Destroyer escort


Destroyer escort was the United States Navy mid-20th-century classification for a warship designed with the endurance necessary to escort mid-ocean convoys of merchant marine ships.
Development of the destroyer escort was promoted by the British need in World War II for anti-submarine ships that could operate in open oceans at speeds of up to 20 knots. These "British Destroyer Escorts" were designed by the US for mass-production under Lend-Lease as a less expensive alternative to fleet destroyers.
The Royal Navy and Commonwealth forces identified such warships as frigates, and that classification was widely accepted when the United States redesignated destroyer escorts as frigates in 1975. From circa 1954 until 1975 new-build US Navy ships designated as destroyer escorts were called ocean escorts. Similar types of warships in other navies of the time included the 46 diesel powered Kaibōkan of the Imperial Japanese Navy, 10 Kriegsmarine F-class escort ships, and the two Amiral Murgescu-class vessels of the Romanian Navy.
Postwar destroyer escorts and frigates were larger than those produced during wartime, with increased anti-aircraft capability, but remained smaller and slower than postwar destroyers. As Cold War destroyer escorts became as large as wartime destroyers, the United States Navy converted some of their World War II destroyers to escort destroyers.

General description

Full-sized destroyers must be able to steam as fast or faster than cruisers and fast capital ships such as fleet carriers. This typically requires a speed of 28-40mph). They must carry torpedoes and a smaller caliber of naval guns to use against enemy ships, anti-aircraft guns, and antisubmarine detection equipment and weapons. While these requirements made the destroyer a fast all-around combatant, this made them too valuable to be relegated to convoy escort duties.
A destroyer escort needed only to be able to maneuver relative to a slow convoy, be able to defend against aircraft, and detect, pursue, and attack submarines. These lower requirements greatly reduce the size, cost, and crew required for the destroyer escort. Destroyer escorts were optimized for antisubmarine warfare, having a tighter turning radius and more specialized armament than fleet destroyers. The slower speed of destroyer escorts was not a liability in this context as sonar was useless at speeds over.
As an alternative to geared steam-turbine propulsion found in sloops of similar purpose, size and speed, many US destroyer escorts of the World War II period had diesel-electric or turboelectric drive, in which the engine rooms functioned as power stations supplying current to electric motors sited close to the propellers. Electric drive was selected because it does not need gearboxes to adjust engine speed to the much lower optimal speed for the propellers. The current from the engine room can be used equally well for other purposes, and after the war, many destroyer escorts were re-used as floating power stations for coastal cities in Latin America under programs funded by the World Bank.. ships were the exception to this and they used a geared diesel engine to drive the propellers directly. s used the typical boiler and geared turbine propulsion system.
Destroyer escorts were also useful for coastal antisubmarine and radar picket ship duty. During World War II, seven destroyer escorts were converted to radar picket destroyer escorts, supplementing radar picket destroyers. Although these were relegated to secondary roles after the war, in the mid-1950s, 36 more DEs were converted to DERs, serving as such until 1960–1965. Their mission was to extend the Distant Early Warning Line on both coasts, in conjunction with 16 s, which were converted Liberty ships.
During World War II, some 95 destroyer escorts were converted by the US to high-speed transports. This involved adding an extra deck which allowed space for about 10 officers and 150 men. Two large davits were also installed, one on either side of the ship, from which landing craft could be launched.

Origins

The Lend-Lease Act was passed into law in the United States in March 1941, enabling the United Kingdom to procure merchant ships, warships, munitions, and other materiel from the US, to help with the war effort. This enabled the UK to commission the US to design, build, and supply an escort vessel that was suitable for antisubmarine warfare in deep open-ocean situations, which they did in June 1941. Captain E.L. Cochrane of the American Bureau of Shipping came up with a design which was known as the British destroyer escort. The BDE designation was retained by the first six destroyer escorts transferred to the United Kingdom ; of the initial order of 50, these were the only ones the Royal Navy received, the rest being reclassified as destroyer escorts on 25 January 1943 and taken over by the United States Navy.
When the United States entered the war, and found they also required an antisubmarine warfare ship and that the destroyer escort fitted their needs perfectly, a system of rationing was put in place whereby out of every five destroyer escorts completed, four would be allocated to the U.S. Navy and one to the Royal Navy.

Alternatives

Destroyer escorts were designed and built to naval construction standards, and as such could only be built at yards experienced with naval standards. The United States Maritime Commission created its S2-S2-AQ1 design – which was based on the British-designed River class – for much the same role but using civilian construction standards. These ships would be classed by the Navy as the Tacoma class frigates. These frigates had a greater range than the superficially similar destroyer escorts, but the US Navy viewed them as decidedly inferior in all other respects. The Tacoma class had a much larger turning circle than destroyer escorts, lacked sufficient ventilation for warm-weather operations, were criticized as far too hot below decks, and, because of the mercantile style of their hulls, had far less resistance to underwater explosions than ships built to naval standards like the destroyer escorts.

Post–World War II U.S. ship reclassification

After World War II, new-build United States Navy destroyer escorts were referred to as ocean escorts, but retained the hull classification symbol DE. However, other navies, most notably those of NATO countries and the USSR, followed different naming conventions for this type of ship, which resulted in some confusion. To remedy this problem, the 1975 ship reclassification declared ocean escorts as frigates. This brought the USN's nomenclature more in line with NATO, and made comparing ship types with the Soviet Union easier. As of 2006, no plans existed for future frigates for the US Navy. and the littoral combat ship were the main ship types planned in this area. However, by 2017 the Navy had reversed course, and put out a Request For Proposals for a new frigate class, temporarily designated FFG. One major problem with ship classification is whether to base it on a ship's role, or on its size. One example of this ambiguity is the air-defense ship class, which is classified as cruiser, though it uses the same hull as the s.

Vietnam War

During the Vietnam War, the Republic of Vietnam Navy received two s from the United States.

US Navy destroyer escort classes

World War II shipbuilding programs

total ships in the table: 507DEs + 56APDs
37 Buckleys listed here as Buckleys were converted to APDs after having been commissioned as destroyer escorts. All APDs listed in the table were completed as conversions. Captains were converted before commissioning as DEs.
BuilderStateEvarts + CaptainBuckley + Captain
CannonEdsallRudderow
Butlertotal
Feb 1942Jul 1942Oct 1942Jun 1942Jul 1943Aug 1943
Feb 1944May 1944Aug 1944Dec 1943Apr 1944Aug 1944
Apr 1943Apr 1943May 1943Apr 1943Dec 1943Dec 1943-
Aug 1944Jul 1944Dec 1944Feb 1944Sep 1944Dec 1945
Consolidated SteelTX12 473493
Bethlehem
MA27 + 4614 87
Bethlehem, San FranciscoCA1212
Boston Navy YardMA21 + 311062
Brown ShipbuildingTX382361
Federal Shipbuilding and Drydock CompanyNJ361652
Mare Island Navy YardCA3131
Philadelphia Navy YardPA5 + 1102 18
Dravo CorporationDE, PA3 15 18
Charleston Navy YardSC152 17
Defoe Shipbuilding CompanyMI134 17
Western Pipe and Steel CompanyCA1212
Norfolk Navy YardVA1010
Tampa Shipbuilding CompanyFL99
Puget Sound Navy YardWA88

companycontractissuedamountdeliverydescription
various navy yards11/41DE-1... DE-50
Consolidated SteelOBS3781/42$110,426,0009/43destroyer escorts DE 129-152
Brown ShipbuildingOBS4031/42$63,558,00010/43destroyer escorts DE 238-255
Federal Shipbuilding and Drydock CompanyOBS4011/42$85,440,0002/44destroyer escorts DE 162-197
Dravo Corporation, WilmingtonOBS3771/42$52,903,0004/44destroyer escorts DE 99-128
Bethlehem, HinghamOBS3762/42$118,800,00012/43destroyer escorts DE 51-98
Brown ShipbuildingOBS3358/42$151,833,0007/44destroyer escorts DE 382-437
Consolidated SteelOBS3348/42$197,505,00011/44destroyer escorts DE 316-381
Bethlehem, San FranciscoOBS3318/42$28,427,0007/44destroyer vessels DE 633-664
Federal Shipbuilding and Drydock CompanyOBS3338/42$44,560,0003/45destroyer escorts DE 438-515
Bethlehem, HinghamOBS3328/42$155,364,0008/45destroyer escorts DE 563-632
Defoe Shipbuilding CompanyOBS79510/42$54,366,0009/44destroyer escorts DE 693-738
Bethlehem, Fore RiverOBS84010/42$35,365,00011/44destroyer escorts DE 675-692
Consolidated SteelOBS84411/42$42,372,0003/44destroyer escorts DE 789-904
Dravo Corporation, PittsburghOBS84111/42$11,845,0004/44destroyer escorts DE 665-674
Western Pipe and Steel CompanyOBS84211/42$44,132,0009/44destroyer escorts DE 739-762
Tampa Shipbuilding CompanyOBS84311/42$31,779,00012/44destroyer escorts DE 763-788

Data from "Ship's Data U.S. Naval Vessels"
ClassCompanyContractValueHulls
WGTC.Steel8/42$2,043,000339-368
WGTfederal8/42$2,785,000438-450, 508-510
WGTBrown8/42$2,517,000402-424
FMRC.Steel1/42$1,988,000129-149
FMRC.Steel8/42$1,539,000316-336
FMRBrown1/42$2,921,000250-252
FMRBrown8/42$2,183,000389-400

hull numbers for WGT and FMR are still incomplete, price of $2,157 for Brown/WGT DE-423 is assumed to be a typo
other classes missing
From the same document, List of Naval Vessels, pp. 11:
TypeHullsCancelled Hulls
GMT5-50
TE51-98
DET99-113114-128
FMR129-152
TE153-161
DET162-197
TE198-223
TEV224-237
FMR238-255
GMT256-283284-300
GMT301-307308-315
FMR316-338
WGT339-372373-381
FMR382-401
WGT402-424425-437
WGT438-450451-507
WGT508-510511-515
GMT516-530
WGT531-542543-562
TE563-578
TEV579-606607-632
TE633-636
GMT637-644
TEV645-664
TE665-673
TEV674
TE675-683
TEV684-692
TE693-705
TEV706-722723-738
DET739-750751-762
DET763-771772-788
TE789-800801-1005