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 ships 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
In this trial, the ship is operated over a measured
trial course at both heavy and light displacement. The
purpose is to determine the ships 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 ships
underwater log is usually calibrated concurrently with
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.
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.
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:
Airborne noise surveys determine the character
of the noise in certain compartments and the
remedial action required to reduce the noise to
Underway radiated noise trials determine the
character and magnitude of the noise radiating
underwater from the ship under various
Self-noise trials determine the interference of the
ships 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.
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.