CASA Part 66: LRU Connection and Maintenance
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Questions and Answers

What is the primary goal of preventative maintenance?

  • To respond to regulatory requirements
  • To upgrade existing systems
  • To identify and fix broken components
  • To keep systems from breaking (correct)

    • What is the basis for judging the efficiency of a maintenance organization?

  • The ability to respond to regulatory requirements
  • The ability to find and fix problems efficiently (correct)
  • The ability to upgrade existing systems
  • The ability to keep aircraft in the air

    • What is the primary difference between ATE and BITE?

  • ATE is used for simple systems, while BITE is used for complex systems
  • ATE is used for routine maintenance, while BITE is used for repair
  • ATE is used for upgrade, while BITE is used for overhaul
  • ATE is removed from the aircraft, while BITE is built-in (correct)

    • What is the purpose of ATE?

    <p>To diagnose and repair complex systems</p> Signup and view all the answers

    What is the primary goal of maintenance tasks?

    <p>To keep systems from breaking</p> Signup and view all the answers

    What is the characteristic of ATE?

    <p>It is a partially or fully automated test capability</p> Signup and view all the answers

    What is the purpose of BITE?

    <p>To provide automated test capabilities within a component</p> Signup and view all the answers

    What is the environment in which maintenance groups are judged?

    <p>Competitive air carrier business environment</p> Signup and view all the answers

    What is the primary purpose of a BITE system?

    <p>To diagnose failures and display repair instructions</p> Signup and view all the answers

    What is a characteristic of a simple BITE system?

    <p>It performs a 'go/no-go' self-test on a specific module</p> Signup and view all the answers

    What is a Flow Chart, in the context of maintenance Job Performance Aids?

    <p>A printed or computerized chart that directs the maintenance technician along a logical testing path</p> Signup and view all the answers

    What is a common problem that affects avionics components disproportionately?

    <p>No Fault Found (NFF) units</p> Signup and view all the answers

    What is the primary advantage of using a Flow Chart in maintenance?

    <p>It provides a logical testing and diagnosis path</p> Signup and view all the answers

    What is a characteristic of a sophisticated BITE system?

    <p>It records performance information over multiple flight legs</p> Signup and view all the answers

    What is the primary reason why unexpected maintenance is more expensive than scheduled repairs?

    <p>Because it is often unexpected and unplanned</p> Signup and view all the answers

    What is a common representation of a Flow Chart?

    <p>A series of 'if-then' statements</p> Signup and view all the answers

    What is the first step in installing an LRU into a connector?

    <p>Inspect the pins in the connector</p> Signup and view all the answers

    What is the purpose of the cup washer in the front hold down screw?

    <p>To hook over the catch on the front of the LRU</p> Signup and view all the answers

    What type of system is used to hold control panels in the cockpit?

    <p>Dzus fastener and rail system</p> Signup and view all the answers

    What should be removed before installing an LRU into a connector?

    <p>The plug covers</p> Signup and view all the answers

    What should be inspected before fitting an LRU into a connector?

    <p>The connector's pins</p> Signup and view all the answers

    What type of knob is used to secure some LRU's at the front lower edge?

    <p>Torque limited knob</p> Signup and view all the answers

    Why is it necessary to settle the LRU onto the rack?

    <p>To ensure the LRU is sitting flush on the base and centralised</p> Signup and view all the answers

    What is the purpose of the support pins in an LRU connector?

    <p>To hold the LRU in place</p> Signup and view all the answers

    What is a major obstacle that researchers have found in troubleshooting faults?

    <p>The difficulty in switching to a different type of problem after solving one</p> Signup and view all the answers

    What is the term used to describe viewing a situation as though through a tunnel?

    <p>Tunnel Vision</p> Signup and view all the answers

    What is the primary goal of the half-split test in troubleshooting?

    <p>To eliminate roughly half the items from a set of possibly failed components</p> Signup and view all the answers

    What is the risk associated with test-induced failures?

    <p>They are only a safety risk when they remain undetected</p> Signup and view all the answers

    What is a common consequence of tunnel vision in troubleshooting?

    <p>Information that confirms the hypothesis is given more weight</p> Signup and view all the answers

    What is the primary challenge in balancing the need for testing with the likelihood of test-induced failures?

    <p>Finding a balance between the need for testing and the risk of test-induced failures</p> Signup and view all the answers

    What is an example of a test-induced failure?

    <p>A connector is disconnected to test for a voltage and when reconnected, a pin is bent</p> Signup and view all the answers

    What is the primary reason why test-induced failures are a safety risk?

    <p>They can cause damage to the system or component being tested</p> Signup and view all the answers

    What should be done before performing extensive testing for a fault?

    <p>Confirm that there is an actual fault to find</p> Signup and view all the answers

    What should an inexperienced technician do once a fault is confirmed?

    <p>Consult diagrams and manuals to gain further information</p> Signup and view all the answers

    What is the benefit of having a sound knowledge of complex systems before troubleshooting?

    <p>It helps to eliminate large chunks of the system</p> Signup and view all the answers

    What should be done to confirm or dispute the operator's report of a fault?

    <p>Conduct a functional test to confirm the fault</p> Signup and view all the answers

    What is the purpose of simulating the conditions reported by the operator?

    <p>To eliminate operator error as the cause of the supposed fault</p> Signup and view all the answers

    What should be done to narrow down the area of the system requiring further testing?

    <p>Consult diagrams and manuals to gain further information</p> Signup and view all the answers

    What is the potential consequence of assuming the operator's debrief is 100% correct?

    <p>It may lead to a false trail</p> Signup and view all the answers

    What should be reviewed to identify possible causes of the fault?

    <p>The symptoms of the fault</p> Signup and view all the answers

    What direction is the fastener rotated to remove it from the LRU slot?

    <p>90 degrees anticlockwise</p> Signup and view all the answers

    What type of mechanism is used to secure the LCD display in the instrument panel?

    <p>Cam mechanism with spring clips</p> Signup and view all the answers

    What is the purpose of the spring in the LRU fastener?

    <p>To push the clip out of the slot</p> Signup and view all the answers

    What is the position of the slot when the LRU is locked in the fastener?

    <p>Across the aircraft or horizontal in a vertical panel</p> Signup and view all the answers

    What is used to secure some LRUs at the front lower edge?

    <p>Specialized knob</p> Signup and view all the answers

    What type of screw is used in some light aircraft to secure the LRU?

    <p>Captive Hex screw</p> Signup and view all the answers

    What is a key distinction between maintenance tasks and preventative maintenance activities?

    <p>One is done in response to regulatory requirements while the other is done to take advantage of technological advances</p> Signup and view all the answers

    Why do maintenance groups have an incentive to keep aircraft safely in the air?

    <p>Because it gives them a competitive advantage</p> Signup and view all the answers

    What is a key characteristic of Built-In Test Equipment (BITE)?

    <p>It is included in the design of a component, module, or subsystem</p> Signup and view all the answers

    What is the primary reason why troubleshooters tend to assume a faulty unit is the same as the one they previously encountered?

    <p>Because they are prone to tunnel vision due to instinctive thinking.</p> Signup and view all the answers

    What is a key difference between Automated Test Equipment (ATE) and Built-In Test Equipment (BITE)?

    <p>ATE is removed from the aircraft for testing while BITE is included in the design</p> Signup and view all the answers

    What is the primary benefit of the half-split test in troubleshooting?

    <p>It provides the most efficient way to diagnose a problem.</p> Signup and view all the answers

    What is the primary focus of preventative maintenance activities?

    <p>To keep things from breaking</p> Signup and view all the answers

    What is the primary risk associated with test-induced failures?

    <p>They can remain undetected and pose safety risks.</p> Signup and view all the answers

    What is a common scenario in which maintenance tasks are performed?

    <p>In response to regulatory requirements or to take advantage of technological advances</p> Signup and view all the answers

    What is the primary consequence of tunnel vision in troubleshooting?

    <p>It causes troubleshooters to overlook other possible causes of the problem.</p> Signup and view all the answers

    What is the primary challenge in balancing the need for testing with the likelihood of test-induced failures?

    <p>Balancing the need for information with the risk of inducing a failure.</p> Signup and view all the answers

    What is an example of a test-induced failure?

    <p>Disconnecting a connector to test for voltage.</p> Signup and view all the answers

    What is the primary issue with the Shotgun Approach method of troubleshooting?

    <p>It is extremely inefficient and expensive</p> Signup and view all the answers

    What is a characteristic of a hypothesis in troubleshooting?

    <p>It is an assumption presumed to be true, but must be proven or disproven</p> Signup and view all the answers

    What is Psychic Blindness, as described in the context of troubleshooting?

    <p>A phenomenon discovered in the early 1940's, shown to exist in different domains</p> Signup and view all the answers

    What is a common mistake that technicians make when adopting a hypothesis during troubleshooting?

    <p>They look for evidence supporting it while discounting evidence that refutes it</p> Signup and view all the answers

    What is the purpose of a CFS list?

    <p>To give a starting point for fault finding</p> Signup and view all the answers

    What is a common limitation of technicians when adopting hypotheses during troubleshooting?

    <p>They tend to adopt only a few hypotheses, even when a much broader range of hypotheses is consistent with the observed problem</p> Signup and view all the answers

    What is the primary reason why the two technicians initially failed to identify the root cause of the radar system problem?

    <p>They jumped to conclusions based on a superficial understanding of the system</p> Signup and view all the answers

    What is the significance of building accurate models of a system and its subsystems in troubleshooting?

    <p>It is a crucial step that takes the longest to complete and is never truly finished</p> Signup and view all the answers

    What is the primary consequence of assuming the part you can easily test is the part that is broken?

    <p>It leads to a false sense of security and delayed identification of the root cause</p> Signup and view all the answers

    What is the benefit of having a problem/solution mindset in troubleshooting?

    <p>It enables the technician to identify the root cause of the problem more quickly</p> Signup and view all the answers

    What is the primary purpose of trying to falsify a theory in troubleshooting?

    <p>To rule out other possible causes of the problem</p> Signup and view all the answers

    What is the primary lesson learned from the troubleshooting example?

    <p>That it is necessary to be thorough and methodical in troubleshooting</p> Signup and view all the answers

    Study Notes

    Avionics Equipment Connectors

    • During connection, ensure plug covers are removed and inspect pins for damage, bent pins, contamination, and corrosion.
    • Set the LRU onto the rack, ensuring it is flush and centralized, then push it back into the rack until the support pins and connector keys engage.
    • Apply firm pressure to fully engage the LRU and secure it with a knurled knob.

    Cockpit LRU Fitment

    • Cockpit control panels are held in place with a Dzus fastener and rail system.
    • Routine preventative maintenance involves inspecting, adjusting, lubricating, and replacing components to prevent breakage.

    BITE (Built-In Test Equipment)

    • BITE is a test capability built into aircraft components, modules, or subsystems to facilitate diagnosis and repair.
    • BITE ranges from simple self-tests to sophisticated systems that record performance data and provide instructions for repair.

    Troubleshooting Flow Chart

    • A flow chart is a printed or computerized guide that directs maintenance technicians along a logical testing and diagnosis path.
    • The chart branches to another test or conclusion based on previous test results.

    No Fault Found (NFF)

    • Repairing or replacing avionics components is expensive, especially when unexpected.
    • NFF is a frustrating maintenance problem where no fault is found despite troubleshooting efforts.

    Tunnel Vision

    • Tunnel vision occurs when maintenance technicians assume a familiar fault and overlook other possible causes.
    • Researchers have found that people tend to stick to a single diagnosis even when told to expect a different malfunction.

    Half-Split Test

    • The most efficient test is one that provides the most information, ideally eliminating half the possible failed components.
    • This type of test is called a "half-split" test.

    Test-Induced Failure

    • Testing a system or component can cause a failure, creating safety risks if undetected.
    • Test-induced failures can occur, for example, when a connector is disconnected and a pin is bent, creating an open circuit.

    Troubleshooting Example

    • To troubleshoot a system, eliminate large chunks of the system by using knowledge of complex systems.
    • Ask questions to confirm the fault and eliminate possible causes before testing.
    • Perform a functional test to confirm the fault and review symptoms to find clues leading to the cause.

    Dzus Fasteners and Rail System

    • Dzus fasteners are used to secure LRUs (Line Replaceable Units) in aircraft instrument panels
    • To remove the fastener, rotate it 90 degrees anticlockwise and a spring will push the clip out; be careful not to force it further as it may damage the clip
    • To fit the fastener, push it down and rotate until locked; the lock is only 90 degrees from where it pushes down
    • The slot of the LRU will be across the aircraft or horizontal in a vertical panel when locked, and along the rail or vertical when unlocked

    Cockpit LRU Dzus Fastener

    • The Dzus fastener in the cockpit has a cam mechanism in the handle that disengages from the rear connector and secures the display into the panel
    • The handle is secured by 2 spring clips

    Alternative LRU Securing Methods

    • Some light aircraft use a single captive Hex screw that, when unscrewed, will push the LRU out of its rack and disconnect it
    • The crew may need to use a long Allen Key of the appropriate size to unscrew the Hex screw
    • The electrical connector may be central or offset to one side, depending on its location

    Maintenance Practices

    • Preventative maintenance involves inspecting, adjusting, lubricating, replacing, and upgrading/overhauling systems and components to keep them from breaking
    • Maintenance tasks are performed in response to regulatory requirements or to take advantage of technological advances
    • The efficiency and effectiveness of a maintenance organization and individual workers are judged on their ability to find and fix problems efficiently

    Built-In Test Equipment (BITE) and Automated Test Equipment (ATE)

    • BITE is included in the design of a component, module, or subsystem to aid in diagnosis and repair
    • ATE is a range of partially or fully automated test capabilities that require the LRU to be removed from the aircraft and sent to the avionics bay
    • ATE is programmed to perform a series of tests without human intervention or can be set up to do so

    Troubleshooting Methods

    • "Shot gunning" involves randomly replacing LRUs until the symptoms of trouble disappear, but it is an inefficient and expensive method
    • A hypothesis is an assumption that must be proven or disproven by objective testing
    • Psychic blindness and tunnel vision can hinder effective troubleshooting
    • Half-split testing is a method that provides the most information by eliminating roughly half the items from a set of possibly failed components
    • Test-induced failures can occur, and it is essential to balance the need for testing against the likelihood of a test-induced failure

    Troubleshooting Example and Lesson Learned

    • A troubleshooting example involving a radar system shows the importance of not taking shortcuts and assuming the first problem found is the only one
    • It is essential to try to falsify your theory instead of just trying to prove it correct

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    Avionics Assembly and Disassembly Techniques PDF

    Description

    This quiz covers the proper procedures for connecting and maintaining LRUs (Line Replaceable Units) in aircraft, including removing plug covers and inspecting pins for damage.

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