I operate a Bombardier Dash 8 Q400. I want to know if aircraft engineers are mandated to close or rectify a defect by only following the fault isolation manual (FIM). Can an engineer instead use his knowledge and experience of the systems to isolate the problem and resolve the defect?

  • 2
    $\begingroup$ what are FIM and AMM? $\endgroup$
    – Manu H
    Nov 25, 2019 at 14:02
  • $\begingroup$ As a pilot or maintenance? $\endgroup$
    – John K
    Nov 25, 2019 at 17:17
  • 1
    $\begingroup$ @ Manu H Fault Isolation Manual and Aircraft Maintenance Manual $\endgroup$
    – John K
    Nov 25, 2019 at 20:21
  • $\begingroup$ It would seem to depend on the particular aircraft, and perhaps whether it's private or commercial. AFAIK there's no such thing as a "fault isolation manual" for my Piper Cherokee. $\endgroup$
    – jamesqf
    Nov 26, 2019 at 18:01
  • $\begingroup$ Engineer, or FAA certified mechanic? Hypothetical, or actual situation? If actual, and if properly diagnosed, I don't see a problem. I could be wrong, but I don't think technicians are bound to using checklists in the way aircrew are. Now if they didn't use a reference and missed something, that's a totally different issue. $\endgroup$ Jan 4, 2020 at 16:13

1 Answer 1


FIM contains procedures for both A/C systems (E.G. EICAS, ECAM, CPDS) messages and pilots/maitenance observations (e.g. smell of burning oil, windshield delamination). All kind of reasonably possible faults should be covered by FIM.

Just simply use yor FIM preambule to determine if it specifies what to do when fault is not covered by FIM and to determine either mechanic judgement or OEM (A/C manufacturer)contact is requied in such case. If such information is not included contact OEM.


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