Troubleshooting Techniques PDF - Aviation Australia

Troubleshooting Techniques General Troubleshooting Process Troubleshooting procedures are similar in most applications, whether the defect is mechanical, hydraulic, pneumatic or electrical. Troubleshooting procedures are adaptable to all aircraft maintenance applications and systems o...

Troubleshooting Techniques General Troubleshooting Process Troubleshooting procedures are similar in most applications, whether the defect is mechanical, hydraulic, pneumatic or electrical. Troubleshooting procedures are adaptable to all aircraft maintenance applications and systems of operation. General troubleshooting process At all times, troubleshooting begins with discussing the defect with the person who identified it. From this point, maintenance data will be consulted to determine possible faults and whether the problem is historical in nature. Remember: Defects occur through cause and effect; once we identify the cause, we can correct the effect. The initial troubleshooting steps are: Discussing the defect with the person who identified it Consulting maintenance data to determine possible faults. There are distinct troubleshooting steps to follow. Troubleshooting steps 2023-11-16 B1-07d Maintenance Practices Page 320 of 335 CASA Part Part 66 - Training Materials Only  Once the defect has been identified, then: Conduct a visual inspection. Conduct an operational check. Classify the defect. Isolate the defect. Locate the defect. Correct the defect. Conduct a final operational check. 2023-11-16 B1-07d Maintenance Practices Page 321 of 335 CASA Part Part 66 - Training Materials Only  Identify the Defect All defects must be transferred to a written record. It is not acceptable practice to rely on word of mouth. A report of a defect will be generated by either: An aircraft technical log entry as a result of an in-service observation An aircraft logbook entry, or similar technical defect record, of a defect found as a result of a routine maintenance procedure An Airworthiness Directive or similar, issued by a regulatory authority A Service Bulletin or similar, issued by the manufacturer. The importance of this, apart from regulatory compliance, is to ensure that the troubleshooting procedure is applied to the correct aircraft. The troubleshooting process then begins: If possible, attempt to gain additional information by discussing the defect with the person who identified it initially. Determine from previous technical entries if the defect has a history, and if so, what previous rectification actions have been taken. Remember that defects occur through cause and effect; once the cause is identified, the effect can be corrected. Consult the Aircraft Maintenance Manual to establish: Any supplementary information to that already gathered The recommended procedure to follow An awareness of other systems that might be affected as a result of the defect or as a result of the rectification The necessary test equipment and ground service equipment The personnel required and likely timeline to complete the rectification. 2023-11-16 B1-07d Maintenance Practices Page 322 of 335 CASA Part Part 66 - Training Materials Only  Conduct a Visual Inspection First, confirm the identity of the aircraft to which the defect refers. Conduct a thorough and searching visual inspection of all likely components implicated in the scope of the defect. This should include evidence of proper installation, material condition, leaks, looseness and security. The initial inspection is critical in assessing the condition and extent of the defect. Performing a visual inspection Conduct an Operational Check In accordance with the maintenance manual, prepare to conduct an operational check of the malfunctioning system or subsystem. This includes placing the aircraft in a suitable location, sourcing external electrical power, sourcing pneumatic air and/or hydraulic fluid, and gathering other ground service equipment such as aircraft jacks. Caution - follow maintenance data 2023-11-16 B1-07d Maintenance Practices Page 323 of 335 CASA Part Part 66 - Training Materials Only  The key here is to place the aircraft and/or system in the condition under which the defect was initially found. An example of this is to place the aircraft in a flying condition, in a hangar, on jacks, with the landing gear up. Aircraft on jacks During the operational test, for example, of an undercarriage retraction, check for external leakage, the correct direction of component movement, its proper sequence of operation and timing, its speed, and whether the complete cycle was obtained. Note: A good maintainer not only observes, but also listens and feels components during operation, safety permitting. 2023-11-16 B1-07d Maintenance Practices Page 324 of 335 CASA Part Part 66 - Training Materials Only  Performing an operational check 2023-11-16 B1-07d Maintenance Practices Page 325 of 335 CASA Part Part 66 - Training Materials Only  Classify the Defect Using the information gained from the above steps, determine under which classification the malfunction occurs. System operational malfunctions usually fall into four basic categories: Mechanical Fluid (Hydraulic, Fuel, Oil, Water, Waste, etc) Pneumatic Electrical. Classifying the defect 2023-11-16 B1-07d Maintenance Practices Page 326 of 335 CASA Part Part 66 - Training Materials Only  Mechanical Most units that operate hydraulically, electrically or pneumatically incorporate a mechanical linkage. If a discrepancy in the linkage exists, it can affect the system’s operation as valves and mechanisms may be restricted in travel. Mechanical discrepancies should be found during the initial visual inspection or observed during the operational check. They are usually in one of the following categories: Worn linkages Broken linkages Improperly adjusted linkages Improperly installed linkages. Checking mechanical linkages 2023-11-16 B1-07d Maintenance Practices Page 327 of 335 CASA Part Part 66 - Training Materials Only  Fluid (Hydraulic, Fuel, Oil, Water, Waste, etc) A problem affecting the normal flow of a fluid in a hydraulic circuit is classified as a hydraulic defect. The flow of fluid may be affected by: External and internal leakage A total or partial restriction Improper lubrication. While an external leak is generally easily observed, be aware that if fuel is used to cool hydraulic fluid, a leak inside a fuel tank is much less obvious. Checking hydraulic components 2023-11-16 B1-07d Maintenance Practices Page 328 of 335 CASA Part Part 66 - Training Materials Only  Electrical Many hydraulic units also incorporate electrical components to operate or control them. Most electrical valves have mechanical indicators to display their operation, and solenoid valves usually produce an audible click when operated. Hydraulic transfer valves, operated electrically to position servo actuators, and electrical position sensors require a comprehensive understanding of the electrical system. Electrical malfunctions are usually: A power failure A wiring fault A component failure. Engine electrical harness 2023-11-16 B1-07d Maintenance Practices Page 329 of 335 CASA Part Part 66 - Training Materials Only  Pneumatic High-pressure air systems exhibit similar faults to those of a hydraulic system. Low-pressure and vacuum system faults can be difficult to isolate, especially leaks, incorrect regulator settings or filter restrictions. Flow rates higher than that which the source is capable of supplying are a common cause of malfunctions. Pneumatic system defect 2023-11-16 B1-07d Maintenance Practices Page 330 of 335 CASA Part Part 66 - Training Materials Only  Isolate the Defect Not all defects are identified by a visual examination or operational test. Aircraft with on-board maintenance systems or Aircraft Maintenance Manuals with a troubleshooting tree of procedures to follow assist with further isolation of the cause of the problem. However, many operational aircraft do not have these aids, so the defect isolation process requires the greatest skill, largely gained from: The benefit of practical experience A full and complete understanding of basic theoretical knowledge A sound understanding of the description and operation of the system, as provided by the manufacturer An awareness of the subtle differences that might exist between systems and components fitted to different models of the same series of aircraft. The Half-Split Rule With the defect classified and using the facts and knowledge gathered from the visual inspection and operational test, attempt to isolate the malfunction by applying the half-split rule. This can be applied to any of the four major systems mentioned above. The basic principle is: Split a system into two parts and perform tests or observe if the fault is still present or has been resolved. On the half of the system that still has a fault, carry out a further equidistant isolation. Each half-split of a system reduces the number of components and/or the system length until the fault area can be pinpointed with confidence. Half-split rule 2023-11-16 B1-07d Maintenance Practices Page 331 of 335 CASA Part Part 66 - Training Materials Only  The necessary logbook entries must be made for every individual item of a component that is removed for fault diagnosis, even if it is not related to the fault. Locate the Defect Both hydraulic and pneumatic malfunctions are verified in the same manner. Maintenance checks may include removing lines and inspecting 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. Defect location Mechanical malfunctions are located by closely observing the suspected unit to see if it is operating in accordance with the applicable AMM. Mechanical discrepancies are usually located during the visual inspection. 2023-11-16 B1-07d Maintenance Practices Page 332 of 335 CASA Part Part 66 - Training Materials Only  Locate the defect 2023-11-16 B1-07d Maintenance Practices Page 333 of 335 CASA Part Part 66 - Training Materials Only  Correct the Defect Defect correction is accomplished only after the trouble has been definitely located and there is no doubt that your diagnosis is correct. Malfunctions are usually corrected by replacing units or components, fine-tuning rigging and adjustments, and bleeding and servicing. Components and systems disturbed as part of the fault-finding process must be restored. Correct the defect 2023-11-16 B1-07d Maintenance Practices Page 334 of 335 CASA Part Part 66 - Training Materials Only  Conduct a Final Operational Check After performing maintenance on some systems, it is a requirement to perform a duplicate inspection of the assembly and functionality. This inspection must be performed and certified by another qualified individual. Be aware that carrying out a maintenance procedure on a particular system to rectify a fault might also impact an associated system. That associated system must also be fully tested and certified for serviceability, possibly in conjunction with another trade. Finally, an operational check which might include exercising a system a minimum number of times is performed as specified by the AMM. Final operational check Once this has been completed, all the paperwork raised must be checked for completion, including the recording of part and serial numbers and release notes of components that have been changed. The appropriate licensed or approved persons provide a Certificate of Release to Service stating that all the work necessary has been performed. Only at this point can the aircraft be returned to service. 2023-11-16 B1-07d Maintenance Practices Page 335 of 335 CASA Part Part 66 - Training Materials Only