AOP-20 safety, arming and functioning systems manual of tests

What it is

AOP-20 is a NATO Allied Ordnance Publication: the common manual of test methods used to generate the safety evidence for a munition's Safety, Arming and Functioning (SAF) System. The Letter of Promulgation records that it "has been approved by the nations in the CNAD AMMUNITION SAFETY GROUP (CASG - AC/326)," and that "the agreement of nations to use this publication is recorded in STANAG 4157" - the same agreement that covers its companion requirements document, AOP-4157. The relationship between the two is direct: AOP-4157 decides which of AOP-20's tests apply to a given SAF System and how they are tailored, and AOP-20 supplies the test methods themselves. The edition in front of a reader today is Edition B, Version 1, promulgated 27 February 2017.

Where testing sits in a SAF System's qualification

AOP-20 does not decide, on its own, whether a SAF System is safe. It is the shared toolbox of test methods that AOP-4157 draws from when it sets a system's own test programme, and the evidence that programme produces feeds the wider safety and suitability for service judgement a National Safety Approving Authority makes. Test selection itself is tied to the system's expected life-cycle environments, and applicability is set by AOP-4157, not by this manual. The manual also distinguishes requirements by when a design started: revised test requirements apply to SAF Systems developed after the relevant change notice, and an older system's testing can be tailored to whichever legacy standards applied when it was designed, subject to the NSAA's approval.

Who builds and runs a test programme

Conduct of a given test can fall to either of two parties, and the manual is explicit about which one decides if they disagree: "the test may be performed by the packaging agency or the SAF System agency; however, since the SAF System is the controlling item, the SAF System agency has the final decision of suitability." Oversight runs through several further, named authorities rather than sitting with the tester alone. A National Safety Approving Authority concurs in the overall test plan before testing starts. A design authority, acting with the NSAA's concurrence, sets a substitute pass criterion where a standard interface test cannot be met. For tests whose detailed requirements vary by system, a Safety System Authority concurs in the test plan, approves any configuration deviation, and separately receives evidence of any fault or anomaly for its own assessment. And "the chosen test strategy and results shall be presented and justified to the appropriate service safety authority" before that strategy is relied on.

Building and documenting a test programme

What the manual fixes, across every test, is the paper trail rather than a single procedure. A test plan has to be built and agreed with the NSAA before testing starts, specifying the test number and title, quantity, sequence, inspection and data methods, any modifications or waivers, alternate or optional tests, and the post-test verification procedure. All test equipment has to meet the conditions the test requires, with its calibration verified, within its validity period, by a registered organisation, to the satisfaction of the procuring activity. Where the test item contains explosive material or components, safety procedures and equipment matched to the hazard level are required, to protect personnel and equipment in the event of an explosion.

During and after testing, a complete record has to cover the test plan, the test item's condition before, during and after each test, the equipment used, the conditions applied, and the results and their analysis, kept so the technical effort can be properly analysed afterwards; any deviation or waiver has to be documented along with the technical reason for it. A visual examination is required at the start or end of any test, or whenever exposure is considered to have affected the item, with any damage recorded in the test item record. Where a SAF System's safety condition after a test is in doubt, "inspection by radiography is recommended prior to disassembly and inspection."

Each test itself is written up in a common chapter format - purpose, description, pass/fail criteria, equipment, procedure, and alternate, optional or related-information subsections - and a separate annex covers the statistical methods used to determine the initiation probability of one-shot devices. This page does not walk through which tests apply, what they examine, or at what levels: selecting and tailoring them is AOP-4157's job and the design or procuring agency's, not this page's.

How you are evaluated

Nobody is certified against AOP-20. The document names no accredited certification body, no notified body, and no NATO scheme that certifies a SAF System or the company that tested it. What it describes instead is government and service oversight of the evidence a supplier generates. For most tests, the pass/fail criteria are not fixed by the manual itself; they are set in the development test plan or the production specification by the design or procuring agency. Nearly every individual test still reaches its decision the same way: breakdown, inspection, other appropriate tests, and engineering judgment together form the basis for whether the item passed, and the result is stated against one of three standardised conditions for the SAF System - safe and operable, safe but not required to be operable, or safe for disposal only.

A national or service safety authority is where that evidence goes. The NSAA concurs in the test plan and, for interface tests that cannot meet a standard criterion, in the substitute a design authority sets. A Safety System Authority separately concurs in a test plan whose requirements vary by system, approves any configuration change, and reviews any fault or anomaly on its own account. And the chosen test strategy and its results are presented and justified to the appropriate service safety authority before they are relied on. Documentation is itself part of how the programme is checked: raw test data and analysed results have to be reported so that an independent party, not just the tester, can review the work.

Standards it references

AOP-20 is covered by STANAG 4157, the agreement recording nations' commitment to use it; the same agreement covers its companion requirements document, AOP-4157, which sets which of AOP-20's tests apply to a given SAF System. That framework sits under the wider safety and suitability for service assessment that AOP-15 and STANAG 4297 describe, and beside STANAG 4629, the broader agreement for safety and suitability for service assessment testing of non-nuclear munitions generally.

A group of design-safety STANAGs sit behind particular SAF System types this manual's tests address: STANAG 4187 for fuzing systems, STANAG 4497 for hand-emplaced munitions, STANAG 4368 for rocket and guided-missile motor ignition systems, and STANAG 4238 for electrical and electromagnetic design environments. A separate group of test-procedure STANAGs sit alongside AOP-20's own chapters for particular hazard responses: STANAG 4240, STANAG 4241, STANAG 4382 and STANAG 4375 - the last of these named in Annex A as an alternative procedure that may optionally be used in place of the drop test the manual itself describes there. STANAG 4370 is the overall environmental-testing agreement behind AOP-20's climatic test chapters, and STANAG 4439 is NATO's policy for introducing and assessing Insensitive Munitions, which this testing supports the evidence for. STANAG 4170 governs qualification of the explosive material itself, a separate and earlier step to the SAF System testing this manual covers.

Initiation-system and electro-explosive-device testing forms its own family, cited alongside rather than inside this manual: STANAG 4363 and AOP-21 for detonating explosive components, and STANAG 4560 and AOP-43 for electro-explosive devices. Individual test chapters also point to the Allied Environmental Conditions and Test Publications series - AECTP-300, AECTP-400 and AECTP-500 - for particular test conditions, alternative procedures, or, at several points in the manual, wording that ties a test's conduct directly to a named leaflet in that series.

NATO's Standardization Document Database is the authoritative source for AOP-20. NATO's documents are free of charge; we credit NATO for the catalogue and neither sell nor host a copy ourselves.

Standards it references

• STANAG 4187Binds
• AOP-4157Background
• STANAG 4497Background
• STANAG 4368Background
• STANAG 4240Background
• STANAG 4241Background
• STANAG 4370Background
• STANAG 4439Background
• STANAG 4170Background
• STANAG 4382Background
• STANAG 4375Background
• STANAG 4238Background
• STANAG 4297Background
• AOP-15Background
• STANAG 4363Background
• STANAG 4629Background
• STANAG 4560Background
• AOP-07Background
• AOP-08Background
• AOP-43Background
• AOP-21Background
• AECTP-300Background
• AECTP-400Background
• AECTP-500Background