A brief history of the US Navy's first hovercraft, or air cushion vehicle, unit conducting combat operations in South Vietnam during 1966.
The following is an account of my personal association with the first US Navy hovercraft unit.
In 1965, I was a pilot flying seaplanes in Patrol Squadron Forty out of Sangley Point in the Philippines. As the war in Viet Nam was starting to escalate, our squadron was assigned to fly patrols along the coast to help locate boats and ships which were known to be smuggling arms and equipment into South Viet Nam for use by the Viet Cong. Originally, we flew our patrols out of Sangley Point which gave us very little time on station. To improve this situation, we established a seadrome off the southern tip of South Viet Nam near the island of Ko Samui. From there, we were able to make a serious contribution.
During these seaplane operations, I became aware of an ALLNAV message requesting LT(jg) volunteers for a one year tour of duty in Viet Nam as officers-in-charge of coastal patrol boats (SWIFT boats.) About that same time, our squadron was due to return to the states. It was my false assumption that this war was going to end before I would again have a chance to participate in it. As a result, I asked my command to endorse my request to volunteer for SWIFT boats, which they did. Shortly after our squadron's return to San Diego, I received orders to report to SWIFT boat training at the Amphibious Base in Coronado, California. To my surprise, of the original 120 or so officer volunteers, I was the only one with an aviator designator.
At some point during the training cycle at the Amphibious Base, I became aware of some very strange looking craft at the base. Other than being naturally curious, I paid them very little mind as I was intent on becoming a small boat skipper. About the same time that I was completing this training, however, I was approached by the commander of what turned out to be this "hovercraft" unit which was simultaneously training its own crews. I was invited to lunch at the officers club where the offer to transfer from SWIFT boats to PACV's (Patrol Air Cushion Vehicles), hovercraft, was made. It was explained that one of the five officers originally trained by Bell Aerosystems in Buffalo, NY had unexpectedly been transferred out of the unit. This individual needed to be replaced but there was no time to send someone back to Bell for training. It was felt that with my experience as a seaplane pilot, I could probably learn to pilot a PACV right there at the Amphibious Base. After being given a tour of the craft and a short ride, I accepted their offer.
AT THE CONTROLS
As it turned out, my aviation experience proved very beneficial but not really necessary to operate one of these craft. I guess it had always been a matter of contention as to whether the craft should be operated and maintained by aviation or surface personnel. The aviation proponents noted that the craft had many aviation similarities: it was propelled by a jet engine; it had rudders and elevators much like those on aircraft; it had a fully-reversible, variable-pitch propeller of aircraft design; there was a "joy-stick", a helicopter-style collective and a rudder pedal set of controls; and it was constructed of aviation-grade aluminum. The surface proponents countered, however, that the craft never really got airborne. The surface community won the argument (and thereby saved the Navy a lot of money.)
Maneuvering the craft was not easy and has been compared to driving a car on a sheet of ice. But it was very forgiving. When all else failed, you just cut the throttle and the craft would settle gently down on the surface as the cushion deflated, even if you had a lot of headway (or sideway, for that matter) at the time. The controls were fairly straightforward. You had a "joystick" between your knees that operated four hydraulic jacks which raised and lowered the rubber skirt thereby tilting the craft in any particular direction. There was a "collective" which you operated with the other hand to control an engine throttle and the pitch of the propeller. You also had foot-operated rudder pedals which provided good directional control at higher speeds. The elevators could be set to control the nose attitude of the craft but were also only effective at higher speeds.
To get the craft moving, you would twist the throttle to increase the engine rpm. The engine controlled the propeller which provided fore and aft thrust. It also controlled a large squirrel-cage fan which provided the lift and filled the cushion with air. The amount of thrust provided by the propeller and the amount of air in the cushion were fully controllable by the operator through the collective. When there was adequate air in the cushion, the craft rose to a maximum of about 4 feet. The bottom of the skirt, however, was always in contact with the surface at least at some point around the craft. At some optimum point between resting on the surface and being fully inflated, forward pitch would be applied to the propeller through the collective and the craft would start its forward movement. At slow speeds, the craft was turned by operating the joystick to raise the skirt on a particular side thereby causing the craft to tilt in that direction. All of the surface friction was now on this tilted side while the opposite side would be clear of the surface, thereby causing the craft to turn. At high speeds, the rudders would provide adequate directional control (with judicious use of the joystick.) Water spray or dust clouds generated by the lifting fan could be controlled by adjusting the fore and aft tilt of the craft with the joystick at slow speeds or the elevator controls at high speeds.
MANEUVERING OVER THE WATER
Under ideal wind and sea conditions, the craft was capable of speeds up to 60 knots (75 mph). When operating under these conditions, the craft was an absolute joy. It was very stable and there was little chance of nosing or plowing in. You had to plan your turns far in advance, but the rudders alone were all that was necessary. Walking or shifting about inside the cabin provided no notice. At these higher speeds, it was actually possible to safely spin the craft around so that it would be going in one direction while pointed in the other. Some operators (myself included) actually felt that this was the best way to bring the craft to a full stop from a high speed run in the shortest distance.
Strong winds and rough seas were a serious problem for the craft. If conditions were such that a reasonable speed could not be attained, then the rudders and elevators would become ineffective. At this point, skirt control might not be enough to counter the directional effects of the wind. Under these conditions, it was possible to loose directional control of the craft. The only recourse in this instance would be to deflate the cushion and request a tow or drift until conditions improved. It was for this reason that we avoided open sea operations and maneuvered primarily along the coast, in bays or on rivers.
Another hazard that we had to avoid, particularly at high speeds, was objects protruding from the water. In Viet Nam, this mostly took the presence of fish traps but tree stumps were also in abundance. Fortunately, we were equipped with a magnificent radar that could pick up these obstacles with plenty of room to maneuver safely around them.
Though it eventually did happen (years later when the craft were being operated by the Coast Guard), it would not be easy to sink a PACV. The entire bottom surface of the solid structure of the craft was honeycombed with compartments each filled with a buoyant material. If roughly half of these were destroyed, there would still be enough buoyancy to keep the craft afloat. The rubber skirt material was also very durable and sustained minimal damage during our deployment.
MANEUVERING OVER TERRAIN
Sustained operations over dry land were not recommended due to the damage that was done to the bottom of the skirt. Also, the dust and dirt that was blown up was more damaging to the craft and the engine than salt spray. This, however, did not mean that we couldn't operate over land.
The craft could maintain a constant speed on a maximum grade of about 1:10. Anything in excess of that and the craft would eventually run out of speed and stop. The craft, if maneuvered properly, could also cross an open ditch of no more than 8-10 feet wide or "bounce" up and over a vertical obstacle no more than about 3.5 feet high. The air pressure inside the cushion was a maximum of only about 4 psi and the cushion, when fully inflated, was very soft and spongy. For this reason, the rubber skirts were not easily damaged.
SOME OF OUR EXPERIENCES
Our deployment to Viet Nam was billed as an "operational test and evaluation." This meant that they weren't really sure what we would be good for, but they planned to find out. Initially, our operations were very tentative and planned to minimize risk. As time went on, however, less and less concern was given to our survivability and there was more emphasis placed on mission capability.
Our original missions mirrored those of the SWIFT boats, except that we stayed out of the rivers and only patrolled the coastline within cruising range of our home base at Cat Lo. We conducted day and night patrols, usually alone. We would cruise a mile or so off shore looking for suspicious activity on radar or with visual lookout. Sometimes we would shut the engine down and drift, operating the radar with power generated from a fairly quiet auxiliary power unit. We had no difficulty swooping in on a contact and going alongside for inspections. We did this sort of thing for a couple of months but never did find anything of military significance. This was probably due to the fact that the ocean waters off Vung Tau were filled mostly with friendly fishermen and not much else.
The next mission they thought our craft might be good for was search and rescue. Our quick response and high speed approach made us seem most suitable. Also, once on scene for a pick up, we were not limited to how long we could stay on station, unlike a helicopter. Without relocating us, however, there just wasn't enough activity in our geographical area for us to justify this kind of mission.
The military planners definitely wanted to see more of us, however, so it was decided that we would start patrolling the rivers. This is when things started to get exciting. We patrolled mainly at night and, as usual, alone. Initially, we patrolled the rivers in and around Cat Lo, but, again due to limited enemy contact, we were sent further and further out. Eventually, we wound up patrolling up and down the rivers all across the mouth of the Mekong Delta. There was still some hesitancy on the part of the planners, however, and to help ensure our survivability, we never went to the same place twice. One of the interesting things that we learned about our river patrols was that the sound our craft made could be heard from a long way off, but the sound would echo up and down the river banks and it was impossible to tell the direction the sound was coming from. Apparently, this terrified the Vietnamese, friend and foe alike.
Having survived several months of night river patrols, the planners wanted to put us to a real test before the end of our evaluation period, but they had one other mission possibility to try out before that. I found this next concept to be the most intriguing. It involved deploying all three craft in the well-deck of the USS Tortuga, an LSD. The ship was then positioned several miles off the coast near the mouths of rivers. Then at night, as usual, we would launch one or two of the PACV's from the well-deck which would then proceed toward the coast and take up a position from which to conduct surveillance. Upon completion of the patrol, the craft would return and dock inside the LSD. We only did this for a couple of weeks, just to prove that the concept was feasible.
The plans were now set in motion for our final mission deployment which would certainly test the true functionality of hovercraft in a combat environment. All three craft departed Cat Lo and proceeded on a journey of over 150 miles up the My Tho river through the heart of the Mekong Delta and deep into the Plain of Reeds to a place called Moc Hoa, just a few miles from the Parrot's Beak in Cambodia. There, we joined a combined operation which included the US Army Special Forces advisors, Vietnamese troops and Army and Navy helicopters. The goal was to enter a geographical area in Viet Nam that had not seen our forces as yet to any extent, but was known to be a haven for the VC. We hoped to catch them by surprise and capture as many as possible as they tried to escape. The actual operation lasted only about a week, but the total deployment was closer to three weeks. During that time, the craft proved that they could go over a combination of places that no other vehicle of any other type could. We went through rice paddies, over dikes, across canals, deep into tree lines, through tall grass, and across fields. Boats have to have water, trucks need land, helicopters can't go into the trees...the PACV could do it all. Plus, we had ample firepower, with a twin 50 caliber turret-mounted machine gun, and two side-mounted M-60 machine guns. In addition, we could mount a full 12-man Vietnamese rifle squad on the outside ramp of each craft.
This last mission was a great success and it was felt that the craft could now return to the US having met it's full objective. Not only did the Navy plan to refurbish and upgrade the craft, train new crews and re-deploy to Viet Nam, but the Army decided to build some craft of their own, based primarily on the lessons learned from our deployment.
There are three additional incidents which I recall which are of interest. On one night patrol out of Cat Lo, a PACV departed the base and proceeded down river. Not long after, two PBR's rounded a point in the river proceeding back to base upon completion of their own patrol. Circumstances were such that a collision ensued between the PACV and one of the PBR's. The PACV bounced up and over the PBR, ejecting one of the crew members out the open front hatch. It also destroyed the PBR in the process but did not significantly injure any of its crew. The PACV crewmember was also recovered without injury. All three craft made it back to base, but the PBR was unsalvageable. The PACV sustained significant damage to the front end of the aluminum structure and also damage to the skirt. Repairs were made with the technical assistance of a civilian aviation structural mechanic that was loaned to us from another command and the craft was back in operation within a few weeks.
Another incident occurred during the Moc Hoa operation. At one point, as the three craft were headed back to our base of operations, one of the craft suffered a rudder or elevator control failure (I can't remember exactly which.) We were close enough to camp to make it back in, but there was no way it could make it back to Cat Lo in this condition. That evening we discussed our options, which included a helevac or even scuttling the craft. The next morning, we were met by a smiling engineer crewmember who said he had fixed the problem. When asked how so, he showed us where he cut through the metal into the damaged control area, removed the broken control rod and replaced it with a broomstick handle that had been reinforced with a flattened sheet of coke can and wrapped with bailing wire. We were suspicious about the whole thing, but decided to give it a go. To this young sailor's great credit, the craft made it safely all the way back to Cat Lo.
The last incident occurred during one of those high wind and heavy seas conditions that we tried to avoid. Returning from a delta river patrol, the decision was made to go straight across the mouth of a large bay, rather than hug the coast, due to fuel considerations. Unfortunately, the weather turned bad as the craft was well out to sea. The decision to turn into calmer waters was not made soon enough and the craft was taking a real beating. At the worst of it, waves were coming over the bow and slamming onto the front wind screens. Finally, the wind screen in front of the operator gave way flooding the cabin with seawater and giving the crew cause to think that the craft might actually sink. Everything that wasn't nailed down was thrown overboard to lighten the weight as the craft crept in closer to the shore. Eventually, everything calmed down and the craft managed to make it back to base.
END OF THE LINE
As an aviator, I had requested this tour of duty with the surface Navy with one stipulation. As stated in my official request, I did not wish to leave the aviation community and would only volunteer if I could be assured that I would receive an aviation assignment upon completion. True to their word, I was in receipt of orders to the Aviation Training Command as a flight instructor even before we departed Viet Nam. Things changed, however, after we arrived back at the Amphibious Base in Coronado. All of the other PACV OIC's were reserve officers who had reached the end of their service obligation and intended to leave active duty. I, on the other hand, was regular Navy and wasn't going anywhere except, I had hoped, to the Training Command. As a result, my orders were canceled and I was told I would be remaining with the PACV's while they were being retrofitted and new crews were being trained. I knew that if I allowed this to happen, my aviation career was as good as over. After meeting with the Admiral himself and convincing him that I really did need to get back into aviation, he saw to it that my orders were reinstated. I departed Coronado shortly thereafter, but I consider that little more than a year to be a highlight of my 28 year Naval career.
Mr. Adair My name is Scott T Adams Sr. and I build scale models as a hobbie. First let me thank you for your service to our country, second I am currently trying to gather any information on the PACVs as I want to build a scale of one to go with my PIBBER that i finnished last year. Any web sites or pictures you could recomend I need help with the interior as I can't find anything. If you could email me I would really appreciate it my address is scott362@bellsouth.net
ReplyDeleteThank You
Scott
My step Father Dennis Robbins served on one of these in Vietnam. I think it was from 66-67. I was looking around trying to find pictures of PACV crew. Do you have any references or know where i could find some? Thank you, and thank you again for your service on this veterans day.
ReplyDeleteRobert Kleppen (remove the word "remove" from my email address)
removerkleppen@hotmail.com