Writing Rules

ASD-STE100 is a controlled natural language. European airlines asked for it, because most of their maintenance staff read English as a second language. A misread instruction on an aircraft can kill people. The standard first shipped in 1986. ASD (the AeroSpace and Defense Industries Association of Europe) maintains it through the Simplified Technical English Maintenance Group. It has been free to download since 2013. The current edition is Issue 9, from January 2025.

The standard has two parts:

• 53 writing rules across 9 sections. They cover word choice, grammar, sentence structure, and style.
• A dictionary of about 900 approved words. Each word has one meaning and one part of speech. About 1,200 more words are listed as words to avoid, each with a replacement.

An organization may add its own approved technical nouns and verbs on top of the base dictionary. That is how a domain term survives the rules: approve it once, define it once, then use it the same way every time.

Detail behind the rules

Verb forms. Use the infinitive, the imperative, the simple present, the simple past, the simple future, and the past participle as an adjective. Do not use the present perfect, the past perfect, or other compound forms. Use an “-ing” form only inside a technical noun, never as a verb form.

Voice. Use the active voice for procedures and instructions. The passive voice is allowed in descriptive text, and only when the actor is unknown or irrelevant to the reader.

Missing words. Do not drop the verb, the subject, or the article to shorten a sentence. The standard warns that this creates ambiguity rather than clarity. This is the rule that most often surprises a writer who equates short with clear.

Safety instructions. Open a safety-critical instruction with the command or the condition. Do not bury it mid-sentence. The reader must know the risk before they read the detail.

What this skill does not do

• It does not reproduce the approved dictionary. When exact approved wording matters, download the standard and check word by word.
• It does not certify a document as STE compliant. It is a clarity tool built on the same rules.

Sources

• ASD-STE100 official site (opens in a new tab)
• ASD Europe: Simplified Technical English (opens in a new tab)
• Simplified Technical English on Wikipedia (opens in a new tab)
• TechScribe: ASD-STE100 Simplified Technical English (opens in a new tab)

This skill is adapted from danyuchn/asd-ste100-skill (opens in a new tab), published under the MIT license.