1. Builder's trial
extent of any injury, defect, or maladjustment that may
have appeared during the postrepair trial.
2. Acceptance trials
A certain number of naval shipyard personnel, such
3. Final contract trials
as technicians, inspectors, and repairmen, accompany
4. Postrepair trials
the ship on a postrepair trial. They check the operation
of machinery that has been overhauled by the yard. If
5. Laying up or preoverhaul trial
a unit of machinery does not operate properly, the yard
6. Recommissioning trials
technicians carefully inspect it to determine the cause of
unsatisfactory operation.
7. Standardization trials
8. Tactical trials
9. Full power trials
Full Power and Economy Trials
10. Economy trials
Trials are necessary to test engineering readiness for
The trials that are considered to be routine ship's
war. Except while authorized to disable or partially
trials are numbers 4, 9, and 10 of the above list.
disable, ships are expected to be able to conduct
Postrepair, full power, and economy trials are the only
prescribed trials at anytime. Ships normally should be
ones discussed in this chapter. Information on the other
allowed approximately a 2-week period after tender
types of trials can be found in, Naval Ship's Technical
overhauls and a 1-month period after shipyard overhaul
Manual, chapter 094.
to permit final checks, tests, and adjustments of
machinery before being called upon to conduct
Postrepair Trial
competitive trials.
The postrepair trial should be made whenever the
Trials are also held from time to time to determine
machinery of a vessel has undergone extensive
machinery efficiency under service conditions, the
overhaul, repair, or alteration, which may affect the
extent, if any, of repairs necessary, the sufficiency of
power or capabilities of the ship or the machinery. A
repairs, and the most economical rate of performance
postrepair trial is usually made when the ship has
under various conditions of service.
completed a routine naval shipyard overhaul period (the
trial is optional whenever machinery has undergone
only partial overhaul or repair). The object of this trial
Inspections and Tests Before Trials
is to determine whether the work has been satisfactorily
completed and efficiently performed and if all parts of
the machinery are ready for service.
The full power and the economy trials, as discussed
in this chapter, are considered in the nature of
The postrepair trial should be held as soon as
competitive trials. It is assumed that the ship has been
practical after the repair work has been completed, the
in full operational status for sufficient time to be in a
preliminary dock trial made, and the persons responsible
good material condition and to have a well-trained crew.
for the work are satisfied that the machinery is, in all
respects, ready for a full power trial. The conditions of
Before the full power trial, inspections and tests of
the trial are largely determined by the character of the
machinery and equipment should be made to ensure that
work that has been performed. The trial should be
no material item will interfere with the successful
conducted in such manner as the commanding officer
operation of the ship at full power. The extent of the
and commander of the shipyard may deem necessary. A
inspections and the tests largely depends on the recent
full power trial is not required in cases where repairs
performance of the ship at high speeds, the material
have been slight, and the commanding officer is
condition of the ship, and the time limits imposed by
satisfied that they have been satisfactorily performed
operational commitments.
and can be tested by other means.
Any unsatisfactory conditions found to be beyond
Not later than one day before a trial, the engineer
the capacity of the ship's force should be corrected by
officer must report to the commanding officer the
the naval shipyard. When necessary, machinery should
condition of the machinery, stating whether or not it is
be opened up and carefully inspected to determine the
in proper condition and fit to proceed with the trial.
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