The U.S. Navy is having a very difficult time maintaining its force of 30 MH-53E helicopters. This aircraft are the only ones that can tow a sled containing naval mine detecting gear. This sort of thing is called AMCM (Airborne Mine Countermeasures) and is considered essential in areas, like the Persian Gulf, where the enemy (Iran) might use a lot of naval mines that would have to be cleared quickly in wartime.
The MH-53E is an update of the original 1960s era CH-53 and entered service in the early 1980s. Fifty MH-53Es were built and they have been worked hard ever since. That’s why only 30 are left and few of them are fit to fly at any one time. Originally the navy planned to retire the MH-53Es in 2008, but replacements (lighter sleds that could be pulled by smaller and more modern helicopters) did not work out as expected. So retirement was pushed to 2012, then 2017 and currently the navy hopes to keep some MH-53Es operational into the 2020s.
Meanwhile the navy is trying to reduce the accident MH-53Es accident rate, which is three times that of the rest of the navy’s helicopters. In the last three decade 6.5 MM-53Es have been lost per 100,000 flight hours. New equipment has been installed in the MH-53Es along with refurbishment (including some rebuilding) and more flight and safety training for the crews. The main problem with the 31 ton MH-53E is that it regularly hauls a truck size ten ton sled through the water for hours while searching for mines. No other helicopter has to deal with that kind of stress.
Meanwhile efforts continue to develop lighter equipment for the mine hunting task. Some of these projects have had limited success. The AQS-24A mine-hunting system looks like a torpedo with extra fins and attachment. It is lowered into the water and dragged by the helicopter at speeds of up to 34 kilometers an hour. The AQS-24A contains a high resolution sonar that seeks out mines than lay on the sea bottom, waiting for ships to pass over. The bottom mine then detonates if a ship type it was programmed to attack is detected. The U.S. Navy has been using this mine hunting approach since the 1980s. The original sled system went through several major upgrades and is considered very reliable and effective. The MH-53E sled is still able to carry more equipment and sweep a larger area faster.
Meanwhile, the U.S. Navy has developed a complementary system, ALMDS (Airborne Laser Mine Detection System). Designed to operate from the MH-60S helicopter, ALMDS uses a Laser Imaging Detection and Ranging blue-green laser to detect, and identify naval mines near the surface. Unlike the AQS-24A, ALMDS operates from the low flying, and smaller, helicopters. Surface mines are either moored (via a chain to the bottom) or floating (a favorite terrorist tactic), and many float just below the surface. The laser works very quickly, and enables the ALMDS equipped helicopter to quickly check out large areas for surface mines. Terrorists have used naval mines before, of the floating variety. Navies tend to use the more sophisticated, expensive and hard-to-get bottom mines (that lie on the bottom, in shallow water).
In late 2012 a massive naval mine clearing exercise in the mouth of the Persian Gulf (the Straits of Hormuz) demonstrated two things. First, mine clearing ships (which many nations have) and mine clearing helicopters (like the MH-53E) were not as successful as hoped. A lot of the practice mines used were not found. Second, one new system, the SeaFox (a remotely controlled underwater system) was very successful. Ten nations already have SeaFox, and while the United States is a new user, it is hustling to make SeaFox work from different ships and aircraft. This involves training ship crews to operate SeaFox and equipping ships with the control equipment. Earlier in 2012 the U.S. Navy ordered several dozen more of the expendable SeaFox UUVs (unmanned underwater vehicles). SeaFox was designed to find and destroy bottom mines (which sit on the seabed) as well as those that float. These UUVs were quickly sent to the Persian Gulf to deal with potential Iranian use of naval mines. The U.S. first used their new Seafox UUVs on some of the U.S. Avenger class mine hunting ships stationed in the Persian Gulf.
SeaFox is a small (1.4x.4x.2 meters/55x16x8 inches) battery powered sub that weighs 43 kg (95 pounds) and has a fiber-optic cable connecting it to a surface ship or hovering helicopter. The controller can move the SeaFox close to a suspected mine (using a small sonar unit to assist navigation), then turn on a spotlight for a video cam to examine the object and determine if it is a mine. If it is then SeaFox gets closer and detonates a shaped charge explosive, sending a shaft of hot plasma through the mine destroying it (and the SeaFox). SeaFox has an endurance of about 100 minutes, a top speed of 10 kilometers an hour, and can dive as deep as 300 meters (930 feet). Operators get to increase their skills and effectiveness using a SeaFox simulator.
These smaller devices can get the job done, but they don’t get done as quickly as the MH-53E and its ten ton sled, also known as the Mk 105 Magnetic Sweep. Towed at about 40 kilometers an hour, the sled contains a gas turbine generator to produce electricity to operate the device that activates magnetic mines. Since the sled is a hydrofoil, the exploding magnetic mines have no effect on the fast moving Mk 105. As long as potential foes still use magnetic mines the Mk 105, and a helicopter powerful enough to tow it, will be extremely useful mine clearing equipment.