A Journey Through the CAST Handbook: Introduction

Join me on a journey through the CAST Handbook.

The CAST Handbook (Leveson 2019) describes the process of applying the Causal Analysis based on System Theory (CAST) to accident investigations. CAST is closely related to Systems-Theoretic Process Analysis (STPA), which has its own handbook (Leveson & Thomas 2018).

• STPA is best done as early in the design process as possible to prevent accidents.
• CAST is accomplished after an accident.

Both are products of the MIT Partnership for Systems Approaches to Safety and Security (PSASS), directed by Dr. Nancy Leveson, who authored both handbooks. The STPA Handbook is co-authored by John Thomas .

I was first introduced to STPA through Dan M. ' PhD work with Dr. Leveson which he brought to the Air Force Test Center and United States Air Force Test Pilot School .

STPA has been a topic in #FlightTest circles for some time now, including the focus of a full 2-day Flight Test Safety Workshop webinar including presentations by Dr. Thomas and Sarah Summers , who also studied at MIT with a focus on the use of STPA in United States Air Force Acquisitions.

At this year's 53rd Symposium of the Society of Flight Test Engineers , STPA became a topic of discussion, thanks in no small part to 3 papers which directly or indirectly referenced the use of STPA in the context of flight test (full text available to SFTE and The Society of Experimental Test Pilots members):

Ben Luther presented a paper, Flight Testing Tomorrow's Complex Systems, advocating for a re-framing of technical and safety planning and recognizing the differences between, simple, complicated, and complex systems, with STPA being especially applicable to complex systems. Jeffrey Canclini presented a talk, The Evolution of Risk Mitigation in Flight Test for Complex Systems, showing the changes in approach to risk mitigation over the years, and highlighting the inadequate explanatory and preventative power of James Reason's famous Swiss Cheese Model of accident causation, suggesting that approaches like STPA may be better suited as systems become more complex. Darren McDonald and his colleagues presented a paper, Systems Theoretic Process Analysis in Flight Test, describing how they applied STPA in development of an automated test maneuver system.

Kenneth Katz presented a historical talk on the B-1 Bomber: Flight Test Lessons Learned. And it was the juxtaposition of the description of the 1984 B-1 fatal flight test accident and the focus on STPA that lead me to ask if a CAST analysis was ever performed on this accident?

I contacted Drs. Leveson and Thomas, and Dr. Leveson confirmed that she had not seen a CAST analysis of the 1984 B-1 accident.

In the subsequent weeks, CAST has been on my mind, and I'm even considering running an analysis of the B-1 accident. But before eating the elephant, I thought it prudent to read the CAST Handbook first, but it's been a low priority.

This morning, an accident occurred in my own home that prompted me to action...

Stay tuned for the next installment: How Not To Cry Over Spilt Coffee