Title: Byzantine Generals Attack an Airbus A320

Author(s): Dewi Daniels

Publication Event: Publication of Proceedings of the Thirty second Safety-Critical Systems Symposium

Publication Date: 2024-02-12

Resource URL: https://scsc.uk/r1904.pdf

Abstract:

Airbus recently published an article in their safety magazine describing a serious incident where the thrust reverser remained deployed on one engine during a go-around. The aircraft veered to the left but became airborne just before reaching the edge of the runway. The flight crew were able to land the aircraft with one engine inoperative. Airbus is to be commended for publishing such a clear and honest account of the incident. This appears to be a variant of Leslie Lamport's Byzantine Generals Problem, which I described in my SSS'22 paper, but not one that I have seen described before. In this case, an implementation of the Byzantine Generals solution would have allowed the two engines to agree whether to stow and lock the thrust reversers. Byzantine failures are rare events, but they seem to keep happening. I'm reminded of the Terry Pratchett quote, “million-to-one chances crop up nine times out of ten”. I wonder whether Leslie Lamport's 1982 paper on the Byzantine Generals Problem is now so old that it has begun to fade from memory?