44 



In its stiff mode, the MCDHS is a rotating crane incorporating a traction winch, 

 a storage reel, and a traveling carriage. The carriage incorporates a gimballed 

 head sheave to facilitate deck handling and over-the-side launch and recovery 

 operations. During deployment and recovery operations, the MCDHS lifts the 

 combined in- air weight of the Primary Cable Termination (PCT) and vehicle, which 

 is 5,897kg (13,000 lbs). An alternate capability permits retrieval of the vehicle 

 separately in the event it is not mated with the PCT. 



The MCDHS winch system is a twin-drum traction winch combined with a lovz- tension, 

 large-capacity Primary Cable storage reel. Deck handling of payloads is achieved 

 by a slewing turntable and by a traveling carriage on the boom. An anti-sway 

 saddle at the boom tip incorporates hydraulic actuators that maintain positive 

 control of the payload orientation about the pitch and roll axes. 



The prime power source is a diesel generator providing 440 volt, three-phase power. 

 One person can operate the MCDHS through all phases of operation. 



The launch, tending and recovery of the RUWS lift package requires the use 

 of three separate modes of operation of the MCDHS. 



1. Stiff Boom Mode - This mode permits operation of the boom as a conven- 

 tional crane and is used for all deck handling work. This mode is also used 

 for handling the vehicle/PCT package at the surface of the water during launch 

 and recovery operations when high boom tip speeds are required. 



2. Passive Mode - This mode is used after launch when the payload is immersed 

 from the surface to depths of 61 m (200 ft) . It is used for motion compensa- 

 tion in Sea State 2 or less and also serves as the power failure mode. In 



this mode, the boom is solely supported by the hydro-pneumatic accumulators which 

 act as pneumatic springs. 



3. Active Mode - This is the mode generally used when the payload is 

 submerged over 61m (200 ft) in Sea State 3, or higher. In this mode, the 



boom tip speed is minimized, which reduces the dynamic load on the Primary Cable. 

 The MCDHS permits work operations in weather conditions up to Sea State 3 

 to Sea State 4. 



Sea state limits for launch/retrieval vary widely between operators and , 

 obviously, depends on the size and type of surface support platform. Generally, 

 most operators can launch/retrieve up to and including State 4 from a conven- 

 tional surface ship. Three North Sea operators (ULS Marine Ltd. , Sub Sea 

 Surveys Ltd., Sonarmarine Ltd.) however, have developed techniques which permit 

 launching in State 6 and retrieval in State 8. One of these operators (ULS 

 Marine) has retrieved their CETUS vehicle is an estimated Sea State 9 (Force 9) ; 

 this, by definition, is a strong gale with seas running from 13 to 14m (41 to 

 47 ft) . 



The type of hull can greatly improve launch/retrieval capabilities. Taylor 

 Diving and Salvage Co. deploys and retrieves their RCV-225 up to and including 

 State 4 from a conventional displacement hull vessel. From a semi-submerged 

 platform the limit increases to State 8. 



Vehicles which are deployed from a launcher can experience some difficulty 

 when docking into the launcher in heavy weather. Since the launcher will 

 follow the ship's roll on an almost 1:1 basis, the vehicle, which is decoupled 



