Talking Proud Archives --- Military

LS-85, Airmen left out on the limb, a leadership failure

September 10, 2017

By Ed Marek, editor

TSQ-81 at Phou Pha Thi Mountain: The process to make it happen, 1966-1967

The most significant shortfall of the TACAN was it could not provide precise bomb release information, direction or guidance. In the end, the pilot depended heavily on his eyes and his experience. The USAF needed something far more accurate. The fundamental difference between the TSQ-81 and TACAN was that the TSQ-81 had an active radar tied by computer to a command-guidance system.

"Heavy Green" was the military operation to emplace a Reeves AN/TSQ-81 Bomb Directing Central on the LS-85 summit adjacent to the TACAN area, particularly for monsoon season bombing of northern North Vietnam. The program was to be handled in great secrecy. The first TSQ-81 was installed at Nakhon Phanom RTAFB (NKP), code name, "Bromo." This is a photo of the TSQ-81 at NKP. As you can see it is a more complicated and a larger system than the TACAN. Its most notable component is its active radar, which, for the ambassador, made it the most controversial component.

As an aside, Correll noted, for all kinds of reasons, it was hard to figure out who was actually in charge of the "Heavy Green" program. That's saying something given Correll was the editor-in-chief of the Air Force Association's
Air Force Magazine.

You will see people use the terminology TSQ-81, MSQ-77 and MSQ interchangeably. The USAF designated the system the TSQ-81 for LS-85. That is because the system, which was a MSQ-77, was now air-transportable, a mandatory requirement to put it on Phou Phathi Mountain.


The program in the RVN and Thailand was known as "Combat Skyspot." I believe five MSQ-77s were deployed to bases in the RVN, and three more at NKP, Udorn and Ubon RTAFBs in Thailand. This photo shows a MSQ-77 Combat Skyspot station at Dong Ha, RVN. You can see the active radar in the left corner of the compound. Note the large hunk of property eaten up by the MSQ-77, and the protective wall. This is why the USAF insisted the system be adjusted so it could be air-transportable and requiring a much smaller footprint on the ground.

In his book, One Day Too Long: Top Secret Site 85 and the Bombing of North Vietnam," Timothy Castle commented the idea to "place a ground-directed radar bombing facility at Site 85 evolved from a February 7, 1965 White House staff memorandum, which urged President Lyndon B. Johnson to undertake a 'policy of sustained reprisal against north Vietnam, in which air and naval action against the North justified by and related to the whole Viet Cong campaign of violence and terror in the South.'"

W. Howard Plunkett, writing
"Radar bombing during rolling thunder--Part II: Combat Lancer and Commando Club" said the USAF and JCS began work to establish a Combat Skyspot ground directed radar station in northern Laos as early as November 1966. Billy Webb said the formal and secretive "Heavy Green" project to locate a command-guidance radar system at LS-85 began in summer 1966.

Obtaining approval for the TSQ-81 at LS-85, installing it and operating it were far more involved and contentious than the TACAN at LS-85 and the TSQ-81 at Nakhon Phanom.

The USAF began developing ground radar systems for automated guidance of aircraft to a bomb release point in 1951. The MSQ-77 Radar Bomb Scoring System (RBSS) was fairly new at the time of its installation in Southeast Asia. It was tested with F-100 fighters in October 1965. It achieved operational status for B-52s and F-100s in March 1966 and deployed to RVN in 1966.

The TSQ-81 was a complex system. Many called it a Ground Directed Bombing (GDB) system. It could display an attacking aircraft's ground speed, altitude and heading. A computer linked to the radar would then create a precision map of where the tracked aircraft was flying. It could continuously predict bomb impact points for a radar track. It then employed control commands that adjusted the aircraft's course. The photo shows the MSQ-77 plotting board inside the system's housing where USAF technicians worked to guide the aircraft to their bombing point. Global Security described it this way:

"These maps could precisely determine where an aircraft was in relation to a chosen target. The computer continuously calculated the altitude, airspeed, wind drift correction, and ground elevation changes, using the ballistics of the bombs that were being carried by the aircraft. The plotting board/computer operators would tell the aircrew to make minor corrections in their flight path, and then the exact moment when to drop their bombs, to ensure that the bombs would be on target."

In his book, Honored and Betrayed, Major General Richard Secord, USAF (Ret.) said:

"Attacking planes would simply follow the ground system's voice commands to weapons release:

"'Ready, ready, now!' and all the pilots would drop their bombs together."


Jacob van Staaveren, a historian and author, in his book Gradual Failure, The Air War Over North Vietnam 1965-1966, said:

"Early in June (1966), combat pilots flying in Route Package 1 (RP-1, just north of the DMZ) began relying on a new MSQ-77 radar system nicknamed Combat Skyspot, using special radar instruments in the aircraft and at ground stations at Nakhon Phanom, Thailand, and Dong Ha, South Vietnam, both marked by red circles (disregard the red circle toward the top of the graphic). The same system had been introduced two months earlier (April 1966) (elsewhere) in South Vietnam to assure more accurate close air support and B-52 strikes."

As shown on the map above, RP-1 was the southern-most route package in NVN. So both those ground stations could "see" RP-1. Even so, they experienced line-of-sight communications problems, limiting them to 140 miles range. An evaluation of effectiveness could not be done because no bomb damage assessments (BDA) were available due to weather and nightfall. However, all things considered, the systems worked very well in the RVN.

The existing MSQ-77s were sufficient to cover all of the RVN, and part of NVN and a good part of southern and central Laos. Once bombing of the Hanoi area was approved, all eyes were focused on RPs 6 and 6A, far to the North. The sites in RVN and Thailand could not reach northern Laos and most important, could not reach Hanoi in NVN. So the problem was the USAF needed one far closer to Hanoi.

The USAF selected LS-85 for that job. Hanoi was about 120 miles from Phou Pha Thi.

In November 1966 the commander-in-chief Pacific Air Forces (CINCPACAF), General Hunter Harris, shown here, asked "authorization to develop a concept and plan for installation of an MSQ-77 in northern Laos and authorization to discuss this matter with Ambassador Sullivan." On November 28, 1966 CINCPAC "authorized CINCPACAF to proceed with plans as requested and directed that American Embassy Vientiane be provided with detailed requirements."

CINCPAC, Admiral Sharp, further urged the Ambassador's concurrence on this proposal and assistance in selection of a suitable site. CINCPAC said Ambassador Sullivan's response, one day later, was "decidedly negative, but would authorize his representatives to discuss (the) proposal with PACAF representatives. Sullivan further doubted that (the) RLG would be willing to accept such a major installation for which they would consequently feel security obligations beyond their means."

This question of security for the site will rise up frequently as we go forward. To a large extent, the concerns about site security emanated from US people in Laos, either from the ambassador and his staff, or from the CIA staff at the embassy and elsewhere. Here it is November 1966 and Ambassador Sullivan has already raised the security issue to the CINCPAC level, and no doubt, to Washington. The TSQ-81 for LS-85 had not yet even been approved.

In December 1966 General Harris sent a message to Ambassador Sullivan, underlined the urgency of this program and offered to brief him at Udorn on December 10, 1966. Sullivan agreed to the meeting but had "grave doubts that the RLG would be willing to permit the installation of the MSQ-77 in Lao territory and that he had even graver doubts that Washington would even authorize him to propose such an installation to the RLG."

On February 25, 1967 Admiral Sharp sent a message to General Earle Wheeler, USA, Chairman Joint Chiefs of Staff (CJCS), shown here, in which he informed him of the following after the Sullivan meeting concluded:

  • Ambassador Sullivan was interested in the tactical merits of an MSQ in northern Laos "but again stated that he had misgivings about its political acceptability. He expressed concern that the RLG would most likely term such an installation as an indication that they would in fact be providing direct support to offensive operations against NVN rather than maintaining a neutral position and taking defensive action only. No commitment was made by Ambassador that he would provide further support to this proposal."
  • Admiral Sharp again discussed the issue with Sullivan on their way to Washington and Sharp's evaluation was that Sullivan would not support the idea at the State Department level.
  • Sharp said he supported the PACAF plan, he understood the USAF had already taken action to repackage the MSQ-77, and, if the plan does not get final approval, the system can be held for contingencies.
  • The MSQ-77 can be operational within 30-45 days of a "Go."
  • Sharp acknowledged Sullivan's concerns about security of the site "which we have overcome to some degree as expressed in" another message. I have not seen this message, though I suspect it had something to do with using relay aircraft as a cover for LS-85's involvement, which I will discuss shortly.

On April 25, 1967 the JCS proposed to Secretary of Defense McNamara that an MSQ-77-type radar be installed at LS-85. The JCS reasoned that it would provide bombing guidance during bad weather for the Rolling Thunder campaign.

McNamara consulted with LBJ and LBJ approved the proposal. So Sullivan lost this part of his battle.


The USAF had prepared itself for such an approval and issued a contract that same month, April 1967 to Reeves Instrument Corp. of New York. The task at hand for Reeves was to assemble an air transportable version of the MSQ-77, which would be called the TSQ-81. The USAF requirement that made this effort difficult was that the system had to be built in components that would not weigh more than 5,000 pounds. The radar dish, shown here at another location, weighed 2,000 pounds alone.

General Momyer seemed to be a fan of the MSQ system in the RVN. Initially he felt targets in RP-6 in northern NVN such as "marshaling yards, military barracks, the Thai Nguyen mill, depots, and transshipment points were suitable for MSQ bombing … (and those) large area targets were good candidates for attack during bad weather."

But Momyer also noted the installation of the system at LS-85 was fraught with political problems:

"The MSQ at Site 85 … was unique because of certain political problems. Ambassador William H. Sullivan was reluctant to permit the site in Laos to provide control of aircraft over North Vietnam. His position was that to direct air strikes over North Vietnam from Laos would appear an escalation of the war, in that Laos could be viewed as a base of operations for attacks against North Vietnam.

"A unique technique was devised to satisfy this political objection; a C-135 relay aircraft (such as shown here), positioned over the Gulf of Tonkin near the 19th parallel, would relay instructions from the MSQ site in Laos to the strike aircraft. The short time delay in the relay operation was accommodated in timing the instructions to release of the bombs.”

This meant TSQ-81 operators would first call in their directions by secure voice transmissions to the C-135, named "Combat Lightning," and the operators aboard that aircraft would send the directions to the fighter-bombers. These latter directions would be sent to the strike aircraft in either code or plain English. General Secord has written this would "make it appear as if the radar instructions were coming from the plane instead of the ground."


I should insert the EC-121D "College Eye" aircraft such as shown here also served as a radio relay.

Momyer would later express more misgivings.

While Sullivan had lost the battle on the TSQ-81 in Laos at the Washington level, he cleverly waited for several months before going to Laotian PM Souvanna to inform him. Among other things, Sullivan said he was worried about the risk to the site itself. He thought it too close to Sam Neua City. Again, security was on his mind.

Secretary of Defense Robert McNamara had been lobbying Secretary of State Dean Rusk hard for the system at LS-85. Rusk, shown here, was resisting the installation, but finally agreed. I'm not sure why Rusk was recalcitrant. On October 12, 1967, he critiqued congressional peace proposals that would limit or stop bombing of NVN. Rusk said at a news conference, "Where would be the incentive for peace?” So he was not against the bombing. The installation of of navigation stations in Laos did violate the Geneva agreements, which prohibited the use of "Laos territory for military purposes." So perhaps he was worried about that. In the end, however, it appears Rusk favored the bombing of NVN more than Laotian neutrality.

With Rusk now acquiescing, McNamara instructed Sullivan to go see Souvanna and tell him the TSQ-81 was coming. So Sullivan went to meet him. Sullivan did not work for McNamara, so it curious he "jumped to" when McNamara instructed him on this.

Sullivan met with Souvanna on July 6, 1967. He notified the State Department that same day that Souvanna agreed to installation of the MSQ-77 (actually the TSQ-81, the mobile version of the MSQ-77) at Site 85. Sullivan assured him that all USAF markings would be removed from the equipment, detonators would permit immediate destruction in case of imminent danger, personnel would be under civilian cover, maximum measures would be taken to camouflage against detection from the air, and electronic camouflage would be undertaken by scrambled transmission to relay aircraft over Gulf of Tonkin.

Souvanna agreed, but had some concerns. He and Sullivan worked out their public relations posture should knowledge of the installation come into the open. Souvanna would simply say he did not know about the installation, or if confronted with a situation where he was uncomfortable, he would say, "I did not know it was there". In both instances, the US would either remain silent or say "no comment."

Sullivan said he assumed the JCS would direct 7th AF to contact the embassy's Air Attaché to get the project moving. He advised that his embassy would handle coordination. He emphasized the installation must be held very close to the vest, and afforded maximum security. He told the State Department, "It should be made clear that a compromise might result in a requirement to remove the installation if it, and the RLG, are sufficiently embarrassed."

In a June 29, 1967 message from Rusk to the embassy in Vientiane, Rusk urged caution on the denial strategy, asserting that many TACANs and navigational aids have been installed in Laos because such were "woefully deficient" throughout the country. Rusk suggested that the embassy talk about the TACANs rather than the TSQ-81 if public disclosure occurred and urged Souvanna hold in abeyance his comments to such a disclosure if it happened. Rusk went on to say:

"It remains Washington judgment that Site 85 is not only the best but the only feasible location. We have understood your analysis supported this judgment. Unless you have alternate proposal we could quickly review, believe justification for this selection must stand." The closing paragraph informed JCS it could proceed with the TSQ-81 installation.

Secord, in an article entitled, "Tragedy Strikes Laos Site 85," published by the Air Commando Association in spring 2012, said that he and Bill Lair attended a meeting at 7/13th AF Headquarters at Udorn in July 1967. At that meeting, General Harris described the plan "directed by JCS and the CIA," to install the TSQ-81 at Phathi. The system was to direct all-weather bombing in NVN.

In her book
Tragic Mountains: The Hmong, the Americans and the Secret Wars for Laos, Jane Hamiton-Merritt, a college professor and photojournalist close to the Hmong people, wrote General Harris came to Thailand to meet senior officials and proposed Phou Pha Thi as the place the USAF should install new radar bombing technology, the TSQ-81. Bill Lair and Major Richard Second, USAF were there. Both worked for CIA out of Udorn. Lair was concerned about the security. He opined Vang Pao could hold it but would find it difficult to sustain in an all-out offensive. Lair was also concerned about the extra load this site would place on the Hmong.

I would note that Harris was not proposing anything. The decision had been made.

Secord wrote that Lair, the paramilitary chief at CIA's COS in Vientiane, raised serious doubts about the Hmong's ability to defend the site against a main force NVA attack. Secord said:

"The paramilitary Chief (Lair) stated clearly that we did not have enough friendly ground forces, mainly Muong (Hmong) irregulars under General Van Pao to defend LS-85 against a main force NVA attack, which would surely come."

So Lair pressed for reliable and consistent USAF close air support (CAS). Secord said:

"We were assured that USAF TACAIR (tactical air) would be provided."

Much more on this in another section. The bottom line in June 1967, before the system was even installed, was that the ambassador and CIA people in the embassy had serious misgivings about their ability to protect the site, and expressed those misgivings to General Harris. Nonetheless, the job of overseeing the TSQ-81's installation, operation and security fell to the embassy, and mainly to the CIA people working: as you shall see, mainly to then Major Richard Secord, USAF.

Linkages: Vietnam and Laos
US tackles the linkages
Challenges to Rolling Thunder pilots
TACAN at LS-85
TSQ-81 at LS-85: Process to make it happen
TSQ-81 at LS-85: Installation
TSQ-81 operations
Situation Assessment: Houaphanh Province
NVA plans attack
NVA moves to attack positions
US threat assessments - actions taken
The NVA attack
The aftermath