Air cargo - Cargo stopper devices - Design and testing (ISO 21894:2020, IDT)
This document specifies the design, performance and testing requirements for "Cargo Stopper" air cargo restraint accessories with a 22 250 N (5 000 lbf) rated load capacity, to be used in conjunction with air cargo restraint straps meeting ISO 16049-1 (TSO/ETSO ̶ C172), or air cargo restraint slings meeting ISO 20291-1, with the same rated load.
Cargo stopper devices designed to this document are intended to be used in either of the following typical instances:
a) to ensure restraint/tie-down of a piece of cargo that does not lend itself to either direct hooking of tie-down straps or passing a strap around without risk of slippage; a common example is long shaped cargo items with a narrow cross-section, whether or not overhanging from the pallet, individual or in bundles, e.g. pipes or beams; see ISO 16049-2:2020, 7.4;
b) to restrain cargo smaller than the pallet net's mesh, or identified as "piercing" cargo, presenting a hazard to the aircraft in the event of it being released during flight;
c) when a crate containing cargo, even though its cross-section is large enough to be directly tied-down with the pallet net or restraint straps, contains or can contain a heavy item, e.g. a piece of machinery, shaft, or similar, with a cross-section lower than the pallet net's mesh size;
NOTE Such "hidden" items have been known to break free from insufficiently strong crates when subjected to in-flight accelerations, then pass due to their small size through the net mesh restraining the crate and be released into the cargo compartment.
d) to assist in tying-down odd-shaped cargo pieces where it is difficult or not allowed to directly attach tie-down straps or pass them around the load in an effective manner.