The  results  of  the  trials  supply  the  data  for  the development  of  operational  information  furnished  to  all ships of the class. Other trials may be experimental to get  data  for  design  purposes.  Trials  also  may  be conducted on ships not considered as new construction or major conversion to determine the effect of newly designed equipment, such as a propeller or rudder. These trials  require  special  instruments  and  are  conducted  by experienced  technical  personnel. NAVSEA selects the ship for a special trial and submits a letter to the CNO asking for the use of the ship. When   CNO   approves,   the   TYCOM   makes arrangements  with  NAVSEA  to  conduct  the  trials. NAVSEA outlines procedures for the trials and assigns responsibilities.  Members  of  the  ship’s  engineering department  usually  act  as  engineering  observers  and record data during the trials. In addition to miscellaneous experimental trials and tests,  there  are  standardization  trials,  tactical  trials,  plant efficiency trials, vibration trials, and noise trials. We wiIl explain   each   of   them   briefly   in   the   following paragraphs. Standardization  Trials In this trial, the ship is operated over a measured trial course at both heavy and light displacement. The purpose is to determine the ship’s speed, shaft rpm, propeller thrust, and shaft horsepower characteristics. Test personnel use the data to prepare standardized curves for the displacement conditions of the trials, and issue them to all ships of the same class and to interested fleet and shore activities. The  Naval  Ships’  Technical Manual  and  the  trial  agenda  prescribe  additional conditions for the standardization trials. The ship’s underwater log is usually calibrated concurrently with standardization   trials. Tactical  Trials The tactical trials usually consist of operational procedures  to  determine  characteristics  of  the  ship relative  to  normal  turning  circles,  acceleration  and deceleration in a straight path, maneuvering, and special turns. Observations are made from stations aboard ship and  ashore.  NAVSEA  will  furnish  personnel  and instrumentation  for  these  trials,  and  will  analyze  and prepare the data for distribution. ECONOMY TRIALS NAVSEA  may  conduct  economy  trials  to  determine the efficiency of the propulsion plant of a representative ship. The trial will depend on the type of propulsion plant in the representative ship and will be prescribed in the trial agenda. Fuel data obtained during the plant efficiency trials are  plotted  directly  on  the  standardization  trial  curves. The  data  represent  the  performance  characteristics  of the ship under ideal conditions and should not be used for  logistics  purposes. NOISE TRIALS The trial agenda prescribes the procedures used to conduct  noise  trials  in  a  representative  ship.  For additional   information,   refer   to   NAVSEA 0900-004-3000,   Ship  Acoustical  Survey.  The  trials conducted   generally   include   one   or   more   of   the following surveys or tests: l l l l l Airborne noise surveys determine the character of the noise in certain compartments and the remedial  action  required  to  reduce  the  noise  to acceptable  limits. Underway radiated noise trials determine the character and magnitude of the noise radiating underwater  from  the  ship  under  various operating   conditions. Self-noise trials determine the interference of the ship’s  noise  with  its  sonar  equipment. Overside  noise  tests  determine  the  character  of noise  radiating  underwater  from  individual equipments  installed  throughout  the  ship. Structural-borne  noise  trials  determine  the source and path of transmission of machinery vibrations to the water. VIBRATION  TRIALS The  trial  agenda  prescribes  procedures  used  to conduct vibration trials in a representative ship. They may include one or more of the following tests: l Hull vibration tests determine the character of vibrations in the hull structure resulting from propeller  and  wave  action. 9-22