When Software Goes Down
The terrifying crash of the Air India flight 171 in Ahmedabad has ignited a number of theories on the cause of the accident. The plane took off and went down immediately as it appeared to lose thrust in both engines. Today's aircraft are considered very safe. The key for the safety record is redundancy of all critical systems. Everything is doubled or tripled or quadrupled. From the probability theory perspective, multiplying the critical components vastly reduces the chance of a total failure, as the individual equipment unit failures are considered to be independent. That is mostly true for legacy / mechanical components. An engine blade failure in one engine does not cause the other engine to fail. Or a chance of two blades (one in each engine) failing at the same time is practically zero. But it turns out when software is involved, equipment failures can be fully synchronous. Which I believe is what happened in this accident. In the Boeing 787 Dreamliner, the fuel pumps are el...