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USS Platte (AO 186) on 15 December 1982 during sea trials.
Click on this photograph for links to larger images of this class.

Class: CIMARRON (AO 177)
Design: SAIP Project 739.75
Displacement (tons): 8,210 light, 27,500 full
Same, jumboized: 11,645 light, 36,977 full
Dimensions (feet): 591.3' oa x 88' e x 33.5' mean
Same, jumboized: 700' oa, 661' wl x 86' wl, 88' e x 32' max nav
Armament: Space and weight for 2 CIWS, these were in AO 180 and 186 by 1983-84 and in 177-179 by 1990. No additional armament in Jumbo
Accommodations: 12 officers and 148 enlisted, accommodations for 221 personnel (246 as jumboized)
Speed (kts.): 20 originally, 19.4 and 19.0 sustained as jumboized
Propulsion (HP): 24,000
Machinery: Steam geared turbines, 2 boilers (600psi), 1 screw

177CIMARRON9 Aug 1976Avondale18 May 197828 Apr 197910 Jan 1981
178MONONGAHELA9 Aug 1976Avondale15 Aug 19784 Aug 19795 Sep 1981
179MERRIMACK25 Jan 1977Avondale16 Jul 197917 May 198014 Nov 1981
180WILLAMETTE11 Apr 1978Avondale4 Aug 198018 Jul 198118 Dec 1982
186PLATTE11 Apr 1978Avondale2 Feb 198130 Jan 198216 Apr 1983

AONameTDecommStrikeDisposalFateMA Sale/Depart
177CIMARRON15 Dec 19983 May 199928 Jul 2001MA7 Nov 2012/D
178MONONGAHELA30 Sep 199930 Sep 199929 Nov 2001MA30 Jan 2015
179MERRIMACK18 Dec 199818 Dec 199829 Nov 2001MA21 May 2013/D
180WILLAMETTE30 Apr 199930 Apr 199928 Jul 2001MA26 Nov 2013/D
186PLATTE30 Jun 199930 Jun 199929 Nov 2001MA4 Nov 2014/D

Class Notes:
The ships were designed to provide two complete refuelings to a conventional aircraft carrier and its six to eight accompanying escort ships. They were navy-manned and designed for operation with the smallest possible crews. Automation of the main propulsion and auxiliary equipment, replenishment stations, cargo handling equipment, etc., was incorporated into their design. Approved characteristics for the FY 75 Fleet Oiler (AO), SAIP Project No. 739.75, were promulgated on 14 November 1973 and updated for the AO 177 class on 27 August 1979 with a single change on 9 October 1981.

All five ships were jumboized at Avondale between March 1989 and September 1992. The objective of the AO 177 class jumboization program was to acquire through the addition of mid-sections to the five existing AO 177 class ships replenishment shuttle ships capable of the rapid transfer of POL to battle group replenishment ships (AOE, AOR, and AO) by means of vertical and connected (traditional) replenishment (VERTREP and CONREP) at sea. In the absence of a battle group station ship the AO 177 (Jumbo) would be capable of operation with the battle group as an attrition filler. The design incorporated the addition of a 109-foot parallel mid-body, providing for an increase in POL capacity from 120,000 to 180,000 barrels. The jumboized ships also incorporated new dry cargo underway replenishment rigs, additional berthing (25 men), and tiedowns for 21 cargo containers including 3 refrigerated. In an ammunition variant POL capacity was reduced to 150,000 barrels (reducing mean draft to 31.5' and full load displacement to 34,800 tons) in exchange for the incorporation in the mid-body of 625 tons of ordnance stowage or additional non-refrigerated break-bulk cargo. Top Level Requirements for the AO-177 (Jumbo) were promulgated on 17 March 1987 and Top Level Requirements for the AO 177 (Jumbo) class (Ammunition Variant) were promulgated on 5 February 1988. Top Level Requirements (TLR), which were not numbered, replaced the earlier numbered Ships Characteristics Board (SCB) projects as a means of defining the characteristics of new designs. In this case they established the requirements for the design and construction of the mid-bodies and new equipment to be added to the existing AO 177 class ships. It does not appear that any of the ships were configured as the ammunition variant.

Ship Notes:
177CIMARRONFY 1976. Jumboized Jun 1990-Mar 1992. To MA custody 9 Feb 1999. Departed NDRF 7 Nov 2012 under domestic sale.
178MONONGAHELAFY 1976. Jumboized Jan 1990-Oct 1991. To MA custody 22 Jun 1999. Departed NDRF 13 Mar 2015 under domestic sale.
179MERRIMACKFY 1977. Jumboized Mar 1989-Dec 1990. To MA custody 21 Dec 1998 on long-term layup pending a transfer to Brazil that did not materialize. Departed NDRF 21 May 2013 under domestic sale.
180WILLAMETTEFY 1978. Jumboized Oct 1989-May 1991. To MA custody 22 Jun 1999. Departed NDRF 26 Nov 2013 under domestic sale.
186PLATTEFY 1978. Jumboized Nov 1990-Sep 1992. To MA custody 14 Jul 1999. Departed NDRF 4 Nov 2014 under domestic sale.

Page Notes:
Compiled: 18 Sep 2021
© Stephen S. Roberts, 2021
Sources: Thomas Wildenberg, Gray Steel and Black Oil (Annapolis, 1996)