AASSEP-10 aircraft oil replenishment fitting

What it is

A common oil-replenishment fitting

AASSEP-10 is a short NATO Allied Aircraft Servicing and Standard Equipment Publication, promulgated in May 2024, that standardises one piece of an aircraft's design: the connection used to replenish a gas turbine engine's oil under pressure. Its aim, at clause 1.2, is to standardise that connection itself, not the practice of reoiling. The document is thin by design: almost all of its substance sits in one agreement clause, 1.3, because it works mostly by pointing at two civil connection standards and one NATO fuels-quality standard rather than restating their content.

What AASSEP-10 requires

Clause 1.3(a) requires the pressure replenishment connection to be built to ISO 451 or ISO 9939, and clause 1.3(b) states plainly that ISO 9939 "replaces and shall be used in lieu of ISO 451 for all new design" - so a newly designed aircraft or dispenser is expected to carry the newer connection, not the older one. The same clause fixes minimum performance for the servicing side: a fill pressure stated relative to atmospheric pressure, a minimum flow rate, a minimum dispenser capacity and a minimum delivery-hose length, each set as a specific figure in the document rather than left to a supplier's judgement. Clause 1.3(f) and (g) require the dispenser's filtration to be "to the standard stipulated in STANAG 3149" and its markings to carry "the NATO marking in accordance with STANAG 3149", NATO's minimum quality surveillance standard for fuels.

Clause 1.4, "Defence Against Terrorism", adds a general security requirement rather than anything specific to reoiling: equipment and materiel must be labelled, processed and stored to prevent unauthorized access or tampering, inspected and certified fit for use before each application, and serviced only by authorized personnel.

Who it addresses, and how it binds

Nothing in AASSEP-10 addresses an inspector or a certification body. Its clauses of substance are addressed to whoever designs and builds the aircraft-side connection and the ground dispensing equipment that mates with it, and to the personnel who carry out the servicing itself.

It binds the way most NATO Allied Publications do: through the agreement nations record. AASSEP-10's own Letter of Promulgation states that "the agreement of nations to use this publication is recorded in STANAG 3595." A nation carries the obligation into its own procurement once it has ratified; a supplier meets AASSEP-10 because a contract, a type specification or a tender calls it up, not because it exists in NATO's catalogue. Two nations have recorded a reservation against it: Greece's delivery hose may fall short of the standard's minimum length, and Norway reserves the right not to modify its own existing equipment to comply, applying the requirement to future procurement only where the manufacturer has the capability to meet it.

How it is assessed

AASSEP-10 names no certification body, audit cycle or inspection regime for the standard itself. Clause 1.4 does require equipment to be inspected and certified fit for use before each application, but that is a routine fitness check on the physical equipment, not an organisation being assessed or certified against AASSEP-10. Conformance is a design and engineering question: a connection either matches ISO 451 or ISO 9939, and a dispenser either meets STANAG 3149's filtration and marking requirement, or it does not.

Standards it references

AASSEP-10 depends on ISO 451 and ISO 9939 for the connection itself, both named at clause 1.1 and required at clause 1.3(a); clause 1.3(b) makes ISO 9939 the one to use for new design. Neither is in our catalogue at the time of writing, so both are named here rather than linked. It requires a dispenser's filtration and marking to follow STANAG 3149 at clause 1.3(f) and (g), which also lists the Allied publication it carries, AFLP-3149, among its related documents. AASSEP-10 is itself carried by STANAG 3595, the NATO agreement recording nations' agreement to use it.

Standards it references

• STANAG 3149Binds
• AFLP-3149Background