Tagged safety

2 pieces

• August 20, 2026 · 7 min read

  Therac-25: When the Untested Assumption Is a Safety Architecture

  The Therac-25 removed the hardware interlocks its reused code assumed and gave the job to software. A race condition reachable by fast operator edits, plus a one byte counter overflowing to zero, bypassed a safety check. Six overdoses, three deaths, and a cause the investigators located in the system rather than in a line.

• August 19, 2026 · 6 min read

  Boeing 737 MAX and MCAS: The Single Sensor Nobody Fault Injected

  MCAS depended on one angle of attack sensor for a function Boeing's own assessment classified as hazardous, a classification that normally precludes single sensor dependence. The safety analysis also understated the system's authority by more than four times. This is a system safety failure, not a missing unit test.