AASSEP-05 aircraft towing attachments and devices

What it is

A common towing-attachment interface

AASSEP-05 is a short NATO Allied Technical Publication, promulgated in November 2014, that standardises one narrow piece of an aircraft's design: the interface between an aircraft's towing attachment points and the towing bars, tow lines and bridles used to move it on the ground. Its aim, at clause 1.2, is to define the form and essential dimensions of the hollow axle and spool attachment points fitted to aircraft, the dimensions of the matching attachment heads on towing and steering bars, and the requirements for alternative towing by tow bar or tow line. Unlike some of its sibling AASSEP publications, which set their requirement by pointing at a civil ISO standard, AASSEP-05 is self-contained: it states its own geometry directly in a dimensions table and two annexes, keyed throughout to bands of aircraft maximum take-off gross weight.

What AASSEP-05 requires

Clause 2.1.1 requires normal towing to use a bar attached to either a hollow axle point, with its form and dimensions given at Annex A, or a spool point, with its form and dimensions given at Annex B. Clause 2.1.2 adds three requirements. Attachment points "should be accessible using a straight tow bar" - a recommendation, not a mandatory "shall", the one place the document steps back from a firm requirement. The attachment heads on towing and steering bars must be dimensionally compatible with the applicable hollow axle or spool point on the aircraft they serve. And towing attachment points must allow an aircraft to be towed both forwards and rearward. Clause 2.1.3 then narrows the whole standard's scope: it applies only to aircraft with wheels.

Clause 2.2.1 covers alternative towing by tow bar or tow line. Aircraft other than those fitted with arrestor and catapult hooks must be provided with lugs or rings sized, by the aircraft's maximum take-off gross weight, to the bands set out in the standard's own dimensions table, so a tow bar or tow line can be attached. The lugs or rings must have a cross-section free of sharp corners and be suitable for coupling, and any hooks on towing bridles used with them must be dimensionally compatible with those same figures. The exclusion is worth reading precisely: aircraft fitted with arrestor and catapult hooks, which is how carrier-capable aircraft launch and recover, are not brought under this particular fitting requirement.

Who it addresses, and how it binds

Nothing in AASSEP-05 mentions an operator, a maintainer or an inspector. Its clauses of substance are addressed to whoever designs and builds an aircraft's towing attachment points, or the towing bars, lugs, rings and bridle hooks meant to mate with them: the requirement is that the hardware matches a specified geometry, which is an engineering check, not an operational one.

It binds the way most NATO Allied Publications do: through the agreement nations record. AASSEP-05's own promulgation letter states that nations' agreement to use the publication "is recorded in STANAG 3278", and NATO's own catalogue lists AASSEP-05 as covered by that STANAG. A nation carries the obligation into its own procurement once it has ratified; a supplier meets AASSEP-05 because a contract, a type specification or a tender calls it up, not because it exists in NATO's catalogue.

How it is assessed

AASSEP-05 names no certification body, no audit cycle and no inspection regime. It is an interface specification: a towing attachment point, a towing-bar head, or a lug, ring or bridle hook either matches the dimensions the standard sets for the relevant aircraft weight class, or it does not, and checking that is a design and engineering review, not a scheme an organisation is certified against.

Standards it references

AASSEP-05 names no related document for its own technical content: clause 1.1 lists related documents as "Nil." It is itself carried by one NATO agreement, STANAG 3278, which records nations' agreement to use it and which NATO's own catalogue lists as covering AASSEP-05.