Definition

ASD-STE100 Simplified Technical English (STE) is an international specification for the preparation of maintenance documentation in a controlled language developed by the Aerospace, Security and Defence Industries Association of Europe (ASD).  STE was developed in the early 1980s (as AECMA Simplified English) to help second-language speakers of English to unambiguously understand technical manuals written in English. It was initially applicable to civil aircraft maintenance documentation but is now widely used in other industries.

In technical documentation, ambiguous text is bad. Each instruction must be clear. STE is a set of Writing Rules and a Dictionary of controlled vocabulary.

Writing Rules

The writing rules differentiate between two types of topics: procedural and descriptive writing. The rules also cover aspects of grammar and style. A non-exhaustive list of the writing rules includes the following concepts:

• Use the approved words and only as the part of speech and meaning given in the dictionary.
• Make instructions as clear and specific as possible.
• Do not use passive voice in procedures.
• Use the active voice as much as possible in descriptive texts.
• Write short sentences: no more than 20 words in instructions (procedures) and no more than 25 words in descriptive texts.
• Do not omit parts of the sentence (e.g. verb, subject, article) to make your text shorter.
• Use vertical lists for complex text.
• Write one instruction per sentence.
• Write only one topic per paragraph.
• Do not write more than 6 sentences in each paragraph.
• Start safety instructions with a clear command or condition.

The Dictionary

The Dictionary has sufficient words to express any technical sentence. The words were chosen for their simplicity and ease of recognition. When there are several words in English for a certain thing or action (synonyms), this Specification selects one of these synonyms to the exclusion of the others (whenever possible, "one word - one meaning"). For example, "start" was chosen instead of "begin", "commence", "initiate", or "originate".  When there are several possible definitions of a word in English, the Specification selects one of these definitions to the exclusion of the others (whenever possible, "one word - one meaning"). For example, "to fall" has the definition of "to move down by the force of gravity", not "decrease". 

Further Reading

• ASD-STE100 Specification