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It is my understanding that bow mounted planes also give the ship greater maneuverability. Our best SSNs have bow mounted diving planes, and their whole mission is to hunt, and that requires the sonars to operate at their best. The superior deign certainly seems to be bow mounted planes. Why would the Navy want to revert to sail mounted planes when you get so much more capability with bow mounted planes?
OK, several misconceptions here. First, you are correct, the term "fairwater planes" refers to planes mounted on the sail. In the case of the SSNs, the planes were moved from the sail to the bow position in the so-called 688I class, the third iteration of the
Los Angeles class design. The motivation was to restore the capability to operate under ice. The sail on the 688 was too short to rotate the planes to a full vertical position (as on the 637
Sturgeon class) for ice breaking. The move back to the bow position allowed the planes to retract fully (into the forward ballast tank) for under ice surfacing. The bow planes are two parts, an "all moving outboard surface" mounted on a small, inboard, non-movable "stub" . The bow planes forward can be smaller than sail planes, as they are further from the ship's CG, and you get more control from a smaller surface. in a simple sense, forward (or sail) planes control the sub's depth, the stern planes control attitude in the water.
Fairwater planes were employed to move the rotating mechanism farther from the bow sonar sphere. A downside to this is the planes are closer to the surface when at periscope depth, and wave action can make it a bit more difficult to maintain depth. The newer sonar installations on the
Virginia class boats have advanced signal processing and wrap around bow transducers, so it is easier to use advanced techniques to filter out bow plane activation noise (and other self noise), as well as flow noise due to the planes. It appears (for now) from the literature that the fairwater planes will be retained in the advanced SSBN (X) design.
There is really no great advantage to one plane installation over another in terms of submarine maneuverability. You don't get "more capability" with bow planes in any meaningful sense. Important submarine capabilities for SSNs are silence at tactical speeds, sonar detection range, ability to rapidly "solve" the shooting solution at long range, and quietly launching torpedoes. Modern torpedoes pay out a long (20 mile) "wire" and the shooting solution is constantly updated from the shooting submarine's passive sonar suite and computers. At current firing ranges, it can be tens of minutes between shooting and the torpedo reaching the target. Once close, the torpedo goes active with its own sonar. Newer submarines such as the
Seawolf and
Virginia classes have Wide Angle Arrays along the length of the hull, which use the baseline of the hull to triangulate targets.
One idea that seems to have gone by the wayside was to adapt the
Virginia design for the SSBN(X). This may have been the source of confusion on use of bow planes, as on the
Virginia class. Retaining the
Virginia SSN design would have necessitated in abandoning the Trident D-5 for a new, smaller missile, as the
Virginia hull diameter would not accommodate the missile. The SSBN(X) will retain the
Ohio diameter and the Trident D-5 (with its long range and MIRV capabilities).