What it is
STANAG 2902 is a NATO Standardization Agreement, currently Edition 3, promulgated 6 February 2019. It is not a technical specification. It is the agreement by which NATO nations commit to implement AEP-2902, Edition A, the Allied Publication that sets out non-ballistic test methods and evaluation criteria for combat helmets. The document's own aim is to respond to an interoperability requirement: "to establish a standard classification to designate the non-ballistic performance of combat helmets when exchanging tactical information in NATO." Its own reasoning for that requirement: "This to ensure interoperability in multinational missions by the use of equipment with matching protection levels against a given threat." Read on its own, STANAG 2902 requires nothing of a helmet manufacturer or supplier. Its obligations run to nations and to NATO bodies, and the test methods themselves sit in AEP-2902, not in this cover.
Who it binds, and how
STANAG 2902 is explicit that it binds nations rather than organisations. Its letter of promulgation describes the enclosed agreement as one "which has been ratified by member nations, as reflected in the NATO Standardization Document Database (NSDD), is promulgated herewith." Under "Agreement," participating nations agree to implement AEP-2902, Edition A - a national commitment, made by ratification, not a duty a supplier signs up to by reading this document. Ratification and implementation stay separate steps: nations that have not already done so are invited to "advise the NSO of their intention regarding its implementation." So "is STANAG 2902 mandatory" has no single answer: it depends on whether a given nation has ratified and implemented it, and this cover names no manufacturer, supplier or test house at all.
What the agreement commits nations to
The STANAG states it "is effective upon receipt and ready to be used by the implementing nations and NATO bodies" - a NATO-wide mechanism, with partner nations separately "invited to adopt this STANAG." Implementation is tracked by ratification response: "participating nations agree to implement STANAG 2902 (Edition 3) in accordance with their ratification responses." Nations are invited to report their effective implementation, and partner nations their adoption, both "in accordance with AAP-03."
A cover agreement, not the test methods themselves
A reader who only has STANAG 2902 in hand does not yet have the test methods it points to. The non-ballistic test criteria, sample sizes and pass thresholds a helmet is actually judged against sit in AEP-2902, Edition A, the publication named under "Standard." STANAG 2902 names one other related document, STANAG 2920, which covers AEP-2920 on the classification of personal armour - the ballistic counterpart to AEP-2902's non-ballistic criteria, and a separate assessment entirely. Edition 3, 6 February 2019, supersedes STANAG 2902, Edition 2 (the source text names the prior edition but prints no date for it).
Reporting and review
National responses on ratification and implementation are recorded in the NATO Standardization Document Database. The STANAG itself "is to be reviewed at least once every five years," with the result recorded in the NSDD, and "nations and NATO bodies may propose changes, at any time, through a standardization proposal to the tasking authority (TA)." The agreement is supervised under the authority of the NATO Army Armaments Group (NAAG), Land Capability Group on Dismounted Systems (LCGDSS), with the United Kingdom's Defence Science and Technology Laboratory (Dstl) named as custodian.
What it does not cover
STANAG 2902 names no ballistic performance criterion of its own - that sits under STANAG 2920 and AEP-2920. It also names no test method, sample size or pass/fail threshold: those sit entirely in AEP-2902, which this agreement covers but does not reproduce. It also names no assessment or certification scheme: the only stated check is that the STANAG itself is reviewed periodically, not that a nation, an organisation or a helmet is certified.