vietnam beginning in April, 1966. Inter-service politics aside, the discussions in Washington did recognize one salient fact: the air force had lots of potential platforms in inventory; the army had none. Project Hawkeye won the USAF a slice of the ARDF pie, but the hard work was still ahead and there wasn't much time in which to do it.

The Hawkeye aircraft, 45-925, would soldier on until August of 1966, when it was returned to the U.S. for installation of production standard ARDF gear. It returned to Vietnam in March, 1967. The writer flew several missions on #925 in 1970-71, but was unaware at the time of the significance of this aircraft in the development of the EC-47.

Readers are encouraged to point out errors and to add to the historical 'data base' of the Electric Goon. A photo or 2 of the Hawkeye aircraft, 45-925, during its experimental phase would be a great addition to the EC-47 story. Also, can anyone confirm that #925 was in Korea during 1963-64? Likewise, any information on the Hilo Hattie C-54 or the Red Chief project would be welcomed.