The Rulebook AI Can't Compile

More than 80 percent of the technicians who service Western commercial aircraft are non-native English speakers, and that single number is why aviation built ASD-STE100: a controlled language of 53 writing rules and about 875 to 900 approved words, run on one axiom — one word, one part of speech, one meaning. Issue 9, published in January 2025, turned it into an international standard.

This episode asks what happens when engineers point that 1986 rulebook at language models, and the answer is deflationary. It is genuinely useful as a prompt heuristic that strips filler and hedging, and as a way to normalise training corpora — but it is not a formal grammar. It has no context-free grammar, its technical nouns and verbs are open-class, and checking a word's part of speech needs a real parse, so it cannot drive logit-level constrained decoding.

Along the way: where the standard came from, why it is free but still proprietary, the 1990s evidence that it works, what adoption costs, and how it compares with Boeing Simplified English, Caterpillar Technical English, Attempto Controlled English and plain language. A 1986 aviation standard, and the limits of constraining machine language.