System test procedures are printed on standard maintenance requirement cards (MRCs). Each system test MRC contains the same information as found on any other equipment MRC. Ships' 3-M Manual, Volume I, OPNAVINST 4790.4, explains MRCs in detail.

The actual test procedure is presented in an easy-to-read step-by-step format. Figure 10-16 shows a sample system test MRC page. Note that the information is listed in four columns:

1. Step-a number to indicate the phase or point in the test sequence.

2. Equipment-the equipment of a station/work center that performs the step.

3. Procedure-what action must be accomplished.

4. Response-the "desired" response or result from a particular step.

Also note that pertinent safety warnings and operational notes (special instructions) precede important steps.

Since a system test normally requires the participation of many individual stations/work centers, coordination is a must. DSOT, for example, can include four or five different stations. Each station will have its own copy of the MRC of the test. That way, all involved personnel can follow along with each step as it occurs.

Test procedures are arranged so one individual serves as the test conductor/coordinator. The test conductor controls and directs the performance of the test (keeps it going). Normally, this individual is located at the WDE, but that varies among ships. The test conductor can also call out each step number and record any response data.

Refer to figure 10-16, step 49. The test conductor calls out "Step 49." You, the EP2 panel operator, must observe the reaction of the ALERT indicator lamp and buzzer of the GMLSs. Knowing how your system operates, you realize the lamp should flash and the buzzer buzz when they are activated. (Step 48 activates them.) If they work properly, you report over the sound-powered phone circuit, "Step 49, flashing and buzzing." The test conductor acknowledges your verbal response and the test goes on. This procedure may vary from ship to ship, but the idea is the same.

Test Evaluation and Fault Isolation

Each system test is divided into independent phases where possible. This division helps in conducting the test and is a fault isolation aid. Particular parts of the system may be checked without conducting an entire test.

Selected parameters under test are sampled or measured to specified tolerances. These tolerances, along with the desired responses, are listed on the MRC following the applicable steps. Step 40 on figure 10-16 shows parameters and tolerances.

Fault isolation directories are located in each MRC and keyed to corresponding test steps

Figure10-16.-Sample system test MRC page.

(fig. 10-17). If an out-of-tolerance condition or incorrect response is observed, the fault isolation direction should be consulted. It lists system and equipment OPs that can be referenced to aid in troubleshooting.

Ideally, the test should be completed without pause for fault isolation. Completing the test permits a more accurate evaluation of the fault. It also results in the most efficient use of manpower.

A significant feature of a GMFCS is its general-purpose digital computer. In addition to solving the tactical fire control problem, the computer is also a test instrument. Digital test programs have been designed to enhance system testing.

Figure10-17.-Sample test fault directory.

Dynamic digital tests are controlled by the computer complex of the GMFCSs or the computer complex of the NTDS/WDSs. The computer stores special test programs and generates a variety of dynamic target problems. The test program solves the fire control problem to arrive at ideal values. These values are then compared with actual test responses to provide error monitoring. Teletypewriters can be used to print out this information for evaluation.

A new concept in digital system testing uses the computer to isolate a fault. This testing can be performed during or separate from normal computer operations. The advantages are obvious-quicker repair times and increased readiness.