Did you know that at one point the US Army had it’s own ships? Its true, take a gander for yourself at this article from the WWII After WWII website.
WWII-era seaplane tenders were on their way out of the US Navy by the time of the Vietnam War. However one, USS Albemarle, would have a second life as a US Army floating repair base during that conflict.
Conversion to ARVH and the Vietnam War
(US Army concept model of USNS Corpus Christi Bay which was differed only in minor details from the finished conversion.)
During the Vietnam War (1960 – 1973) the US Army flew over 11,800 individual helicopters in theatre. Obviously not all were in use at the same time; none the less during the late 1960s / early 1970s there were thousands of being flown in South Vietnam at any given moment.
Never before in history had a nation deployed such a huge rotary-wing force halfway across the world. At the same time, helicopters themselves had matured compared to the little piston-engined designs of WWII and the Korean War. Even the UH-1 Iroquois (aka Huey), which was the most basic and (by far) the most numerous kind, had a turboshaft engine, modern flight instruments, and fully-metal airframe.
Normally, depot-level maintenance of helicopters was done at the Army Aeronautical Depot Maintenance Center (ARADMAC) at Corpus Christi, TX. This facility was established in 1961, when 15 disused acres and buildings of the US Navy’s WWII Corpus Christi training airbase was transferred to the US Army. At its peak, ARADMAC was the largest helicopter repair facility on Earth.
(ARADMAC during the Vietnam War era.)
Mid- and top-level repairs and upkeep of the massive helicopter force in South Vietnam was a huge headache for the United States by the mid-1960s. To even get helicopters there to begin with required a long sea journey aboard one of the converted WWII aircraft carriers.
(A US Army UH-1 Iroquois prepared for shipment aboard the converted WWII aircraft carrier behind it. Helicopters always shipped unrotored. The US Army experimented with different anti-salt spray measures: here, doped fabric; later blown plastic and finally peel-off plastic which was deemed best.)
Helicopter maintenance facilities in South Vietnam were established but were limited in what they could accomplish. Repairs were limited to the training level of soldiers there, and a lot of the special technical gear was not really amenable to being shoved around quonset huts and tents. These forward helicopter bases were already overstretched doing normal low-level day-to-day work.
(Example photo of US Army helicopter maintenance in South Vietnam. Here, a Huey’s rotor blade is being removed.)
As was the nature of the Vietnam War, helicopter staging areas made very tempting targets for irregular harassment by Viet Cong mortar teams.
There was another, political, aspect in that every dollar spent to establish semi-permanent or permanent American military buildings in South Vietnam implied the war being an open-ended affair with no light at the end of the tunnel.
When a US Army helicopter took damage, or was at its flight-hour limit for high-end upkeep; the entire process had to be reversed: the helicopter had to be made ready for sea shipment again, space aboard one of the “seatrain” chartered freighters or one of the converted WWII carriers (themselves wearing out fast) had to be found, and the helicopter shipped across the Pacific and through the Panama Canal to ARADMAC in Texas. After the repairs at Corpus Christi were done, the process repeated itself yet again as the helicopter went back to the war zone.
All of this was incredibly expensive, both in freight dollars and more importantly, in time. Repairs that actually only took a week of real-time labor ended up taking two months.
What was desired was a non-permanent way by which many or most of ARADMAC’s abilities could be duplicated in South Vietnam.
This concept was not altogether new. Late in WWII, the US Army foresaw the need to support B-29 Superfortress bombers and their P-51 Mustang escorts as the “bomber line” inched across the Pacific closer to mainland Japan. Six project “Ivory Soap” units were established, aboard ships with trained mechanics and pre-staged repair parts.
(Shipboard service to the propeller of a land-based warplane by the US Army’s 2nd Aircraft Repair Unit – Floating during WWII.)
At the start of the 1960s, the US Army considered a concept called FAMF (Floating Aircraft Maintenance Facility), a relocatable way to support aircraft far abroad. The early concept mentioned “…in Asia”, as it looked more and more likely that the USA’s involvement in the former French Indochina was going to deepen.
The FAMF concept gained support and in the early 1960s, Army Materiel Command established a top-level Project Management Office called “Project Flat-Top”. As might be guessed, “Flat-Top” originally envisioned acquiring and converting a mothballed WWII US Navy small aircraft carrier.
(As a representative example the mothballed WWII escort carrier ex-USS Salerno Bay (CVE-110) in Boston during 1961.) (photo via Christian Science Monitor newspaper)
Although the office’s name remained, this idea was soon abandoned. The Army’s “de-mothballing” costs of a WWII escort carrier would be prohibitive, and some of the reactivated ship would be superfluous to what the FAMF was supposed to be.
Instead the “Flat-Top” office studied a variety of other mothballed WWII types: LSTs, seaplane tenders, and cargo ships. Of these the seaplane tender was most ideal.
As the ex-USS Albemarle had just decommissioned, and the hull had no further interest by the US Navy, it was selected.
MSTS / MSC during the Vietnam War
The ex-USS Albemarle‘s title, which was then in custody of the US Maritime Administration, transferred back to the US Navy on behalf of Military Sea Transportation Service (MSTS). MSTS was founded in 1949 as part of the Department Of The Navy (but, not actually part of “the” active US Navy) to put all of the five armed forces various sea shipping assets under one umbrella. MSTS was renamed Military Sealift Command (MSC) in 1970; the name it retains today.
MSTS / MSC ships are not commissioned warships and thus, are prefixed United States Naval Vessel (USNS) instead of USS. Per legislation they were unarmed. They were crewed by civilian sailors and captained by a Ship’s Master of the US Merchant Marine. During the Vietnam War, MSTS / MSC ships were a mix of newer civilian merchants and converted WWII ex-US Navy types.
(As an example ship USNS LeRoy Eltinge in South Vietnam during the 1960s. This MSTS vessel had previously been USS General LeRoy Eltinge (AP-154) during WWII.)
The MSTS / MSC headquarters in South Vietnam was located in this late-19th century waterfront Saigon building, the “Dragon House”, address 1 Trình Minh Thê St. It was formerly a civilian French freight company (Messageries Impériales, hence the “MI”) during the Indochina War and during WWII, a logistics station of the Imperial Japanese Navy.
As a sidenote, as of 2020 this building (now #1 Nguyên Tat Thành St) still exists; now a small museum of Ho Chi Minh’s life. The Vietnamese restored the building to the pre-WWII appearance, removing the American radio antennas and opening up both floors of lanai which were windowed in during the Vietnam War.
During WWII, a “total war”, loss of merchant shipping was certainly viewed as part of the conflict. During the Vietnam War, Military Sealift Command’s civilian-manned presence in what was essentially a war zone became something of a legal grey zone for the American military.
(The ex-USS Albemarle being transformed into USNS Corpus Christi Bay at Charleston.)
In 1964 “Project Flat-Top” was awarded $11 million to convert the ex-USS Albemarle into the first FAMF. The work was carried out by Charleston Naval Shipyard, SC and was to be completed no later than 1 January 1966.
On 27 March 1964 the ship was renamed USNS Corpus Christi Bay, in a nod to ARADMAC in Corpus Christi. The new hull designation was T-ARVH-1.
All of the Seamaster conversion work was un-done. The ride-up stern area was blanked off with a flat transom.
The one remaining WWII crane was removed. Any remaining WWII weapons, and their rangefinders, magazines, and support gear; were removed. A pair of identical 20 ton cranes, smaller and more compact than the WWII design, were installed as seen below. There were also two smaller cranes forward.
The aft end of the ship was built up into a 24′ deep working area, topped by a 50’x150′ helipad. It was served by a hatch big enough for a whole helicopter to be craned down into the work area, and also by a small freight elevator.
(The aft working area and main helipad being constructed.)
(The large hatch being constructed.)
The forward deck had a much smaller basic helicopter landing area, called the “admin pad”. It was not connected to the main repair areas aft and was used by helicopters not involved in repair activities.
(The “admin pad” and two secondary cranes. This photo was taken during the post-conversion sea trials; a loose anchor was not normally carried on deck.)
During the conversion, all remaining WWII electronics were stripped off, as were any related to the Seamaster project. The main mast was fitted for two radars; externally similar but operating in different frequency bands. One was capable of basic nautical search but both were optimized for air traffic control. The top of the mainmast held a huge periodic log-style antenna called the “Three Four”, which was for transmit-only high frequency radio.
(The two new radars and the big “Three Four” HF radio antenna.)
Atop the forward superstructure a small air traffic control tower was built. It occupied the spot previously used by the gunnery director for the 5″ guns during WWII; now all removed.
(Close-up and location of the ATC tower.)
The internal repair area aft had 26 “production shops” and 16 “support shops”. These could accomplish most any kind of repair that a helicopter would ever need.
(One feature in the metals shop was a heat treat over where metal parts manufactured aboard the ship could be made ready for immediate use.)
The shops varied greatly. There were engine test cells where helicopter turboshafts could be run up onboard. There transmission repair facilities, a hydraulics shop, a sheet metal shop, a gunsmith, a foundry, an electronics shop, and so on. Repairs were not necessarily limited by spare parts, as the ship could manufacture some items from scratch.
But primarily, spare parts were used when possible. More than 20,000 kinds of aviation-related spare parts were carried.
(Some of the thousands of spare parts being onloaded in Texas prior to the ship departing for Vietnam.)
There was a laboratory where the purity and viscosity of lubricants and hydraulic fluids could be tested.
One notable item aboard USNS Corpus Christi Bay was a IBM 360/20 computer. Computers aboard warships were then in their infancy, and this was one of the more (by early 1960s standards) powerful computers ever sent to sea then.
This computer was 16 bit and had a 32 KB core memory. For reference, the above jpg picture file of the computer is larger than the computer itself’s core memory. None the less, during the Vietnam War it was a useful advancement.
The crew level of the ship was drastically reduced from WWII. As USS Albemarle the US Navy manning was 100 officers and 1,035 enlisted sailors. Now as USNS Corpus Christi Bay, the ship had a MSTS/MSC captain, 128 civilian sailors, and a maximum of 361 US Army soldiers. Most of the living spaces and some of the work areas were now air conditioned.
(The sick bay had a surgery room and was staffed by an Army doctor trained in aeromedicine.)
(USNS Corpus Christi Bay had a ship’s cobbler who could mend combat boots of helicopter crews.)
More than 180,000 helicopter blueprints were carried, along with a library of technical books. Some of the onboard shops were wired up with a closed-circuit tv network, whereby the shop could request a central blueprint librarian retrieve a particular drawing and project it onto the monitor. Essentially a stone age LAN (local area network), this setup was not as successful as hoped.
(Although it would be anchored for its core mission, USNS Corpus Christi Bay still had to be capable of open seas navigation. This is the post-refit bridge.)
On 12 January 1966 all conversion and work-up efforts were completed and USNS Corpus Christi Bay was ready for use in the Vietnam War.
(The converted ship relighting boilers in drydock.) (photo from All Hands, the US Navy’s magazine)
(Following the Civil War, the US Navy instituted the Board Of Inspection & Survey, or INSURV, for all military vessels. This is an ultra-rigorous inspection done every five years or when a ship recommissions. The above photo shows USNS Corpus Christi Bay’s INSURV team comparing FAMF specifications with the stack of shipyard work receipts. The ship passed its INSURV.)
(USNS Corpus Christi Bay passes under US Highway 181 during sea trials after the conversion.)
During the post-conversion sea trials, it was found that the ship was excessively topheavy. This is not hard to believe, just by looking at the huge new aft section which was high above the centre-of-gravity. Several tons of concrete ballast were poured into the bilges to rectify this.
(Pleasure boats pass USNS Corpus Christi Bay in its namesake body of water. The ship visited Texas to onload spare helicopter parts prior to sailing for Vietnam.)
(At sea during the post-conversion workup.)
the Vietnam War
USNS Corpus Christi Bay departed for South Vietnam in 1966. Aboard were 308 US Army soldiers of the 1st Transportation Battalion – Aircraft Maintenance (Seaborne).
The initial Army contingent was almost all volunteers specifically for this mission, and over a third were career soldiers with at least 10 years in uniform already. Some were sent to a special high-intensity training program at Ft. Benning, GA while the ship was conducting sea trials.
Per legislation at that time, as a MSC ship USNS Corpus Christi Bay itself mounted no weapons but the US Army contingent aboard was not restricted by this and had M14 rifles and M1911 sidearms.
The ship was also fitted for carriage of one “J-boat”, one of a US Army series of motorboats varying in details. During the Vietnam War they were used as inport patrol boats. For USNS Corpus Christ Bay, the ship was usually anchored far enough offshore in Vietnam that Viet Cong swimmers were not really a concern and the J-boat was infrequently used in its intended role.
(The J-boat is visible here alongside the starboard crane by the small freight elevator. The huge hatch on the flight deck is also visible. This photo also shows the big periodic log HF radio antenna from above.)
USNS Corpus Christi Bay arrived at Cam Ranh Bay on 2 April 1966. The ship was nominally under the 34th Aviation Support Group at Tan Son Nhut AFB but was basically its own thing.
(USNS Corpus Christi Bay in Cam Ranh Bay in 1966.)
Contrary to what one might imagine, the least desirable repair route was flying whole helicopters onto the ship. Instead it was preferable to extract components or sub-components at bases ashore, and then transport them aboard. The most expeditious method was using helicopter shuttles; but more common was to bring them out by an amtruc (wheeled 15-ton amphibious truck) or a “mike boat” (converted WWII landing craft). Often a spacing barge was tied alongside USNS Corpus Christi Bay, to which the amtruc or boat moored so the crane operator had better visibility.
(CH-47 Chinook delivering helicopter components needing repair.)
(Taken during 1966, this photo shows a UH-1 Iroquois of the 101st Airborne unloading items needing repair. The stand-up forklift could make tighter turns aboard ship than a 4-wheeled forklift.)
(USNS Corpus Christi Bay with a barge moored alongside.)
The ship did occasionally tie up in South Vietnamese ports, but this was done sparingly. It did expose the ship to increased danger, while offering no real benefit to bringing things aboard.
(USNS Corpus Christi Bay pierside at Ða Nang with a Huey leaving the “admin pad”.)
About a dozen of the US Army contingent were “sand crabs” assigned and barracked ashore. Especially at Vung Tao, this was useful for pre-staging helicopter components to be repaired so they were sent to the ship in the most beneficial order. The US Army installed a AN/TRC-24 system aboard USNS Corpus Christi Bay while it was in-country. This allowed the ship a short-range 12-channel FM voice link with US Army bases ashore.
(Aviation components being serviced aboard USNS Corpus Christi Bay.)
The skill level and creativity aboard were so great that USNS Corpus Christi Bay branched out from repairs and developed and manufactured “on the spot” flash suppressors for machine guns aboard US Army helicopters, and a type of skid shoe for OH-6 Osage helicopters.
In late 1969, the US Army detachment aboard was stunned to receive an order from the Army Audit Agency recalling USNS Corpus Christi Bay to the United States. The vague reasoning was that during the 1967 fiscal year, the ship had supposedly failed to attain a Pentagon “goalpost” of parts repaired. The ship remained in use in South Vietnam while the recall was vehemently appealed against. It was eventually rescinded. Even today it is difficult to imagine what the AAA was possibly thinking wanting to pull such a valuable asset out of the war.
Despite some problems (for example the air conditioning system was never great to begin with and eventually failed altogether) USNS Corpus Christi Bay continued to excel at its mission. Productivity peaked in late 1969 and early 1970, when USNS Corpus Christi Bay repaired, on average, about $3.76 million worth of helicopter parts every month.
(USNS Corpus Christi Bay off of Vung Tau.)
Although the ship’s work never slowed, President Nixon’s efforts to shift more of the war’s burden onto South Vietnam coincided with a change in the nature of US Army helicopter repair needs. American helicopters obviously still needed upkeep, but by 1971 battle-damaged helicopters were declining – this being, they seemed to either be shot down completely or took damage which could be repaired at local forward bases. For example by the end of the year, there was actually a slight surplus of entire Lycoming T53 engines ashore in South Vietnam. Hueys with a broken-down or damaged engine just had the whole thing swapped out instead of a part repaired.
In 1972, the US Army decided that the ship’s mission was at its end. USNS Corpus Christi Bay departed South Vietnam having spent over 6½ years in theatre. On 19 December 1972, USNS Corpus Christi Bay moored at Corpus Christi, TX.
There is a ton more to that article to make sure to go check out the rest. The whole website is a treasure trove of interesting articles of what happened to all the equipment after the war