Chip Light at 2315: Revision Mismatch and an Out-of-Calibration Wrench
It is 2315 at a regional airport in the Visayas. A turboprop commuter aircraft is AOG with a chip detector caution on the right engine, and the 0600 departure is already sold. You are the only licensed AMT on shift and have been on duty since 1000, including a two-hour road transfer. Your helper is a trainee in his third week who earlier today signed off a panel reinstallation under your supervision. The task card requires a chip detector inspection, oil filter removal and inspection, and a spinner torque check. The tablet holding your maintenance library is offline, so the trainee is working from a printed card marked 'Rev 6'; you saw 'Rev 8' in the library this morning. The torque wrench used for the spinner shows a calibration sticker that expired last month; the trainee used it, and says the second torque was 'close enough'. Operations calls every 20 minutes for an ETA.
1. Identify the human factors and MRM hazards in this shift and rank which one is most likely to produce an error.
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The hazards stack up:
- Fatigue: 13+ hours on duty, night hours, plus a road transfer - the classic window for attention lapses and slow rule-based errors.
- Time pressure: 0600 departure, calls every 20 minutes, a sold cabin - pressure to accept 'close enough'.
- Documentation ambiguity: Rev 6 card versus Rev 8 library. Tasks have been added or changed between revisions, so following Rev 6 risks omitting a step.
- Supervision gap: a third-week trainee signing work off, with the licensed AMT also task-saturated.
- Normalisation: 'close enough' on torque, and a calibration sticker nobody checked before use.
- Single-point dependency: one licensed AMT, one trainee, no second set of eyes.
Ranked: the calibration failure is the highest-risk item because it has already contaminated completed work silently. Torque errors do not announce themselves until a spinner departs. Fatigue and time pressure are the amplifiers that allowed it.
2. What must happen with the Rev 6 task card and the out-of-calibration torque wrench before any further work is signed?
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Both issues stop the release until resolved.
Task card: work from the current revision. Get Rev 8 from the library - restore the tablet connection, download it, or obtain a controlled copy from maintenance control. Compare Rev 6 against Rev 8 line by line to find what changed; if a step was added and not done, do it and record it. A printed card with no revision control is not approved data.
Torque wrench:
- Quarantine it immediately and tag it out of service.
- Identify every task torqued with it since calibration expired, not just tonight's spinner - that means a register search and a review of recent work orders.
- Re-torque those fasteners to the specified values with a calibrated instrument, after checking whether the manual permits re-torquing without fastener replacement.
- Raise a nonconformance report so the recall and tool-control process is corrected, not just this one wrench.
The 'close enough' comment is the real finding: it is a norm, and norms outlive the shift.
3. How should the handover and the reporting be handled - to the next shift, to quality, and to the operator's safety management system?
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Written, specific, and before anyone leaves the hangar.
Handover should state, per task: what was done, by whom, with which tool and which revision; what is open; what was quarantined; what was re-torqued; and what is still unverified. Vague handovers ('chip light checked, all ok') are how defects travel. If fatigue makes you unfit to certify, say so and hand the release to a rested licensed AMT.
Reporting:
- Quality manager: the calibration breach, the revision mismatch, and the completed-work recall.
- SMS: a voluntary report describing the latent conditions - night shift staffing, lone licensed AMT, offline library, tool recall. The operator's SMS exists to fix those, not to blame the trainee.
- If a defect was released unserviceable, report it through the occurrence process; do not quietly re-torque and move on.
Just-culture point: the trainee followed the example set by the shift. Fix the system, coach the person, and record it so the next 2315 shift has something to learn from.