You find a recurring fault code on a regional jet's flight control computer during pre-flight checks. Walk me through how you would diagnose and resolve the issue.
Technical
Avionics Troubleshooting
Regulatory Compliance
Technical Documentation
Junior avionics technicians must quickly and methodically diagnose avionics faults to keep aircraft safe and on schedule. This question tests technical troubleshooting, use of maintenance documentation, and adherence to safety and regulatory procedures.
How to answer
- Start by describing your initial safety and documentation steps: confirm the aircraft is grounded, power state, and logbook/defect entry checks.
- Explain how you'd consult applicable documents (MRs, AMM, wiring diagrams, fault isolation manuals, and MEL) and any company-specific procedures (e.g., Singapore Airlines or ST Engineering SOPs).
- Describe a structured troubleshooting approach: reproduce the fault if safe, note fault code specifics, check recent maintenance history and software versions, and verify cockpit/display indications with ground test equipment.
- Detail hands-on checks you would perform: harness and connector inspection, power and signal verification with multimeter/oscilloscope, line-replaceable unit (LRU) swap procedures if authorized, and use of built-in test equipment (BITE).
- Explain how you'd coordinate with senior technicians/engineering: when to escalate, request wiring diagrams, or obtain repair-release/engineering orders.
- Conclude with documentation and follow-up: update the technical log, record troubleshooting steps and test results, ensure corrective actions meet regulatory requirements, and confirm aircraft release to service with appropriate signatures.
What not to say
- Skipping documentation or not consulting the AMM/MEL before starting hands-on work.
- Making guesses (e.g., 'it's probably the computer') without systematic tests or evidence.
- Attempting repairs outside your certifying authority or not escalating when unsure.
- Failing to mention safety precautions (e.g., removing power, tagging, ESD protection) or regulatory compliance.
Sample answer
“First I'd ensure the aircraft is properly de-powered and the defect is recorded in the tech log. I'd look up the specific fault code in the aircraft AMM and the fault isolation manual. If the procedures allow, I'd attempt to reproduce the fault using BITE and verify related indications in the cockpit. I'd visually inspect connectors and wiring for signs of damage and check power rails with a multimeter. If initial checks point to an LRU fault and the manual allows, I'd swap the LRU with a serviceable unit and re-run tests. Throughout, I'd liaise with a senior technician or engineering if the fault persists or requires an engineering order. Finally, I'd document all steps, test results, and the reason for the aircraft release in the logbook, following company SOPs and regulatory requirements.”
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