Warnings, cautions, and notes in technical manuals

A warning, a caution, and a note are the three advisory notices of a U.S. military technical manual. A warning protects people, a caution protects equipment, and a note draws attention to information. Three standards define them for different services: MIL-STD-38784B, dated 16 November 2020, MIL-STD-40051E, now at Change 1 of 30 July 2025, and NAVAIR's MIL-STD-3001-1A, dated 1 December 2016. They agree that warnings and cautions come before the text they guard. They differ on what a warning covers, on capitals, and on grouping.

Which standard governs which manual

MIL-STD-38784B is approved for all Department of Defense (DoD) components, but its foreword limits Naval Air Systems Command (NAVAIR) use to legacy data and manuals. MIL-STD-40051E is approved for the Army and the Marine Corps and is available to all DoD components. The Defense Logistics Agency's ASSIST record lists Revision E dated 25 March 2025 and Change 1 dated 30 July 2025, both under Distribution Statement A. The revision superseded the separate parts MIL-STD-40051-1D and -2D, so one text now covers page-based and electronic manuals. The ASSIST record for the IETM part shows it canceled on 25 March 2025.

MIL-STD-3001 is the NAVAIR standard for work package technical manuals. Part 1, the copy read here, carries Distribution Statement A.

A fourth source sits beside the standards. The Naval Aviation Maintenance Program (NAMP), COMNAVAIRFORINST 4790.2E of 28 October 2024, defines the same three words for its own text. So the maintenance policy and the manuals it points to can word the same terms differently.

The definitions side by side

Source	Warning	Caution	Note
MIL-STD-38784B (2020)	Injury, death, or long-term health hazards	Damage to or destruction of equipment, or loss of mission effectiveness	An essential procedure, condition, or statement; never a substitute for a step
MIL-STD-40051E (2025)	Injury to or death of personnel	Damage to or destruction of equipment, or loss of mission effectiveness	An unusual procedure or condition needing special attention
MIL-STD-3001-1A (2016)	Long-term health hazard, injury, or death	Damage to or destruction of equipment, or loss of mission effectiveness	Information of special importance or interest
NAMP 4790.2E (2024)	Injury, long-term health hazards, or death	Damage to or destruction of equipment	A procedure or condition that requires emphasis

The core wording is shared. MIL-STD-38784B's warning covers a practice that "could result in injury to, or death of, personnel or long term health hazards." MIL-STD-40051E's warning stops at injury or death. MIL-STD-40051E adds a rule of its own: when a procedure carries danger of injury or death and also of damage to equipment or the environment, the notice is a warning.

The caution wording moved too. The IETM part, MIL-STD-40051-1D with Change 1 of 22 November 2021, defined a caution only as a clear risk of damage to the equipment. Revision E added loss of mission effectiveness.

Placement: before the step

MIL-STD-3001 is the shortest: warnings and cautions "shall precede the text to which they apply." Notes normally go before the text but may follow it when clarity requires.

MIL-STD-38784B adds a layer. For a primary sidehead paragraph, the warning or caution follows the heading and precedes the text. For lower-level paragraphs and procedural steps, it precedes the paragraph or step. Notes may precede or follow, except that Army and Marine Corps notes must precede. Appendix A asks that warnings sit immediately before the step they guard, and allows a warning not to be repeated within a procedure if its impact is not lost.

MIL-STD-40051E sets placement in a table. A notice for one step goes immediately before that step. A notice for a whole work package goes immediately after the initial setup. A notice for a whole task follows the procedure title, and a notice for several steps goes before the first of them. All three standards order stacked notices the same way: warnings, then cautions, then notes.

Format, signal words, and prohibitions

The signal words are WARNING, CAUTION, and NOTE, set as headings. MIL-STD-3001 and MIL-STD-38784B both build a warning or caution from four parts: the signal word, the hazard, the minimum precautions, and the possible result. MIL-STD-38784B lets an authorized icon serve as the signal word. MIL-STD-40051E asks a warning to say how to avoid the hazard and what to do on contact with it, and to state any immediate first-aid action.

None of the three allows procedural steps inside a notice, and none numbers the headings. The details then split:

• Capitals. MIL-STD-40051E puts the headers in capitals but bars all capitals in the text. MIL-STD-38784B requires Marine Corps warnings in all capitals.
• Grouping. MIL-STD-3001 bars unrelated topics under one heading. MIL-STD-40051E allows unrelated warnings under one header when they pertain to the same task, but never mixes warnings with cautions.
• Bullets. MIL-STD-3001 bars bulleted lists in notices. MIL-STD-40051E allows bullets when grouping. MIL-STD-38784B allows Marine Corps bullets for three or more paragraphs.
• Color. For interactive electronic technical manuals, MIL-STD-40051E puts WARNING in a red box, CAUTION in a yellow box, and NOTE in a blue box.

MIL-STD-38784B also warns against overuse: "if you warn about everything, you warn about nothing."

What to check

• Which standard and revision governs the manual: MIL-STD-38784B, MIL-STD-40051E with Change 1, or MIL-STD-3001-1A with Change 1?
• Does every warning and caution sit before the step, paragraph, or task it guards, in the order warning, caution, note?
• Does any notice hide a procedural step, such as a pressure limit that belongs in the steps?
• Is a long-term health hazard marked as a warning? MIL-STD-38784B, MIL-STD-3001, and the NAMP name it; the MIL-STD-40051E definition does not.
• When a viewer renders a manual, does it keep each notice with its step and keep the source's capitals, grouping, and colors?

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.

Sources

1. 1MIL-STD-38784B, General Style and Format Requirements for Technical Manuals · EverySpec (dated 16 November 2020)
2. 2MIL-STD-40051, Preparation of Digital Technical Information for Technical Manuals (TMs) (ASSIST-QuickSearch Document Details) · Defense Logistics Agency, ASSIST-QuickSearch (Revision E with Change 1, 30 July 2025)
3. 3MIL-STD-40051-1, Preparation of Digital Technical Information for Interactive Electronic Technical Manuals (IETMs) (ASSIST-QuickSearch Document Details) · Defense Logistics Agency, ASSIST-QuickSearch (Revision D with Change 1, 22 November 2021)
4. 4MIL-STD-3001-1A (w/Change 1), Preparation of Digital Technical Information for Multi-Output Presentation of Technical Manuals (Part 1 of 8 Parts) · EverySpec (dated 1 December 2016)
5. 5The Naval Aviation Maintenance Program (NAMP), COMNAVAIRFORINST 4790.2E, 28 Oct 2024 · Commander, Naval Air Forces, posted by Naval Air Systems Command

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.