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Specification ASD-STE100

European Community Trade Mark No. 004901195

International specification for the preparation of maintenance documentation in a controlled language


The international language of the aerospace industry is English, and English is the language most used for writing technical documentation. However, it is often not the native language of the readers of such documentation. Many readers have a knowledge of English that is limited, and are easily confused by complex sentence structures and by the number of meanings and synonyms which English words can have.

In the late 1970s, the Association of European Airlines (AEA) asked the European Association of Aerospace Industries (AECMA) to investigate the readability of maintenance documentation in the civilian aircraft industry. AECMA asked the Aerospace Industries Association (AIA) of America to assist in this project. The resulting project groups from AECMA and AIA researched the procedural texts in maintenance manuals. The product of this effort was the AECMA Simplified English Guide.

AECMA Simplified English was developed to help the users of English-language documentation in the aerospace sector understand what they read, particularly in multinational programs. Since the first publication of the AECMA Simplified English Guide, other non-aerospace industries have adopted the principles of AECMA Simplified English for their own documentation.

AECMA Simplified English is now the Specification ASD Simplified Technical English. It is not only for those who do not have English as their native language, but also for those who do.

What is ASD Simplified Technical English (STE)?

STE is a set of Writing Rules (Part 1) and a Dictionary of controlled vocabulary (Part 2).

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 is a choice between American English and British English words and spelling, the American version is used (Merriam-Webster’s Dictionary).


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".

History of ASD-STE100

The Specification was first released in 1986 as the AECMA Document, PSC-85-16598. Subsequently, several changes, issues and revisions were released up to the present Issue 6. The Specification is fully owned by ASD, Brussels, Belgium.

The Simplified Technical English Maintenance Group (STEMG)

The STE specification is maintained by the ASD STEMG consisting of representatives from ASD member countries and non-ASD member countries. The STEMG was originally formed in 1983 as a working group to develop AECMA Simplified English and subsequently, in 2004, when ASD was created, the group changed its name to the STEMG. The STEMG is reporting to the ASD Product Support Group (PSG).