AASSEP-02 aircraft pressure refuelling connections and defuelling

What it is

What AASSEP-02 covers

AASSEP-02 is the NATO Allied Technical Publication that standardizes the pressure refuelling connection fitted to an aircraft and the arrangements for defuelling it, so that one nation's ground crew can service another nation's aircraft using a connection everyone recognises. STANAG 3105 is the agreement that gives it force: a nation ratifies that STANAG, and AASSEP-02 is the technical text nations then apply. It covers the aircraft's pressure refuelling connection, an alternative refuelling capability for back-up, the adaptor's location relative to other servicing work, and how an aircraft is defuelled selectively, including in a wheels-up landing.

How it comes to bind

AASSEP-02 binds through STANAG 3105 rather than by existing on its own: a nation implements that STANAG domestically, and for a supplier the obligation typically arrives as a national specification or a contract for an aircraft type, or for work on its fuel system, that names AASSEP-02. The document is a short, focused technical text: an aim clause and two requirement clauses, with no annexes and no recorded reservations.

What it requires, clause by clause

Clause 2.1 sets the aircraft's pressure refuelling connection against the dimensions in ISO 45 and a minimum fuel acceptance rate, and requires every aircraft to carry an alternative refuelling capability in each main tank as a back-up if the pressure adaptor is damaged. Where an aircraft needs several servicing functions carried out while it refuels, the adaptor has to sit where those operations can happen at the same time and, as a design objective, without needing ground support elevating equipment just to connect the refuelling nozzle. Refuelling controls and quantity gauges sit next to the adaptor, and where an aircraft can be refuelled with an engine running, the adaptor and its controls are positioned to keep refuelling and maintenance personnel out of hazard.

Clause 2.2 requires a way to defuel each aircraft tank selectively, normally through the refuelling connection itself or, where that is not possible, by suction through an accessible aperture. Where practicable, the same routes handle a wheels-up landing, and the normal refuelling safety precautions carry over to defuelling at its highest rate. The design has to keep the ability to defuel each tank even with a single failure in the aircraft's fuel system, and to avoid negative pressures that could collapse a flexible tank. None of the dimensions, rates or pressures themselves are reproduced here; they are what a designer buys the document for.

How it is assessed

AASSEP-02 names no certification or assessment scheme, and no accredited body, notified body or self-declaration mechanism appears anywhere in the text. It is a technical characteristics document: conformity in practice is whatever the organisation accepting the aircraft design checks the connection and defuelling provision against, and, in service, whether a cross-servicing connection to another nation's aircraft actually succeeds.

Standards it references

• [STANAG 3105](/standards/stanag-3105) - the NATO agreement recorded in the Letter of

Promulgation that gives AASSEP-02 its force.

• [STANAG 3632](/standards/stanag-3632) - named in the document's own Related Documents

list, covering electrical connections for static grounding of aircraft and ground support equipment.

• [STANAG 3681](/standards#q=STANAG%203681) - named in the same list, covering the criteria

for pressure fuelling and defuelling of aircraft.

• [STANAG 3682](/standards#q=STANAG%203682) - named in the same list, covering electrostatic

safety connection procedures for aviation fuel handling and loading/unloading operations.

• ISO 45 - the civil standard the pressure refuelling connection's own dimensions are

specified against; outside our catalogue.

Standards it references

• STANAG 3632Background
• STANAG 3681Background
• STANAG 3682Background