Learning Objective: Recognize the definition of troubleshooting, and identifiy the seven steps in the troubleshooting procedures.

Troubleshooting/trouble analysis may prove to be the most challenging part of system maintenance. Troubleshooting is the logical or deductive reasoning procedure used when you are determining what unit is causing a particular system malfunction. The MIM for each aircraft generally provides troubleshooting aids that encompass seven steps. The steps are conduct a visual inspection, conduct an operational check, classify the trouble, isolate the trouble, locate the trouble, correct the trouble, and conduct a final operational check. The various MIMs provide a variety of troubleshooting aids. Table 3-1 shows a representative troubleshooting table. The troubles in this table are numbered to correspond with the step of the operational check procedures where the trouble will become apparent. Other MIMs use trouble analysis sheets to pursue a trouble to a satisfactory solution by the process of elimination. The symptom is defined in tabular form with a remedy for each symptom. An example of trouble analysis sheets is shown in tables 3-2 and 3-3. The sheets used with the checkout procedures relate to checkout procedures by direct reference or to discrepancies occurring in flight or during ground operations. Each table provides a remedy for each symptom. When the remedy is as simple as replacing a component or making an adjustment, this fact is so stated. When the remedy requires further analysis, the entry in the REMEDY column will be a reference to an applicable paragraph, figure, or possibly another manual. See tables 3-1 and 3-2.

Table 3-3.-Troubleshooting Emergency/Parking Brake System

Each trouble analysis procedure provides preliminary data, such as tools and equipment, manpower requirements, and material. In the block type of troubleshooting sheets, the procedure is arranged in the order of most likely occurrence. The sheet contains a NO-YES response to direct maintenance personnel through a logical series of steps. These directed responses assist in isolating the malfunction. When the requirements of a step are satisfactory, you go to the YES column and perform the referenced step. When the requirements of a step are not satisfactory, you go to the NO column and perform the referenced step. This method is continued until the malfunction is isolated and corrected. The original checkout procedure must then be repeated to ensure that the malfunction has been corrected.

Troubleshooting procedures are similar in practically all applications, whether they be mechanical, hydraulic, pneumatic, or electrical. These procedures are certainly adaptable to all aircraft maintenance, as well as other types of installations. Auto mechanics use these steps to find and repair malfunctions in automobiles. You will use the same procedure to find and repair malfunctions within aircraft systems. Clarification of the seven distinct troubleshooting steps previously mentioned are as follows:

1. Conduct a visual inspection. This inspection should be thorough and searching-checking all lines, units, mechanical linkage, and components for evidence of leaks, looseness, security, material condition, and proper installation. During this visual inspection, the hydraulic system should be checked for proper servicing-reservoir for proper level, accumulators for specified preload, etc.

2. Conduct an operational check. The mal-functioning system or subsystem is checked for proper operation. This is normally accomplished by attaching the support equipment to the aircraft, which supplies a source of electrical power and pressurized fluid to operate the hydraulic system. In some instances, however, the aircraft may be ground checked by using aircraft power and equipment. Whatever the case, during movement of the malfunctioning unit, the AM checks for external leakage, the correct direction of component movement, its proper sequence of operation, speed, and whether the complete cycle was obtained. 

3. Classify the trouble. Malfunctions usually fall into four basic categorieshydraulic, pneumatic, mechanical, and/or electrical. Using the information gained from steps 1 and 2, the AM determines under which classification the malfunction occurs. Something affecting normal flow of hydraulic fluid would be classified under the hydraulic classification. The flow of fluid may be affected by external and internal leakage, total or partial restriction, or improper lubrication.

Something affecting the normal flow of compressed gases is classified as a pneumatic malfunction. This type of malfunction stems from the same general sources as hydraulic malfunctions mentioned in the previous paragraph.

Most units that operate hydraulically or pneumat-ically incorporate mechanical linkage. If a discrepancy in the linkage exists, it will affect the systems operation. Mechanical discrepancies should be found during visual inspections, and they are usually in one of the following categories: worn linkages, broken linkages, improperly adjusted linkages, or improperly installed linkages. Many hydraulic units incorporate electrical compo-nents to operate or control them. You must be able to determine if the electrical system is functioning normallyelectrical malfunctions will usually be a complete power failure, circuit failure, or component failure.

4. Isolate the trouble. This step calls for sound reasoning, a full and complete knowledge of hydraulic theory, as well as a complete understanding of the affected hydraulic system. During this step, you must use your knowledge and the known facts to determine where the malfunction exists in the system. Usually the trouble can be pinned down to one or two areas. This is done by eliminating those units that could not cause the known symptoms and those that can be proved to be operating normally.

5. Locate the trouble. This step is used to eliminate unnecessary parts removal, thus saving money, valuable time, and man-hours. Often, you have determined what unit or units in the system could have caused the malfunction, thus verifying the isolation step. Both hydraulic and pneumatic malfunctions are verified in the same manner. You remove lines and inspect them for the correct flow in or at the suspected unit. Internal leaks may occur in valves, actuators, or other hydraulic units. Any unit that has a line that could carry fluid to "return" is capable of internal leakage. Mechanical malfunctions are located by closely observing the suspected unit to see if it is operating in

Figure 3-10.A typical multimeter.

accordance with the applicable aircraft MIM. Mechanical discrepancies are usually located during the visual inspection in step 1. Electrical malfunctions are located, with the assistance of AEs, by tracing electrical power require-ments throughout the affected system.

6. Correct the trouble. This step is accomplished only after the trouble has been definitely located and there is no doubt that your diagnosis is correct. Mal-functions are usually corrected by replacement of units or components, rigging and adjustments, and bleeding and servicing.

NOTE: Always check the applicable MIM for CAUTION, WARNING, and SAFETY notes concerning maintenance procedures.

7. Conduct a final operational check. The affected system must be actuated a minimum of five times, or until a thorough check has been made to determine that its operation and adjustments are satisfactory.