What is ASD-STE100 Simplified Technical English?

ASD-STE100 Simplified Technical English, usually shortened to STE, is a controlled natural language for writing technical documentation. The STEMG site describes it as an international standard, fully owned by ASD, the Aerospace, Security and Defence Industries Association of Europe in Brussels, and gives the current version as Issue 9, dated January 15, 2025. The standard has two parts: a set of writing rules that restrict grammar and style, and a controlled dictionary that lists the general words a writer may use, each with one meaning. This post covers who maintains the standard, how the rules and the dictionary work, what changed between Issue 8 and Issue 9, how to get the free copy, where STE is required, and how it relates to S1000D and to the U.S. military technical manual standards.

Who writes ASD-STE100: ASD and the STEMG

The ASD Simplified Technical English Maintenance Group (STEMG) is responsible for the development, production, publication, and maintenance of ASD-STE100. The STEMG page says the group includes experts from ASD countries, called members, and international experts from countries that are not ASD members, called partners. The group was formed in 1983 as a working group to develop AECMA Simplified English and took the STEMG name in 2004, when ASD was created. The STEMG reports to the ASD Services Commission, meets twice a year, and has held more than 90 working meetings in 13 countries and 26 cities.

The membership list on that page shows where the standard is written. The chair, Orlando Chiarello, represents Secondo Mona and the Italian association AIAD; the vice chair, Jennifer Bennor, represents Vestas and the German association BDLI. Members come from Airbus, Dassault Aviation, Saab, Kongsberg, Schiebel, and other European companies. Partners include a Pratt & Whitney representative from the United States, a representative of the Australian Government Department of Defence, Scandinavian Airlines, and a Japanese member of ISO Technical Committee 37.

The Terms of Reference page says the terms were first produced in the early 2000s and that ASD approved the most recent revision in March 2025. The STEMG's listed tasks are to keep ASD-STE100 up to date, review change requests and release new issues, report to the ASD Services Commission, advise STE users, produce the electronic source files, cooperate in distribution, promote STE, and safeguard the integrity of the standard.

Below the STEMG sit STE Support Teams. The support teams page lists eight: French-speaking countries, German-speaking countries, Italy, Nordic countries, Portuguese-speaking countries, Spanish-speaking countries, the United Kingdom, and the United States. They meet before the plenary STEMG meetings, review change forms at the national or language level, and together represent about 80 percent of STE users. The same page describes an Artificial Intelligence Task Team with one expert from each support team, formed to monitor AI tools in relation to STE. The home page states that Simplified Technical English and ASD-STE100 are a copyright and trademark of ASD, registered as European Union Trade Mark No. 017966390.

How STE started: from AECMA Simplified English to ASD-STE100

The STEMG FAQ tells the origin story. In 1979 there were far more aircraft manufacturers than today, and although all of them wrote in English to the same ATA Specification 100, their writing styles differed. Some wrote American English, some British English, and some, such as Fokker, Aeritalia, Aerospatiale, and the companies that formed Airbus, wrote English as a second language. Some European airlines had to translate parts of their maintenance documentation into local languages so their mechanics could use it. The airlines approached AECMA, the European Association of Aerospace Industries, in 1979 and asked the manufacturers to investigate a controlled form of English that all of them would use.

AECMA looked at controlled languages in other industries, decided to produce its own, and in 1983 set up a project group led by Fokker. The American industry took part through the Aerospace Industries Association (AIA), some of whose companies had already done similar standardization. The result was the AECMA Simplified English Guide. The About page dates the first release to 1986, as AECMA Document PSC-85-16598, and counts 17 releases since, including full issues, changes, and revisions.

The name changed with the organization. In 2004 AECMA merged with two other associations to form ASD, and the guide became ASD Simplified Technical English, Specification ASD-STE100. The home page adds that it became an international specification in 2005 and an international standard in 2025, and the FAQ notes the European Union trade mark came in 2006.

The About page states the purpose plainly. English is the international language of many industries and the most widely used language for technical documentation, but it is often not the native language of either the readers or the writers. The driver was a request from airlines, 80 percent of which were not from English-speaking countries, to ensure accurate maintenance practices. Complex technical instructions can be misunderstood, and misunderstandings can lead to accidents, so STE is framed as a human factors measure as much as a writing style.

The STE writing rules

Part 1 of the standard is the writing rules. The About page gives the count: 53 writing rules in 9 sections that cover word choice, grammar, sentence structure, and style. ASD's basics page summarizes the principles as using the active voice, giving one instruction per sentence, avoiding unnecessary synonyms and jargon, keeping the number of words per sentence down, and staying consistent across documents and teams. ASD's STE overview lists the same traits: active voice, short sentences, logical structure, and a controlled vocabulary in which each approved word has one meaning.

The STEMG FAQ explains several rules that searchers ask about:

• No -ing verb forms. Words ending in -ing can be different parts of speech, can appear in verbal constructions that readers with basic English find hard, and in verb tenses imply a duration that is not always clear. The dictionary keeps a few -ing words, but only as nouns, adjectives, and prepositions: opening, remaining, during.
• Imperative in procedures. Procedures use the language a writer would use standing next to the mechanic: "Install the component," not "The component must be installed." The FAQ says a passive sentence is not a direct instruction and could be ambiguous.
• Active voice in description. Descriptive text uses the active voice as much as possible and the passive only when necessary, such as when describing an item that receives the action of another item.
• Conditions first when safety depends on it. A conditional clause does not always have to come first, but when the operator must know a condition before doing a step, the FAQ says it is often more logical and safer to put the condition at the start, as in "If hot oil touches your skin, it can cause burns."
• Warnings and cautions. Some legal departments control the wording of warnings and cautions. The FAQ says technical staff can often work with lawyers to produce language that reduces liability risk and complies with STE.

The exact limits inside each rule, such as the maximum sentence lengths for procedural and descriptive text, are in the text of the specification itself, which the STEMG supplies free on request. The public pages describe the rules without reproducing them. The STEMG also stresses that STE is written for the reader, not the writer. The training page says writing correctly in STE is a demanding task that requires a strong command of English and a comprehensive understanding of the subject, that the ASD-STE100 document is the only reference and there is "no substitute for it," and that writers without training tend to focus on the dictionary and neglect the rules.

The Simplified Technical English dictionary

Part 2 of the standard is the dictionary. The About page says it contains approximately 900 approved words, each with one meaning and one part of speech, and a list of approximately 1,200 words that are not approved, with alternative suggestions. The approved words were chosen because they were simple and easy to recognize. The FAQ gives the selection criteria as simplicity, flexibility, and frequency of use: "do" is simpler, more flexible, and more frequent than "achieve," "carry out," or "accomplish."

The one-meaning rule is what makes the dictionary controlled. Where English has several words for the same thing, STE approves one and excludes the rest: "start" rather than "begin," "commence," "initiate," or "originate." A word that has several meanings in general English keeps only one in STE. The FAQ gives "fall," approved as moving down by the force of gravity and not as decreasing, and "about," approved as meaning concerned with and not as approximately or around, which are approved words of their own. Part of speech is also fixed: "check" is approved only as a noun, as in "do a check," and not as a verb. Approved meanings and spelling follow American English as given in Merriam-Webster's dictionary.

The dictionary does not try to contain every word a technical writer needs. The FAQ says it holds a controlled general vocabulary sufficient to write any technical sentence, and that company-specific or project-oriented words are handled separately as technical names and technical verbs, defined in the rules by the categories they belong to. Issue 9 renamed these designations technical nouns and technical verbs, in line with ISO 1087-1:2019, according to the About page. If an unapproved dictionary word is used as part of a technical noun or technical verb, it becomes part of that term and is acceptable, though the FAQ advises limiting that use.

A change form is the only way to add a word or a meaning. The FAQ says a writer cannot use a proposed word immediately; the STEMG reviews the request and changes appear in a future issue if approved. The dictionary is Part 2 of the specification and comes with it, by request, not as a separate download.

Issue 9, Issue 8, and how the standard changes

Searchers still type "ste100 issue 8" because Issue 8 was current for almost four years. The older STEMG FAQ says Issue 8 was released in May 2021 and dated April 30, 2021, and that Issue 9 was scheduled for 2024. The older request page, still online, offers a request form for Issue 8 under the heading "Issue 8, April 30, 2021." The current home page and About page both give Issue 9, dated January 15, 2025, as the version in force.

The About page describes Issue 9 as the result of three years of work by the STEMG and the national and multi-country support teams. More than half of the 53 writing rules were refined for clarity, and 555 dictionary entries were updated. Terminological classifications were modernized in line with ISO 1087-1:2019, which introduced the designations technical nouns and technical verbs, subject field classifications were expanded, and the dictionary was streamlined. The transition from "specification" to "standard" gave the document a new subtitle, Standard for Technical Documentation. The About page also notes that STE is referenced in ISO 24620-4:2023, the language resource management standard.

The release cycle is stated two ways. The older STEMG FAQ says the frequency of issues is a minimum of two years and a maximum of four. ASD's STE FAQ says the STEMG releases new issues at regular intervals, usually every three years, with changes based mainly on user feedback and internal reviews.

Change forms drive the content. The downloads page offers a change form template to send to the STEMG by email, with images and supporting files attached, or a text-only web form. The STEMG reviews every change form and incorporates agreed updates into the next issue. The older FAQ adds that users with a national representative send forms to that person first, that the STEMG keeps records of all change forms and their assessments, and that originators are usually told the outcome.

How to get ASD-STE100 for free

The specification costs nothing, but there is no direct download link. The STEMG FAQ says the specification is available to everybody at no cost, and the downloads page asks the user to fill in a request form for a free official copy of Issue 9. ASD's STE pages offer the same copy through a form that, in ASD's words, collects statistical data to help it understand the use of STE. ASD's FAQ describes ASD-STE100 as an open-source standard that is free to download and advises using authorized sources.

The STEMG draws a line around commercial products. The older FAQ says no checker or software product is necessary to write in STE, that commercial grammar checkers supporting STE cannot replace the specification, and that ASD and the STEMG do not endorse or certify products declared "fully compliant" with ASD-STE100. Such companies have no authorization to use the ASD logo, copyright, or trademark.

Training works the same way. The training page says STEMG members and partners provide certified basic training for writers, reviewers, and proofreaders, that UNINETTUNO University provides certified training under an agreement with ASD and can certify other trainers, and that commercial trainers with no link to the STEMG provide uncontrolled training with no ASD endorsement. The downloads page also offers a STEMG white paper on STE and artificial intelligence, which warns that AI-generated text can appear consistent with STE without correctly applying the rules and vocabulary.

STE and S1000D

ASD owns both ASD-STE100 and S1000D, and the two are built to be used together. The s1000d.org external links page lists ASD-STE100 under related specifications, describing it as the ASD Simplified Technical English standard for technical documentation. The STEMG About page says STE is a recommendation in the S1000D specification, and the FAQ notes that S1000D details the use of STE for land and sea vehicles as well as aircraft. S1000D itself, the specification for technical publications built from XML data modules, is the subject of a separate post.

The U.S. military rules for S1000D show how the recommendation lands in practice. MIL-STD-3031, the Army business rules for S1000D dated September 30, 2009, lists Simplified Technical English under project decisions in paragraph 5.11.2.1: "The project shall decide whether to require the use of Simplified Technical English or not." Paragraph 5.19.1.3 then sets the data module attribute languageIsoCode to en for English or sx for Simplified Technical English, with countryIsoCode set to US. MIL-STD-3048A, the Air Force business rules dated April 29, 2016, lists ASD-STE100 among its applicable documents, with a note that copies are obtained from ASD in Brussels, and paragraph 5.14.1.2 gives the same en or sx choice for languageIsoCode. The current Revision B with Change 1 of MIL-STD-3031, dated July 31, 2025, keeps both points: the STE choice is decision point BRDP-S1-00021 in paragraph 5.10.2.1, and the en or sx rule is paragraph 5.19.1.5.

The sx code matters in a common source database. A data module written in STE carries a different language code from one written in unrestricted English, so a project that requires STE can tell at the metadata level which modules claim to comply. Neither standard says how compliance is checked; that is left to the project, consistent with the STEMG's position that software checkers are optional.

Where Simplified Technical English is required

The About page lists the places where STE is required or recommended. In commercial aviation, STE became a requirement in 1986 for the ATA 100 specification for technical publications, now ATA iSpec 2200, and for the ATA 104 specification for training. The page says STE later became a requirement for defense projects, including land and sea vehicles, and that today maintenance manuals and technical texts are mostly written in STE. EDSTAR, the European Defence Standards Reference, recommends STE as a best practice standard for technical documentation in defense contracting by European Defence Agency member states. The STEMG also states that STE is a requirement in official directives on continued airworthiness issued by aviation authorities such as EASA, the FAA, and the Civil Aviation Administration of China; this post relies on the STEMG's statement for that claim and did not locate the directives themselves.

Use has spread beyond aerospace into language services, translation, and academia, according to the About page. The FAQ answers the translation question directly: STE can eliminate the need for translation if readers have a basic knowledge of English, and where translation is still needed, controlled vocabulary and sentence structure make the work easier for translators and translation machines.

The U.S. military's general style standard takes a different route to the same goal. MIL-STD-38784C, the Department of Defense standard practice for general style and format of technical manuals dated September 4, 2024, which superseded Revision B of November 16, 2020, requires the second person imperative mood for procedures and the third person indicative for description, and sets a Reading Grade Level of nine unless the acquiring activity specifies otherwise. That is a readability score, not a controlled language. The STEMG FAQ addresses the difference: STE produces text that readers at lower grade levels can understand, but it does not guarantee compliance with reading grade levels. A program that needs both must check both.

What to check

• Which issue of ASD-STE100 does the contract or style guide name? Issue 9, dated January 15, 2025, is current, and Issue 8, dated April 30, 2021, still appears on older pages.
• For an S1000D project, has the project decided whether STE is required, the decision MIL-STD-3031 leaves open, and do the data modules carry languageIsoCode sx or en to match?
• Are the project's technical nouns and technical verbs listed somewhere, given that the dictionary does not contain them?
• Do procedures use the imperative, avoid -ing verb forms, and put conditions before the step they govern?
• Were the writers trained, given the STEMG's statement that a copy of the standard alone is not enough?
• Does the manual also have to meet a readability requirement such as the Reading Grade Level in MIL-STD-38784, which STE does not guarantee?

Azcuna's TRACE is one offline viewer for S1000D, MIL-STD-3001 XML, and PDF technical manuals. It keeps the source location and the markings of everything it shows and never modifies the source. It was proposed to NAVAIR under Navy SBIR Phase I topic DON26BZ05-NV078, and the proposal was submitted on September 23, 2026.

Questions people ask

What is ASD-STE100?

ASD-STE100 is the document that defines Simplified Technical English, a controlled natural language for technical documentation. The STEMG site describes it as an international standard fully owned by ASD, the Aerospace, Security and Defence Industries Association of Europe in Brussels. The standard has two parts: writing rules that restrict grammar and style, and a controlled dictionary of approved general words, each with one meaning and one part of speech. The current version is Issue 9, dated January 15, 2025.

What does STE stand for?

STE stands for Simplified Technical English. The full name of the standard is ASD-STE100 Simplified Technical English, and the STEMG site says the subtitle became Standard for Technical Documentation with Issue 9. The STEMG FAQ explains that the language began as AECMA Simplified English, named for the European association that produced it, and took the ASD-STE100 name in 2004 after AECMA merged with two other associations to form ASD.

What are the STE writing rules?

The STEMG About page says the standard contains 53 writing rules in 9 sections covering word choice, grammar, sentence structure, and style. The ASD basics page summarizes them as active voice, one instruction per sentence, no unnecessary synonyms or jargon, as few words per sentence as possible, and consistency. The STEMG FAQ adds that verbs ending in -ing are not allowed, procedures use the imperative, and a condition the operator must know before a step is often better placed at the start of the sentence.

How many words are in the Simplified Technical English dictionary?

The STEMG About page says the dictionary contains approximately 900 approved words, each with one meaning and one part of speech, plus a list of approximately 1,200 words that are not approved, with alternative suggestions. The STEMG FAQ says approved meanings and spelling follow American English as given in Merriam-Webster's dictionary, and that writers may add technical nouns and technical verbs from their own company, project, or subject field, which the dictionary does not list.

Why does STE not allow -ing forms?

The STEMG FAQ says words ending in -ing can belong to different parts of speech, can appear in verbal constructions that non-native readers with basic English find hard to understand, and in verb tenses imply a duration that is not always clearly expressed. Since maintenance documentation requires clarity and no ambiguity, the STEMG decided to avoid them. The dictionary still contains some -ing words, but only as nouns, adjectives, and prepositions, such as opening, remaining, and during.

Is ASD-STE100 free to download?

Yes, but by request rather than a direct link. The STEMG FAQ says the specification is available to everybody at no cost, and the STEMG downloads page asks users to fill in a request form for Issue 9. ASD's own STE pages offer the free copy of Issue 9 through a form that collects statistical data on how STE is used. The older STEMG request page, still online, offers Issue 8 by the same method.

What is the current issue of ASD-STE100?

Issue 9, dated January 15, 2025, according to the STEMG home page and About page. The STEMG says Issue 9 followed three years of work, refined more than half of the 53 writing rules, updated 555 dictionary entries, aligned terminology with ISO 1087-1:2019, and marked the change from a specification to a standard. The previous version was Issue 8, which the older STEMG FAQ dates to April 30, 2021 and says was released in May 2021.

Does S1000D require Simplified Technical English?

S1000D recommends it. The STEMG About page says STE is a recommendation in the S1000D specification, and the s1000d.org external links page lists ASD-STE100 among related specifications. In the U.S. military rules for S1000D, MIL-STD-3031 says the project shall decide whether to require STE, and both MIL-STD-3031 and MIL-STD-3048A set the data module attribute languageIsoCode to en for English or sx for Simplified Technical English, with countryIsoCode set to US.

Who uses Simplified Technical English?

The STEMG About page says STE became a requirement in 1986 for the ATA 100 specification for technical publications, now ATA iSpec 2200, and for the ATA 104 training specification, and later became a requirement for defense projects including land and sea vehicles. The same page says EDSTAR recommends STE for defense contracting by European Defence Agency member states, that aviation authorities cite it in continued airworthiness directives, and that language services and academia now use it.

Does the U.S. military require STE?

Not across the board. MIL-STD-3031, the Army business rules for S1000D, lists Simplified Technical English as a project decision: the project shall decide whether to require it. MIL-STD-3048A, the Air Force rules, lists ASD-STE100 among its applicable documents and provides the sx language code for data modules written in STE. MIL-STD-38784C, the general style and format standard, takes a different approach and sets a Reading Grade Level of nine unless the acquiring activity specifies otherwise.

Sources

1. 1ASD-STE100 Simplified Technical English, home page · ASD Simplified Technical English Maintenance Group (STEMG)
2. 2About ASD-STE100 · ASD Simplified Technical English Maintenance Group (STEMG)
3. 3ASD STEMG, Simplified Technical English Maintenance Group · ASD Simplified Technical English Maintenance Group (STEMG)
4. 4STEMG Terms of Reference (ToR) · ASD Simplified Technical English Maintenance Group (STEMG)
5. 5STE Support Teams · ASD Simplified Technical English Maintenance Group (STEMG)
6. 6STE Downloads · ASD Simplified Technical English Maintenance Group (STEMG)
7. 7STE Training · ASD Simplified Technical English Maintenance Group (STEMG)
8. 8ASD-STE100 FAQs · ASD Simplified Technical English Maintenance Group (STEMG)
9. 9Specification Request, Issue 8, April 30, 2021 · ASD Simplified Technical English Maintenance Group (STEMG)
10. 10ASD-STE100 Simplified Technical English · ASD, Aerospace, Security and Defence Industries Association of Europe
11. 11What are the basics of Simplified Technical English? · ASD, Aerospace, Security and Defence Industries Association of Europe
12. 12FAQ - Simplified Technical English (STE) · ASD, Aerospace, Security and Defence Industries Association of Europe
13. 13External Links · S1000D Council and Steering Committee (s1000d.org)
14. 14MIL-STD-3048A, Air Force Business Rules for the Implementation of S1000D · Department of the Air Force, April 29, 2016, via EverySpec
15. 15MIL-STD-3031, Army Business Rules for S1000D · Department of the Army, September 30, 2009, via EverySpec
16. 16MIL-STD-3031, Army Business Rules for S1000D (ASSIST-QuickSearch Document Details) · Defense Logistics Agency, ASSIST-QuickSearch
17. 17MIL-STD-38784, General Style and Format Requirements for Technical Manuals (ASSIST-QuickSearch Document Details) · Defense Logistics Agency, ASSIST-QuickSearch; Revision C, September 4, 2024

Where this shows up in our work

• TRACE, the offline S1000D and IETM viewer opens S1000D, MIL-STD-3001 and PDF technical manuals on a tablet with every marking intact.
• ELLMENT, the offline LLM for E-2D crews answers a crew's question from the aircraft's own manuals and cites the page, with no network.