Talking Proud Archives --- Military

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

September 10, 2017

By Ed Marek, editor

TACAN at Phou Pha Thi Mountain, LS-85

I said early on navigation aids would be installed by the US at LS-85, Phou Pha Thi, Laos. So let's get into that. We are now preparing to walk the path of events that led up to the devastating NVA attack on LS-85 on March 10-11, 1968.

We'll take a look at the equipment. I'm not going to go into a lot of detail about how it works, but I do want to show it to you and underscore the difference between the two systems installed at LS-85.


The USAF's 1st Mobile Communications Group (MOB) selected the Tactical Air Navigation System (TACAN) for installation in Thailand and Laos. The 1st MOB installed five in Thailand in 1965, and three in Laos, one at Phou Kate in southern Laos (not shown on map), another on Skyline Ridge overlooking the highly contested Plaines des Jars (PDJ), and another at LS-36, Na Khang, the latter two in the North. According to Billy Webb, in his book Secret War, installation at LS-36 did not proceed because of dangerous levels of enemy activity there. In fact, in February 1966 the NVA took Na Khang. Unfortunately, Vang Pao was hit by gun fire during the attack and eventually had to have surgery. He survived. USAF F-105s then came in and leveled the site. Webb said it was a "shallow victory for the Communists."

Vang Pao's forces retook Na Khang in May 1966 and sustained a tough NVA attack in January 1967. Just to close this out, a TACAN was finally installed at LS-36 in July 1968 following the loss of LS-85. LS-36 was again lost the NVA in March 1969 so that TACAN was lost as well.

Webb noted Ambassador Sullivan favored installation of navigational aid sites in Laos. He was concerned about the impact stepped up US bombing might have on injuring or killing civilians in Laos. So he was supportive of helping attack pilots be more accurate.

The tempo of the air war had been accelerating over NVN. Billy Webb commented the TACAN site at Skyline Ridge was not cutting the mustard for air operations over NVN and far northeast Laos. Webb said Vang Pao recommended LS-185 at Phou Tia. Its elevation was 4,500 ft. But it was considered unsafe because of hostilities in the region. Interestingly, a paper prepared by Victor B. Anthony and Richard R. Sexton for the Center for Air Force History, "The War in Northern Laos, 1954-1973," the authors' perspective was a bit different. They said:

"Eventually Lima Site 185 was tentatively selected as a new TACAN site … While Vang Pao thought the navigational aid could be set up at Lima Site 185 without much trouble, he worried over security. The North Vietnamese constantly swept the area, and he felt a better location was Lima Site 85 at Phou Pha Thi."

Anthony and Sexton said Sullivan consulted with his advisers and "decided the security at LS-85 was sufficiently strong." The
USAF consulted with the 1st MOB for the next TACAN system to be placed in Laos. Its people surveyed three sites: LS-50 at Phu Cum, close to Skyline Ridge, Luang Prabang and Phou Phathi at LS-85.

BorosWilliam GrimesRichard

First Lt. William "Gary" Boros (left) and SSgt. Richard Grimes (right) conducted the survey at LS-85.

Recall from my introduction Phathi served as a CIA-Hmong command and control facility and Hmong staging base for commando missions in northeastern Laos. That was the state of LS-85 at that time, July 1966. However, it was about to get another mission: Boros and Grimes recommended LS-85 for the fourth system.

The USAF required the approval of the US ambassador to Laos, William Sullivan. Sullivan agreed with the installation at LS-85. He asked Laotian Prime Minister Souvanna Phouma. Souvanna approved on the condition it would not be manned by any US military people. Sullivan agreed with that too. Sullivan at the time felt security was good at Phathi.

On July 14, 1966 the commander-in-chief Pacific (CINCPAC), Admiral Ulysses Grant Sharp, shown here, approved the installation. Why did Sharp get a say? Back to the command arrangements: CINCPAC controlled air operations in Laos although the US ambassador to Laos had to approve them. CINCPAC was also responsible for the air war over NVN, except for SAC B-52s, which were controlled by the commander-in-chief SAC. COMUSMACV in Saigon was responsible for air operations in the RVN and up to the 20th parallel in NVN. The Navy did its own thing through the 7th Fleet. Not a good command and control arrangement? Correct, as discussed earlier.

Lt. Boros, the team chief and SSgt. Grimes remained at Udorn after studying LS-85. Boros called for one more staff sergeant and two airmen first class to do the installation. The installation team was all USAF, which the ambassador authorized, though they were given a cover.


In August 1966, the rest of the 1st MOB installation crew deployed with the TACAN, generators and support equipment in a C-130 such as shown here from Clark AB, Philippines. They flew to Udorn RTAFB, Thailand. Boros and Grimes met them at Udorn. Boros and Grimes briefed the men on their ultimate destination and provided them the needed background, including the secrecy of the effort.

The team was told everything was classified; next of kin cannot be told anything about the mission or location; at Udorn they wore civilians clothes, had to live off base, and drove an unmarked truck. But the team was not given a cover story for its first month at Udorn, and it had no identification. After complaining, the team received US Agency for International Development (USAID) identification cards and were provided a cover story: they were USAID workers. USAID is an element of the Sate Department and has often been used as a cover for CIA people and covert activities.


The team then loaded the TACAN "box" on to a C-123 "Provider" transport. I am not certain whether an USAF or Air America C-123 was used; I suspect the latter. This photo shows an Air America C-123 at LS-20A, Long Tieng, Laos.Two Army CH-47s flew in from RVN to transport the equipment and crew to their ultimate destination, LS-85.


The team then loaded ancillary equipment, personal gear, and themselves onto the two CH-47 Chinook helicopters. The C-123 and two CH-47s then flew to LS-20 at Sam Thong, Laos.


This is a view of Sam Thong in modern times. The photo was taken by Chris Corbett, a friend of mine who travels Laos by motobike. He offers motobike tours.


I thought I'd show you a photo of Sam Thong. You are looking at an Air American C-7A Caribou obtained form the Army heading down the Sam Thong runway, quite a primitive environment but normal for landing strips in Laos. Jonathan Pote remarked the strip "offered little margin for error and a requirement for superb airmanship." The C-123 carrying the TACAN was a much larger aircraft than this C-7.


While at LS-20, the team off-loaded the TACAN from the C-123 and attached it to the sling of one of the CH-47s.


The CH-47 with the TACAN box hanging below and the other CH-47 then flew to LS-36 at Na Khang for fuel. Both CH-47s carried machine guns in each window. They then flew on to to LS-85. One CH-47 dropped the TACAN in place, while the other landed, dropping off the installation team and their support equipment.

In sum, that must have been quite a ride! I know one of the 1st MOB crew commented, "Boy, what have I got myself into?"

Ed Rasimus, a F-105 pilot who flew over NVN, in his book When Thunder Rolled, described the TACAN in layman's terms:

"The primary means of fighter jet navigation, it depends on ground-based stations to emit radio signals offering a bearing to the station and a distance from the station. Locations can be described relative to a TACAN station by giving a radial DME (Distance Measuring Equipment) … DME is an instrument readout that provides distance in nautical miles from a TACAN station or to a Doppler destination … The Doppler navigation, in particular, was accurate to an unheard-of degree. If I updated off a TACAN station after takeoff, the coordinates displayed were always right."


This is the display of the Horizontal Situation Indicator from the pilot's flight manual T.O. 1F-105D-1. When the pilot selects the TACAN mode, the DME is displayed in nautical miles on item 12, Range Indicator. In this case, it looks like he is about 173 miles from his target location or Doppler destination and should proceed on a course of four degrees north on item 10, Course selector.

A Doppler destination is a known point on the globe. Pilots insert these points prior to flight; for example, their home base, way points along the flight route, and the target location. The net effect was the combination of the TACAN signal and Doppler destination would get the pilot to his target.

Another F-105 pilot has told me his perspective is not quite as laudatory as that provided by Rasimus:

"(The Doppler navigation system aboard the F-105) was sufficiently accurate to get you near enough to the destination (target) to locate it visually; the needle and mileage were usually off slightly more often than not."

As a result, he said, he really wanted visual contact with his target. Broadly speaking, I think most of the pilots wanted visual contact with the target. The Doppler-TACAN got them close enough. But recall earlier discussions about terrain and weather.

I had planned to describe this installation in some depth. However I found a great web site done by Richard Grimes and William "Gary" Boros. Boros at the time was a first lieutenant and the officer in charge (OIC) of the TACAN installation. SSgt. Grimes was the non-commissioned officer in charge (NCOIC) of the installation. I commend their story to you. They have useful photography and their story is interesting. Plus it explains the installation.


Oversight of the installation came from the CIA people at either the embassy or Udorn. Boros' team worked with the Hmong to get the job done. The Hmong had already cleared about 20 meters off the mountain to create a level place for the equipment. They also set up a tent for living quarters. The Hmong in this photo used 55 gallon drums as rock sleds at LS-85. The team and the Hmong also had to lay cable, and they did so.


Boros' team began installation in August 1966. The CH-47 had placed the TACAN on the edge of the mountain top, on the western side of the mountain, overlooking the sheer cliff down. It was fully operational on September 24, 1966. Four from Lt. Boros' team operated the system, two on site, two in Udorn, rotating mostly by helicopter, Pony Express as described in an earlier section. That situation remained until Page Communications Engineers Inc. people took it over.

The TACAN was code-named "Clara," known to the pilots as "Channel 97." So, all a pilot had to do was dial in the frequency for Channel 97 and he would start receiving the bearing and distance information. This ground system was not automatic. It required two men to operate on the mountain.

I want to highlight the description of security provided by a member of the team:


"Security was provided for us by the Hmong living on the mountain and General Vang Pao's troops at the base of the mountain. Also a Thai PARU (Police Aerial Reinforcement Unit) crew a few yards from us. Shortly after getting operational, we were warned that an attack was likely to happen that night (which would be during September 1966).The PARU, instead of going on a search and destroy, hid in our tent. Because of that Gary (Lt. Boros) tried to get the Thai removed from the mountain. That was unsuccessful. This photo shows Lt. Boros with three Thai PARU members alongside the tent.

"Everyone considered the place impenetrable. The TACAN was on top and a sheer drop on three sides. The Hmong were armed with everything including cross bows and hand made flintlock rifles. No way are the North Vietnamese or Pathet Lao going to make it to our site."

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