There are a number of different types of trials which are carried out under specified conditions.

A list comprising most of them is given here:

1. Builders trial.

2. Acceptance trials.

3. Final contract trials.

4. Post repair trials.

5. Laying up or pre-overhaul trial.

6. Recommissioning trials.

7. Standardization trials.

8. Tactical trials.

9. Full power trials.

10. Economy trials.

The trials that are considered to be routine ships trials are numbers 3, 9, and 10 of the above list. Post repair, full power, and economy trials are the only ones discussed in this chapter, but information on the other types of trials can be found in Naval Ships Technical Manual, chapter 094.

Post Repair Trial

The post repair trial should be made whenever the machinery of a vessel has undergone exten-sive overhaul, repair, or alteration which may affect the power or capabilities of the ship or the machinery. A post repair trial is usually made when the ship has 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 is to ascertain if the work has been satisfactorily com-pleted and efficiently performed, and if all parts of the machinery. are ready, for service.

The post repair trial should be held as soon as practicable after the repair work has been com-pleted, the preliminary dock trial made, and the persons responsible for the work are satisfied that the machinery is in all respects ready for a full power trial. The conditions of the trial are largely determined by the character of the work that has been performed. The trial should be con-ducted in such manner as the commanding officer and commander of the shipyard may deem necessary. In cases where repairs have been slight and the commanding officer is satisfied that they are satisfactorily performed and can be tested without a full power trial, such trial may be dispensed with.

Any unsatisfactory, conditions found to be beyond the capacity of the ships force should be corrected by the naval shipyard. When necessary, machinery should be opened up and carefully inspected to determine the extent of any injury, defect, or maladjustment which may have appeared during the post trial.

A certain number of naval shipyard personneltechnicians, inspectors, and repairmenaccompany the ship on a post repair trial. They check the operation of machinery that has been overhauled by the yard. If a unit of machinery does not operate properly, the yard technicians carefully inspect it to determine the cause of unsatisfactory operation.