While the fundamentals of shiphandling and hydrodynamics never change, the physical design of the Freedom-class littoral combat ship (LCS) and its bridge team composition are considerably different from those of the other Navy ships on which officers serve before reporting to an LCS. The Freedom class has unique engineering features and watch-team dynamics. There are several lessons that can be learned from LCS special shiphandling evolutions—lessons markedly different from those a junior officer will absorb driving a traditional ship with propellers and rudders instead of waterjet propulsion.
Engineering and Hull Design
The Freedom class is propelled by a waterjet system similar to that found on a recreational Jet Ski. It is outfitted with two Rolls-Royce Kamewa steerable jets and two booster jets. The steerable waterjets are in outboard positions in relation to the boost jets, allowing for higher maneuverability and precision. Using steerable waterjets, the LCS can produce thrust vectors to create purely lateral motion. Unlike a ship with propellers and rudders, the LCS can thrust in separate directions with ahead and astern thrust vectors.
This thrust vectoring also allows for tight pivoting and rotation while maintaining zero headway, using a “toed in” (waterjets directing thrust toward each other) or a “toed out” (waterjets directing thrust away from each other) method. With the transom acting as a combination of a thrust bearing and a pseudo-pivot point, the LCS can easily conduct tight maneuvering evolutions that would be extremely difficult or impossible on a destroyer, for example.
Finally, the shape of the Freedom class has a big impact on its ability to go fast. The semiplaning, monohull construction allows for a very shallow draft while still maintaining the ability to maneuver at high speeds. To achieve maximum speed, an interceptor functioning as a trim tab creates a high-pressure zone at the stern and enables the ship to get on plane much sooner.
On a destroyer, the bridge team comprises an officer of the deck (OOD), junior officer of the deck (JOOD), conning officer, helmsman, lee helmsman, quartermaster of the watch, boatswain’s mate of the watch, and lookouts, with support from a second navigation plot in the mission control center (the LCS version of the combat information center, or CIC), including a shipping officer during special evolutions. The LCS bridge team has an OOD (primary ship driver) and a JOOD (primary navigation) supplemented with a single lookout roaming the bridge wings and monitoring the network of high-definition cameras inside and outside the hull. This small-team dynamic limits the chances of miscommunication and promotes trust.
A big factor contributing to the small team’s efficiency is the sensor displays. Using the BridgeMaster E radar display, the OOD and JOOD can maintain short- and long-range shipping pictures simultaneously. The OOD console is normally configured to display the X-band radar. While limited in range, X-band maintains a more accurate picture than the BridgeMaster E for close contacts. Keeping the X-band at the 12-nautical-mile (nm) range provides good surface tracking beyond the horizon. Conversely, the JOOD will normally have S-band displayed. S-band sacrifices accuracy in favor of greater range, so the JOOD can see up to four times as far as the OOD, but video display will lose fidelity within 10 nm.
The LCS OOD normally performs the role of conning officer, helmsman, and lee helmsman. Instead of a helm- and engine-order telegraph, the LCS is controlled by combinators that pivot left and right 30 degrees and have a throttle setting of 1 to 10 in either the forward or aft direction. There are three common ways (Direct Mode, Common Lever, and Autopilot) and one uncommon way (Tiller Mode) to maneuver the ship, each with its own benefits. Mastering all four is essential for LCS shiphandlers.
As implied, Direct Mode provides the OOD with the most direct control of the ship. In Direct Mode, the left and right combinators control the corresponding steerable waterjets. By manipulating these controls independently, the OOD can walk the ship laterally, rendering tug lines slack during most pier work. This also is how an LCS can remain stationary while twisting in any direction.
Common Lever is used mostly in special evolutions or restricted-water transits. It takes the two combinators from Direct Mode and simply condenses control to one lever that controls the jets. This most closely simulates driving a screw-and-rudder ship.
Autopilot is most commonly used on the bridge during normal underway steaming. A computer continuously steers the waterjets to maintain heading. Speed is still regulated on the combinator, but the ship is maintained in a centerline position. The OOD must ensure the autopilot settings are configured for the evolution being conducted (flight quarters, replenishment at sea, etc.) and that environmental factors, such as sea state, are continuously being calculated and accounted for. Autopilot allows the OOD to monitor the ship’s steering as if he had a conning officer, helmsman, and lee helmsman and provides him time to give contact reports to the watch team for the JOOD to validate electronically and the lookout to verify visually.
With the OOD’s time consumed by driving and contact management, the JOOD maintains the primary navigation plot. In keeping with Navy standards, navigation is accomplished purely by electronic means, and it is the JOOD’s responsibility to verify that electronic-fix data are accurate. Validating position sources, radar overlays, and Automatic Identification System integration on the Voyage Management System (VMS) is critical to the JOOD’s success. For this reason, every watchstander must be a certified VMS operator.
The JOOD also acts as boatswain’s mate of the watch and deck-log keeper. The JOOD keeps all checklists for special evolutions and collects twelve o’clock reports, runs the 1 Main Circuit for shipwide communication, monitors communication with the mission control center, and maintains the long-range shipping plot. The most common phrases said between OOD and JOOD are “eyes down” and “eyes up.” Knowing who is looking where is critical to the watch-team relationship. The OOD and JOOD seats have good visual coverage forward of the beam, but not much aft of it. The lookout’s job is to monitor all the closed-circuit cameras, but at least one display is always configured to see behind the ship off each quarter and the flight deck.
The LCS watch-team dynamic has become a reliable model with a crew of 71, including just 10 officers. Each watchstander must be an expert mariner. The LCS OOD and JOOD courses in Newport, Rhode Island, teach topics ranging from deck seamanship, weather observation, automatic radar-plotting-aid operation, and rules of the road, to waterjet theory and hydrodynamics. There are also weeks of simulator time. OOD and JOOD simulators are not “participation” courses. Many students fail. Those who do pass, however, are enrolled in OOD or JOOD Capstone, which builds on those fundamentals to address responding to casualties and combat situations. These training tracks are intensive and time-consuming.
The Physics of Movement
Waterjet theory provides great advantages for shiphandlers able to master its finer details. This is not a simulator-only theory; it is a rare day if an LCS uses tugs to get under way. The vector math involved with maneuvering an LCS with waterjets, specifically in a harbor, requires an intricate combination of thrust vectors. Therefore, unless specifically noted, all maneuvering described as follows will be in Direct Mode with either both diesel or both gas-turbine engines online.
Where an LPD conning officer thinks of a pivot point as a factor of a lever around which to twist (or pivot), an LCS OOD sees it more as a target. The goal of LCS pier work is to aim the waterjets toward the pivot point. For example, if the LCS OOD intends to walk to starboard, the port bucket is toed out 6 to 10 degrees with an ahead bell, creating force vectors at 000 relative and 090 relative. The starboard bucket being toed out 6 to 10 degrees with an astern bell will create force vectors at 180 relative and 090 relative. The 000 and 180 relative force vectors will cancel each other out, resulting in a single combined force vector at 090 relative.
This force vector allows the LCS to move laterally to starboard with no movement forward or aft. This lateral movement also changes the pivot point from centerline toward the direction of movement, so the OOD regularly has to make small corrections. If the waterjets are not aligned to aim at the pivot point, the result is a twist. In the same scenario for the starboard walk just described, if the waterjets are toed out to 30 degrees, the result will be a port twist.
When toed out, the point at which the vectors intersect creates a lever-arm effect that causes the movement of the stern to starboard and the bow to port, while forward and aft vectors cancel each other out as they did before. When toed in, the point of intersection is behind the stern. As a result, the pivot point moves aft. In our experience, twisting while toed out is much easier to manage in a harbor, because the pivot point is closer to the pilot house and the waterjets are already toed out for the walk.
Replenishment at Sea
One of the largest factors that must be considered when coming alongside an oiler is the pressure zones. Every ship has three significant pressure zones: A positive zone on the bow, a negative zone on the beam, and a positive zone on the stern. The Freedom class has an average displacement of 3,000 tons, and an oiler has a displacement as great as 80,000 tons. This difference in size, combined with the draft of the LCS being approximately 15 feet, means there is less surface area beneath the water to keep the LCS stable when compared with other Navy ships, many with drafts greater than 25 feet. Because the LCS is just 387 feet long, the positive pressure the bow creates usually falls in the negative pressure area of the oiler. While alongside, the LCS bow is constantly trying to go toward the oiler, which results in a need to position the waterjets at a constant 5 to 10 degrees of opposite jet angle. Also, the positive pressure aft of the stern is generally in line with the positive pressure of the oiler’s stern, which presents a unique and challenging situation for the autopilot to steer.
Before making the initial approach, some configurations must be made. The standard engineering configuration for a replenishment at sea is both MT-30 gas-turbine engines online and making turns on the steerable waterjet shafts. The radar is set up with two parallel index lines (PIL, one at 180 feet, .03 nm; and one at 300 feet, .05 nm), a variable range mark (VRM) at 500 yards, and an electronic bearing line (EBL) 12 degrees offset to port from Romeo Corpen. When all these configurations are made, the OOD has an electronic visualization of the 300-foot separation. The contacts on the automatic radar-plotting aid should be configured to relative vectors; this will assist in driving the contact into the “crosshairs” the PIL, VRM, and EBL make at 500 yards.
Until this point, the OOD has retained the conn. When ordered to waiting station prior to approaching the oiler, an independent conning officer will assume control and take position on the bridge wing. A qualified OOD or JOOD is stationed at the ship’s control console as the master helmsman, monitoring the autopilot and making speed changes as ordered. While making the approach, speed changes should be ordered in throttle settings (“All ahead T-5”).
Because of the different pressure zones, the best practice for an approach is to come in much wider than what is normal for other ship classes. We have found 300 feet to work the best. Once abeam at 300 feet of lateral separation, the conning officer will begin to walk in at 2- to 4-degree increments left of the base course, depending on the strength of wind and seas. The walk will slowly decrease the lateral distance, but if the speed is not changed when walking, the ship will begin to fall behind the delivery ship. To counter this, the conning officer must increase speed slightly. The walk will continue until there is the standard separation of 180 feet from the oiler.
Once alongside, just as with any ship, the conning officer is constantly looking and cycling from bow, beam, and stern, verifying that everything he or she is seeing matches the reports being received from the bow, the laser-range finder, and the line up from Station 2 to the oiler’s fueling station. When connected, the phone-and-distance line is the primary visual cue of the lateral separation for the conning officer. Station 2 informs the bridge in feet how far ahead or behind the ship needs to be to have a perfect lineup.
These changes must be made through incredibly accurate and precise movements on the combinator. The lever must be moved in approximately 1/16th inch increments to achieve a 5 RPM change (this is roughly the thickness of the indicator lines of the combinator, so one “line width” equates to about 5 RPM). To verify the shaft RPMs ordered, the helmsman must communicate to the plant control officer what shaft RPMs he sees from the Machinery Plant Control and Monitoring System console.
The final step of the replenishment at sea is the breakaway, leaving the delivery ship astern and making way clear of it. Once all lines are clear, there are usually two engineering plant configuration options, which will mainly affect how quickly the LCS separates from the delivery ship. The OOD can maintain just the steerable waterjets or engage the boost jets. The speed difference with the boost jets is about 10 knots.
When all lines are clear, the conning officer will immediately order the highest throttle setting in the plant configuration and come to starboard 2 degrees, monitor the swing of the ship, and continue turning to starboard in 2-degree increments until the desired course is achieved. The bow must be out of the negative pressure zone of the oiler as quickly and safely as possible. Once the desired distance is reached, the OOD will assume the conn and come to the determined plant configuration.
Preparing for the LCS
The changing face of the fleet is resulting in many more assignments for officers and sailors to littoral combat ships. The transition is going to be smooth for many, but for some, the paradigm shift in seamanship basics will be more difficult. It is imperative that the surface force prepare its officers and sailors as much as possible for this change. We have attempted to take fundamentals and lessons learned from our experiences to aid future wardrooms and students in their preparation to eventually drive one of these great ships.
For those coming directly from (or with extensive experience on) traditional screw-and-rudder ships, the essential principles are the same. Getting under way, open-ocean steaming, and special evolutions demand that the LCS OOD understand where the pivot point of the ship is. There is still high pressure on the bow when moving forward, and this must be considered when executing underway replenishments and high-speed operations. These are tenets of seamanship that do not change for any ship.
There are some differences, however, that may prove more difficult to master. With waterjets, the LCS OOD can directly interact with the pivot point, which leads to critical differences in some evolutions, especially pier work. As a result, an officer detailed to an LCS would benefit from a refresher read on vector math. He or she would also benefit from discussing early with his or her future wardroom, navigator, or captain how the watch teams are expected to operate.
If driving a cruiser, destroyer, or amphibious ship is similar to driving an 18-wheeler, driving a Freedom-class LCS is more like driving a sports car; the fundamentals of driving are the same, but the methods for driving on the highway, pulling over on the shoulder, and parking are all slightly different. We cannot describe every dissimilarity between driving an LCS and a traditional ship, but hopefully we have covered the fundamentals of taking the deck on a Freedom-class LCS. But, as with any other ship in the fleet, the only way to truly comprehend how to drive one is to take the deck yourself.