AEP-107 sense and avoid for unmanned aircraft systems

What it is

AEP-107, Sense and Avoid for Unmanned Aircraft Systems, is a NATO Allied Engineering Publication, Edition B Version 1, promulgated in August 2025. It sets the certification requirements and acceptable means of compliance for sense and avoid (SAA) systems fitted to military unmanned aircraft systems (UAS): the technology that lets an uncrewed military aircraft detect other aircraft and avoid them, the way a manned aircraft's crew and collision-avoidance systems do. Nations record their agreement to use it in STANAG 4811, and NATO's objective behind it is for a military UAS operated by one Alliance member to be able to fly across the border into another NATO nation's airspace with confidence comparable to manned military aircraft.

The document is performance-based rather than prescriptive: it defines what an SAA-equipped UAS has to achieve, expressed as a measurable risk ratio, rather than how to build the equipment that achieves it. It leans heavily on its own companion guidance document, AEP-107.1 (which carries the background, rationale and concepts behind the requirements, and was originally published as AEP-101 in 2018), and it draws extensively on civil aviation material from ICAO, RTCA and EUROCAE, because a military UAS fitted with SAA still has to operate safely alongside civil traffic in shared airspace.

The airspace safety performance a system has to demonstrate

Three metrics anchor the whole standard: a mid-air collision, a near mid-air collision (an infringement of the collision volume), and an infringement of the well clear volume, ranked Catastrophic, Hazardous and Major severity respectively. Nominal risk-ratio thresholds are set separately for encounters with transponder-equipped traffic and with non-cooperative traffic, and a second, looser set of thresholds covers off-nominal conditions such as equipment failures or a degraded command and control link. Before any of that can be demonstrated, an applicant has to characterise the airspace the UAS is designated to operate in: the traffic to be expected, representative encounter geometries, traffic densities, airspace classification, atmospheric conditions, and the UAS's own usage pattern, each one a numbered requirement in its own right.

Certification requirements for the SAA system itself

Functionally, the SAA system has to provide traffic surveillance, alerting for remain well clear and for collision avoidance, resolution guidance, and support functions for status reporting and data recording. Alerting is split by urgency: a caution-level alert when the UA is expected to infringe the well clear volume, and a warning-level alert when it is expected to enter the collision volume. Guidance and automatic manoeuvring are mostly recommended rather than mandatory - notably, an automatic collision-avoidance function is not itself required if the applicant can demonstrate the standard's safety objectives are met without it. Installation and integration requirements cover environmental qualification, non-interference with other UAS functions, field of regard, human factors validation of the crew interface, the operator's traffic display, health and integrity monitoring, and a training module specific to the SAA system.

The document also works through right-of-way geometry in detail: which aircraft has the right of way in a head-on, overtaking, or converging encounter, and which way the UA should manoeuvre. That distinction only applies to remain-well-clear guidance - once collision avoidance is the last resort, any manoeuvre that maximises separation from the intruder may be used regardless of right of way. Terrain avoidance, where relevant, takes priority over traffic avoidance.

A separate section covers requirements unique to military systems: coping with formation flight and air-to-air refuelling without nuisance alerts, interception by friendly aircraft that deliberately switch off cooperative equipment, mission-driven ID changes and silent modes, the use of military sensors such as Link 16, IFF, IRST or ESM within the SAA function, and the added cyber exposure that comes with non-cybersafe technologies like Mode S and ADS-B.

Who reviews it, and who approves a UAS to fly

AEP-107 names three distinct roles, and does not describe any accredited or NATO-recognised certification of a company - no organisation is "AEP-107 certified". A certification authority reviews the SAA system against the certification basis the standard provides; an airworthiness authority approves how it is installed and integrated into the UAS; and an operational approval authority decides whether the resulting UAS can actually fly the mission. That operational approval authorises an operator to carry out defined UAS operations with an SAA-equipped UAS in a designated environment, and it covers airworthiness, continued airworthiness, and flight operations together.

What these reviewers actually look at is evidence: a Failure Mode, Effects and Criticality Analysis for the SAA system and every item in it, a Monte Carlo risk-ratio simulation independently verified and validated, flight test validation of detection range and tracking accuracy, human-in-the-loop testing of the alerting and guidance interface, and, before final operational approval, an operational validation report covering a recommended minimum of 300 flight hours (AMC.2509). None of this runs to a fixed calendar; it runs against a programme's own certification and approval milestones.

What it does not cover

SAA is scoped narrowly, by the document's own definition: it addresses only the sense and avoid of other aircraft in flight, not additional hazards such as birds, terrain, obstacles, weather, or aircraft on the ground. Ground risk from a UA crash sits outside this standard too, addressed instead by the UAS's own separate airworthiness safety case. And AEP-107 is explicit that it is not trying to replace industry or ICAO detect-and-avoid standards - RTCA, EUROCAE and ASTM prescriptive standards, and the ICAO DAA standards still under development, sit alongside it rather than being superseded by it.

Where it sits among the other NATO standards

AEP-107 is covered by STANAG 4811, the agreement NATO nations ratify to use it. It builds its safety assignments on top of STANAG 4671, the UAS airworthiness certification standard - both the airworthiness and the airspace safety objectives have to be satisfied together. It draws on STANREC 4685 for human systems integration guidance throughout its display, alerting and command-interface material, and on STANAG 4670 for the minimum training requirements behind its own SAA-specific training module. STANAG 4370 is named among the standards usable for environmental qualification, AOP-15 supplies the document's own definition of an "SAA system", and ATP-3.3.8.1 is cited alongside STANAG 4671 for the definition of "UA Operator". As with all NATO documents, AEP-107 is free of charge and not sold; it is retrieved from the NATO Standardization Document Database or through a national standardization authority, never from a third-party copy.

Standards it references

• ADatP-02Background
• STANAG 4671Background
• AOP-15Background
• ATP-3.3.8.1Background
• AAP-03Background
• STANREC 4685Background
• STANAG 4370Background
• STANAG 4670Background