In preliminary design, the SQQ-23 sonar was selected as the FFG-7 hull-mounted sonar. The US Navy, however, later decided to replace it with the AN/SQS-56 sonar. This decision was based on cost, space, and personnel considerations and the decision to 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 the Secretary of Defense reviewed the results 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.
Increased production capabilities could be better though 
