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ATP-3.3.4.6
NATO nations that ratify STANAG 3447, and the designers of tanker and receiver aircraft air-to-air refuelling equipment whose contracts invoke it
ATP-3.3.4.6 sets the mating dimensions, clearance envelope, engagement force, latch operation and fuel-pressure limits for the probe-drogue interface between NATO tanker and receiver aircraft, binding nations through STANAG 3447.
ATP-3.3.4.6 is the NATO Allied Technical Publication that fixes the physical interface between a tanker aircraft's trailing drogue and hose and a receiver aircraft's refuelling probe, the probe-drogue method of air-to-air refuelling. Edition A, Version 1 was promulgated in June 2016 and is effective on receipt; the document does not describe itself as superseding an earlier edition. It is short and almost entirely dimensional: an introduction, a four-clause specification chapter with five further design notes, and four annexes of dimensioned drawings and a test-gauge tolerance table.
Its stated aim is "to provide the air-to-air refueling (AAR) systems requirements and to standardize the interfaces required to engage in probe-drogue refueling operations to facilitate AAR between aircraft of NATO forces." Participating nations "agree to use the probe-drogue system and interface requirements established in this NATO STANDARD and its ANNEXES."
An Allied Technical Publication is not itself a contract or a law. It is content that acquires force through the STANAG that covers it: here, STANAG 3447, which the publication's own promulgation letter names as the record of "the agreement of nations to use this publication." A nation implements ATP-3.3.4.6 by instructing that future AAR equipment it develops, or has built under contract, will conform to the specifications here, and by identifying any exceptions for aircraft or equipment that already existed when the publication was promulgated. The document's operative language throughout is about what a nation instructs and identifies, not about a named Supplier or Acquirer role.
A company is drawn in only once a nation's instruction, or a contract or tender referencing this publication, requires the tanker or receiver equipment being built to conform to it. Within the document, the closest thing to direct address to a company sits in the annexes, which speak to whoever is doing the engineering: notes for "new receiver design" and "new tanker design," and guidance addressed to "receiver aircraft designers." Adoption is also visibly uneven rather than automatic: this edition's own record of reservations shows Germany unable to meet the universal pressure limit for one aircraft type, and France limiting its adoption to new equipment while excluding two clauses outright.
Chapter 2 works through the interface clause by clause, each tied to an annex or a figure. The mating dimensions of the reception coupling and the probe nozzle have to conform to the drawings in Annexes A and B (clause 2.1). A clearance envelope around the probe nozzle and probe mast installation follows Annex C, with receiver aircraft structure kept outside its hatched area and the tanker's drogue parts kept inside it (clause 2.2). The force to engage the nozzle in the coupling must not exceed 155 lbf at a head pressure of 10 psig (clause 2.3), and functional latch operation is verified with the Annex D test gauge, passed over the latches in both directions, with a maximum of 20 lbf (89 N) engaging and 50 lbf (223 N) disengaging (clause 2.4).
Fuel pressure is specified separately from the mechanical interface. Where a tanker can deliver more than 55 psig (379 kPa), it has to regulate steady-state delivery pressure downstream of the nozzle outlet to that limit at every flow rate down to zero flow (clause 2.5), and pressure surges from either aircraft must not exceed the other's design proof pressure (clauses 2.6 and 2.7). Two further note sections address legacy equipment rather than adding new requirements: clause 2.8 records that some existing tanker drogue systems need up to 30 cc/min flow to hold their regulated 55 psig, so a new receiver drawing less than that at top-off may see higher steady-state pressures, and that some existing systems allow up to 65 psig under no-flow or low-flow conditions; clause 2.9 notes that some legacy receivers (helicopters are given as an example) may need a lower interface pressure, that some legacy receiver probes are not compliant with this publication, and that some legacy receivers have a fuel system proof pressure of only 120 psig (828 kPa).
Annex C also carries design notes rather than binding limits: it records that its clearance figure does not account for relative movement between drogue and receiver during a mis-engagement, that a minimum of 12 inches (305 mm) is provided between the drogue's outer edge and the aircraft canopy once engaged, and that the figure is drawn for fixed-wing aircraft, with three of its dimensions not necessarily applying to rotary-wing design. None of this is offered here as guidance to act on; it is reported from the clause that states it, for a reader to take to the specification itself.
The document names no certification, audit or third-party assessment scheme, and no accredited or government body is described as checking anyone's conformity to it. What it describes instead is a nation checking its own equipment: clause 1.4 requires a nation to identify any exceptions to the specifications for aircraft or equipment that predate the publication, or that it later modifies, rather than an outside party making that determination. At the hardware level, the only verification step in the document is functional, the Annex D gauge test for latch operation. There is nothing resembling a certificate, and no sector scheme is named.
ATP-3.3.4.6 is covered by STANAG 3447, which is what gives it force between nations. It names two related publications as background rather than as prerequisites: STANAG 3971, which covers ATP-3.3.4.2, the general air-to-air refuelling requirements document this one narrows to the probe-drogue interface, and STANAG 7191, which covers ATP-3.3.4.5, the sibling publication for the different boom-receptacle refuelling method. It also lists a set of US Military Specifications and Standards for individual parts (a hose assembly, a nozzle, a coupling and drogue-cone components), the DoD Joint Service Specification Guide JSSG-2001, and two Aerial Refueling Systems Advisory Group reports on pressure definitions and technical data; none of these sit in our catalogue, so they are named here rather than linked.
NATO publishes ATP-3.3.4.6 through the NATO Standardization Document Database at no charge. ComplyTrain does not sell it or host a copy; the NSDD listing for ATP-3.3.4.6 is the source.
ATP-3.3.4.6 is operational and technical doctrine, not a management-system standard: there is no certificate to hold against it, and the work it describes, building a probe, nozzle, coupling or drogue to a dimensioned drawing and a force or pressure limit, then proving it with a physical test gauge, happens on an engineering bench and in flight test, not in a document system. This page offers no design or flying guidance of its own on any of it.
Where ComplyTrain fits is the paperwork a defence customer, prime contractor or national authority asks a supplier to produce around that engineering work: controlled records of the mating-dimension and clearance-envelope checks against the Annexes, the latch-gauge test result for a given unit, and a documented account of any exception a programme has identified for legacy equipment, the contractor's equivalent of the reservations nations record themselves. ComplyTrain holds those procedures, test records and exceptions as controlled, auditable documents, so a supplier has a place to show what was built, tested and excepted, and when.
ComplyTrain does not design a probe-drogue interface, run an engagement-force or latch-gauge test, or make any determination about whether a tanker or receiver aircraft is fit to conduct air-to-air refuelling. That judgement stays with the nations, their airworthiness authorities and the engineers who design and test the equipment. Which tier of NATO refuelling interoperability a given contract requires, and which related publications it pulls in, is set by the contract and the customer's quality clause, not by us; the standards explorer shows what sits alongside ATP-3.3.4.6, and we're glad to talk through what a specific tender is asking for.
Tell us how you need to work with ATP-3.3.4.6 and what you need from it. We will come back to you about what ComplyTrain can do.
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Not directly. It binds through STANAG 3447, which NATO nations ratify and then implement by instructing their own programmes; a supplier meets it only when a contract or tender specifies that tanker or receiver equipment must conform to it. There is no general answer to whether it applies, only a contractual one.
No. The document describes no accredited certification scheme and no third-party audit. Conformance works through a nation instructing its own programmes and identifying exceptions for existing equipment, and through the functional latch-gauge test the document itself specifies.
ATP-3.3.4.6 covers the probe-drogue interface for air-to-air refuelling, and it is covered by STANAG 3447. ATP-3.3.4.5 covers the different boom-receptacle system and interface, and is covered by a separate agreement, STANAG 7191. The two are related, sibling publications rather than one superseding or building on the other.
Yes. A nation can record a reservation against a clause it cannot fully apply. This edition's own record shows Germany unable to meet the universal pressure limit in clause 2.5 for one aircraft type, and France limiting its adoption to new equipment while excluding clauses 2.6 and 2.7 entirely, with the NATO Standardization Database holding the complete, current list.
From NATO's own Standardization Document Database, which lists the catalogue entry for ATP-3.3.4.6. NATO's publications are free of charge; we do not sell or host copies of them.
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