Root Cause Analysis Is The Foundation of Risk Management

I had a conversation with a Risk Management author about Risk Registers, Root Cause Analysis, and a few other topics. He references a book, The Failure of Risk Management and How to Fix It, in his blog post. In this book, the Sioux City, Iowa crash of United 232 is an example of common cause failure - one of the failures of risk management.

In the book, it is stated...

During the flight, the DC-10’s tail-mounted engine failed catastrophically, causing the fast-spinning turbine blades to fly out like shrapnel in all directions. The debris from the turbine managed to cut the lines to all three redundant hydraulic systems, making the aircraft nearly uncontrollable. Although the crew was able to guide the aircraft in the direction of the airport by varying thrust to the two remaining wing-mounted engines, the lack of tail control made a normal landing impossible.

This correctly describes the failure mode, but it fails to reach the root cause.

First, it was not the turbine blades that cracked but a crack in the hub that bound the turbine blades of the first compress to the turbine engine shaft. 

Investigators were able to determine the root cause of the accident, which killed 112 of 296 people on board the DC-10, after performing tests on an engine part found earlier this month in an Iowa cornfield. Anthony J. Broderick, acting executive director of the Federal Aviation Administration, said the flaw was detected in a 300-pound titanium disk that spins the blades in the engine’s forward fan assembly. Broderick, confirming a report by the Washington Post, said the imperfection developed when the titanium was manufactured in 1970 at the Henderson, Nev., plant of Timet, a division of the Titanium Metals Corp. of America. [1]

The assumption - wrongly concluded by the author of The Failure of Risk Management and How to Fix It  - was that the turbine blades cracked, is an example of a solution looking for a problem to solve, and the failure of root cause analysis applied to the root cause analysis process itself.

But Yes, the failure of the hub holding the blades did sever the hydraulic line, which ran through a single channel in the vertical stabilizer, causing all flight control surfaces to lose control. 

Proximate Cause is not the Root Cause

One of the failings of the Failure of Risk Management book and other risk management voices is the failure to understand that proximate cause is not Root Causes.

But that was not the Root Cause. The Root Cause was the casting of the hub 

• The proximate cause of the failure of the turbine blades was The propagation of one or more cracks under prolonged fatigue stresses, which led to the catastrophic failure of the fan rotor and expulsion of fragmented fan blades, which severed and removed all three hydraulic control systems
• The Root Causes were Latent manufacturing defects, Failed detection of the hub cracks, and Lack of Procedure and training on manually handling the aircraft when the flight control surfaces were no longer powered.

The Apollo Method of Root Cause Analysis

The Apollo Method, which is used in aerospace, defense, and energy domains

Here's the link to the Apollo Method. In this approach, there are two elements that result from the Seven Steps described in Seven Steps To Effective Problem-Solving and Strategies for Personal Success, Dean Gano.

1. Define the problem
2. Determine the known causal relationships to include each effect's actions and conditions.
3. Provide a graphical representation of the causal relationships, including specific actions and conditional causes.
4. Provide evidence to support the existence of each cause.
5. Determine if each set of causes is sufficient and necessary to cause the effect.
6. Provide effective solutions that remove, change, or control one or more causes of the event. Solutions must be shown to prevent recurrence, meet our goals and objectives, be within our control, and not cause other problems.
7. Implement and track the effectiveness of each solution.

The picture below is the Apollo method's model of the Deep Water Horizon blow out.

Ignorance is a most wonderful thing, it facilitates magic. It allows the masses to be led. It provides answers when there are none. It allows happiness in the presence of danger. All

All this, while the pursuit of knowledge can only destroy the illision. Is it any wonder that humanity chooses ignorance?

- Dean Gano

[1] Iowa Air Crash Laid to Metallurgical Flaw : Investigation: Tests performed on the tail engine part confirm the root cause of the accident. Paul Houston, OCT. 29, 1989, Los Angeles Times.

[2] Comparisons and Lessons Learned from UA232 Sioux City and AA383 Chicago Uncontained Events, David Chapel and Daniel Kemme, GE Aviation.

[3] "No Left Turns: United Airlines Flight 232 Crash" Leadership ViTS Meeting,  July 2008, Bryan O’Connor Chief, Safety and Mission Assurance, Jim Lloyd, Deputy Chief Safety and Mission Assurance.