General Rules for Trials
satisfactory condition. If the machinery's condition is
found to be unsatisfactory, all defects and deficiencies
During all full power trials and during other
should be fully described and recommendations made
machinery trials, the following general rules should be
for correcting them.
observed:
Trial Requirements
1. Before a power trial, the machinery should be
thoroughly warmed up; this can be accomplished by
Trial requirements for each ship cover the rpm for
operating at a high fractional power.
full power at various displacements and injection
2. The speed of the engines should be gradually
temperatures. They are furnished to commanders and
increased to the speed specified for the trial.
units concerned by the CNO Operations Readiness
Division).
3. The machinery should be operated
As far as reports are concerned, full power trials
economically, and designed pressures, temperatures,
have a 4-hour duration. The usual procedure is to
and number of revolutions must not be exceeded
operate the ship at full power for a sufficient length of
4. The full power trial should not be conducted in
time until all readings are constant, and then start the
shallow water, which is conducive to excessive
official 4-hour trial period Economy trials have a
vibration, loss of speed, and overloading of the
6-hour duration, with a different speed being run at each
propulsion plant.
time a trial is made.
5. If a full power trial should continue beyond the
Once scheduled, trials should be run unless
length originally specified, then all observations should
prevented by such circumstances as the following:
be continued until the trial is finished.
1. Weather conditions which might cause damage
6. The trial should be continuous and without
to the ship
interruption. If a trial at a constant rpm must be
discontinued for any reason, that trial should be
2. Material troubles that force the ship to
considered unsatisfactory and a new start made.
discontinue the trial
7. No major changes of the plant setup or
3. Any situation where running or completing the
arrangement should be made during economy trials.
trial would endanger human life
If a trial performance is unsatisfactory, the ship
Underway Report Data
concerned will normally be required to hold a retrial of
such character as the type commander may consider
Reports of trials include all the attending
appropriate.
circumstances, to include the following:
The fact that a ship failed to make the required rpm
Z Draft forward, draft aft, mean draft, and
for any hour during the trial and the amount by which it
corresponding displacement of the ship at the
failed, should be noted in the trial report.
middle of the trial
The condition of the ship's bottom
Observation of Trials
The last time the ship was dry-docked
When full power trials are scheduled, observing
parties are appointed from another ship whenever
The consumption of fuel per hour
practical. When a ship is scheduled to conduct a trial
The average speed of the ship through the water
while proceeding independently beween ports or under
the other conditions where it is considered impactical
The average revolutions of the propelling engines.
to provide observers from another ship, the ship under
The methods by which the speed was determined should
trial may be directed to appoint the observers.
also be described.
The number of personnel assigned to an observing
Reports should also include tabulations of gauge
party varies according to size and type of ship. The
and thermometer readings of the machinery in use and
duties of the observing party are usually as follows:
the revolutions or strokes of pertinent auxiliaries. The
1. The chief observers organize, instruct, and
auxiliaries in use during the trial should be stated. Each
station the observing party. They check the ship's draft,
report should state whether the machinery is in a
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