Root Cause
Why engineered systems fail, told through the investigation report — the mechanism, drawn as a blueprint.
Kegworth: The Gauge Was Right and Nobody Looked at It
In January 1989 a fan blade broke inside the left engine of a new Boeing 737-400, and nineteen seconds later the crew throttled back the right one. For three minutes the left engin...
Esso Longford: They Fixed the Wrong Exchanger
On a September morning in 1998, an Australian gas plant lost the flow of oil that kept two heat exchangers from freezing. One of them was leaking, so operators sent hot oil back th...
Piper Alpha: The Gas Chart Read the Valve, Not the Pipeline
On the night Piper Alpha burned, two neighboring platforms were watching instruments that were telling them the truth, and reading them as calm. On Tartan, a pressure chart went fl...
Piper Alpha: The Permit Cleared the Job, Not the Pump
The story everyone tells about Piper Alpha is a night shift that started a pump with no safety valve on it because nobody knew. The valve was written down: permit 23434, signed by ...
Flixborough: The Pipe Was Strong Enough
The story everyone tells about Flixborough is a temporary pipe drawn in chalk on a workshop floor. That is in the report. So is this: the pipe was made properly and could stand pre...
Ocean Ranger: The Cover No Rule Told Anyone to Close
The story everyone tells about the Ocean Ranger is the storm. Two other rigs worked the same field that night and both rode it out, and the stability calculations say the wind push...
The Kielland Rig Was Already Cracked When It Left the Yard
The story everyone tells about the Alexander L. Kielland is a bad weld. That is where the Norwegian commission's report begins. The same brace carried a second hole, less than a fo...
The DC-10 Crack That No Rule Required Anyone to Report
The story everyone tells about Flight 191 is an airline that took a shortcut with a forklift. That is in the report. What is also in the report is that the shortcut was adopted on ...
The DC-10 Memo That Predicted the Crash and Vanished
The story everyone tells about the DC-10's cargo doors is a lone whistleblower, ignored by a cold company. That memo is real. But the engineer who wrote it wasn't the first person ...
Three Mile Island's Warning Was Written Four Times, Then Filed
Everyone who tells the Three Mile Island story tells the same second half: an inspector warned two federal regulators days before the accident, and it was too late. That's true — a...
Three Mile Island Didn't Fail From a Stuck Valve — It Failed From a Light Never Wired to Check It
Three Mile Island is remembered as a stuck valve and operators who got it wrong. The Kemeny Commission's own account says something narrower: the control room had no way to know th...
The Challenger O-Ring Didn't Crack in the Cold — It Was Simply Too Slow
The story everyone already knows gets most of it right — cold, an O-ring, engineers who warned, managers who launched anyway. This episode corrects the one detail most retellings g...
The Silver Bridge Didn't Fail From Corrosion — It Failed From a Crack No One Could Ever Have Seen
Every bridge in this series failed because a control that existed on paper was never run — a calculation nobody made, a check nobody performed. This one is different. The National ...
The I-35W Bridge Did Not Fail From Neglect — It Failed From a Calculation Nobody Made
Within days, this became the story of American infrastructure: an old bridge, decades of deferred maintenance, a country that had stopped taking care of its roads. The National Tra...
The Hyatt Regency Walkways Were Never Safe — Not Even Before the Change
The sentence everyone knows is true: a fabricator changed one continuous rod into two and doubled the load on a connection nobody recalculated. Here is what it leaves out. The Nati...
The 2003 Blackout Was Not Caused by a Software Bug
Two sentences carry this case: a tree in Ohio, and a software bug. Both are true, and neither is the cause. The final report of the U.S.-Canada Power System Outage Task Force names...
The Apollo 13 Oxygen Tank Did Not Explode
Everyone knows the sentence: an oxygen tank exploded. The Apollo 13 Review Board's own numbers say something else. The pressure in that tank rose from 887 to 1,008 psi, against a b...
The Millennium Bridge Wobble Was Never About People Walking in Step
London's Millennium Bridge opened on 10 June 2000, swayed sideways by around 70 mm under the crowd, and closed two days later for twenty months. The famous explanation is that pede...
The Skyscraper That Was Secretly Rebuilt at Night
A 59-storey tower in midtown Manhattan stands on four columns placed at the middle of each side, not at the corners, because a church owned the corner and would not sell. The build...
The Tacoma Narrows Bridge Did Not Fail From Resonance
Almost every physics textbook that shows you the Tacoma Narrows film calls it resonance. The three engineers who investigated the collapse wrote the opposite, and they wrote it dow...