PIRAZ (Positive Identification Radar Advisory Zone), more commonly known by the callsign “RED CROWN,” was the most important station given to ships of the Cruiser/Destroyer force and was responsible for control of Navy airstrikes against North Vietnam. RED CROWN frequently controlled Air Force strike packages as well, and many USAF pilots preferred working with RED CROWN, a testament to the professionalism of whatever ship was assigned such duties.
PIRAZ as a concept was introduced in 1966. In late April and early May 1966 the SAR forces in the Northern Gulf of Tonkin were augmented by the USS Topeka (CLG-8) whose task was to evaluate the concept of one ship performing the following functions within a designated zone in the Gulf of Tonkin:
- Positive identification and tracking of all aircraft in the zone.
- CAP control.
- Flight following.
- SAR assistance.
As a result of the evaluation the PIRAZ was established on 15 June 1966, with the USS Chicago given the inaugural nod. The PIRAZ area included NVN territory and the international water of the Gulf of Tonkin north of 18-30N and east of 105-00E. All aircraft entering the zone were required to check in with the PIRAZ ship. Initially considerable difficulty was encountered in effecting necessary coordination and communication linkages, but over time these problems subsided and the situation continued to improve.
Although PIRAZ was established primarily for force defense, the PIRAZ ship concept also included the following functions:
- Vectoring strike elements for rendezvous.
- Vectoring aircraft in distress to a tanker or to positions requested by the pilots.
- Provide navigation assistance to strike elements.
- Control CAP in protecting AF units operating in the Gulf.
- Issue warning of MiG activity.
- Issue warnings when friendly aircraft approach too close to the border of the People’s Republic of China.
Ships assigned to PIRAZ duty needed at a minimum a good air search radar (typically the AN/SPS-48) and more importantly, the Navy Tactical Data System (NTDS). NTDS provided a means of overlaying identifying symbols over raw video (much like the system today’s air traffic controllers use), and further provided the ability to link with other NTDS-equipped ships, in effect extending the overall picture beyond that of each individual ship’s radar. PIRAZ ships were all cruisers, destroyer leaders (DLG) or occasionally, a guided missile destroyer (DDG). These three types of ships had enough NTDS consoles to adequately control air strikes over Vietnam.
In addition to having the proper equipment in the Combat Information Center, PIRAZ and North SAR ships also needed an embarked Naval Security Group Detachment. On the larger ships (cruisers and Belknap class DLGs) the NSG Det worked from a space called Supplemental Radio (SupRad). Dets embarked in the older DLGs and DDGs operated from a van bolted to the ship, usually near the signal bridge. These vans were called Quic Vans, and a number of them were maintained by Fleet Electronic Support (FES) at Subic Bay Naval Base in the Philippines. The vans were installed or removed as ships rotated in and out of WestPac.
NSG Dets played a key role in the success of the PIRAZ concept by providing early detection of hostile air activity, and in most cases the detachment was also able to provide information regarding hostile intent of enemy aircraft. This information could be passed in near real time via a sound-powered phone circuit directly to someone in CIC (frequently the NSG Detachment officer), enabling rapid entry of the information into NTDS. Hostile air activity was often detected prior to acquisition by radar, tipping the radar operators to focus on a specific area.
In addition to information produced by the Det itself, the Det also served as a conduit for information sent from other locations, including the BIG LOOK aircraft that flew daily missions in the GOT.
A typical detachment consisted of an Officer-in-Charge, a Division Chief, a Leading CTR who was the analyst and report writer, six CTR operators, at least one (usually two) CTI Vietnamese linguists, three CTO comms operators, and one CTM maintenance technician. In most cases underway watches were stood port and starboard (12 on, 12 off). Line periods were nominally 30 days, although one detachment in 1972 spent 100 days straight at sea, cross-decking a number of times before finally arriving at Subic Bay.
This post is a quick summary of PIRAZ and NSG’s role, but there is more to be told. For all who were a part of “Red Crown,” whether at the beginning, in the middle, or at the end, your comments and stories are welcome.
By LCDR Robert E. Morrison, USN, Ret