110 



in addition to the pilot and other operating personnel, a large number of 

 support personnel also occupy the van where the pilot is working. Consequently, 

 the ambient noise and congestion distracts the pilot so that he cannot maintain 

 full-time concentration on the TV monitor and the control/display console. 



4.16 VEHICLE FREEBOARD 



All ROVs have a freeboard which is not much more than a few centimeters. 

 Under routine conditions the lack of substantial freeboard does not represent 

 a problem. But when the vehicle has surfaced without its umbilical, visually 

 locating it on the surface is made extremely difficult in all but the calmest 

 of seas. In one instance the vehicle's tether broke during recovery and 

 visual contact with the vehicle could not be maintained during the time it 

 took to get the support ship underway. Consequently, the vehicle was lost 

 for a period of some 50 days until it was found washed up on the beach. 



Virtually all vehicles have a flashing strobe light which aids in location. 

 Some have an acoustic pinger which is self-powered and remains submerged 

 although the vehicle itself has surfaced. Such devices can aid in locating 

 the vehicle, but they are time-limited in duration and sea state limited in 

 effectiveness. Several vehicles have been lost owing to their low visibility 

 on the surface although it was a safe assumption that at least one of these 

 devices was operating. The surface location problem is obviously enhanced 

 when the sea state increases since the amount of time the vehicle or its 

 light is visible from the support ship is significantly reduced. 



One potential solution to this problem has been to advance the concept of a 

 negatively buoyant vehicle' instead of a positively buoyant one. The argument 

 is made that if it is necessary to cut the vehicle's umbilical, it is better 

 for the vehicle to sink and remain in one known underwater location rather 

 than surface and be subjected to the vagaries of wind, sea and currents. 

 The argument is not without merit since several vehicles have been left on 

 the bottom until fairer weather allowed a submerged pickup and retrieval 

 by either a diver or a manned vehicle. 



The lack of freeboard is, of course, only seen as a problem primarily by 

 those operators who have lost a vehicle on the surface. But it is a potential 

 problem to all. One operator is actively working on this problem and is 

 investigating a variety of surface locating aids, such as self-inflating, 

 self-activating balloons, radio beacons or pyrotechnic signals, to solve this 

 problem. 



4.17 ELECTRICAL SHOCKS 



There is only one reported incident where the deck crew of an ROV sustained 

 electrical shocks in the course of operations. In this incident the shock 

 was no more than a tingling sensation (perhaps 1 to 3 milliamps AC) and at 

 no time reached, what is termed, a "let-go current", of 9 to 16 milliamps AC. 

 The immediate solution was to wear rubber-lined gloves when handling the 

 vehicle on deck. A subsequent solution will involve installation of a ground 

 strap on the vehicle as it is retrieved aboardship. 



