Don't Forget the Sea Dragons

By Frank Colucci

The U.S. Navy regards helicopters and surface mine countermeasures ships as complementary. Helicopters operate safely above minefields and sweep shallow coastal waters better than ships, which have the electrical and towing power to sweep deeper. Helicopters can reach trouble spots rapidly and sweep faster, while ships can stay on station for weeks at a time and sweep day and night. Standard operating procedure during Operations Desert Shield and Desert Storm used helicopters to sweep ahead of the surface minesweepers.

HM-14 operated six MH-53Es in the Persian Gulf from October 1990 to July 1991; HM-15 flew logistics missions. The minesweeping helicopters cleared 768 square miles of sea lanes-nearly 8,000 linear miles-with 93% effectiveness against moored mines. They cut loose 30 moored mines with mechanical sweep gear, located 7 bottom mines with sonar, and detonated 2 influence mines with magnetic sweep sleds.

Many of the Iraqi mines deployed in the Gulf were armed improperly, so the small number detonated by magnetic and acoustic influence sweeps understates the threat. The severe damage done by a contact mine to the USS Tripoli (LPH-10) and by influence mines to the USS Princeton (CG-59) when the ships strayed from swept lanes illustrates the problem. During Desert Storm, the mine threat restricted the movement of Coalition forces off Kuwait and deterred amphibious landings. Given today's refocus on littoral actions, AMCM will be even more important.

Unfortunately, dedicated AMCM does not come cheap. Operating costs of the three-engine, seven-bladed MH-53E Sea Dragon approach those of the F/A-18. Each mine countermeasures squadron has about 700 active-duty and reserve personnel and devotes nearly all its flying hours to minesweeping training. The MH53E is the only U.S. Navy helicopter equipped for aerial refueling to self-deploy over long distances, but rapid deployment still requires strategic airlift. An Air Force C-5 can carry two MH-53Es, which can be at work anywhere in the world days after an order is given. Airlifted MH-53Es can operate from shore bases, the newly refurbished mine countermeasures support ship USS Inchon (MCS-12), or amphibious warfare ships. (See "The New Inchon Goes to Sea," Proceedings, August 1996, pages 73-75.)

To cut costs and improve deployed force self-sufficiency, the Navy wants to put organic mine countermeasures capability on multipurpose ships and aircraft. The Magic Lantern laser mine detector, the rapid airborne mine clearing system (RAMICS), and other advanced systems may enable SH-2G, SH-60, and later CH-60 helicopters or an (H)V-22 tilt rotor to perform some AMCM missions in addition to their primary roles.

Studies are under way to determine aircraft and mission system requirements to provide the desired organic capability but only the big Sea Dragon has the size, power, and endurance to employ the full range of present and future mine countermeasures.

The MH-53E is cleared to fly at gross weights to 69,750 pounds with sustained tow tension up to 25,000 pounds; surge tow tension in high sea states can exceed 30,000 pounds. The Sea Dragons' enormous fuselage sponsons hold up to 21,000 pounds of fuel for 4.5 hours endurance while providing fuel to feed the generators on magnetic sweep sleds. Thanks to their fuel capacity, aerial refueling capabilities, and automatic flight control system (AFCS), MH-53Es were able to fly seven- to eight-hour AMCM missions during Desert Shield and Desert Storm.

The big helicopters tow different systems to counter contact, magnetic, or acoustic/seismic mines:

  • The Mark 103 mechanical cutter array, oldest of the AMCM systems, severs mooring cables to permit mines to surface, where they can be detonated by gunfire or disarmed by explosive ordnance disposal (EOD) divers. Arrays can be transferred from one MH-53E to another to continue sweeps uninterrupted.
  • The new ANN-37U-1 moored-mine clearing set, which sweeps much deeper than the Mark 103, functions in the same fashion.
  • The Mark 104 acoustic sweep device can trigger acoustic mines or seismic mines that are lying on the bottom.
  • The AN/ALQ-141 is a newer acoustic sweeper that incorporates electronic countermeasures to defeat modern threats. Its towed device and associated electronics have surveillance and sweep-to-detonate modes.
  • The Vietnam War-era Mark 105 magnetic minesweeping sled is being upgraded with a more reliable power plant, 350-kilowatt turbine generator, and improved electrodes to sweep deeper; it weighs more than 8,000 pounds. A noisemaker can be attached to the sled's long electrode create a Mark 106 magnetic acoustic sweep rig.
  • The AN/SPU-IW magnetic orange pipe (MOP) also can generate an acoustic signature. Several can be towed in trail to simulate a convoy for mines smart enough to let escorts pass before detonating.
  • The AN/AQS-14 minehunting sonar introduced in 1984 is now being upgraded to -14A standards with more reliable digital electronics and more user-friendly controls and displays.

Other AMCM systems are in development or in limited production:

  • The Magic Lantern airborne laser minehunting system gives the SH-2G LAMPS I helicopters of Naval Reserve squadron HSL-94 a contingency AMCM capability; the 900-pound system can be installed in MH-53Es. Future versions may be integrated into the SH-60.
  • The shallow water influence mine system (SWIMS) was first deployed last year by HM-14 in the Baltic during Exercise Blue Harrier. Unlike the Mk 105 sled, SWIMS is a self-contained magnetic sweeper deployed from the MH-53E on arrival. It promises faster transit to the suspected mine area and higher sweep speeds. Further demonstrations are planned this summer in the Mediterranean, and studies are under way to see if the system is compatible with the H-60.
  • The AN/AQS-20 advanced minehunting sonar now in advanced development promises to detect and classify mines with a single pass and works at greater depths than the AQS-14. The 900-pound system contains five sonars to scan large volumes of ocean quickly.
  • RAMICS fires a specially designed 20mm projectile to detonate surface or subsurface sea mines; it can use the Magic Lantern or other lasers to detect mines and aim the weapon. A 20-mm supercavitating round promises to be effective on mines 10-60 feet below the surface.
  • The airborne mine neutralization system (AMNS) also works with Magic Lantern or other minehunting sonars to reacquire designated mines and neutralize them with a homing torpedo-like device.

Despite these advances, helicopter minesweeping is still a mix of tactical finesse and brute force. The 70,000-pound MH-53E has the tow power to sweep in high sea states; a cabin big enough for palletized sonars, tow cable winches, and other AMCM equipment; a dedicated hydraulic system to drive the winches; and a rear ramp to deploy and recover AMCM systems. Magic Lantern, RAMICS, and other systems light enough and small enough for the 23,0W-pound H-60 are shallow-water countermeasures. SWIMS, for example, is designed to sweep magnetic mines down to 80 feet. Sweeping greater depths still requires a Mark 105 sled, an AN/N37U-1 moored mine clearing set, and the tow power of the MH-53E.

Even if smaller helicopters could tow the four-ton sled in calm seas, they would never be able to exploit its capabilities in high sea states. In addition, towing operations impose extraordinary flight loads on dynamic components. In the early days of RH-3A minesweeping operations, Sikorsky engineers calculated that each hour of AMCM towing was the equivalent of eight hours' normal flying; overhaul intervals had to be adjusted accordingly. The impact on component life and operating costs could be dramatic for helicopters that were not designed with towing operations in mind.

The MH-53E was designed to tow the enormous AN/ALQ-166 magnetic sweep sled. The sled was canceled, but the power margins and fuel designed in early gave the MH-53E the performance essential to AMCM. As a rough measure of AMCM tow power, the Sea Dragon is cleared for 25,000-pounds maximum sustained tow tension. For reference, the twin-engined RH-53D pulled 15,000 pounds; the early RH-3A struggled with 8,000 pounds. Sustained tow tension for the CH-60 is estimated to be 10,000 to 12,000 pounds.

The MH-53E's large cabin can accommodate winches, cutter arrays, sonar pallets, and the people to work on them. Cabin-crew requirements range from three people for the simple Mark 104 noisemaker to five for cutter, sonar, or sled. The MH53E also has a vertical drop rear ramp to deploy internal AMCM systems. Cutter arrays and noisemakers were once laboriously deployed from RH-3As via side doors, but repackaging today's AQS-14 sonar, the heavier AQS-20, and the AMNS to deploy easily from cabin side doors will be an engineering and budgetary challenge.

Operating a twin-engine helicopter loaded with fuel, tow gear, and aircrew over minefields also reintroduces an element of risk to airborne mine countermeasures. Yesterday's twin-engined AMCM-configured RH-3As and RH-53Ds, heavy with fuel and equipment-operating at low altitudes and relatively slow speeds-were in trouble if they lost an engine. With one engine out, the three-engine MH-53E with T64-GE419 engines can keep flying.

The MH-53E's power and range also give the Navy a valuable multimission support asset. Home-based at Sigonella, HC-4 supports the Sixth Fleet and maintains a permanent detachment in Bahrain for the Fifth Fleet. The squadron routinely deploys detachments on board amphibious assault ships. At 65,000 pounds, a typical operating weight, MH-53Es routinely carry 6,000-10,000 pounds of cargo and 10-30 passengers. Maximum external sling load is 25,000 pounds, but most cargo is carried internally. The squadron has recovered fixed-wing aircraft and helicopters using external slings. For vertical onboard delivery (VOD), the MH53E is the only fleet helicopter big enough to carry F-14, F/A-18, and S-3 engines internally. The cabin can accommodate helicopter main gearboxes, tow tractors, and carrier arresting-cable spools.

The Sea Dragon can carry 55 passengers; HC-4 has supported carrier turnovers, disaster relief, peacekeeping, and evacuation operations in Sierra Leone, Somalia, Turkey and Northern Iraq, and the Adriatic, routinely covering overwater legs in excess of 500 nautical miles One mission, for example, flew from Souda Bay, Crete, to a carrier anchored at the mouth of the Suez Canal. Aerial refueling was used during Operation Restore Hope in Somalia and to deploy from Hurghada, Egypt, to Incirlik, Turkey, for Operation Provide Comfort.

During Fiscal Year 1996, HC-4 carried more than 10,000 passengers, 1.7 million pounds of mail, and 4.9 million pounds of cargo. The squadron participated in ten operational exercises, provided presidential support in Europe, and transported the prime minister of Israel, along with high-ranking Israeli officials, to and from U.S. warships in the Mediterranean.

Capable as it is, the MH-53E can be upgraded. Even with three T64-GE-416A 4,380-shaft horsepower (SHP) engines, Sea Dragons on training missions must fly with reduced fuel loads to stay within safe two-engine operating weights. The 4,750-SHP -419 turboshaft has a 5,000SHP contingency rating to bring the aircraft home in an emergency, and fleet modifications are scheduled this year.

An assessment program is under way to define a service life extension program (SLEP), to take the airframe beyond its present 6,000-hour life to more than 10,000 flight hours. A parallel study of logistics engineering change proposals (LECPs) is identifying potential changes that can pay for themselves in five to seven years.

Some improvements already are in the works. Seal and gear improvements for the CH-53E and MH-53E main gearbox are already in the fleet. The aircraft's AFCS computer, which provides functions unique to the minesweeping mission, is based on 1970s' technology; a new computer for both Navy MH-53Es and Marine CH53Es promises dramatic improvements in reliability and significant savings in a common box used across the larger fleet.

Other near-term engineering change proposals include composite main rotor tip caps, better seals and coatings on primary control servos, and changes to main rotor dampers, the centerline cargo winch, and engine cowlings. A new tailrotor disconnect coupling and a bearing monitor system are in development.

Budget pressures canceled the navigation-communications system (NCS) upgrade in June, and with it near-term hopes for the new cockpit-important for AMCM effectiveness and lifecycle costs. The boiler-gauge cockpit of the Sea Dragon is a high-workload environment filled with maintenance-intensive electro-mechanical flight instruments and one-of-a-kind navigation gear incompatible with other forces. Minesweeping relies on precise navigation to clear well defined Q-routes or safe channels, and the squadrons long used Raydist or Hyperfix networks to define their sweep area from shore. The MH-53Es deployed to the Persian Gulf were equipped with AN/ARN-151(V) receivers for the Global Positioning System (GPS), which matched the Hyperfix grid accuracy in the Gulf while improving reliability and providing a common navigation reference for EOD divers and other forces.

The canceled NCS integrated new horizontal situation displays with a GPSbased navigation suite and powerful new mission-planning station. The partial glass cockpit would have displayed routes and given air crews and commanders a post-mission capability to review sweep tracks and determine the effectiveness of the minesweeping effort. It also would have given the Sea Dragon a badly needed 1553B data bus for further systems integration, and a night-vision environment. AMCM remains a daylight, visual flight rules operation, despite the MH53E's sophisticated AFCS. The Naval Coastal Systems Command is just beginning to explore night-tow capabilities and requirements.

With or without a cockpit upgrade, the MH-53E remains the only helicopter totally capable of the full range of airborne mine countermeasures. While organic AMCM can indeed improve the effectiveness of deployed task forces, the scope and complexity of the threat demands special expertise and the power to apply it.

Historically, minesweeping and heavy-lift helicopters are underused and underappreciated in peacetime. History, nevertheless, repeats itself, and U.S. naval forces faced with a real mine threat would do well to upgrade their most capable airborne minesweeping system.


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