Bridge Collapse Inquiry Yielding Information

During my stint at The Milwaukee Journal and Journal Sentinel, I more or less fell into a reporting speciality - - aviation accident investigations - - and I can see similarities in those airplane crash aftermaths and probes to the course of events unfolding after the I-35W bridge collapse in Minnesota.

Similar protocols are being followed (the National Transportation Safety Board is involved in major transportation fatal events) - - and those procedures are less-designed to point fingers than they are aimed at producing spin-free findings to improve public safety.

The bridge collapse investigation process, just like the probe into an airliner crash, will take time, as every clue is analyed and information released on the way to final conclusions, hearings and recommendations.

So the disclosure of major, water-related erosion from bridge stormwater runoff near one of the bridge piers is probably not related to the tragedy, sources say, but the finding could lead to more public awareness and remedial steps - - even if there is no direct cause-and-effect linkage to the collapse.

And it's also possible that while the erosion damage did not cause or initiate the collapse, it may also turn out to be one contributing factor in a chain of cascading events.

That's usually the explanation for a plane crash: one thing leads to another - - human, mechanical or exterior forces that might seem isolated, but are linked in a coincidental, perhaps impossible sequence, advancing to one unforgiving, fatal point.

For example, I remember studying the crash of a commuter airliner crash in Texas when a piece of tail fell off.

A million initial questions? Pilot error? Bird strike? Weather factors?

Or did the plane come from the factory with a defective tail or connected part or system?

After a year or so, the findings were released.

A key tail piece did indeed fall off, but not because of bad production or substandard metal, severe weather, poor piloting, or errant birds .

The tail piece fell off because when it had been removed for maintenance it was not completely screwed back into position.

Failing to reinstall 47 airliner tail assembly screws back is bad enough, but human failings like that are supposed to get caught when a supervisor checks the job in the hangar.

And then the supervisor signs a form to that effect: repair job OK. No spare pieces lying on the mechanics' tables.

But in this case there was slipshod double-checking - - further evidence of internal management problems and of federal regulatory oversight, too - - but the plane went back into service, where the stress of a few more hours of normal flight created enough vibration to rip free the partially-bolted-tail piece free.

That sent the plane into its uncontrollable plunge, killing 14 people.

That's how a cascading failure works - - small things involving people and machines and technology begin improperly, quietly - - and end in disaster.

(I pretty much remembered the details correctly, but went to a federal data base to look it up. You can read the report summaries here.)

When the bridge collapse investigation is finished, the conclusion will surely find a combination of problems and factors, some small, some substantial.

The erosion finding is interesting on its own, and we will learn a great deal more about engineering, construction, inspections, weather, financing and many other circumstances as the investigation proceeds.

And expect many recommendations in the science, technology and human behavior areas, all to prevent a repeat collapse.