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Have there been any studies that gathered statistics on overlooked items on preflight inspections, or even statistics on how many pilots actually perform a good preflight (following a checklist, etc.)?

If such a study exists, did it uncover anything that proved to be something that was often overlooked?

Is there an industry "best practices" document for preflight inspections (beyond just following the manufacturer's checklist found in the POH)?

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  • $\begingroup$ The corollary would also be interesting too, how many perform a postflight inspection, or even follow shutdown checklists? I regularly charter a plane at a local FBO and it's not uncommon that it's sitting in the hangar with the flaps down (first item on the after landing checklist, flaps: up, makes you wonder what other items they didn't do)... $\endgroup$
    – falstro
    Jan 13, 2014 at 9:02
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    $\begingroup$ Yeah, I'm wondering if there has been any formal studies that would move it from anecdote to something more concrete. I have a feeling postflight inspections are rare, but I wonder if there are some numbers to that. Also, I'm looking for ways to improve safety that go beyond following a checklist. Something someone told me once was to "rock the wings" while performing the preflight and before sumping fuel, as that would dislodge any water from behind wrinkles in the fuel tank. Something that I've added to my preflight but you won't find on a manufacturer's checklist. $\endgroup$
    – Canuk
    Jan 13, 2014 at 9:07
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    $\begingroup$ For light GA aircraft, based on how often we seem to have fuel exhaustion incidents, I'd say the part about "Look in the tanks to see how much fuel you have" is overlooked far more often than it should be. $\endgroup$
    – voretaq7
    Jan 13, 2014 at 16:17
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    $\begingroup$ @voretaq7 yep. I visually inspect the fuel level every time! $\endgroup$
    – Canuk
    Jan 13, 2014 at 19:26
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    $\begingroup$ @Canuk Wouldn't mixing up the water and fuel right before sumping potentially cause you to miss water in the fuel? Sumping works because water (being heavier) settles to the bottom of the tank, but if you mix it up right before sumping, couldn't that cause you to miss it? $\endgroup$
    – reirab
    Apr 15, 2015 at 18:34

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This FAA article is about using electronic checklists for airline flights (it concludes that they're better than paper ones) and includes this quote:

They found the crews averaged 3.2 checklist errors per flight (one of the observed flights had 14.) The most-common checklist error involved the omission or deferral of an item, which was later forgotten.

NASA commissioned a general study into checklists in 1990, but it doesn't identify specific items that are commonly overlooked. It does say that as the number of items on a checklist increases, the chances of overlooking any individual one does too:

Swain and Guttman (1983), in their study of nuclear power plant operations “recognized the fact that as the list of items grows, there may be a higher probability of overlooking any given item” (chap. 15, p. 13)

The final section of the paper has recommendations for checklist design, which could be considered the "best practices" you mentioned, but of course it's a very general list, e.g.

The most critical items on the task-checklist should be listed as close as possible to the beginning of the task-checklist, in order to increase the likelihood of completing the item before interruptions may occur

AOPA's Flight Training magazine has an article on "frequently forgotten" checks that is more specific and most of the checks seem to apply to most (light) aircraft, but it doesn't provide any authoritative sources. They also have a "how to preflight" article that gives more information and includes this interesting observation:

As an experiment, I held a preflight contest with a "bugged" trainer. I reversed the rigging on the ailerons so their movement was contrary to control inputs. Every one of the contestants checked control movement and freedom, but no one caught the problem.

Putting all that together suggests - only to me, and I'm not an expert - that it's less important to think about specific items that you might forget, and more important to ensure that you complete the checklist fully and really verify the results of each check. If you consider some checklist items to be 'more important' than others then it could also lead to mistakes because you overlook the 'less important' ones.

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    $\begingroup$ Thanks for the great, well-researched answer. It appears to me that it's not one particular item that gets overlooked, but rather a habit or distraction that can cause something to get overlooked. I particularly like the idea of the important items at the top of the checklist. I also found an interesting book that talks about the phsycology of creating checklists that was fascinating: "The Checklist Manifesto" by Atul Gawande (amzn.com/0312430000) $\endgroup$
    – Canuk
    Jan 13, 2014 at 19:31

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