` USS Alacrity (AG 520, ex MSO) Class
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USS Assurance (AG 521) in a photo received in 1977.

USS Assurance (AG 521) in a photo received in 1977.
Click on this photograph for links to larger images of this class.

Class: ALACRITY (AG 520, ex MSO)
Design: SCB 45B (Navy MSO 519)
Displacement (tons): 801 light, 934 full
Dimensions (feet): 190' oa, 182' wl x 36' e/wl x 12'
Armament: none
Accommodations: 8 officers, 75 enlisted
Speed (kts.): 15
Propulsion (HP): 2,700
Machinery: Geared diesel, 2 screws

520ALACRITY1 Jun 1973Peterson3 May 19568 Jun 1957(Oct 1973)
521ASSURANCE1 Mar 1973Peterson28 Jan 195731 Aug 1957(Oct 1973)

AGNameTDecommStrikeDisposalFateMA Sale
520ALACRITY30 Sep 197730 Sep 19771 Jul 1978Navy sale--
521ASSURANCE30 Sep 197730 Sep 19771 Jul 1978Navy sale--

Class Notes:
Approved characteristics for an Ocean Minesweeper (MSO) of a new 182' type (wooden hull), SCB Project 45B, were promulgated on 16 March 1955 and three MSOs were ordered to this design on 26 October 1955 from Peterson. (Project 45A for a Minesweeper (AM) had been promulgated on 10 September 1953.) A fourth, MSO 522, was ordered on 25 June 1958 under the foreign assistance program and became the Belgian VAN HAVERBEKE. On 11 Jun 1970 the first of the three U.S. ships, ABILITY (MSO 519), began a SCB 502.69 minehunter modernization (approved characteristics promulgated 31 July 1965 and 27 May 1970) under a contract of 2 February 1970 with Todd, Brooklyn, but this project was cancelled on 16 Oct 1970 with other MSO modernizations and MSO 519 was struck on 1 February 1971 and sold on 3 December 1971. It was planned to inactivate her two unmodified sisters as well but this was cancelled in mid-December 1970 and they resumed mine warfare operations.

On 18 January 1973 CNO reclassified MSO 521 (ASSURANCE) to AG 521 effective 1 March 1973 and MSO 520 (ALACRITY) to AG 520 effective 1 June 1973, retaining their MSO hull numbers. On 23 March 1973 ASSURANCE sailed to Fort George Island, Florida, for overhaul by the Atlantic Drydock Corp. During this work her minesweeping gear was removed and she was converted for use as a trials ship for the AN/SQR-15 tactical towed array sonar system (TASS). Her fuel tanks were also modified and habitability was improved. The most visible conversion feature was the replacement of the minesweeping cable reels aft of the stack with a deck structure or van, presumably for TASS electronics. From 10 May to 23 July 1973 ALACRITY underwent similar modifications at Detyen's Shipyard in Mount Pleasant, S.C., followed by further alterations at the Atlantic Drydock Co. from 7 August to 19 October 1973. ASSURANCE operated off Port Everglades, Florida, for tests in November 1973 and in the Bahamas in January 1974, both probably using the underwater sound ranges there. Following operational testing of TASS with the 6th Fleet in the Mediterranean from mid-1970 to late 1973 by three DEALEY class DEs (DE 1015, 1021, and 1022), ASSURANCE and ALACRITY operated with the 6th Fleet during the second half of 1974. ASSURANCE returned to the Caribbean during the first third of 1975 and conducted special operations in the western Atlantic Ocean in April-June 1976 and again in April 1977. The AN/SQR-15 was fitted in the mid-1970s to the two frigates of the BRONSTEIN (FF-1037) class and also saw service in some frigates of the GARCIA (FF-1040) class and six destroyers of the SPRUANCE (DD-963) class.

Ship Notes:
520ALACRITY(ex-MSO 520,ex-AM 520, comm 1 Oct 1958). Reportedly resold 28 Dec 1979.
521ASSURANCE(ex-MSO 521,ex-AM 520, comm 21 Nov 1958).

Page Notes:
Compiled: 18 Oct 2021
© Stephen S. Roberts, 2021