19 December 2015

Navy Observation Squadron SIXTY-SEVEN (VO-67): Sub Hunters on the Ho Chi Minh Trail

Squadron patch of VO-67
(VO-67 Association)
Given the restrictions by the Johnson Administration that adopted as policy in prosecuting the war in Vietnam that the port of Haiphong was off limits as well as overland supply routes from China, the only way to stem the material support and infiltration of South Vietnam was the interdiction of traffic along the Ho Chi Minh Trail that ran west of Vietnam through Laos and Vietnam. Supplies and personnel flowed down the trail to Viet Cong insurgents operating throughout South Vietnam. Despite Laos' neutrality established in 1962, North Vietnam moved freely through Laos up and down the supply routes. In April 1965, with the permission of the Laotian government, the United States initiated Operation Steel Tiger to try and disrupt trail traffic. All targets on the trail were identified visually, a challenging proposition with dense jungle and often uncooperative tropical weather. Army ground teams were introduced to Operation Steel Tiger in October 1965. A progressive ramp up of airborne and ground reconnaissance failed to deprive the Viet Cong of the virtual river of supplies flowing through Laos. Needless to say, this state of affairs preoccupied the Secretary of Defense, Robert McNamara, who believed technology could provide a solution. Through the summer of 1966, academic and technology experts came up with the Jason Study. It suggested an electronic fence of detectors combined with airborne assets to stop the flow of materiel down the trail. The Defense Communications Planning Group (DCPG) was established by McNamara in September 1966 to develop and deploy the technology for the "electronic fence". To keep a handle on costs, the DCPG examined existing military technology to see what could be adapted for use on the Ho Chi Minh Trail. 

The modifications that resulted in the OP-2E Neptune
(ARC Forums)
The DCPG found that sonobuoys, used by the Navy for hunting submarines since the Second World War, could be adapted for land use, fitted with not only acoustic sensors but also seismic equipment to detect traffic on the Ho Chi Minh Trail. There were obvious parallels to finding an elusive enemy in the thick jungle and hunting Soviet subs in the open oceans. These land-based sonobuoys could then relay their findings to overhead aircraft to summon air strikes. In January 1967, McNamara briefed the White House on "Practice Nine" which was the code name for what become Operation Igloo White. "Muscle Shoals" was the code name for the electronic surveillance of the Ho Chi Minh Trail- "Igloo White" referred to the technologies used in adapting the Navy's sonobuoys into what were called spikebuoys (equipped with seismic sensors) and acoubuoys (acoustic sensors). Camouflaged and their aerials designed to look like branches, the spikebuoys implanted themselves in the ground while the acoubuoys were designed to snag the branches of the jungle canopy and hang in the trees. Given that the sensors were based on sonobuoy technology, the US Navy was tasked with seeding the Ho Chi Minh Trail by air with the new devices. 

By this point in the war, the North had fortified the trail with anti aircraft guns and there were discussions on how best to deliver the sensors. While the US Air Force prepared for the delivery of the sensors with F-4 Phantoms which would be less vulnerable, the Navy provided interim capability with a twelve-aircraft squadron using heavily modified Lockheed P-2 Neptunes. As the Navy's maritime patrol mission was being taken over the Lockheed P-3 Orion, surplus Neptunes were readily available. Martin Aircraft outside of Baltimore was tasked with the modification process which entailed the removal of the ASW equipment from the P-2s. Extensive armor plating was installed to protect the crews while the defensive weapons included underwing gun pods as well as two hatches in the aft fuselage for pintle-mounted M60 machine guns. A terrain-avoidance radar was added in a chin radome along with a whole host of defensive electronic warfare equipment. 

The MR tail code led to its radio call sign "Mud River"
(San Diego Air and Space Museum Archives)
With Navy crews well versed with low level sonobuoy delivery, there were no issues with delivering the acoustic sensors which would hang in the jungle canopy. However, the seismic sensors had to be dropped from higher altitudes as they had to implant themselves in the ground to detect truck traffic. The altitudes needed were much different than that used for sonobuoy delivery and it was found that old Norden bombsights in the nose worked well following a convincing demonstration at Eglin AFB in Florida. Twelve Norden sights were secured from storage and overhauled- since the bomb sights hadn't been used in years, the Navy had to locate retired Norden bombsight technicians to carry out the work. The USAF supplied an instructor who used to train bombardiers on the sight and he was sent to NAS Alameda to train the crews of the new secret Navy squadron which was designated VO-67. A training film on the use of the Norden was found at the Smithsonian Institution and was sent to VO-67. 

Designated the OP-2E Neptune, the first three VO-67 aircraft departed NAS Alameda on 6 November 1967 for RTAFB Nakhon Phanom in Thailand (nicknamed "Naked Fanny" by US crews or simply abbreviated "NKP"). At NKP, the crews of VO-67 flew with USAF forward air controller (FAC) pilots to see for themselves their operating areas over the Ho Chi Minh Trail. In fact, VO-67 personnel formed a close working relationship and even friendship with the USAF FAC pilots. FAC pilots who had just returned from patrols over the area often were met by VO-67 crews to review what the FAC pilots encountered over the trail. Each crew planned its own mission- the acoustic sensors were dropped at high speed and at low altitude, usually 500 feet, with plenty of jinking to avoid AAA fire. Terrain masking was frequently used. Often the Neptune pilots would dive down from 12,000 as they approached their target areas, drop a string of acoustic sensors and then use the terrain to egress the area. Seismic sensors were initially dropped from 2500 feet, later 5000 feet. Some Neptune crews would dive down during their seismic sensor drops to build up speed for the egress. Often times the underwing gun pods and rear M60 mounts were used for suppressive fire to keep the enemy's heads down during their target runs. 

CDR Paul Millius
(US Navy)
The missions were demanding and losses did take place- January 1968 (one aircraft lost), February 1968 (two aircraft lost). The last of the modified OP-2E aircraft joined the squadron at NKP just days after the third loss. During the Tet Offensive, the Marine fire base at Khe Sanh was under siege by an estimated 200,000 North Vietnamese troops. Along with some of the most intensive close air support of the Vietnam War, the Neptunes of VO-67 also dashed into the area to lay acoustic sensors to help detect NVA advances. By May of 1968, the USAF was ready to start delivering the sensors with its Phantoms with the job assigned to the 25th Tactical Fighter Squadron (part of the "Wolfpack" 8th Tactical Fighter Wing). The Phantoms would be less vulnerable than the lumbering Neptunes over the increasingly thick air defenses over the Ho Chi Minh Trail. The last VO-67 sensor drop mission took place on 25 June 1968 with the squadron being disestablished on 1 July 1968 and its personnel and aircraft returning to the United States. 

During its brief tour of duty, VO-67 lost one-quarter of its aircraft and 20 crewmen- and thanks to the airmanship of the crews and the invaluable help of the USAF FAC pilots who worked with VO-67, this loss rate is only half of what was expected at the start of VO-67's deployment. One pilot, Commander Paul Millius, was lost in action after his aircraft was hit at heavy caliber anti aircraft fire. One crewman was killed instantly and he kept flying until the other seven of his crew could bail out and survive. He was seen bailing out last, but was never found. He was promoted to the rank of Captain in 1972 and in 1978, he was presumed killed in action and posthumously awarded the Navy Cross. In 1995, the Navy launched the Arleigh Burke-class AEGIS destroyer USS Millius (DDG 69) in his honor, one of the few ships named for a naval aviator. The motto of the ship is "Alii Prae Me" (Others before me).

Related reading: 

Sources: Batcats: The United States Air Force 553rd Reconnaissance Wing in Southeast Asia by Jack Sikora and Larry Westin. iUniverse Publishing, 2003, pp 11-18, 73-75. VO-67 Association's Squadron History page at http://www.vo-67.org/vo67_history.html. 

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