FFG-7 OLIVER HAZARD PERRY-class Design
The FFG-7 class was designed from the keel up as a total warfare system, capable of operating independently or as an integral part of a carrier or surface action group. Innovations in high speed digital computer technology enable the on-board weapons system to instantly detect and evaluate contacts at greater ranges with minimum human interface, thus providing increased reaction time.
The United States Navy completed design of what was called the Patrol Frigate during the early 1970s. These ships are intended to provide ocean escort of Navy amphibious, underway replenishment, and auxiliary ships, and of merchant ships. The increasing capabilities of Soviet naval forces to attack U.S. and NATO ships at sea with advanced, missile-armed aircraft, surface ships, and submarines, made it necessary for such allied escort ships to have improved sensors and weapons for countering varied threats.
The patrol frigate differed from destroyer-type warships, from which they have evolved, in that destroyers generally are larger, faster, and are fitted with more capable weapons and electronic equipment to permit them to operate with fast aircraft carriers. The ocean escort ships operate with slower amphibious, auxiliary, and merchant ships that have a maximum sustained speed of about 20 knots whereas aircraft carriers require destroyers that can steam in excess of 30 knots.
The armament for the patrol frigate called for an emphasis on anti-air/anti-ship capabilities while still being able to counter advanced enemy submarines. The PF has a launcher forward capable of firing both Standard anti-aircraft missiles and Harpoon anti-ship missiles. The ship has a "mixed" magazine, permitting more of one or the other type missiles to be carried, depending upon the anticipated threat. The missile launcher is complemented by a 76-mm rapid-fire gun. For close-in defense against enemy missile the PF had a short-range, very-rapid-fire gun system called the Close-In Weapon System (CIWS). With both destroyer escorts and ships of the PF design assigned to a convoy or task group escort force a viable defense can be provided against hostile air, surface, and submarine threats.
The Navy developed the FFG 7 class using the minimal manning concept. This concept has a profound effect on engineering organization. Supervisors must accomplish all tasks with fewer people than larger ships. Below decks, two gas turbine engines (similar the engines on the wings of a DC-10) provide power for propulsion that enables the ships to reach speeds in excess of 25 knots. Gas turbine engines are more cost effective than steam or diesel propulsion ships. These advanced propulsion units allow a ship to get underway quickly and rapidly change operating modes. The propulsion plant as well as the electrical power plant is computer controlled and monitored to ensure a smooth running and efficient system. The gas turbine engines can be started and be ready to come up to full power in five minutes. This quick reaction time allows the ship to be more maneuverable and reduces the preparation time to get underway.
The FFG-7 is designed under a logistics support concept that emphasizes reduced shipboard manning. The ship had a crew of about 70 fewer personnel than the comparable size frigate then in operation. The lower manning is attained partly through (1) the use of gas turbine propulsion versus steam power used on previous combatants, and (2) the centralization and automation of the control of weaponry and other equipment. Some naval representatives believed, however, that the manning level of 185 to 191 may not be adequate to meet all of the ship's needs.
To enhance the on-board anti-surface/anti-submarine capabilities, the new LAMPS Mark III Helicopter System adds significantly to the ship's sensor and weapons delivery range. Although the ships were intended to operate the LAMPS-III ASW helicopter, FFG 7-35, as completed, lacked the equipment necessary to handle them. Beginning with the FY 79 ships (FFG 36 and later), helicopter support equipment was aboard on completion: fin stabilizers, RAST (Recovery Assist, Secure, and Traverse system-not fitted as completed until FFG 50), and other systems. The RAST system permits helicopter launch and recovery with the ship rolling through 28 degrees and pitching 5 degrees. The equipment was first installed in MCINERNEY (FFG 8), which was reconstructed, in 1981 at Bath Iron Works, to act as LAMPS-III/SH-60B Seahawk helicopter trials ship.
The FFG-7 frigates underwent an extensive stern redesign to enable the ship to accommodate the LANPS-MK III helicopter, its hauldown system, and tne towed sonar system. The Navy planned to incorporate this modified stern into the fiscal year 1979-1980 ship design packages. It did not, however, incorporate tne modification directly into the 26 US FFG-7 class frigates already under contract. The LAMPS-MK III helicopter, its haul-down system, and the towed sonar system were not developed wnan the FFG-7 was designed in tne early 1970s. However, weight and space were reserved on board for a haul-down system, and space was reserved for the towed sonar. By early 1977, as the design for the sonar and the helicopter haul-down system began to firmup, it became apparent that the compartments and bulkheads in the entire stern section below deck would have to be rearranged to install these systems on the ship.
A change in the landing pattern of the LAMPS-MK III helicopter also affected the stern design. For safety reasons, the helicopter would land straight-in from the stern, rather than obliquely as was the case before. All equipment positioned on the ship's fantail had to be removed because it could interfere with the helicopter's landing approach. To accommodate this equipment, the FFG-7 class frigate's transom was tilted and a "step" -- extending rearward 6 to 10 feet and recessed 25 inches below the main deck level -- was added to the stern.
The Navy knew, at least as early as September 1976, that the stern would require modification. Despite this the Navy did not analyze the economic feasibility of incorporating the modified stern into all, or some, of the first 26 U.S. FFG-7 frigates during their construction. Nor did the Navy contact the shipyards to determine whether the stern modification could be incorporated into all, or some, of the first 26 US follow ships duriny construction, and what cost and schedule effect this action might have on the ships involved.
The Navy had plans to begin retrofitting the first 26 U.S. FFG-7 class frigates in 1985. A Navy best guess estimate, developed in early 1978, indicated that it will cost at least $7.2 million per ship to retrofit the modified stern into the ships. Sucn a retrofit could result in each ship beiny drydocked 6 to 12 months or longer. GAO wrote to the Secretary of Defense expressing a belief that the Navy's decision to defer incorporating the modified stern until the ships covered by fiscal year 1979-1980 contracts ships was made without considering all relevant factors. As of October 1, 1978, fabrication on 12 of the first 26 U.S. ships had not yet begun. The Navy estimated that construction on these ships -- from start of fabrication to delivery -- would average 2 l/2 years to 3 l/2 years each, with the final FFG scheduled for delivery in January 1983. Since the Navy was scheduled to have detailed design drawings for the stern modification by June 30, 1979, GAO questioned why the Navy had not planned to incorporate this modification into at least some of these ships during their construction.
In preliminary design, the SQQ-23 sonar was selected as the FFG-7 hull-mounted sonar. The Navy, however, later decided to replace it with the AN/SQS-56 sonar. The decision to change to The decision to change to the AN/SQS-56 sonar was based on cost, space, and personnel considerations and the decision that add the capability to handle a second LAMPS helicopter. The AN/SQS-56 is a less costly, less effective system, which initially encountered serious developmental problems. The Navy upgraded the system to overcome its effectiveness and suitability deficiencies.
The primary threat to the FFG-7 and its escorted forces was Soviet submarines armed with both torpedoes and missiles. Overall protection, therefore, depended largely on the effectiveness of the FFG-7 frigate's anti-submarine warfare systems. Since the AN/SQS-56 sonar was a short-range active sonar, the ship depended on the development of towed sonar for longer-range submarine detections. Until the towed sonar was approved for service use, the FFG-7 frigates had to rely on the short-range AN/SQS-56 sonar. The improved AN/SQS-56 sonar underwent tests at sea in 1978. The test results indicated that it was operationally effective against its primary target and thus had been provisionally approved for service use pending determination of its reliability. However, since the system did not meet all of its operational performance criteria, a waiver was issued so production could begin. The Office of tne Secretary of Defense reviewed the resulrs of the follow-on test and evaluation in the fall of 1979 to confirm the operational suitability of the AN/SQS-56.
The Navy believed that the FFG-7 with the improved AN/SQS-56 sonar and two LAMPS MK-1 helicopters, operating in conjunction with other ASW forces, was an effective ASW platform. With towed sonar and a LAMPS-MK III, the FFG-7 was considerably more effective in prosecuting submarines at longer ranges.
The FFG-7 class frigate was designed under strict cost and weight constraints. This resulted in a minimum emphasis on providing the ship with protection for carrying out its missions after a "low" level enemy attack, (such as aircraft rockets and 3-inch and S-inch surface ship projectiles, rather than cruise missiles and torpedoes.) According to a 1975 Navy assessment of the ship's survivability protection, the ship (and other U.S. ships) was quite vulnerable to low level enemy threats. Survivability improvements for the FFG-7 class were evaluated, and corrective actions were planned. However, opportunities for improvement were limited because the ship is small, there were cost and weight constraints as well as state-of-the-art limitations.
The Navy's surface combatant ships were vulnerable to the so-called "cheap kill." A cheap kill occurs wnen a damaged system on a ship prevents the ship from completing its mission even though there is little or no physical damage to the ship's structure. Although the ship continues to float, it serves no useful purpose. Some of the most common causes of cheap kills include: (1) small metal fragments from near-misses or proximity-fused weapons which destroy exposed, inadequately armored vital equipment and (2) shock from an underwater explosion which damages improperly designed vital equipment on warships. In addition to these cheap kills, protection was also inadequate against chemical and biological agents. This inability to survive the cheap kill was both unacceptable and avoidable.
The Navy recognized the need for improved protection as early as January 1975 when it established a survivability improvement program. This program could have resulted in substantial improvements, but delays in implementing it have limited its effectiveness. Congressional interest and complaints from several Navy officials, including the Commander in Chiefeof the Atlantic Fleet, increased the attention devoted to this issue. A higher priority was demonstrated in the late 1970s by the development of two long-range improvement plans by the Navy. These plans called for an expansion of research and development efforts and improvements to existing ships.
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