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How aircraft
repair manuals
are written

For people meeting ASD-STE100 for the first time,
and why it works so well for making AI talk like a human
No. 43Thinking ClearlyPart 9 of 12Fact-checked Oct 3, 2026Updated Oct 4, 2026
Video2:35 · English voice (AI) · English subtitles

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Read the transcript

The full narration of the video.

The manuals that aircraft mechanics read follow a very strict writing rulebook: every sentence can mean only one thing. Why so strict? Mechanics around the world speak all kinds of first languages. If a manual is vague, one wrong turn of a bolt can cause an accident. In the late 1970s, European airlines asked the industry to fix how manuals were written. In 1986, the first rulebook came out.

Today it's called ASD-STE100. In plain words: Simplified Technical English. Here's an example. The usual way: "Only after ensuring the relevant parts have properly cooled may removal proceed." How cool is "properly"? Does "may" mean you must wait, or you should? The reader has to guess.

The simplified way is two sentences: Let the part cool. Then remove the part. Nothing to guess. There are fifty-three rules. Four matter most. One: each sentence says one thing. Two actions, two sentences.

Two: keep it short. An instruction gets twenty English words at most. Three: one word, one meaning. For example, you write start, never begin. Four: say who does what. Write "tighten the bolt", not "the bolt should be tightened".

What does this have to do with AI? The rulebook is public, and AI knows the name. Just add one line: "Explain this in ASD-STE100 style." No need to list it all — shorter sentences, no detours, no hard words. One name brings it all.

Too stiff? Just say: "Eighty percent is fine." Still short sentences, but easier to read. But it makes things clear, not moving. Use it for a love letter or an ad, and it falls flat. And it only stops you from misreading — it doesn't make the content true. Facts still need checking.

So next time AI talks in circles, don't ask it to keep it simple. Just add one line: "Use ASD-STE100 style, at eighty percent."

1

In one sentence

The manuals used by aircraft mechanics
follow a very strict writing rule:
every sentence can mean only one thing.

It's called ASD-STE100, short for "Simplified Technical English". Aircraft mechanics around the world speak all kinds of native languages, and if a manual is vague, one wrong turn of a screw can cause an accident. So the aviation industry created this rulebook.

2

How it differs
from everyday
writing

EVERYDAY WRITING
“Once it has been ensured that the relevant components have been adequately cooled, removal may be carried out.”
Sounds very formal, but how cool is "adequately"? Does "may" mean you must wait, or that waiting is nice to have? The reader has to guess.
SIMPLIFIED WRITING
“Wait for the part to get cold.
Then remove the part.”
Two sentences, two actions, the order perfectly clear. Not one word needs guessing.

In plain words: everyday writing leaves the reader to work it out themselves. Simplified writing makes it impossible to misread.

3

The four
most important
rules

① One thing per sentenceTwo actions means two sentences. Don't chain them together with "and also" or "at the same time".
② Short sentencesA sentence that tells someone what to do stays under 20 words. If it's longer, split it.
③ One word, one meaningMostly only words from one small dictionary (each industry may add its own technical nouns), and each is fixed to a single meaning. The same word never means one thing here and another thing there.
④ Say who does whatWrite "Tighten the screw", not "The screw should be tightened". You can tell at a glance that it's telling you to act.
4

What it has
to do with AI

The rulebook is public, and AI knows it by name.
You only need to add one sentence.

ASK LIKE THIS
“Use ASD-STE100 style
to explain this to me…”
No need to spell out "keep sentences short, no detours, no hard words" one by one. That single name brings the whole list along.
TOO STIFF?
“Just do 80% of ASD‑STE100.”
The original rules are strict, and reading a lot of it feels like a manual. Say "80%" and it relaxes a little: still short sentences, still no detours, but it reads more smoothly.
5

Where this
style fits

Step-by-step tasksShift handover, opening and closing the shop
Instructions for your parentsHow to use the new TV or new phone
Group chat noticesWhat time, where, what to bring
Having AI explain new thingsIf you don't get it, make it rewrite
6

What it's
not good for

It handles "clear",
not "moving"
Love letters, ads and stories turn dry and flavorless if you use it.

It was made as a rulebook for English. In other languages, you borrow its way of thinking: short sentences, one point per sentence, no detours. You don't have to copy it word for word.

What it guarantees is "can't be misread", not that the content is right. However clearly an AI writes, the facts still need checking.
What does this
have to do with me?
Next time an AI leaves you lost in the fog,
don't keep asking "can you make it simpler?".
Just add one line:
"Use ASD-STE100 style,
at 80%."
Corrections

We saidAI already knows this rulebook well; only words from one small dictionary are allowed.

Now it saysThe rulebook is public and AI knows it by name; mostly words from one small dictionary, and each industry may add its own technical nouns.

Re-checked against ASD-STE100 Issue 9 while making the video: "AI knows it well" can't be verified, and the standard lets each industry add its own terms. Sources added.

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