ATP-3.3.4.10 automated air-to-air refuelling (A3R)

What it is

ATP-3.3.4.10, Automated Air-to-Air Refuelling (A3R), is a NATO Allied Tactical Publication covering "air-to-air refuelling events involving at least one unmanned or automated tanker and/or receiver" (Chapter 1, paragraph 1). It is a concept of operations, not a finished interface specification: its stated purpose is "to provide guidelines for the development of A3R systems to ensure the solutions are interoperable within the international community" (Chapter 1, paragraph 1). It is rooted in an Aerial Refuelling Systems Advisory Group document, number 42-13-17, dated 9 June 2017, and is understood to become the basis of a future A3R section within the existing manned publication ATP-3.3.4.2 (Chapter 1, paragraph 1). Edition A, Version 1 was promulgated in October 2021. This edition covers only one tanker refuelling one receiver; combinations with multiple tankers or multiple receivers are left to a future version (Chapter 1, paragraph 4).

The document addresses the people who would build an A3R capability, "the international air refuelling community" developing these systems (Chapter 1, paragraph 1), and, through the roles and messages it defines, the Air Vehicle Operators (AVOs) and tanker crews who would direct an A3R system once one exists. It reaches a supplier or manufacturer the way any Allied Publication does, through a nation's own programme or a contract, not by existing on its own. NATO nations can ratify with a limitation: Estonia's recorded reservation states it "will implement the standard with the following limitation: Estonia will conduct only the procedural part - air-to-air refuelling operations management and coordination via CRC Tallinn."

Built on the existing manned procedures

A3R does not start from a blank page. The document is built to "strive to use existing operational procedures as laid out in ATP-3.3.4.2 to the greatest extent possible," and it repeatedly hands off to that publication rather than redefining ground it already covers: standard AAR positions ("all AAR positions are as defined in ATP-3.3.4.2 unless otherwise noted in Table 3-1"), the seven types of rendezvous, and the Loss of Visual Contact, breakaway, overrun and toboggan-manoeuvre procedures. The one position ATP-3.3.4.10 introduces that ATP-3.3.4.2 does not have is the Transition Point, used to check an unmanned receiver's relative navigation performance before it moves closer to the tanker.

The conceptual system

Chapter 2 describes an A3R system as four segments: the unmanned tanker or receiver (counted once, since either role uses the same systems), the manned tanker, the manned receiver, and the AVO stations. Table 2-1 lists the notional systems needed: a precision navigation system for guidance, navigation and control; voice and data communications; an automated boom system; and an automated probe/drogue system. The datalink is described as needing to be "a robust datalink will be needed with the capability of sending and receiving high volumes of relative navigation data with low latency and high integrity." Three tanker/receiver combinations are addressed; a manned tanker refuelling a manned receiver needs no new systems or procedures and is not covered.

Standard positions and the data-link message set

Table 3-1 names the standard A3R positions: Transition Point, Echelon Left, Astern (Left, Right, Centre), Contact, Echelon Right, Breakaway, Safe Position(s), and AAR Exit Point. Tables 3-2 through 3-5 set out functional message sets, Tanker Messages, Receiver Messages, Precision Navigation System Messages and Network Status Messages, that "translates the existing voice command and control messages/procedures as described in ATP-3.3.4.2 into data link messages." These tables are functional descriptions for CONOPS purposes, and the document says so plainly: "specific format and content of the messages will need to be defined in a NATO standard." Section 3.5 walks one rendezvous type, RV Alpha, through a full message sequence from network join to departure, as a worked example of how the message tables and the standard positions fit together.

Phases of flight and contingencies

Eight phases of flight are defined, Rendezvous, Approach, Formation, Astern, Contact, Departure, Breakaway, and Tanking (unmanned tankers only), each triggered by a specific message so that "the response of the air vehicle in each phase of flight is precisely defined, predictable and consistent." Chapter 4 covers contingencies: Breakaway, degraded communication and navigation, Overrun, Boom Flight Control Malfunction, Controlled Tension Disconnect, Fuel Leakage, Toboggan Manoeuvre, Manual Boom Latching and Pressure Refuelling. Most of these hand off to ATP-3.3.4.2 for the actual procedure. One contingency is specific to the automated system itself: because of the latency inherent in beyond-line-of-sight links, "due to latencies involved with BLOS, the receiver automatically executes a breakaway" on loss of the tanker-to-receiver command and control link, without the AVO commanding it.

What is genuinely unusual, and what the document says it does not cover

Safety-critical commands are the one message category the CONOPS insists on sending "direct tanker to receiver communications implemented without AVO intervention," a deliberate exception to the AVO-in-the-loop model the rest of the document assumes. Two exclusions are worth knowing before relying on this document for anything more: it "does not address Boom Drogue Adapter for A3R operations," and it does not itself fix message content, message format, or the accuracy, integrity, continuity and availability of navigation data a real interface would need, stating those "will need to be developed." New A3R airworthiness criteria are left to future work in the same clause. A reader treating ATP-3.3.4.10 as a complete, buildable interface specification has read further into it than the document claims for itself.

Where to get it

ATP-3.3.4.10 is published by the NATO Standardization Office and, like all NATO standardization documents, it is free of charge. NATO's Standardization Document Database is the authoritative source; we credit NATO for the catalogue and do not sell or host a copy of the document ourselves.

Standards it references

• ATP-3.3.4.2Binds