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The Air War against North Vietnam: the Thanh Hoa Railroad and Highway Bridge (Part 2).

When the US did not succeed in dropping the Thanh Hoa Railroad and Highway Bridge, possibilities were looked at to achieve this like tactics and improved weapons. In the end it was decided to try it in a very unorthodox way: a nightly attack with floating mines, to be released by a C-130E Hercules: Operation Carolina Moon.

In order to get the operation off the ground, it became part of Project 1559 as Task 55. The approach of "1559" was to give a quick answer in terms of research and development (R&D) to problems with regard to limited warfare or counterinsurgency problems through test and evaluation. It had to involve promising equipment 'off the shelf or near-term equipment. One of the advantages was a drastic reduction of the time generally required to formally establish and finance a project in the normal R&D process.


In September 1965, Air Force Systems Command was ordered by the Air Force Staff to develop and test a floating mine for the destruction of bridges. The Technology Branch of the Air Force Armament Laboratory (AFATL) at Eglin Air Force Base, Florida, then designed a mine with a 1.8 meter mass focus warhead in diameter with 209 kilos of HE, high explosives. It was assumed that after the mine had been released upstream and floated under the bridge, it was to explode as soon as the sensors detected the metal of the bridge structure.

The commander of the 2nd Air Division (2AD) at Tan Son Nhut Air Base, South Vietnam, Lieutenant General Joseph H. Moore, was informed about the new weapon and its potential against bridges, particularly the Thanh Hoa Bridge. The problem was that the weapon was too big for employment by aircraft like the F--105 Thunderchief and F--4 Phantom and therefore would have to be carried by a transport plane. However, Moore considered the risk of losing a transport aircraft that was to be used directly against the bridge, as too large and suggested studying methods to release the mines upstream of it.

The Tactical Air Warfare Center (TAWC) at Eglin analyzed the proposed operation and concluded that the chances of success were small because the mines would run to the ground if they were released far enough upstream to avoid the anti-aircraft defenses. But alternative proposals offered an even smaller chance of success.

Sheet metal

Actual work on the production of twenty live and ten inert mines began in October 1965. The final design, with a steel casing manufactured to AFATL specifications by the Atomic Energy Commission's contractor Union Carbide in Oak Ridge, Tennessee, and a floating system, had a diameter of 2.44 meters, a height of 80 centimeters and a weight of about 1,700 kilos. AFATL's Target Division designed and built the optical sensors and the safe-and-arm assembly with parts fabricated by a local contractor. Picatinny Arsenal, the Army's Joint Center for Guns and Ammunition in Morris County (New Jersey), modified thirty Bomarc (the Boeing CIM--10 Bomarc was an Air Force surface-to-air missile) radar sensors. Final assembly of the mine was accomplished by the Air Proving Ground Center (APGC) at Eglin. For this purpose eighteen sheet metal workers had to be brought in from the San Antonio Air Materiel Area in Texas. For the organization it created a major un-programmed workload of 3,320 direct man-hours as the work was beyond the capability of the requesting organization. To procure the mines, some $600,000 was expended in addition to the wages of personnel.

Operations Directive

While the mines were being manufactured, on November 24, 1965, APGC published Operations Directive #1559W1, "Carolina Moon." It had an APGC priority of 1B6 and an USAF priority of 3-70. The project was mentioned in APGC's Project Summary as of November 1, 1965, and through April 1, 1966. For reasons of safety, a detailed weapon description and operation concept were only known to personnel on the basis of "need-to-know." The project was a combined effort by the Directorate of Armament Development, TAWC, Special Air Warfare Center (SAWC) and APGC to design, fabricate, test, develop tactics, and deliver a new munitions. The project schedule showed the testing to begin on October 26,1965 (!) and to be completed on February 15, 1966 with the letter report being completed on March 1, 1965.

The objectives were (1) to obtain munitions release and ballistic characteristics when extracted from the C--123 and/or C--130 aircraft; (2) to evaluate the performance of the fusing systems and determine the reliability of each system; (3) to evaluate the performance of the safety and arming system; and (4) to obtain terminal effect data on the munitions. SAWC and TAWC would be responsible to develop delivery techniques during the testing phase, with TAWC providing a C--130 and a helicopter to take pictures and SAWC providing a C--123 aircraft, flight crews, forward air controllers, and being responsible for rigging of the delivery devices.

Sixty missions and five ground trials were planned. The missions would be flown both above land and water by a C--123 or C--130 that was instrumented and equipped with Mitchell cameras and recording equipment. The ground trials would be filmed with high speed cameras.

Regarding water recovery, the Operations Directive stated for example that on each of the forty missions, a two-ton item, with two to three parachutes, had to be recovered with the possibility that as many as ten such items were to be recovered on one mission. The item would be inert on most drops, but with explosive components on at least ten drops. Items and parachutes were to be recovered for reuse.

Technical services included the requirement of one or more boats to support on-board tests of munitions components, the majority being conducted at night. A 70 sq. ft. deck space for a 4,000-lb. item would be required for some of those tests. Also, special targets were required on the land ranges. However, details were classified and a request for their construction would be submitted under separate cover.

"1559W1" also stated, among others, that up to fifty sorties involving parachute drops into water were required with some involving fuse functioning and detonation of tetryl boosters. One or two drops were to be made with high explosives over a water and land range, but without fuses. Various types of targets on Ranges 74L and 72 South would be available to statically detonate high explosives against. Eglin was to fabricate and assemble a heavy munitions.

R&D testing

Although the vast Eglin ranges had no suitable areas to perform a full destruction test of the mine's armed munitions warhead, it was possible to test the system thoroughly for reliability of detonation in the armed position, and for safety when unarmed by deliberately firing the munition with a special circuit in the safe position. Both the radar and optical sensors were tested in dummy mines against the boom of a floating crane and a bridge. The safe-and-arm assembly was tested extensively and successfully.

The operation of the parachutes would be important to delay the fall of the mine after it had been released. Specialist personnel were made available by Tactical Air Command (TAC) to help rig the parachutes. During the R&D phase, forty-one sorties were flown, of which seventeen by the C--123 and twenty-four by the C--130. Seventy-one dummy mines were dropped into the water near Eglin to develop a workable procedure and rigging design, of which about fifty with parachutes into the water. During those tests mines repeatedly separated from their parachutes. Test photography revealed the causes, resulting in corrective measures being incorporated. Ultimately, two parachutes of 19.2 meters each would be used per mine. A mechanism ensured that the parachutes would disconnect the moment they hit the water.

It was shown that in the testing of the explosive head against simulated bridge beams and a concrete bridge pier, the warhead was adequate for the purpose. Test data gave a theoretical estimate of an explosion six to nine meters above the weapon that corresponded to one kiloton.

Interim report

In a 1/1703Z February 1966, 1st Combat Applications Group (Eglin) message, "Bridge Munition," SAWC and TAWC jointly sent the interim report about Carolina Moon to TAC with the final report to follow. The interim report stated that the project had been completed on January 28, although a small number of engineering sorties might have to be flown at a later date. The main body of temporary duty (TDY) personnel was released on January 28 except for five personnel to prepare checklists for rigging and loading procedures, and to clear supply accounts. They were to be released on February 4. The report concluded that although the feasibility of this type of bridge munitions delivery was proven, it was not recommended to use transport aircraft. When it was decided to use cargo aircraft, it was recommended to use the C--130 for various reasons to include, (1) could carry five items; (2) radar to aid in navigation and release accuracy; and (3) higher speed. The C--123 on the other hand could carry only three items, had a slower speed and under certain release malfunctions, center of gravity of the aircraft would be exceeded.


Most of the R&D C--130 test drops were performed by the E models from Sewart AFB (Tennessee), one being 64-0513. The crew of Major Richard Remers, 62nd Troop Carrier Squadron (TCS) was assigned to it. The aircraft was unique as it was the only Hercules that was equipped with the experimental Sperry Gyroscope APN--161 Ka-band navigation radar. It had a four times finer resolution than the standard C--130 APN--59 X-band with the same size antenna dish. That was amazing for the time. It was the prototype of the Adverse Weather Aerial Delivery System which made it possible to perform air-drops in adverse weather. Testing of the APN--161 had taken place by TAWC between July 30 and September 20, 1965. The aircraft was also equipped with a Canadian Marconi APN--147 Doppler system that calculated the ground speed and provided drift information.

The navigator on "513" was Capt Norman Clanton. He had been assigned to test the APN--161 after the first navigator had been reassigned. Beginning in November 1965, his crew had been flying to Eglin every week, typically leaving on Monday and returning on Friday. Besides flying R&D test sorties for Carolina Moon, test missions for TAWC were flown, including involvement in the early tandem testing of low-altitude parachute-extracting system (LAPES). Capt Clanton:
In a test on December 3 we released our first 'big tub' into the
Apalachicola Bay, using the 463L rail system with conventional heavy
equipment parachutes and techniques. We did not know what they were and
no one would tell us. As I recall, they were roughly octagonal and
somewhat bowl shaped, about eight feet in diameter and perhaps three
feet or a little more deep. I am inclined to think that we released the
devices primarily for the purpose of testing their drop
characteristics, as opposed to training, as the procedures were
essentially standard heavy-equipment procedures.

On November 29, 1965, "513" had made the first trip to McGhee Tyson Airport (Tennessee) to pick up four 'blivets', as Capt Clanton called the devices, with Eglin as destination. In December, another nine blivets were picked up by the crew of Major Remers.

Highly sensitive

In the meantime, TAC had been instructed by the Air Staff to support Pacific Air Command (PACAF) in carrying out a "highly sensitive mission in Southeast Asia." The objective was to bring down at least one span of the Thanh Hoa Bridge. It was estimated that the bridge would be unusable then for one to six months. Also, that probably the existing ferry, southeast of the bridge, would be put back into use. TAC in turn instructed TAWC to equip two C--130s (of which one with APN--161 radar) and to train two crews at Eglin who had to be at the destination on/around May 19.

In support of the operation, TAWC, on April 4, published an Operation Plan, OPLAN 155 "Carolina Moon." The objective was to collapse at least one span of the Bridge. It also became clear which two C--130 crews had been selected for the mission. It was no surprise that one of them was the crew of APN--161 radar-equipped C--130E 40513 with Norm Clanton as navigator. Also, that the mission was against the Than Hoa Bridge with floating mines and how they worked. Each of the two C--130s had room on board for five mines. After having been released, the mine would float downstream the Song Ma towards the bridge. As soon as the mine had arrived under the bridge, it was supposed to explode as soon as the sensors detected the metal of the bridge structure. Clanton stated:
This did not mean at all that we could discuss the mission with others.
Everything was Top Secret and we knew that the only hope for survival
would be to keep it this way. For instance, my wife Sylvia thought I
was at Eglin while in reality I was at Da Nang.

The second C--130E was 64-0511 assigned to Major Thomas Case and his crew of the 61st TCS. On December 1, 1965 both the 61st and 62nd were reassigned to Troop Carrier Wing Provisional, 4413 when the parent 314th Troop Carrier Wing (TCW) was PCS-ed to Kung Kuan on Taiwan.

A certain basis for "155" had already been laid in a Plan of Operation that 2AD at Than Son Nhut had sent to PACAF on February 28, 1966, with the Thanh Hoa Bridge as primary target, but also involving later strikes against bridges at Viet Tri and Ninh Binh. With regard to the primary target, it was initially planned that the C--130 would rendezvous with a flight of two F--4Cs ten miles offshore from the mouth of the Song Ma River. Those Phantoms were to initiate strikes against military targets of opportunity in the area of the mouth of the River. A second flight of two Phantoms was to initiate a diversionary attack on Highway 1A south of Thanh Hoa. Two flights of RB--66Bs would conduct active jamming and provide SA--2 warning. With regard to the Thanh Hoa Bridge, 2AD stated, among other things, that it was heavily defended by (radar-guided) anti-aircraft defenses and that there were strong indications for the presence of SA--2 installations. 2AD stated it had no C--130s or crews assigned to carry out the mission. It was recommended strongly to use the test crew on a 30 days TDY status. The aircraft had to be equipped with the APN--161 and a terrain avoidance capacity was highly desirable, if available. The use of a C--123 was not desirable. 2AD anticipated that the mission would be flown from Da Nang Air Base (South Vietnam) in the period May 29- June 9. Weapons should be shipped direct to Da Nang to arrive on/around May 15. Platforms, parachutes and rigging items should accompany either aircraft or weapons.


The 54-page operation plan, with various annexes and appendices, was the guideline to execute the operation and contained all possible information about its implementation. Due to the sensitivity, certain details about the weapon and the real purpose were omitted and only briefed on the basis of need-to-know. Topics were, for example, mission profile, training, which organization was to do what, information about the North Vietnamese opponent, the mission and its execution, when, what time and what departure base would be (C-day was May 15 at 10 am local time from Eglin), and who would have operational control (TAC east of 140 [degrees]W and PACAF west of it). Detailed mission briefings would only be given at the deployment location, based on recent intelligence information. The number of crewmembers per C--130 was brought to seven: two pilots, two navigators, a flight engineer and two loadmasters. This meant an extra navigator per aircraft. His job would be to stand behind the pilots to assist them with visual information. In addition, he would be the map reading navigator for the primary nav.

The crew that was to fly the Carolina Moon mission would be appointed after arrival by the Task Force Commander. Return to Eglin was planned around June 17, 1966.


In the period of April 11 to May 13, training was accomplished at Eglin under the operational control of TAWC. On April 14, selected personnel from Sewart reported to Eglin for intensive training. Aircrew training setup was 158 hours and included seventy-five flying hours, three hours mission orientation, forty hours weapons system, twenty hours each for target study and mission planning. Three different flight profiles were worked out to get to a suitable release point after reaching the ingress point and to minimize the time over the target (TOT) and thus for anti-aircraft defenses. For that purpose extensive use was made of aerial photographs. The intention was to use terrain masking as much as possible.

Flying consisted of twenty-five hours for eight day sorties per crew and fifty hours for fifteen night missions per crew with two and five weapon drops respectively. Dropping procedures into the water were tested, finding out how close to the target and from which altitude the mine could be dropped to be successful, rigging of the parachutes and overall validation. During the sorties, the tactics to be used were simulated as closely as possible. For example, the crews gradually worked their way down until they were cruising at 230 knots at fifty feet above the water at night. The plan was to stay blacked out, with the radar in standby, until landfall had been made near the mouth of the Song Ma River. In the May 2-10 period the crew of Maj Remers flew six sorties, of which four in the dark and at low altitude. According to Clanton he had flown some eighty test and training sorties for Carolina Moon.

Meanwhile, on April 12, 1966, PACOM commander (the "boss" of all U.S. forces in the Pacific), Admiral Ulysses Grant Sharp, had authorized PACAF to execute Operation Carolina Moon. This approval was based on PACAF's message of April 7, providing proposed aircraft and personnel deployment to Da Nang, and USMACVs April 12 message, advising that base loading at the base would allow the deployment. Seven days later, April 19, PACAF authorized Seventh Air Force (7AF), which had succeeded 2AD on April 1, 1966, to execute a single attack against the Bridge during the period May 29- June 9, in accordance with the 2AD message of February. 7AF was requested to advise the Command of the launch date/time soonest after determination. The mission would have to be coordinated with Navy's Task Force 77 in the South China Sea and with MACSOG to insure no conflict with Rolling Thunder (RT) and 34A operations. 7AF was to assume operational control of the TAC detachment upon its arrival at Da Nang. For everything else the detachment would be attached to the local 35th Tactical Fighter Wing (TFW). Upon completion of the mission, a detailed report had to be submitted with information like tactics employed, BDA and recommendations concerning future operations employing this concept. PACAF was to send this report to CINCPAC.


Before departure both C--130Es had been camouflaged by TEMCO at Donaldson Center Airport in Greenville (SC) and the Ka-band of "513" was extended with an X-band receiver/transmitter because the Ka-band by itself was not suitable for long-range navigation and weather penetration. According to Norm Clanton that was a fairly complicated arrangement, with two feed horns on the same dish, azimuth offsets, etc. He recalled that keeping the system pressurized for high-altitude operation was a challenge as well. Initially it was planned to equip the C--130s with an Electronic Counter Measures (ECM) system, but when it was decided to utilize (R)B--66s for ECM support, the plan was dropped.

On May 15, 1966 the main contingent including both aircraft departed Eglin for the first leg of the trip to Da Nang, Travis AFB on the US West coast. However, the two C--130Es did not make the trip together. Every Hercules had its crew chiefs and five mines onboard. Next destinations were Hickam (Hawaii), Wake Island, and Andersen (Guam) respectively before arrival on May 19 at 1330L at the final destination, Da Nang, with call signs Urake 31 and Aften 47. At the enroute stops, the C--130s were parked in a remote area, which was a standard practice for any aircraft with live ordnance aboard. Support personnel traveled separately. The last personnel of the contingent arrived on the 22nd.

On May 21, however, due to the danger from rebel forces in Da Nang, tactical aircraft stationed at the base were evacuated to other bases in SEA. The two C--130Es diverted to Tan Son Nhut. The rebel forces were South Vietnamese Army (ARVN) units of the First Division and local militiamen loyal to the Corps I commander, MG Nguyen Chanh Thi, who had been fired by Air Vice Marshal and Prime Minister Nguyen Cao Ky supposedly because of the general's good relations with the Buddhists and so regarded as a security risk. Thi was placed under house arrest. On May 15, Ky sent four battalions of South Vietnamese paratroopers and marines to Da Nang, who needed a little over a week to stop the resistance at a cost of hundreds of killed and wounded AKVN troops and civilians. Both aircraft returned on the 25th.

This "TDY' enabled the 7AF/Current Plans Division to discuss all mission details with the C--130 crews. It resulted on May 26 in an updated Current Plan of Operation which was forwarded to PACAF. It was stated that execution was planned on May 29 with a TOT of 30/0035L. This decision was based on favorable Song Ma River tides, the weather forecast and moon phase. Information on weather and tidal conditions had been received from the Navy Oceanographic Service in Washington, DC and updated with in-theater intelligence to assure greatest probability of success. The plan included one C--130E, four F--4C and two (R)B--66 ECM/ELINT aircraft. The Hercules was to make a minimum altitude over water approach to ingress point (IP), proceed minimum altitude above ground level (AGL) followed by a direct left turn to the roll out point, and heading to the release zone to release the five mines at 350 feet AGL. The aircraft then was to descend to minimum safe navigational altitude for escape route of either a right turn immediately after release to 1747N/10556E, or a left turn to 153 ION/1055145E for overwater exit. Low-level flight had to be maintained until the C--130 was at least 25 NM off shore. The aircraft would be over land for 9 minutes and 40 seconds. Self destruct timer would be set for 120 minutes. When the Hercules had reached the IP, the four 'Night Owl' Phantoms were to initiate diversionary armed recce on Route 1A, ten nautical miles (NM) south of Thanh Hoa, using flares and CBU--2A munitions. The two Destroyers would conduct active jamming of three Fire Can gun-laying radars in the target area and provide SA--2 warning for the F--4Cs. Recent photo recce had indicated that the water level of the Song Ma was high, which should preclude 'stranding' of the mines on the sand bar at about 4,000 feet upstream. The TOT would assure high outgoing tidal flow. If weather precluded the May 29 mission, it would be rescheduled for May 30 with a TOT of 31/0110L. 7AF requested the Navy for a SAR destroyer to cover position 'Betty' during the mission and on any alternate days. On May 28, a local sortie was flown from Da Nang.

Frag order

Although intelligence had indicated on May 27 that another five anti-aircraft artillery sites had been discovered in the vicinity of the Bridge, it was concluded after a re-evaluation of the Operation that this would not prevent its execution. On 28 May/0415Z May, 7AF issued frag order 204 for 29 May (which was the 30th local time) "Special Carolina Moon mission and Alfa RT 50C--59N-1 (Nite)." It was stated that access to or knowledge of the message was to be limited to minimum essential required for mission success.

The 35th TFW was to supply one C--130E (call sign Radium), the 8th TFW at Ubon Royal Thai Air Base (RTAB) four F--4Cs (Neon 01 through 04) and the 41st Tactical Reconnaissance Squadron at RTAB Tahkli one B--66B and one RB--66B (Robin 01 and 22 respectively). Radium would carry five mines. The setting of the igniters would depend on the estimated flow rate of the river. Neon 01 and 03 were each to be configured with two CBU-2As and two SUU-25s and Neon 02 and 04 with two CBU-2As. The Phantoms would receive in-flight refueling from one Kadena-based KC--135.

The frag order closely followed 7AF's Current Plan of Operation of May 26. Some additions included, (1) From Da Nang, Radium had to maintain course with a minimum of 25 NM off shore until establishing inbound track to the IP; (2) Radium was to maintain maximum feasible degree of radio silence until egressing North Vietnam unless an emergency would arise or the mission was aborted. When safely 'feet wet', Radium would contact Neon and Robin flights and state 'Mission completed'; When the decision was made to abort the mission before 'feet dry', Radium would state 'Radium aborting'. In the latter case, Neon would not execute its mission and was supposed to return the ordnance, fuel permitting. The mission would also be aborted when Radium observed the inland ceilings to be below 1,500 feet; (3) Neon's flight commander would plan tactics so that the first element remained in the area for seven minutes and the second element for five. After re-joining, Neon had to monitor the primary strike frequency for Radium's egress report at approximately 30/0038L; (4) The mission would be aborted before landfall if the ECM support was not on station; (5) SAR destroyers Speedbird and Downwind were to be on station Betty from 29/2300-30/0200L; (6) Robin was to jam all intercepted early warning/acquisition radars and frequency restrictions on radar jamming were lifted for this mission. The aircraft were also required to provide Fan Song warning and jamming as re-quired in support of the F--4Cs. Communications jamming was not authorized. Recovery of the support aircraft at Da Nang was authorized to refuel, if required; (7) Analysis of photography regarding the anti-aircraft order of battle (AAOB) disclosed that the immediate target area was defended by twenty-one AW, nineteen 37-57mm and seven 85mm sites.

Mission briefing

It was not a real surprise when the crew of Maj Remers and their C--130 were selected to fly the Carolina Moon mission. Capt Clanton thinks that the APN--161 radar in "513" had been the decisive factor. Both C--130 crews participated in the mission briefing. Although the crews brought along three different flight profiles to the release zone which they had worked out at Eglin, a fourth was prepared at Da Nang after looking at the latest intelligence information. It was decided to use this fourth profile. The plan was to release the five mines at about 3.7 kilometers upstream of the bridge. When circumstances would allow it, the crew would fly their aircraft to the alternative release point, 1.5 kilometers closer to the bridge.

The weather forecasters predicted scattered clouds at 610 meters, a visibility of 24 kilometers and occasional ground fog for the Thanh Hoa area.

Capt Clanton said:
Before the mission there was no coordination with the F--4 Phantoms or
B--66 Destroyers because we did not necessarily have to know this. Even
the diversion attacks were unknown to us.

One of the six civilians who had deployed to Da Nang to support the Operation was Dale Shane, who was Sperry's lead engineer on the APN--161. His final task was to see that 'fresh' new Ka-band crystals had been installed in the radar RT unit in order to provide maximum range on the ground paint for the navigator. It was to be his coworker Tom Walsh's job. Said Sperry's Shane:
Tom was against it. The Hercules was in a revetment with no breeze and
with 120-degree heat broiling up from the black tarmac. Walsh's concern
was that if either the old or new crystals, which were smaller than a
10-amp fuse, slipped out of his sweaty fingers, the radar might not be
operational for the mission. Tom concluded that it would be better to
leave the old ones in and let the range shrink a little. But I insisted
and we both sweated it out, but the C--130 departed with new Ka-band

The crews were then brought to their aircraft in their revetments to make preparations for the take off.


On 29/2325L May, C--130Es 40513 and "511" (as spare) took off from Da Nang, each with a crew of seven and with five mines. In the meantime the F--4Cs and (R)B--66s had taken off from their bases in Thailand.

At a low but safe altitude and at least 40 kilometers from the coast, both C--130s flew northward over the Gulf of Tonkin to the ingress point. This leg was about 290 nautical miles long and took about an hour. There it turned out there was no need for the spare, which then returned to Da Nang where it landed at 30/0118L. Weather conditions were not an obstacle for "513" either.

After reaching 'feet dry', Maj Remers flew at an altitude of 30 meters AGL to a point just north of the Bridge and then to the southeast to the roll out point above the Song Ma. Then, at about 3.7 kilometers upstream of the bridge, directly to the release zone where the five mines were to be released. ToT was 30/0034L. Because the C--130 had not been discovered and as a result there was no anti-aircraft fire, it was decided to fly 1.5 kilometers further to the alternative release point at 2.2 kilometers from the Bridge. Thirty seconds before dropping the mines, using the standard 463L system, the aircraft climbed to 120 meters. This altitude was reached 20 seconds later while the speed had been reduced to the airdrop speed of 240 kilometers per hour to open the door and ramp. Navigator Clanton said:
The moment the computed air release point was reached I gave the
command 'Green light'. Immediately thereafter the co-pilot pressed the
button on the central console which activated the release mechanism in
the bomb shackle.

Then it all went automatically (the two loadmasters had already made the necessary preparations). The extraction parachute for the first mine, which had been loaded into the bomb shackle above the aircraft ramp, was released and ended up in the slipstream and by the opening of it, the mine was pulled out of the Hercules. The extraction parachute was then automatically disconnected, after which the two parachutes of the mine opened to slow down its fall. While the first mine left the aircraft, the extraction parachute for the second mine was activated, and so on. During this period anti-aircraft fire was opened on the C--130 but it was not accurate.

Clanton further stated:
I didn't have the opportunity to look out the window much that night,
with my head mostly in the radar scope. However, the APN--161 was of
great value. Visual droppings in the dark are already a challenge, but
to do this in a hostile environment and above unknown terrain as well,
it gets many times bigger. The radar made the dropping much more

In his opinion, the entire process had taken less than three minutes. There was a drawback after all, however. The radar paint camera had been inoperative, so the route could not be verified.


Immediately after release of the fifth and last mine, the ramp and door were closed, a right turn was made while descending to thirty meters AGL and speed was increased to fly back around to the north and east of the hill east of the bridge for the route to the coast. This altitude was maintained until the C--130 was forty kilometers from the coast after which Maj Remers broadcasted the 'mission completed'. Further altitude to 610 meters was gained for the flight back to Da Nang where the aircraft touched down at 30/0158L. By then, Remers had informed Da Nang that the mission had been 'successful' and that the mines had been released according to frag order 204. The entire mission had lasted 2 hours and 33 minutes, of which almost 10 minutes above land in North Vietnam. The F--4Cs expended seven CBU-2As and 32 flares along Route 1A. One CBU-2A was returned to base as it could not be expended. The navigator stated:
The mission was flown as planned, the months of training and planning
certainly contributed to it. The mines were released over the river
but, due to the necessary maneuvering because of the anti-aircraft fire
and the increase in speed, we did not see that they also ended up in
the water.

After we landed in the middle of the night, Colonel Allan Rankin, who
had assumed command of the 35th TFW on May 10, came on board. He
brought a bottle of Jim Beam whiskey with him and small glasses for the
officers and a can of beer for the three airmen to toast to the good
outcome. Rankin also said he would request a Silver Star for all of us,
which -of course- did not materialize.


More than ten hours before Maj Remers and his crew started their mission, 7AF on 29/0604Z May, published frag order 208 for "Special Carolina Moon Mission/RT 50C--60N-1 Nite" for May 30 (the 31st locally) for a second mission against the Thanh Hoa Bridge. It almost matched the first one. However, it stated an important proviso: "This is an alternative day frag. If Carolina Moon is successfully executed as planned for May 29, this entire fragmentary order will not be executed."

In a 30/1030Z May message, 7AF informed PACAF that the first Carolina Moon mission had been executed 29/1735Z May and that they were informed it had been successful with the mines released in accordance with frag order 204. Also, that BDA by an RF--4C (call sign King Pin, Blue Tree mission UE 297E, night) and two RF-101Cs (Machete, UE 305E, day) had not shown any further damage to the bridge. Thorough study of up-river approaches did not indicate any reason for mine hang-up or self-destruct of mines. However, the RF--101 photos showed a new, serviceable pontoon bridge about 2,400 feet south of the Bridge. Three ferry boats were located 3,300 feet south along the west bank of the river. A railroad transshipment point 1,500 feet southeast of the Bridge contained 22 units of rolling stock with 12 small river boats situated along the river adjacent to this area.

7AF also stated that the conditions were favorable for the alternate schedule date of 30 May and that it was being planned accordingly. Apparently, 'successful' for 7AF meant something different than for the crew of Maj Remers! The mission was flown with disastrous consequences and resulting in lots of questions by the highest levels.


ToT for the second mission was scheduled for 31/0110L and the call sign for the (R)B-66s was Lark. Adjustment to the TOT of the first mission was made to take advantage of favorable outgoing tidal conditions and to vary time of re-attack. Route and tactics were identical to the first mission and were fragged and briefed with the exception that the (approach) route could be deviated as necessary based on the experience gained during the first mission. The primary drop zone as fragged was briefed with the option for the crew to proceed to the secondary drop zone about 5,000 feet down river if the aircraft had not been subjected to AAA.

A disadvantage for Maj Case was that his Hercules was not equipped with an APN--161 and that his crew had not been trained to fly the mission with "513." In addition it would have been almost impossible to transfer the mines from his aircraft to the other one.

According to Norm Clanton, the delighted mood of his crew turned into horror when they heard that Maj Case's crew had been ordered to attack the bridge again that night with almost the same profile as the first attack. Clanton felt:
With the absence of the surprise element, the chances for success would
be virtually nil. The decision to fly that mission was, in my opinion,
the worst decision I have been involved in in my 21-year Air Force

He then also understood that 1Lt Edmondson, the 'extra' navigator in his crew, had offered his services to Maj Case who gladly accepted.

According to The Tale of Two Bridges the fact was that either a parachute or a flak vest could be worn, but not both. Maj Remers decided that his crew would wear their parachutes with the flak vests stacked on the floor by their seats. Maj Case, however, decided that his crew would wear their vests and store their parachutes. Maj Remers felt that his aircraft would be tough enough to survive moderate AAA hits and gain enough altitude for a possible bailout. Maj Case agreed with this, but believed that the low-level flight would preclude a controlled bail-out.

Clanton was the last person to leave Case's Hercules before the door was closed to taxi for takeoff. He remembered and still remembers this moment very well as a very dreary one. Ten minutes later than scheduled, Maj Case and his crew took off at 31/0010L from Da Nang. The remaining six crew members of "513" stayed up to wait for the return of the C--130. Clanton said:
I remember us waiting in wing ops until I calculated that they had to
be out of fuel and could no longer be airborne, and we had heard
nothing. At that time, we had no idea where they had gone down.


At 31/0112L May and about three seconds after his last transmission, Neon 04 saw an explosion in the water of the Tonkin Gulf. At 1850Z, 7AF informed PACAF that an F--4C was missing and probably lost off the coast about 30 kilometers south of Thanh Hoa. No parachutes were seen or beepers heard. The Phantom was one of the four aircraft that had provided diversion for Carolina Moon. Two hours later it became clear that it was Neon 03, F--4C 63-7664 assigned to the 555th TFS, although the crewmembers flying it, Maj Dayton Ragland and lLt Ned Herrold were assigned to the 497th TFS. It was assumed the Phantom had been hit by AAA. At first light, the Navy found among others a partly collapsed raft, two parachutes and an oil spill in the water, but without a trace of the crew. At 30/1903Z, 7AF advised the PACAF Command Post that Radium was missing and that there had been no contact with the aircraft. The Navy was in the area searching. At 2209Z, 7AF's OPREP-3 #20293 informed the National Military Command Center (NMCC) and CINCPAC of Radium's assumed loss. At 31/0434Z, the NMCC and CINCPAC were informed that the crewmembers of Radium were Maj Thomas Case (pilot), lLt Harold Zook (copilot), the navigators lLt Armon Shingledecker, Capt Emmet McDonald, and lLt W. Edmondson, SSgt Bobby Alberton (flight engineer) and load masters A1C Elroy Harworth and A1C Phillip Stickney for a total of eight crewmembers. At 31/0108L, members of Neon flight had seen AAA and a large flash on the ground in the Thanh Hoa area. This was two minutes before Radium's scheduled TOT. The SAR effort continued. Due to the complete radio silence, it was not known if Maj Case had caught up on the ten lost minutes. Therefore it was also unknown if the Hercules had actually reached the target area.

Maj Remers received permission to fly a search sortie for survivors or the C--130 wreckage. Said Clanton:
We took off somewhere around midday and flew the mission track over
water to within sight of the North Vietnamese beach before reversing
course and searching on the way back to Danang. Of course, we saw
nothing. It was a terrible day.

At 31/0500L May, an organized search was initiated which terminated at 31/2100L. A total of twenty Air Force and Navy aircraft and four surface ships participated. Aircraft, including USAF HU--16B and C--123 aircraft, completed fourteen inshore sweeps and forty-four seaward sweeps. No findings or sightings were observed and the SAR continued on June 1. On 1/1200Z June, Detachment 1 of the 3rd Air Rescue and Recovery Group (Da Nang) stated that its participation in the SAR was ended as there were no indications that further SAR would lead to any results. They had admittedly found two large camouflaged fuel tanks, but it was not clear if they had been part of any of the missing aircraft. Four days later, 7AF decided to stop all SAR. Crews transiting the area were requested to remain vigilant, electronically and visually.


The apparent loss of the two aircraft with a total of ten crew members created a lot of consternation. The Air Force Command Post (AFCP) called PACAF on 30/1915Z and asked a number of questions, including requesting a complete narrative of both missions and what the rationale had been to execute the second Carolina Moon mission. On 31/0107Z, PACAF in turn forwarded the questions to 7AF. Less than an hour later, PACAF asked 7AF two additional questions in line with AFCP's: (1) Whether 7AF had considered the first mission on May 29 to be abortive. (On April 20, PACAF had authorized a single mission against the Thanh Hoa Bridge. In the sequel thereafter, 7AF had indicated on May 4 that it initially involved just one mission and that it was only to be flown again when the first one had failed); (2) Whether the approach route and route after the release of the mines for the second mission had been changed significantly. (During the first mission, the selected release point was located 1,500 meters further downstream than initially planned as AAA had been missing up to then). PACAF's message was concluded with, 'Please clarify and add any other pertinent details'.

In response to a request from CINCPAC, PACAF, at 31/0745Z May, forwarded, after careful investigation, a statement to the AFCP and CINCPAC, explaining why 7AF had decided to schedule the second Carolina Moon mission. PACAF also stated that 7AF's intent of the second strike was received at PACAF as the mission was getting airborne and that, consequently, PACAF had not participated in the decision making.

In a lengthy 31/1420Z May message to PACAF, consisting of three sections and two parts, 7AF went into great detail regarding both Carolina Moon missions. In addition, 7AF reacted to the two PACAF questions regarding the decision to execute the second mission. Part 1 involved the first mission and part two the second. In section three, 7AF reacted to PACAF's two additional questions. As to the first question, 7AF stated, among others, that it had not been possible to determine if the mines had actually hit the water in the first mission. Thus, test of the system could not be ascertained. This could have enabled the North Vietnamese to discover the characteristics of the mine when they had not self-destructed, followed quickly by measures like installation of cables across the Song Ma upstream of the bridge and the increase of air defenses. Furthermore, the current would be favorable for another two days and unfavorable the next seven days with the weather then being as an uncertain factor. In addition, the first mission had drawn only light flak. The conclusion was that a quick second mission would reduce the probability of an analysis by the North Vietnamese of the attack technique and thus the risk for the C--130 crew was regarded as acceptable.

As to the second question (route), 7AF stated that for the second mission the primary release zone from the frag order was briefed with the option for the crew to fly to the alternative release point, 1.8 kilometers upstream, when there would be no AAA. In connection with the terrain in the immediate vicinity of the bridge, a turn to the left would be made and the flying altitude decreased immediately after dropping the mines. The route to the egress point would then take three minutes.

When forwarding 7AF's responses on 7 May to CINCPAC and the Air Force, PACAF stated explicitly that the Command had not been involved in 7AF's decision to order the second mission. This decision resulted from an operational standpoint and for several reasons: the bridge was still intact and the light air defenses would be an acceptable risk.

On 1/1208Z June, 7AF informed PACAF that Operation Carolina Moon had ended. There were still thirty-six personnel, ten officers, twenty airmen and six civilians and one C--130E at Da Nang. At that time, the final report was being written by the TAWC project leader, LtCol R. Johnson, and intel officer, 1Lt F. Dillon. 7AF recommended to return the personnel and the aircraft to Eglin and asked PACAF for a decision.

In a 2/0050Z June message, PACAF authorized the return and indicated that the Command would like the aircrew, Johnson and Dillon to stay at Hickam two days longer to review the missions and the concept of the final report. 7AF responded that the planned departure for Hickam would be 3/2300Z June with arrival at Hickam on the 5th where billets were requested for thirty personnel. Arrival at Eglin was planned for June 9. The flight was made via Tan Son Nhut on June 2, where the crew briefed the 7AF Staff, arriving at Hickam two days later. The Hercules landed at Sewart on the 8th.

Final report

On 3/1410Z June, the Air Staff asked PACAF information about the training status of both C--130E aircrews and how many mines every crew had dropped during the training sessions. The requested information should validate whether the training received was in accordance with TAWC OPLAN 155. The questions were then passed on to 7AF with a CC to LtCol Johnson. Responses were expected within four hours. Ten minutes before the 'ultimatum' was to expire, 7AF sent the answers to the Air Force. Eight day sorties were scheduled for each crew; Remers flew eleven and Case twelve. Fifteen night sorties were scheduled and each crew flew 14. All planned weapon releases (2/day and 5/night) were executed. Every crew released 13 weapons. ECM procedures were not practiced because the mission was to be supported by (R)B--66s. The routes on the Eglin complex were varied as much as possible. On navigation flights, for example, a small bridge in the Elbo area (Florida) was approached in two different ways, from the north and the south.

On 11/0150Z June, PACAF forwarded LtCol Johnson's final report on Carolina Moon to TAC at Langley and TAWC, info Air Staff. Johnson stated that the first mission was carried out as planned. It was unknown what had happened during the second mission, for instance as to the drop zone because the aircraft had been lost. (In a July 26, 1966 Recapitulation of the Carolina Moon activities, signed by Lt Gen Hewit Wheless, Assistant Vice Chief of Staff, it was stated that it was unofficially believed that "511" had reached the Thanh Hoa area. The Recapitulation was sent to the Secretary of the Air Force the same day). Photo reconnaissance after the second Carolina mission had shown that the Thanh Hoa Bridge was still intact and probably in use. Also, that a cable had been installed across the river at about 1,500 feet upstream from the Bridge, which had no relation with the local ferry crossing. It was suspected that a submerged net was attached to the cable. This indicated that the mine dropping concept had been compromised. It was recommended to adapt the mine for use by fighter-bombers and to stop using transport aircraft for strikes against the Thanh Hoa Railroad and Highway Bridge and the two other bridges that were considered for the presently developed weapon, the Viet Tri and Ninh Binh Railroad & Highway Bridges.


PACAF reacted to the final report in a 09/1926Z Aug 66 message to the Air Staff, info TAC and TAWC The Command stated that the report had been reviewed and considered correct in view of the intelligence available at that time. After careful evaluation of the report, PACAF recommended that (1) The Carolina Moon weapon in its present configuration should not be considered for further employment in PACOM, the Pacific Command; and (2) If further development was contemplated, the mine should be redesigned to allow delivery by fighter or tactical bomber aircraft; and (3) That a future design would insure the capability to achieve the desired effects.

In a 16/2106Z Aug 66 message to AFSC, the Air Staff stated that information gained from available sources indicated that four out of the five mines delivered on the first mission had reached the target and detonated, resulting in only minor damage. Failure to achieve destruction of the Bridge might have been due to fuse or warhead deficiencies. The fifth mine was recovered by the North Vietnamese due to the failure of the self-destruct feature. It was concluded that as an operational concept for delivery it appeared to have been successful.

AFSC was informed of PACAF's August 9 recommendations. In view of these, AFSC was authorized to dispose of Carolina Moon assets within the Command in a way to achieve greatest benefit to USAF exploratory development programs. Also, additional in-house functional tests of mines at Eglin was authorized. They were to be of value in confirming basic mine principles and capability of mine fusing to effect functioning within limits of mine lethal envelope.

Fate of the crewmembers

The crewmembers of Neon 04, Maj Dayton Ragland and lLt Ned Herrold were never found and are being indicated as "Presumptive finding of death," meaning death being inferred from proof of the person's long, unexplained absence, usually after seven years.

Not too long after the loss of Case's aircraft and crew, a Japanese TV crew visited and filmed the crash site. The Hercules had supposedly been downed by Air Defense Artillery Regiment 231. It crashed near the village of Tho Binh (Trieu Son District, Thanh Hoa Province), approximately 38 kilometers west of the Bridge. The Japanese were told by the North Vietnamese that none of the crewmembers had survived. Norm Clanton said:
The movie suggests fire damage to the vertical stabilizer and also to
the interior of the fuselage. The vertical stabilizer is relatively
intact and upright. But it is interesting that so much structure
remains intact following an unsuppressed fire. This suggests that the
aircraft impacted the ground in a relatively level altitude.

The clip also showed villagers carrying away and then camouflaging debris. Also shown was a mine which was upside down and seemingly to be intact. According to an eye witness, the aircraft flew from south to north and was on fire.

On April 10, 1986 the North Vietnamese repatriated five sets of remains to the Americans. They had been buried after the crash by local militia. The North Vietnamese stated then they had been unable to recover remains of other crewmembers. Three could be identified fairly quickly through their dental records (Case, Zook and Harworth), but as to the other two sets there were not enough elements for identification. This proved to be possible after all as one set was identified after twelve years (Shingledecker) and the fifth after 18 years. As to the latter, the Defense POW/MIA Accounting Agency went back to the Tho Binh site in late 1997. Osseous material from that site was returned on January 16, 1998 and joined evidence originally turned over in April 1986. With DNA and a family reference sample, it was possible to identify Stickney. This leaves the fate of three crewmembers as unknown (McDonald, Edmondson and Alberton). They are also being indicated as "Presumptive finding of death." Since 1995, the Defense POW/MIA Accounting Agency sent a team to Tho Binh nine times. For instance, teams were sent to the associated location in 2003 and 2014 in hopes recovering the remaining personnel, but both those excavations did not yield any material or osseous evidence. Therefore, the case is still open and it is being considered to send another team to Tho Binh.


The defense for years of the Dragon's Jaw by the North Vietnamese resulted in a museum on the grounds of a police station, to be opened by request only. Which they did for the author! Besides many photos and artifacts, the museum also had several books on display. One of them was Dragon's Jaw: The Historic Clash, published in 2010 by the Thanh Hoa Publishing House. With regard to the May 31, 1966, attacks the book stated, among others, that the enemy had tried a new tactic. By taking advantage of the bad weather, a C--130 was used to drop six mines into the Song Ma 500 meters north of the Bridge. Also, that as soon as the mines hit the water, personnel from the 7th Armed Public Security Sub-unit and Yen Vuc militia personnel used ropes to haul the mines up onto the riverbank where they were disarmed safely. The C--130 had turned away toward the southwest, where it and its crew of six were shot down by the 231st Anti-Aircraft Artillery Regiment.

In a different publication, Memories of Defending the Skies Over the Fatherland, published in 2013 by the People's Army Publishing House, it was stated that only one mine was still onboard when the Hercules crashed. Also, that the 1st Battery of the 231st Anti-Aircraft Artillery Regiment had needed twenty-one 57mm rounds to down 511. On June 1, 1966 the aircraft's insignia was cut out by the 231st Regiment. Along with the C--130's propellers, it was transported to the Air Defense Command Headquarters in Hanoi.

The Military Engineers Museum is part of the Vietnam Military History Museum in Hanoi. It shows all kinds of used (US) ordnance and weaponry. One of the most eye-catching weapons on display is the casing of one of the Carolina Moon mines. It is not known if this is one of the mines of the first mission that was 'captured' or the one that was found at Radium's crash site.

To be concluded.

Thanks to Lt Col Norman Clanton, USAF retired. On May 24,1969 his AC--130A (54-1629 of the 16th Special Operations Squadron at Ubon) was hit by 37mm anti-aircraft fire during a combat mission over Laos. With a lot of pain and difficulty the pilots were able to fly the aircraft to Ubon, where the aircraft commander ordered most of the crew, including Norm, to leave the aircraft. On landing, the Hercules slid off the runway and caught fire. In total, two crew members were killed. Norm flew 106 AC--130 combat sorties, the last one on March 1, 1970. Instead of a Silver Star, Norm Clanton, on June 29, 1966 was awarded the Air Medal for meritorious achievement while participating in aerial flight on 30 May. The citation read in part, "On that date, Capt Clanton participated in a night parachute delivery of classified munitions against a heavily defended target in North Vietnam. During this flight, conducted in the early morning hours, Capt Clanton demonstrated exceptional courage and professional ability in the face of known concentrations of anti-aircraft weapons at great personnel risk by successfully completing the mission with outstanding results." Maj Remers was awarded the Distinguished Flying Cross (DFC), while the other crewmembers also received the Air Medal. The second crew was also put in for a Silver Star by Col. Rankin, but this was downgraded by 7AF on July 6, 1966 to the DFC.

Theo van Geffen has been an aviation journalist and historian since 1977. He is from Utrecht, The Netherlands. His focus is the history of the F--105 Thunderchief and the units it flew with, and of the Air War in Southeast Asia. Mr. van Geffen has flown in USAF aircraft like the B--1B Lancer, EC--130E ABCCQ Century fighters F--101B Voodoo, F--105F, and F--106B Delta Dart, F--15B/D Eagle and the F--16B Fighting Falcon. He was the first program speaker at the THUD-OUT at Hill AFB on February 25,1984 and one week later he became the last F--105 back seater ever while flying the next to last flyable F--105F to Little Rock AFB. He is the responsible editor for the Foreign News Department of Onze Luchtmacht, the official magazine of the Royal Netherlands Air Force Association.
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Author:Geffen, Theo van
Publication:Air Power History
Date:Dec 22, 2018
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