by LtCol John Van Nortwick USMC
The unique experience of the 1974 CMC Aviation Efficiency Trophy Winner, HMH-463, during Operation Endsweep, are recalled by the squadron's former CO LtCol John Van Nortwick. Marine helicopters implemented the Navy-developed Airborne Mine Countermeasures program in Haiphong Harbor. A former enlisted man, LtCol Van Nortwick received his wings in 1956. He holds a master's degree from the University of Southern California.
The following article, which was featured in the May 1974 issue of Marine Corps Gazette, is reprinted with permission of the Author LtCol John Van Nortwick.
by LtCol John Van Nortwick
The Marine Corps implements a Navy-developed
countermeasures technique to clear enemy harbors
of mines - using the heavy helicopter.
|The Navy Sea Mine has been
successfully used many times
since the Civil War to control
strategic sea areas. In October
1952, the landing of the First
Marine Division in Wonson,
North Korea, was delayed for
six days by 3,000 mines laid by
a technically unsophisticated
force in sampans and small
The mining of North Vietnamese
My personal observation of the apparent importance to the North Vietnamese of subsequent U.S. mine clearing operations only reinforces the strategic importance of the sea mine.
Soviet, Soviet Bloc, and Chinese Communist Navies all maintain an active minelaying capability. The Soviet Navy has over 100 ships of various classes with this capability. Bloc nations such as Egypt, Cuba, and North Vietnam also maintain a similar capability with Soviet assistance. The Chinese Communist Navy is self-sufficient in this area with the ability to deploy minelaying destroyers and corvettes to Western Pacific areas of strategic importance quickly.
To counter this threat the Navy has developed the Airborne Mine Countermeasures (AMCM) program which transfers the surface mine clearance or countermeasures operation to an airborne platform, specifically the helicopter. The helicopter tows various devices thru the water of a minefield. These devices un turn cause the magnetic influenced mine and the acoustic mine to detonate in place. In the case of the moored contact mine, the device cuts it from its anchor allowing the mine to rise to the surface where it is detonated by small arms fire. A detailed discussion is found in the inner portion of this article. Concurrent with the development of the mine countermeasures helicopter has been the attainment of a world-wide quick reaction capability. RH-53D or CH-53D helicopters, AMCM tow systems, and support personnel can be rapidly airlifted by C-5A to specific strategic areas considerably faster than previous surface mine warfare forces could deploy.
The concept of using helicopters for Airborne Mine Countermeasures originated during the Korean conflict when Navy helicopters were used to spot mines. As a result, the Bureau of Aeronautics undertook the exploration of the tow capability inherent in rotary wing aircraft. The earliest feasibility studies and tests, conducted with the HRP-1 helicopter in the early 1950's, concluded that a suitable configured helicopter could perform well as a towing vehicle and that AMCM was a feasible concept.
The promise shown by these early successes led to the establishment of the U.S. Naval Air Mine Defense Development Unit (NANDDU) with a mission to assist the Bureau of Aeronautics in the development and evaluation of airborne equipment and tactics for all aspects of AMCM. The functions of this unit were later assumed by the U.S. Naval Coastal Systems Laboratory.
After further studies, tests, and demonstrations, the SH-3A helicopter, modified to an AMCM configuration (RH-3A), was approved for service use as the first operational minesweeping helicopter. RH-3A helicopters assigned to the fleet in 1965 were capable of operating from two dedicated AMCM support ships. As new minesweeping equipment was developed, the performance limitations of the RH-3A were exceeded and the RH-53D and the CH-53D were selected as replacement helicopters for the primary and emergency minesweeping missions.
The development of an airborne acoustic and magnetic minesweeping capability so enhanced the AMCM concept that in 1970 the Chief of Naval Operations directed action to affect a transition from a surface dominated MCM force to one principally utilizing AMCM helicopter units operating from suitable support platforms.
In April 1971, a helicopter squadron, Helicopter Mine Countermeasures Squadron Twelve (HM-12), was commissioned at Norfolk, Virginia, and tasked with a primary mission of worldwide AMCM. The squadron functions under the operational control of Commander, Mine Warfare Force, Charleston, South Carolina. Initially, HM-12 was equipped with CH-53A's on loan from the Marine Corps. The helicopters were brought up to CH-53D specifications by Sikorsky Aircraft Corporation prior to commencing AMCM operations. The squadron is now equipped with the RH-53D, the primary minesweeping helicopter.
In the later part of 1972 it became apparent that the Vietnam War would end and that the clearance of U.S. - laid mines from North Vietnamese waters would be required. Major elements of the Mine Warfare Force, including Mobile Mine Command (MOMCOM), Mine Warfare Support Group (MWFSG), and HM-12 were airlifted by C-5A to NAS, Cubi Point, Republic of the Philippines. These Navy mine warfare experts formed the nucleus of Task Force 78, under the command of RAdm Brian McCauley, for this unique operation to be known as OPERATION ENDSWEEP.
As the scope of the operation was realized, the need for additional helicopter assets became apparent. Responding to the Navy request for assistance, CG FMFPAC directed that HMH-463 deploy from MCAS Kaneohe Bay, Hawaii, to NAS, Cubi Point, to join Task Force 78. On 27 November, 1972, with the efficient support of Col Bill Crocker's MAG-24, the pineapple people of 463 embarked at Pearl Harbor aboard USS Inchon (LPH-12), which was en route from Norfolk to augment Seventh Fleet Amphibious Forces and to participate in ENDSWEEP.
After a crossing highlighted by shipboard qualifications for all pilots HMH-463 arrived at Cubi on 9 December 1972. Representatives from MAG-36, 1st MAW and TF 78 met the squadron and assisted in preparing for the unique mission.
The remainder of December and the first three weeks of January 1973 were spent awaiting direction from higher authority while the Paris Peace Talks continued. However, on 15 January 1973, activity picked up when HMH-463 was directed to modify all squadron aircraft to the AMCM role. On 26 January 1973, authority to commence actual AMCM training was received, and the squadron, with assistance from HM-12, developed and carried out a training program for its own crews as well as the CH-53D crews from two composite squadrons, HMM-154 and HMM-165, of Col Bill Maloney's MAG-35. In the short period between 26 January and 14 February, approximately 50 pilots and 50 crewmen each received at least three magnetic pipe training flights. During this period, HMH-463 formed an AMCM detachment of three CH-53D's, eight pilots, and thirty-six maintenance personnel. It embarked on the TF 78 flagship, USS New Orleans (LPH-11) in support of HM-12. This detachment participated in a mine exercise in Subic Bay until 13 February, when due to a change in task organization, they cross-decked to USS Cleveland (LPD-7) to form AMCM unit Delta where they were operationally controlled by Cdr Mel Ronzo of the MOMCOM staff. Three CH-53D's of HMM-165 were then placed in support of HM-12. Simultaneously, the remainder of HMH-463 reembarked upon their old friend, USS Inchon, commanded by Capt. J.K. Thomas. The squadron, with six CH-53D's formed AMCM unit Charlie under the direction of Cdr Dan Powell of MOMCOM. The remaining three embarked CH-53D's were dedicated to the support of Detachment Delta aboard Cleveland. Joining the squadron at this time was a detachment of six CH-46D's and two UH-1E's of HMM-164 to provide utility and rescue functions.
AMCM units Charlie and Delta conducted a successful minex in Subic Bay 16-23 February to polish their newly learned AMCM skills, and sailed on 26 February aboard Inchon and Cleveland to join TF 78 in Haiphong Harbor on 28 February. The task force was made up from a sizable portion of WestPac Navy assets, two LPH's, three LPD's, two DD's, two LST's, four MSO's, and numerous auxiliaries and support vessels. Marine aviation units, other than HMH-463, were HMM-165, commanded by LtCol Doc Egger and later, LtCol Bruce Colbert; and Detachment HMM-164, whose OiC's were Maj Bill Simmons and Maj Dave Amey. Additionally, many individual Marines were involved in public affairs, photography, and liaison. Senior Marine on the TF 78 staff was LtCol Carroll Redman, who was later relieved by LtCol Vic Lee.
Anxious to begin the operation after months of delay, both Marines and sailors were again to be disappointed. Political considerations at higher levels delayed commencement of AMCM operations until 12 March. However, the waiting period was well spent. The aircrews used the time to polish their instrument flying skills. This practice proved to be a real asset because of the marginal weather later encountered in the area of operations.
On 12 March, AMCM unit Delta (Detachment Delta, HMH-463) commenced magnetic and acoustic minesweeping operations in the Lach Huyen area of Haiphong Harbor. To keep one CH-53D sweeping in the minefield continuously from dawn until dusk, it was necessary to launch a half-dozen three-hour sorties per day. Generally, Detachment Delta, under its able OIC, Capt Ron Rensch, flew three or four of these sorties, the remainder were flown by HMH-463 crews from Inchon.
A typical minesweep sortie began with the towing of the magnetic pipe from the LPD to the minefield under radar control, approximately a 30-minute evolution. At this time, radar coverage from the LPD was lost and the actual two-hour sweep was conducted by pilot judgment utilizing previously prepared charts. A 30-minute return to the LPD followed. If operational planning was correct and no mechanical difficulties were encountered, an incoming relief helicopter passed the outgoing one at the minefield boundary. Five days after the initial start in Haiphong Harbor the squadron was totally committed when authorization to commence sweeping the channel to the Port of Hon Gai was received. The managerial talents of HMH-463's operations officer, Maj Bruce Shapiro, and aircraft maintenance officer, Capt Ernie Noll, were taxed to meet each day's schedule. While still providing two or three sorties a day in support of Detachment Delta, now located about twelve miles away, the squadron launched several three-hour sorties into the Hon Gai minefield utilizing an entirely different procedure. It involved externally lifting the magnetic pipe and acoustic device from the number seven spot of the LPH flight deck, carrying it some ten miles to the minefield vicinity, hovering and streaming the pipe and device in the water behind the helicopter. This operation took about fifteen minutes and was followed by a two and one-half hour sweep in the minefield and then a reversal of the entry procedure followed by a return flight to the ship. Control in this field was accomplished by radar using TACRON controllers on board a mine sweeper near the field.
During this period, HMH-463 was flying over 200 per cent of CNO utilization on a daily basis. This sustained high performance was achieved thru the efforts of such professionals as Capt Don Dugan, squadron maintenance control officer, and CWO-2 Don Cavinder, squadron material officer, the many fine Marines under them, and particularly, the CH-53D crew chiefs and first mechanics.
It is important to note that the CH-46D's and UH-1E's of HMM-165 and Detachment HMM-164 were providing valuable admin and utility support to the task force, including daily flights into the North Vietnamese airfield at Cat Bi. HMM-165's three CH-53D's were also providing AMCM support to HM-12 and gained valuable experience with the MARK 105 Seaborne Equipment Platform. The updated CH-53A's of HM-12 were conducting MARK 105 AMCM operations from two LPD's located in other parts of Haiphong Harbor.
On 26 March, the Lach Huyen field was completed and the detachment's assignment was shifted across Haiphong Harbor to the vicinity of the Do Son Peninsula. Sweeping continued until 1 April when Inchon and Cleveland departed Haiphong for a routine upkeep period in Subic. While there, the squadron performed much needed heavy aircraft maintenance and even took a day or two off. Returning to Haiphong on 15 April and expecting to finish the job, HMH-463 was unhappily surprised when TF 78 sailed into the Tonkin Gulf and approximately a week later returned to Subic. Again, the Task Force was a victim of higher level political requirements. What followed was a two-month period of uncertainty while diplomatic maneuvering continued. Many changes took place within the Task Force. USS Tripoli (LPH-10) replaced New Orleans as flagship, Cleveland returned to Long Beach and was relieved by Dubuque (LPD-2), necessitating that Detachment Delta cross-deck to this latter ship. Personally, the most significant change was my relinquishing command of HMM-463 to Maj Bill Smith on 5 June. During this period, also, Capt Art Sifuentes took over a demanding and important assignment as OiC, Detachment Delta.
On 14 June, TF 78 was directed to resume operations. HMM-463, now embarked on Inchon and Ogden after yet another detachment cross-deck move, arrived in the Hoi Gai area on 20 June. It commenced operations to complete the Hoi Gai Channel and commenced a new field located further north near Cam Pha. A third minesweeping technique was used in this area. The triple magnetic pipe which consisted of three pipes towed in tandem and trailed some 2,700 feet behind the helicopter was utilized. In this case, the air-to-air transfer method was used to maintain one CH-53D sweeping at all times. The first sortie of the day towed the triple pipe in the field and at the end of three hours transferred the tow line to the relieving helicopter thru the use of a marker float and grappling hook procedure. This was continued throughout the sweep day and the triple pipe was returned to the ship by the last sortie.
HMH-463 completed the Hon Gai and Cam Pha fields on 26 June and proceeded to Vinh, the next assigned area. Sweeping in this area commenced on 28 June and was completed on 3 July. Inchon returned to Haiphong once more for an additional assignment until mid-July when it returned to Subic. At this time HMH-463 was directed to cross-deck to Ogden and Dubuque, for the return trip to Hawaii. This was accomplished in approximately twelve hours and on 21 July the main body of the squadron departed Subic for Hawaii. On 1 August 1973, the pineapple people of HMH-463 arrived at MCAS Kaneohe Bay, Hawaii, and on 2 August 1973, the Navy announced that Operation ENDSWEEP was officially over. The three helicopter squadrons involved, HMH-463, HMM-165 and the Navy's HM-12, towed mine clearance devices over 27,000 miles, more than the circumference if the earth, while logging over 2,000 hours of tow time. HMH-463 flew approximately half of these totals.
Summing it up, Operation ENDSWEEP was unique in many ways. Entirely new techniques were quickly and efficiently mastered. The CH-53D again proved its worth as it had in the past. Marine aircrews proved themselves capable of meeting new challenges. Finally, the frustrations of working in a sensitive political atmosphere were experienced. In total, Marine Aviation delivered when it was asked to.
The sea mine threat to amphibious operations is easily envisioned. To
combat this threat, the Navy has
converted from a surface mine countermeasures force to an airborne
one. However, it is entirely conceivable
that Marine Aviation will be requested
to assist in mine clearance operations in support of amphibious operations in the future. Therefore, it is important to look
at our capability. The Commandant has stated that the Marine Corps will
continue to provide emergency AMCM support during amphibious operations
when requested. However, no formal training program exists at this time and
the AMCM expertise gained by Marine Aviation during Operation ENDSWEEP
is rapidly being lost as time and transfers take their toll.
An analysis of the total AMCM system is required in order to determine future Marine Corps actions needed to maintain an emergency readiness capability. The AMCM system is made up of the following five subsystem.
The subsystems of trained personnel is divided into pilots and crewmembers, tow systems operators, support personnel, and command and control personnel.
HMH-463 pilots and crewmembers rapidly learned the fundamentals of AMCM. The average pilot was considered qualified after three flights of three-hour duration each, and the average crewman after five such flights. This initial success, however, should not be construed as an indicator of future training requirements for the following reasons:
The only AMCM training syllabus currently in use is presented in Charleston, South Carolina, and Norfolk, Virginia, by HM-12. The pilot AMCM syllabus consists of a five-day ground school at Charleston which covers airborne mine warfare familiarization and is followed by AMCM flight training in Norfolk, Virginia. This flight training consists of eight, three-hour training sorties. It introduces pilots to all AMCM modification kits and tow systems and the procedures involved in their use from both shore and ship. A shipboard minex occurs during this phase to familiarize pilots with shipboard procedures. The AMCM flight syllabus covers procedures for streaming, towing, and recovering the tow systems as well as for air to air, air to ship, and ship to air transfers of the systems. It also covers emergency procedures.
The crewmember AMCM syllabus consists of a two week ground school in Charleston which covers airborne mine warfare familiarization and aircrew procedures for AMCM tow systems. This is followed by AMCM flight training at Norfolk. This flight training consists of fifteen, three-hour AMCM training sorties. It introduces crewmembers to all AMCM modification kits and tow systems and the procedures involved in their use from both shore and ship.
Consideration should be given to maintaining a nucleus of AMCM trained pilots and crewmembers in HMH squadrons. It is acknowledged that this would have relatively low priority in view of other commitments, however, a minimum number of trained personnel could quickly qualify the remainder of an AMCM committed HMH squadron should the requirement arise.
Tow systems operators
The five AMCM tow systems require from one to four crewmen in addition to the helicopter crewchief in the aft cabin compartment depending upon which system is employed. Training requirements to deploy, operate, and recover these systems range from moderate for the magnetic pipe (MOP), to extensive for Mark 103 moored minesweeping system. Crew and training requirements are shown below:
At this time, no information is available which indicates whether Navy or marine tow systems operators will be utilized during future Marine supported AMCM operations.
In view of the complexity of the systems, and the emergency only role of the Marine CH-53D's, the employment of Navy tow systems operators is desirable in order to provide rapid response to future operational requirements.
Support personnel are those designated to provide technical assistance and to maintain AMCM tow systems and associated equipment. In view of the fact that this equipment is relatively complex and is in Navy custody until needed, personnel of the Mine Warfare Support Group (MWFSG) will provide the necessary support.
Command and control of all Operation ENDSWEEP helicopters was provided by Navy personnel from Mobile Mine Command and Tactical Control Squadron Eleven utilizing a variety of techniques. These techniques included:
At this time there is no way to predict the adjacent terrain characteristics or the peculiar features of any future minefield. However, any of the above methods or any combination of or variation on them may be utilized. It is important to understand that flexibility and ingenuity are valuable assets that future mine warfare planners will use.
Statistical minesweeping is a complex and time-consuming operation that must be meticulously planned by an experienced mine warfare staff and then conducted as precisely as is possible. For these reasons Marine units committed to minesweeping will be under the operational control of a Navy command with the necessary mine warfare planning expertise.
The RH-53D is the primary mine countermeasures helicopter. However, all Marine CH-53D's now have the required airframe changes to accept AMCM modification kits and AMCM tow systems. The modification of CH-53D helicopters during Operation ENDSWEEP proceeded smoothly and presented no problems.
The helicopter modification kits are of two basic types-the tow kit and the streaming winch kit. The tow kit contains the necessary parts, assemblies, and components to accomplish two of the six tow missions. The helicopter equipped only with the tow kit is utilized for Mark 105/106 and triple pipe operations. The tow kit includes provisions for an amber/red selection of the underside rotating beacon required by NATO agreement for tow helicopters; automatic flight control system interconnections to provide automatic cable yaw angle retention, and aircraft attitude and heading hold, and adjustable rear view mirrors with controls for both the pilot and copilot. A combination tensiometer, cable yaw angle indicator with an adjustable automatic cable release is also provided. The instrument features an adjustable high and low limit warning light. The tow boom transmits the tow load to the airframe through the range of zero to 20,000 pounds and can be extended to permit rotation of the bellmouth, release of the hook retention maws, and lowering of the hook using the cargo winch cable. The tow hook is provided with pilot controlled electrical release and crew operated manual release systems as well as an adjustable automatic release. Guillotines, which are pilot actuated, accomplish emergency release in the event of hydro-electrical system malfunctions. A dam is provided to restrict water entry into the cabin in the event of a water landing prior to closing the lower ramp. Guide rollers attached to the end of the lower ramp and upper ramp door hinge area protect the airframe and tail rotor from inadvertent damage from cables.
The streaming winch kit contains a twin winch installation with each winch separately controlled by a crewman.
The helicopter equipped with both the tow kit and the streaming winch kit is utilized for Mark 103/104, and single magnetic pipe operations. An emergency shut-off capability is provided for both winches by a single control switch on either winch. The winches are hydraulically powered by the aircraft utility hydraulic system. In addition, streaming rollers are provided to restrict cables within the aircraft, protecting the area so that crewmen can carry out their duties.
There are five AMCM tow systems. They are the Mark 103 moored minesweeping system, the Mark 104 acoustic minesweeping system, the Mark 105 influence minesweeping system, the Mark 106 influence/acoustic minesweeping system, and the AMCM magnetic pipe in various combinations and configurations.
MK-103 Mechanical Minesweeping System
The Mark 103 moored minesweeping system contains a complete right hand and left hand sweep system. Racks are installed on both sides of the aircraft providing stowage of the sweep gear, including cutters.
The equipment consists of a depressor, otters or paravanes, and floats, all interconnected with cable. These cables are the tow cable, sweep wire, and float pendants. Cartridge-actuated cutters are spaced along the sweep wire. There are ten cutters per sweep wire leg, and four legs making a total of 40 cutters. The Mark 103 can be used in several assembly variations. For instance, Assembly 01 is the entire sweep, that is, all four legs. Assembly 03 may be half a set with both legs on one side. These are all tactically useful configurations that can be used as the operational situation dictates.
The Mark 104 acoustic minesweeping system consists vehicle and the necessary
cradles for inflight stowage. A davit is used to lift the vehicle in
and out of the cradle. Polypropylene tow cable on storage drums is
used with the streaming winch to deploy the Mark 104 acoustic system.
The Mark 104 acoustic minesweeping system consists of vehicle and the necessary cradles for inflight stowage. A davit is used to lift the vehicle in and out of the cradle. Polypropylene tow cable on storage drums is used with the streaming winch to deploy the Mark 104 acoustic system.
The major components of the Mark 105 influence minesweeping system is the seaborne equipment platform. The equipment platform consists of the floats which provide the basic structure for the hydrofoil elements, the buoyancy, and the fuel containers; the power pack which is a small gas turbine engine; the wing, which supports the power pack; connects the floats, and supports the sweep boom; the lifting or retrieval rig; and the foils. The foils contain upper and lower foils in the front. The lower foil and the aft foils are sub-cavitating foils. The upper foils are super-cavitating and are used primarily in rough seas. The sweep boom is the support for the tail and electrodes. The platform is towed by the helicopter in the basic tow configuration.
When the Mark 104 acoustic device is attached to the Mark 105 magnetic minesweeping device the combination is referred to as the Mark 106.
AMCM magnetic pipe
This device is a 30-foot pipe, weighing 1,000 pounds, having a 10 3/4-inch diameter filled with polystyrene foam. The pipe has a plate at each end to make the device watertight and may be towed from either end. The pipe is given a magnetic charge prior to each sweep mission.
Three magnetic pipe combinations exist. They are:
All CH-53D AMCM tow system combinations may be operated from either LPH or LPD shipping or from a shore base with one exception. The triple pipe must be towed either from the stern gate of an LPD or from a shore base. The LPD is the preferred platform from which to support AMCM operations. However, its utilization in this role severely hampers its ability to support simultaneous amphibious operations. The reasons for this are:
Although the LPD is generally preferable, alternate utilization of the LPH as a support platform for all but the triple pipe will free LPD's to provide amphibious support.
This review of AMCM would not be complete without addresal of of the areas of logistics, vulnerability and operational planning.
The concept of logistics support to AMCM units is unchanged from that to any other unit with one exception. AMCM equipment, both CH-53D modification kits and AMCM tow systems, occupies considerable space on board amphibious shipping. Planning and coordination must be made early with ship's personnel to insure sufficient space is made available, particularly if other aviation units or ground units are embarked.
Vietnam taught us that the low-flying, slow-moving helicopter is extremely vulnerable to enemy action. AMCM helicopters operate at 125 to 150 feet at speeds below 20 knots. They possess no defense capability other than two .50 caliber machine guns and are incapable of maneuver to escape destruction. Therefore, it is paramount to plan early for the provision of adequate means to insure their survivability. These means include:
Operational planning for AMCM operations is detailed and must begin as early as is possible. Mine warfare force personnel must be co-located with the HMH as soon as possible to mesh all the components of the AMCM system into a cohesive and coordinated AMCM unit. Continuous coordination with higher, adjacent, and supporting commands is maintained to provide efficient and effective AMCM planning, preparation, and training.
This review has shown that the majority of the assets required to conduct successful emergency AMCM operations in the future are available on a routine basis within the Marine Corps and Navy. The only critical shortcoming is lack of AMCM trained Marine pilots and crewmembers. This deficiency can be overcome through the utilization of existing training programs and facilities.
Last revised on 25 December, 1999 © Airborne Mine Countermeasures Association, Virginia Beach, Virginia. Webmaster - Barry Marple Virginia Beach, VA. Domain name property of Barry Marple. All rights reserved.