Introduction. The TACS in the RVN was designed for comprehensive and responsive control of all TACAIR. It was a closely-knit composite of 7th Air Force/VNAF/USMC personnel, equipment, and operations centers. In addition to controlling 7th Air Force, VNAF, and USMC (strike and reconnaissance only) air operations, the TACS coordinated and integrated USN and SAC operations in the RVN.
Organization of the TACS. The TACS was centered on a joint combined VNAF/USAF/USMC operations center at Tan Son Nhut Air Base, the Tactical Air Control Center (TACC). In outline, the higher echelons of the TACS are shown in the diagram below.
DASC.There were four DASC under operational control of the TACC. Three of them were combined USAF/VNAF centers (I DASC, II DASC, and III DASC) which supported FWMAF, ARVN, and US ground commanders in ARVN I CTZ, II CTZ, and III CTZ. There was no US or FWMAF ground forces supported by US TACAIR in ARVN IV CTZ and IV DASC were entirely under VNAF control.
USAF TACP. USAF TACP, operating under each DASC, were positioned with the ARVN corps, divisions, and regiments and the I and II FFORCEV divisions and brigades, as shown below. The 7th Air Force provided the equipment and the Tactical Air Control Party (TACP) personnel to work closely with ground commanders. The USMC provided its own ALO, TACP, and FAC to work with its ground units.
Units that Operated the TACS. Operation of the TACS in 1970 was the responsibility of 505th Tactical Control Group (TCG). Detail of the units that formed the 505 TCG are given here. It appears that the 620 TCS and 20 TASS would have been the units that was mainly involved with the mission of aircraft A84-231 on 3 Nov 1970.
Radar Coverage. Radar coverage was basic to the operation of the TACS. Sites were located throughout the RVN for complete coverage. For radar control purposes, the RVN was divided into two sectors; each sector contained a large high-performance radar at the CRC. Aircraft track data at the CRC was augmented by similar information provided by outlying radars at CRP.
Method of Operating. The radar and extensive communication network of the TACS made possible the quick responsiveness of the system. All aircraft on strike missions were picked up on radar and identification was usually established within five minutes after takeoff. Radar direction was provided to the pilot to the rendezvous point with the FAC or, in the case of GDB missions, to establish contact with the relevant Ground Controller. After the strike, radar contact was re-established with the controlling radar facility for the return to base. Should an aircraft need emergency assistance, the radar network was capable of providing vectors to the nearest suitable base or bailout area.