Re: [SystemSafety] 2012 Super Puma Ditchings

From: Peter Bernard Ladkin < >
Date: Fri, 13 Jun 2014 22:46:47 +0200


On 2014-06-13 11:21 , Andrew Rae wrote:
> ....Did you notice that the accident report has a huge volume of
> analysis looking at why the original
> finite element modelling of the lubrication shaft underestimated the stresses, but seems to accept
> the incorrectly wired switch as
> just one of those things that happens?

I probably would have if I'd actually looked at the report :-)

(I hope to get around to it next week, but I am a little tied up at the moment.)

> No recommendations are made about change management, or obsolescence management.

As I understand it, commercial flight operators are nowadays supposed to have a "Safety Management System" (SMS) in place.

> I'd be highly surprised if there weren't processes supposed to address all three of these, so
> there's a step back again to ask why they didn't happen or didn't work.

Spot on. I would take you to be talking about the SMS and asking why it didn't work.

> Is this one of those cases where some use of accident modelling would really help the investigators?
> A simple AcciMap or Why-Because Graph of the causes mentioned in the report
> would find two nodes connecting into the outcome (the lubrication failure and the backup system
> "failure"), one with a long web of causes, and the other barely investigated.

Well, I'd think so, but then I would, wouldn't I?

I think of Accimaps more as a visual presentation of causal conclusions than a modelling or investigatory method. I note, though, that what you suggest Accimaps or a WBG could show is actually some property of the causal graph, and in our experience enabling such observations is very dependent on the layout used. The ATSB used Accimaps first in the Lockhart River report and their Accimaps got to be visually quite confusing with more than 15 or 20 nodes. Whereas WBGs with 20 nodes seem trivial and they remain quite clear up to at least 70 or 80 nodes. That's in large part due to the layout engine. I have thought for many years that the importance of presentation is underestimated. But I still don't seem to be able to convince many colleagues of that.

PBL Prof. Peter Bernard Ladkin, Faculty of Technology, University of Bielefeld, 33594 Bielefeld, Germany Tel+msg +49 (0)521 880 7319 www.rvs.uni-bielefeld.de



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