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opposite direction. A more potentially damaging factor is launch/retrieval 

 of the vehicle in high sea states, this is discussed in the following section. 



4.11 LAUNCH/RETRIEVAL DAMAGE 



Coincident with the effects of high sea states is the damage inflicted upon 

 ROVs when they collide with the support ship during the launch/retrieval 

 process. There are several instances where such damage has occurred, and 

 it primarily occurred during the retrieval process. 



Most damage occurring during the launch/retrieval procedure is minor, resulting 

 in bent guard frames. One operator, however, in addition to bending the 

 vehicle's guard frames, cracked the upper buoyancy chamber which caused 

 significant delays and expensive repairs. A more recent North Sea incident 

 resulted in virtually a total loss of the vehicle. 



Those vehicles which are deployed from an undersea launcher are in a somewhat 

 better position in this respect since the launcher also acts as a protective 

 framework. However, the launcher itself can be damaged to an extent requiring 

 delay of the operation with attendant costs for repairs. 



While the major components of most ROVs are ruggedly designed, some of the 

 sub-components are not, and severe jolts can render them inoperative. To 

 avoid such shock-induced damage, one manufacturer has shock-mounted the 

 more sensitive components, such as the television pan/tilt mechanism. 



4.12 VEHICLE STATION KEEPING 



Station-keeping with respect to the vehicle implies its ability to hover at 

 a particular spot in the water column or to maintain a constant altitude 

 above the bottom when underway. 



Undoubtedly the most obvious culprit is the ROV pilot, and in several instances 

 the pilot's lack of experience or expertise was identified as the weak link 

 in the system. Several other aspects, in addition to pilot competency, of the 

 ROV system were also identified as inhibiting the vehicle's ability to station- 

 keep. 



A frequent problem encountered by operators of small vehicles is the vehicle's 

 inability to remain in one spot within relatively slow currents. The low 

 mass and particularly, the low horesepower of the vehicle is seen as causing 

 the problem. It is significant to note that operators of the same vehicle 

 viewed them differently in regard to demonstrating an adequate station-keeping 

 ability. The controlling factor is the nature of the work. For most inspection/ 

 documentation tasks there is no need for complete and total stability, some 

 vehicle drifting is tolerable. But when inspection of structures for hairline 

 cracks or corrosion is the task, even the slightest vibration can be intolerable. 

 Not only do such vibrations make TV viewing difficult, but they can also cause 

 still photographs to be out of focus. 



